OPC applications

Introduction

Mercury’s surface is characterized by large and well-preserved impact basis. They represent important records regarding the magnitude and timing of the “Late Heavy Bombardment” in the early inner solar system. It has been suggested that Mercury and Moon had the same early impactor population based on their similar crater size frequency distributions [1,2]. In this study we investigated the basins using complementary topography and gravity data sets derived by MESSENGER [3,4]. Gravitational data in combination with the surface morphology of the basins may help improve our understanding of their formation processes and alterations with time. Gravity anomalies hint at complex interior structures, such as mass and density distributions in the upper crust of the planet, which is beneficial for identifying highly degraded or buried basins.

In this study, we present an inventory of basins larger than 150 km, for which we introduce a classification scheme according to morphological and gravitational signatures.

Methods and data sets

The topographic digital terrain model (DTM) used in this study was derived by the Mercury Dual Imaging System (MDIS), involving a narrow-angle- as well as a wide-angle camera [3]. Gravity data data of the MESSENGER spacecraft, which resulted in a gravity field model with a resolution of degree and order 160, equivalent to approximately 28 km in the spatial domain [4].

Fig 1: DTM of Mercury’s topography. Circles mark the identified basins.

Results

Our preliminary basin inventory hosts 311 basins (Fig.1). A clear correlation is noticed between the topography and gravity data, in particular impact basins are well detectable in both data sets. Their global distribution is non-uniform. Around 60% of basins are located on the western hemisphere. This asymmetric pattern may be caused by (I) lateral thermal variances of the crust [1], (II) synchronous spin- and orbital periods of the planet in its early history, which later changed to its presently observed 3:2 spin-orbit resonance [2], (III) resurfacing events that includes the northern smooth plains and following flooding of existing basins on the eastern hemisphere, which would eventually bury smaller complex basins.

With increasing diameter basins were found to show more complex gravity- and topography signatures. Basins with smaller diameter (<160 km) display a central peak. With increasing size, the morphology changes to a peak ring in the center. The transition from peak ring to multi-ring basins is suggested to occur at 350 km as is attested by a distinct change in the gravitational signal. The gravity disturbance remains mostly in strong negative values. This value shifts to a positive one for basins larger than 350 km.

High positive gravity signals were also recognized in the Bouguer anomaly map. Some basins (>350 km) possess a positive Bouguer anomaly in the basin center surrounded by a negative anomaly annulus (bullseye pattern) (Fig 2). Gravity data are reflecting mass/density deficits and excesses in the planet’s subsurface structures. The high mass and density concentrations may be caused by an uplift of mantle material after the crater excavation phase [5]. The excavation was followed by an isostatic adjustment caused by cooling and contraction of the melt pool. Subsequently, crust is expected to be thinner.

Fig 2: Left: Profile of Bouguer anomaly, Right: Bouguer anomaly map; showing positive strong anomaly in center surrounded by negative annulus.

However, basins with small diameter (<200 km) were found to show strong positive anomalies as well, that indicate a mantle uplift after their formations. Due to limited data resolution (particularly in the south) the localization and accuracy of the Bouguer anomalies is not certain.

Other 208 basins where identified, but could not be characterized in detail due to their high degradation state (rim <50%). Most of these are filled by secondary material. Future data with improved resolution would be required to verify these results.

We investigated the amplitude of Bouguer anomalies in the basin centers and surroundings as a measure of crustal thinning, which may hint at basin relaxation state. Lunar observations showed, that young basins with large diameters should contain strong positive anomalies because of limited relaxation due to high viscosity of a cooler planet [6]. In contrast, a less pronounced gravity anomalies hint at higher relaxation due to lower viscosity and a hotter crust in the planet’s earlier history (Fig 3).

Fig. 3: Bouguer anomaly contrast from rim to centre versus rim diameter. Basin classes: b_deg- degraded basin (<50% rim preserved), centr_peak- central peak basin, peakr- peak ring basin, com- complex basin (>50% rim preserved).

Acknowledgements

This work is supported by the Deutsche Forschungsgemeinschaft (SFB-TRR170, A6).

References

[1] Orgel et al., 2020, Re-examination of the Population, Statigraphy and Sequence of Mercurian Basins: Implications for Mercury’s Early Impact History and Comparison with the Moon, J. Geophys. Res. 125(8), doi:10.1029/2019JE006212

[2] Fassett C. I., et al., (2012), Large impact basins on Mercury: Global distribution, characteristics, and modification history from MESSENGER orbital data, J. Geophys. Res. 117, E00L08, doi:10.1029/2012JE004154

[3] Preusker et al., Towards high-resolution global topography of Mercury from MESSENGER orbital stereo imaging: A prototype model for the H6 (Kuiper) quadrangle, Planetary and Space Science 142 (2017) 26-37 

[4] Konopliv et al., The Mercury gravity field, orientation, love number, and ephemeris from the MESSENGER radiometric tracking data, Icarus, Volume 335, 2020, 113386, ISSN 0019-1035,https://doi.org/10.1016/j.icarus.2019.07.020.

[5] Wieczorek, M., The gravity and topography of terrestrial planets, Treatise on geophysica, 2006

[6] Neumann et al., 2015. Lunar impact basins revealed by Gravity Recovery and Interior Laboratory measurements. Science Advances 1(9), 1-10.

How to cite: Szczech, C. C., Oberst, J., and Preusker, F.: Classification of Mercury’s Impact Basins, Based on Topography- and Gravity Signatures in MESSENGER Data, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-595, https://doi.org/10.5194/epsc2022-595, 2022.

Data from NASA MESSENGER spacecraft highlighted that Mercury’s surface and composition are more varied than previously thought. Despite being the closest planet to the Sun, indeed, Mercury is rich in volatiles and its surface shows evidence of volatile-driven processes such as the formation of hollows and explosive volcanism. Even MESSENGER’s color-derived basemaps, moreover, highlight relevant color variations of the hermean surface possibly indicating age and compositional differences between adjacent materials.

The ongoing mapping for the eastern H9 Eminescu quadrangle (22.5°N-22.5°S, 108°E-144°E) [1] led to a thorough knowledge of the area that allowed the definition of scientific targets of interest to be investigated by the SIMBIO-SYS cameras [2] onboard the ESA-JAXA BepiColombo mission [3] coupled with other instruments such as MERTIS, BELA, MGNS and MIXS.

Proposed targets range from hollows to volcanic features, from craters and deformational structures and specific terrains and aim at shedding light on scientific questions concerning Mercury’s origin and evolution [4]. In particular, proposed targets aim to i) determine the abundance and distribution of key elements, minerals and rocks on the hermean crust, ii) characterize and correlate geomorphological features with compositional variations, iii) investigate the nature, evolution, composition and mechanisms of effusive and explosive events, iv) determine the formation and growth rates of hollows, the nature of processes related with volatile loss and their mineralogical and elemental composition of volatiles, v) determine the displacement and kinematics of tectonic deformations and the mechanisms responsible for their formation and vi) verify the occurrence of any detectable change in and around hollows and pyroclastic deposits since MESSENGER observations.

Acknowledgements: We acknowledge support from the Italian Space Agency (ASI) under ASI-INAF agreement 2017-47-H.0.

References: [1] El Yazidi et al., 2021, EPSC. [2] Cremonese et al., 2020, Sp. Sci. Rev. [3] Benkhoff et al., 2010, Plan. Sp. Sci. [4] Rothery et al., 2020, Sp. Sci. Rev.

How to cite: Tognon, G. and Massironi, M.: Definition of scientific targets of interest for BepiColombo in the eastern Eminescu (H9) quadrangle, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-624, https://doi.org/10.5194/epsc2022-624, 2022.

The study of the micro-meteoroid environment is relevant to planetary science, space weathering of airless bodies, as Mercury, and their upper atmospheric chemistry. In this case, the meteoroids hit directly the surface without any interaction with the atmospheric particles, producing impact debris and contributing to shape its thin exosphere.

This work is focused on study and modelling of the Mercury’s exosphere formation through the process of Micro-Meteoroids Impact Vaporization (MMIV) from the planetary surface.

The MESSENGER/NASA mission visited Mercury in the period 2008-2015, providing measurements of unprecedented quality of Mercury’s exosphere, which permit the study of the seasonal variations of metals like Calcium. The Ca in Mercury’s exosphere exhibited very high energies, with a scale height consistent with a temperature > 20,000 K, seen mainly on the dawnside of the planet. The origin of this high-energy, asymmetric source is unknown. The generating mechanism is believed to be a combination of different processes including the release of atomic and molecular surface particles and the photodissociation of exospheric molecules.

We work on models of Mercury’s impactors: we consider the arrival geometry of the Mercury-intercepting particles and provide a detailed Ca-source extraction model simulating the expected 3-D CaO and Ca density distribution in Mercury’s exosphere due to the MIV mechanism. We simulate the photodissociation of the initially released CaO molecules that populates the exosphere with thermal Ca atoms and energetic Ca components generated from the dissociative ionization and neutralization processes, excluding specific events like comet stream crossing. We study how the impact vapor varies with heliocentric distance and compare the results to the MESSENGER observations. Our results show that the 3-D morphology of the MIV-generated Ca exosphere is consistent with the UVVS observations, these support the idea that the Ca source peaks near the dawn region: CaO exosphere is denser above the dawn hemisphere where the molecules are preferentially ejected into the exosphere by MIV process; Ca is preferentially seen in the midnight-to-dawn quadrant where CaO molecules are released by micrometeroid impacts and dissociated by the sunlight. 

The results presented in this work will be useful for the exosphere observations planning and for the data interpretation in the frame of the ESA/JAXA BepiColombo mission, that will study Mercury orbiting around the planet from 2025. More specifically, the resulting molecular distributions will be compared to the measurements of the SERENA-STROFIO mass spectrometer that will be the only instrument able to identify the molecular components. 

How to cite: Moroni, M., Anna, M., Alessandro, M., Nicolas, A., Christina, P., Valeria, M., Stefano, M., Stefano, O., Alessandro, A., Elisabetta, D. A., Rosanna, R., Roberto, S., Adrian, K., and Dario, D. M.: Micro-meteoroids impact vaporization (MMIV) as source for Ca and CaO exosphere along Mercury’s orbit, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-890, https://doi.org/10.5194/epsc2022-890, 2022.

Since the era of Messenger, many observational constraints on Mercury’s thermal evolution and magnetic field have strengthened the idea that the outermost layer of Mercury’s fluid core is stably stratified. The presence of such a stably stratified zone can significantly alter the core flow compared to the flow in a completely homogeneous fluid core. This is on the one hand because stratified layers can impede fluid motions that are parallel to the density gradient, which in the case of Mercury would mean that radial flows are strongly suppressed. On the other hand this is because a stably stratified layer can support different types of waves that are affected by the buoyancy force.

In this study we have created a numerical model to investigate flow in Mercury’s fluid outer core that includes a radial background stratification. The exact structure of the density profile in the planet’s core is unknown, and we assume profiles based on recent findings of the interior evolution of the planet. We studied core flow that is excited by Mercury’s librations, oscillations of the mean rotation rate due to the solar gravitational torque acting on Mercury’s triaxial shape. Based on the work by Rekier et. al. (2019) we represent the librational forcing by the superposition of three different decoupled motions: a horizontal component, which represents the viscous drag of the core fluid by the librating mantle and spherical inner core, and two radial components that are representing the radial push that the core flow would experience due to the librating triaxial boundaries.

We show that especially the second component has a profound effect, inducing a large non-axisymmetric flow close to the core-mantle boundary. It turns out that even though the origin of said flow is radial, the horizontal component of the flow is far larger than it’s radial counterpart. This indicates that the stratified layer acts to convert radial motions into strong horizontal motions.

We show how the strength and existence of this flow depend on the strength of the stratification of the layer and discuss implications of this flow for the magnetic field.

References:

Rekier, J., Trinh, A., Triana, S. A., & Dehant, V. (2019). Internal energy dissipation in Enceladus's subsurface ocean from tides and libration and the role of inertial waves. Journal of Geophysical Research: Planets, 124, 2198–2212. https://doi.org/10.1029/2019JE005988

How to cite: Seuren, F., Rekier, J., Triana, S. A., and Van Hoolst, T.: The core flow induced by Mercury’s libration: density stratification and magnetic fields, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-934, https://doi.org/10.5194/epsc2022-934, 2022.

Introduction:

Within the next decade, there are plans to carry out at least three space missions - Envision, DAVINCI+ and VERITAS - with which we could significantly broaden our current knowledge about Venus from the astrobiological point of view. A great supplement of the in-situ research carried out on Venus are the experimental tests carried out on Earth in a specially designed testing chamber with the reconstructed conditions encountered on Venus clouds. The need for such research, both in situ by probes and spacecraft on Venus, as well as in Earth's research laboratories, is suggested by the latest research results and formulated research hypotheses regarding potential life in the lower part of Venus clouds (at an altitude of 47.5-50.5 km above its surface) [1]. On the other hand, 3D-climate models indicate that this planet for a long time could have been characterized by an inhabited climate and have an ocean of water on its surface [2]. The discovery of phosphine in the clouds of Venus may also indicate the presence of microorganisms in the clouds of Venus [3].

Results and discussion:

Spectrophotometric UV-Vis-NIR tests of Acidithiobacillus ferrooxidans - strain 583 DSM have been carried out and the experimental data that have been obtained were compared with their counterparts characteristic of Venus clouds on the same wavelength [4]. The obtained dependence incident radiation wavelength vs. the transmittance for the studied bacteria Acidithiobacillus ferrooxidans, strain 583 DSM and Venus show similarity for specific wavelengths λ, which may indicate the potential existence in the clouds of Venus of microorganisms that are analogues of the terrestrial bacteria Acidithiobacillus ferrooxidans, strain 583 DSM with similar physicochemical properties. Further research of different types of acidophilic bacteria in the testing chamber with the reconstructed conditions encountered on the lower layer of Venus clouds will allow for the identification of further Earthly analogues of microorganisms potentially inhabiting Venus clouds.

References:

[1] Limaye S.S. et al. (2018) Astrobiology, 18, 1181-1198.

[2] Way  M.J  et  al. (2016) Geophys. Res. Lett., 43, 16,

      8376-8383.

[3] Greaves, J.S. et al. (2021) Nature Astronomy, 5, 655-

      664.

[4] Kuiper,  G.P. (1969) Comm. Lunar Planet. Lab., 101, 1-

      21.

Figure 1 
Scanning electron micrographs of Acidithiobacillus ferrooxidans, strain DSM 583.

How to cite: Stryjska, A., Słowik, G., and Dąbrowski, P.: Could Acidithiobacillus ferrooxidans be analogs of microorganisms potentially inhabiting Venus clouds?, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-941, https://doi.org/10.5194/epsc2022-941, 2022.

Introduction

Lunar robotic and human exploration efforts are ramping up, as exemplified by ongoing studies and missions from different space agencies, such as NASA and ESA with the Artemis program (e.g. NASA, 2020). In this scenario, the identification of potential resource deposits is of primary importance for the future exploration of planetary bodies (e.g. Lewis et al., 1993; van der Bogert et al., 2021). One of the most important deposits on Earth, but not well studied outside our planet, are the intrusive igneous processes and their derivative features. This work is the first step in ongoing research to evaluate the potential of this kind of geological setting on the Moon. We conducted a detailed analysis of an intrusive complex named Valentine Domes.

The Valentien Domes are located at the west margin of the Serenitatis Basin (30.69° N, 10.20° E). According to Wöhler and Lena (2009), they consist of two different edifices, a small one to the north and a big asymmetric dome 70 km wide to the south. The same authors identified a large fault at the east side of the bigger edifice, indicating that it originated as a laccolith (Schmiedel et al., 2017).

Data

In order to conduct the geomorphological and tectonic interpretation of the zone, we collected and processed 23 images taken by the Narrow-Angle Camera (NAC) onboard the Lunar Reconnaissance Orbiter (LRO). A high-resolution stereo-derived DEM was also generated using the Ames Stereo Pipeline (ASP)(Beyer et al., 2022). We also used some basemaps of the Moon, such as a global visible mosaic made with takes from the Wide Angle Camera (WAC), and a digital elevation model (DEM) derived from the Kaguya mission.

We coupled the prior analysis with mineralogical information derived from two hyperspectral cubes taken by the Moon Mineralogy Mapper (M3), onboard Chandrayann-1.

Results

Figure 1 shows the geomorphological map of the zone. 

The area is dominated by lava flood plains that show variations in their albedo. Darker lavas accumulated close to the rim of the basin, while in the centre of the Serenitatis and Imbrium basins the lavas have a lighter tone. The two domic features identified by Wöhler and Lena (2009) lie close to the rim of the basin, but we identified what looks to be a third dome to the south of the principal structure. This newly identified dome has a maximum altitude of 90 meters and it steeps gently to the surroundings. No faulting is visible near the dome, which leads us to classify it as a domed laccolith (Schmiedel et al., 2017).

The uplands located on the rim of the Serenitatis Basin can be divided into  Hilly materials (Him) and more dissected Hummocky materials (Hum). These materials at a first glance appear similar to a handful of small mounds located inside and around the Valentine Domes, this led Lena et al. (2018) to describe these features as kipukas from the floor of the basin. From the analysis using data from M³, we found that there is an apparent difference in composition between these mounds and the Him and Hum units. The units of the rim seem to have a major amount of plagioclase, which could point to a genetic difference between them and the mounds inside de domes. Thus, we mapped these features as different units: Secondary domes (Sd) and Secondary linear features (Slf).

We identified linear rilles crossing the main structure dome and the newly discovered dome. These lineations cross both domes almost by their centre, and in the case of the main dome, the rile is weakly aligned with the secondary domes inside it.

Figure 1: Geomorphological map of the Valentine Domes and northwest Serenitatis Basin.

Discussion and conclusions 

The discovery of a new dome south of the principal structure could imply that the Valentine Domes complex is more intricate than previously thought. This is supported by the presence of linear riles crossing the domes, which according to Head and Wilson (1992), points to the existence of stagnated dykes not far beneath the surface. The secondary domes and the thrust fault cutting the main structure are hints that plutonic rocks could be located on the surface, alongside useful mineralizations.

Acknowledgments

This project has received funding from the European Union’s Horizon 2020 research and innovation program under grant agreement No 101004214.

How to cite: Suarez Valencia, J. E. and Pio Rossi, A.: Geomorphologic mapping of the Valentine Domes in the Moon, intrusive domes, and their mineral resource potential, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-923, https://doi.org/10.5194/epsc2022-923, 2022.

• Introduction

When solar wind hits the lunar surface, a fraction of it is reflected back from the Moon instead of being absorbed by its surface. Evidence of neutral hydrogen atoms [1] and solar wind protons [2] being reflected from the surface are provided by numerous studies; however, no measurements of negative ions have been done so far. It is unknown whether or not a significant negative ion population exists near the lunar surface. The Negative Ions at the Lunar Surface (NILS) instrument, the first-ever dedicated negative ion instrument flown beyond the Earth, will address this question. NILS is being developed at the Swedish Institute for Space Physics for the Chinese Chang’E-6 sample return mission. Chang’E-6 is expected to launch in 2024 and will soft-land on the lunar far-side at approximately 41°S and 180°E. NILS will operate at least 30 minutes after the landing to achieve its main science objective. NILS operations will end with the lift-off of the sample return module.

• Main science objective

Negative ions are a not yet observed plasma component at the Moon. NILS’s main objective is to detect negative ions emitted from the lunar surface as a result of the interaction with solar wind and establish the upper limits for their fluxes. That requires NILS to distinguish and resolve the energy distributions of scattered H- and sputtered lunar negative ions, as well as to coarsely resolve different mass groups. The overarching scientific question is to estimate the importance of negative ions for space-surface interactions and environments of planetary bodies with surface-bound exospheres.

• Instrument design

NILS is the 9th generation of the SWIM family [3], a series of compact, adaptive, and capable mass spectrometers analysing ions, electrons or energetic neutral atoms at the sub-keV energy range. NILS combines a compact electrostatic analyser and a time-of-flight cell to measure the energy per charge and the mass per charge of incident ions. An additional deflection system consisting of two cylindrical electrodes allows for a one-dimensional 160° scanning of the viewing direction. NILS instantaneously records negative ions and electrons from a single direction and requires electrostatic scanning to change the viewing direction. Negative ions and electrons can be separated by an electron suppression system placed between the deflection system and the first-order focusing 127° long cylindrical electrostatic analyser. The latter is equipped with micro serrations on the outer electrode to maximize suppression of UV photons and scattered particles.

Prior to entering the time-of-flight cell, ions are post-accelerated by a -400V potential improving the sensor detection efficiency. The time-of-flight start signal is generated by a channel electron multiplier, which detects the secondary electrons generated when that particle is interacting at grazing incidence with a tungsten single crystal start surface. After the reflection on the tungsten surface, the particle travels to a stop surface, where a second secondary electron is generated that then subsequently is detected by a second channel electron multiplier, providing the time-of-flight stop signal. The time difference between the start and stop signals combined with the energy setting of the electrostatic analyser allows determining the mass per charge of the particle.

• References

[1] M. Wieser, S. Barabash, Y. Futaana, M. Holmström, A. Bhardwaj, R. Sridharan, M. B. Dhanya, A. Schaufelberger, P. Wurz, and K. Asamura. First observation of a mini-magnetosphere above a lunar magnetic anomaly using energetic neutral atoms. Geophys. Res. Lett., 37(5), 03 2010.

[2] Y. Saito, S. Yokota, T. Tanaka, K. Asamura, M. N. Nishino, M. Fujimoto, H. Tsunakawa, H. Shibuya, M. Matsushima, H. Shimizu, F. Takahashi, T. Mukai, and T. Terasawa. Solar wind proton reflection at the lunar surface: Low energy ion measurement by map-pace onboard selene (kaguya). Geophys. Res. Lett., 35, 12 2008.

[3] M. Wieser and S. Barabash. A family for miniature, easily reconfigurable particle sensors for space plasma measurements. Journal of Geophysical Research: Space Physics, 2016

How to cite: Canu-Blot, R., Wieser, M., and Barabash, S.: The Negative Ions at the Lunar Surface (NILS): first dedicated negative ion instrument on the Chang’E-6 mission to the Moon., Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-992, https://doi.org/10.5194/epsc2022-992, 2022.

Introduction: Despite the large amount of information from orbital and in situ missions, the characteristics and evolution of Mars’ early climate are still widely debated among the scientific community. Morphological evidence dating back to about 3-4 billion years ago, such as valley networks [1], and the presence of several hydrated minerals [2] seem to indicate that Mars once had a “warm and wet” climate with abundant water on the surface and possibly even an ocean in the northern lowlands [1-3]. These conditions eventually changed through time leading up to the hyperarid and cold planet we observe today. 

The area of Meridiani Planum (MP), located SW of Arabia Terra, is well known for retaining multiple evidence of past aqueous activity [4] and a varied hydrated mineralogy [5]. The majority of the terrains exposed in MP formed at the Noachian-Hesperian boundary [6], that is between two important epochs of Mars: the Noachian (4.1-3.7 Ga), where most of the evidence for water is found, and the Hesperian (3.7-3.0 Ga), which is characterized by increasingly water-limited conditions. Constraining the potential water environment at the NH boundary is fundamental to understand Mars’ early climate and its evolution.

In this study, we select 7 craters in Northern MP (figure 1) showing evidence of NH sediment infillings with hydrated materials (e.g., clays and sulfates) to assess in detail the stratigraphic sequence of the mineralogical units and understand their origin and diagenetic history. The craters are roughly aligned SE to NW following the general slope of the area from the highlands to the lowlands. If Mars experienced a “warm and wet” period, MP would represent a transition zone between the subaerial alteration environment of the highlands and the subaqueous environment of the Martian ocean. Therefore, the area would be easily affected by climatic changes whose evidence should be retained in its sedimentary sequences.

We show here some preliminary results from 2 out of the 7 craters selected for the study:

1) a 15-km-wide crater named Mikumi, centered at Lat. 2.45°N, Lon. 359.96°E; 
2) an 18-km-wide unnamed crater centered at Lat. 4.25°N, Lon. 2.85°E.

Figure 1: THEMIS daytime image of Meridiani Planum. Selected craters are evidenced with points. Name (if given) and coordinates of the center for each crater are also indicated with a label. Most of the craters are unnamed. The arrows indicate the two craters described in this abstract.

Datasets and methods: We investigate the mineralogy of the craters’ terrains through CRISM [7] hyperspectral data cubes mainly in the range 1.0-2.6 μm. This interval retains part of the key spectral features of primary rock-forming minerals, which constitute the Martian crust, and of most minerals produced by secondary processes such as aqueous circulation and alteration (e.g., clays and sulfates). MOLA, THEMIS, CTX and HiRISE data are then used for morpho-stratigraphy and camera imaging.

Results: Two types of clays (smectites) with different Fe/Mg content, polyhydrated sulfates and monohydrated sulfates are observed in both craters (figure 2). Fe/Mg-clay spectra (e.g., nontronite and saponite) show absorptions at around 1.4, 1.9 and 2.3 μm with additional overtones at 2.4 μm. The exact position of the 2.3 μm feature depends on the relative Fe/Mg content in the clay mineral. We find some areas with clays richer in iron (e.g., nontronite), showing this feature centered at 2.305 μm, and clays richer in magnesium (e.g., saponite) where the absorption is centered at 2.310-2.315 μm. In Mikumi crater, polyhydrated sulfates (Mg sulfate) and monohydrated sulfates (kieserite) are detected stratigraphically below the clay-bearing layer. For the unnamed crater, the stratigraphic relationship of the units is still to be investigated.

Figure 2: (top) CRISM spectra of detected mineralogy. Fe/Mg clays (smectites) are from Mikumi crater, mono and polyhydrated sulfates are from the Unnamed crater. The spectra are extracted from FRT0000BEF5 and FRT00009B5A TRR datasets respectively. (bottom) Laboratory spectra of clays and sulfates from the CRISM spectral library [8] (Mg Sulfate ID: CJB366; Kieserite ID: F1CC15; Saponite ID: LASA51; Nontronite ID: NCJB26).

Discussion and conclusions: Clays and sulfates on Mars appear to have formed at different times and under different climatic conditions [9]. Clays are usually associated to Noachian terrains and may have formed under alkaline conditions in a “warm and wet” ancient Mars, whereas sulfates are typically associated to Hesperian surfaces and may have formed under a dryer and more acidic environment. Therefore, sulfates are expected to be found stratigraphically on top of clays, as they should have formed later in Mars’ history. However, this distinction between a clay-rich Noachian and a sulfate-rich Hesperian oversimplifies the history of the aqueous chemistry and climate of Mars especially near the NH boundary.

Our analysis suggests a stratigraphic sequence with interleaving clays and sulfates at the NH boundary.  Similar stratigraphic sequences have also been observed in other areas of MP (Southern MP) by [5].  In the case of [5], a clay-bearing layer is overlain by other sulfates, generating a sulfate/clay/sulfate stratigraphic sequence. All this argues is in favor of several distinct climatic episodes pacing the NH climatic transition.

The results obtained so far will be enriched by further analysis of these areas along with a thorough investigation of the remaining 5 craters selected. 

Acknowledgments: Featured CRISM data were downloaded from the Planetary Data System (PDS). This project is partially supported by Europlanet RI20-24 GMAP project.

References: [1] M. H. Carr and J. W. Head (2010) Earth and Planet. Sci. Lett., 293, 185-203. [2] B. L. Ehlmann and C. S. Edwards (2014) Annu. Rev. Earth Planet. Sci., 42, 291-315. [3] R. A. Craddock and A. D. Howard (2002) JGR, 107 (E11), 5111. [4] R. M. E. Williams et al. (2017) GRL, 44, 1669-1678. [5] J. Flahaut et al. (2015) Icarus, 248, 269-288. [6] B. M. Hynek et al. (2002) JGR, 107 (E10), 5088. [7] S. Murchie et al. (2007) JGR, 112 (E5), E05S03. [8] C. E. Viviano-Beck et al. (2015) MRO CRISM Type Spectra Library, NASA Planetary Data System. https://crismtypespectra.rsl.wustl.edu [9] J. P. Bibring et al. (2006) Science, 312, 400-404.

How to cite: Baschetti, B., Massironi, M., Carli, C., Altieri, F., and Frigeri, A.: Clay and sulfate-bearing terrains in Northern Meridiani Planum, Mars: constraining the characteristics of Mars’ early climate at the Noachian-Hesperian boundary, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-222, https://doi.org/10.5194/epsc2022-222, 2022.

1. Introduction

   Plagioclase feldspar (Plg) is a common mineral in terrestrial rocks. It is a solid solution between a Ca-rich (anorthite) and a Na-rich (albite) endmember, and it is most commonly classified based on its anorthite (An) content. Powders of anorthite-rich Plg were previously studied using reflectance spectroscopy in the visible near-infrared (VNIR) range [1]. They showed that Plg display a band centered around 1.3µm due to Fe²⁺ substitutions, and that the position of this absorption band is a function of the An content.

   Other studies have investigated mixture of binary powders and showed that the Plg spectral signature is no longer visible when 10%, or more, of mafic minerals are added [2, 3]. According to these studies, a minimum of 90% of Plg are necessary in the rock composition for its spectral signature to be visible on the average spectrum of the rock. A more recent study, mixing large Plg and pyroxene grains [4], showed that at least 50% of mafic minerals are needed to mask the Plg spectral signature.

   Therefore, in addition to the An content, the size of the grains and the associated minerals influence the spectral signature of Plg. Thus, the analysis of whole rocks, and not powders, appears to be more relevant as a comparison with remote sensing analysis of planetary surfaces.

   The present study seeks to understand when Plg signatures are detectable, and how the Plg absorption band is affected by the nature of the host rock. In other words, does the spectral signature of Plg differ from one rock type to another, and if so, can a reflectance spectrum in VNIR be associated with a specific feldspathic rock type?

2. Method

   We combined petrological and spectral laboratory analyses of five terrestrial rock samples that contain Plg: an anorthosite (NM6), a granite (NJ11), two porphyritic basalts (NR1 and NR2) and a dacite (NJ2) (Figure 1).

   Firstly, reflectance spectroscopy measurements were carried out on the macroscopic samples using an ASD Fieldspec 4 point-spectrometer. The instrument operates in three different wavelength ranges: VNIR (0.35 – 1 µm), SWIR 1 (1.001 – 1.801 µm), and SWIR 2 (1.801 – 2.5 µm), with a spectral resolution between 3 and 8 nm.

   All resulting spectra (Figure 2) have an absorption band centered around 1.3µm with broad shoulders located around 0.8µm and 1.7µm. In order to accurately determine if this band is related to Plg in the rocks, additional analyses were performed.

   A petrographic study of each sample mineralogy (Figure 1) was carried out using an optical microscope as shown for sample NR1 in Figure 3.

   The use of hyperspectral cameras made it possible to further determine the spectral signature of each grain contained in these rocks (Figure 1). Hyperspectral cubes were acquired with the HySpex VNIR-3000-N and SWIR-640 cameras that acquire high-resolution data respectively from 0.4µm to 1µm, and from 0.96µm to 2.5µm, at a distance of 30cm from the sample. The resulting pixel size is about 29 µm in the VNIR, and 130 µm in the SWIR. The hyperspectral cubes are converted to reflectance using a reference target, and then analyzed with the ENVI software to classify the image pixels according to their spectral signature. Therefore, the different minerals in the rocks, which are often on a millimeter scale, are grouped into different classes. The statistics give the mean spectrum of each class, and therefore each mineral group (Figure 4).

3. Results and Discussion

   For each sample, the mineralogical composition (Figure 3) and spectral signature of each mineral (Figure 4) are determined. We observe that only Plg has an absorption band centered at 1.3µm with broad shoulders at 0.8 and 1.7µm. In conclusion, this same absorption band, that we see on the average spectrum of the rock (Figure 2), is the spectral signature of Plg. However, it should also be noted that in the matrix of Figure 4, composed of Plg and iddingsitized olivine, this band is no longer visible. This is also the case for the other samples: some minerals can mask the spectral signature of Plg by overlaying or attenuating its absorption band.

   Looking at the reflectance spectra (Figure 2), the position of the band seems to vary. It is centered around 1.2µm for dacite (NJ2) and granite (NJ11), around 1.25µm for basalts (NR1 and NR2), and 1.3µm for anorthosite (NM6). However, one must be careful with the interpretation: this shape might be related to the Plg chemical composition, but also the grain size, and the presence of other minerals contributing to the average rock spectra.

   Our study, therefore, shows that it is indeed possible to detect the presence of Plg in a whole feldspathic rock, even though it does not contain 90% of feldspar, and regardless of its nature (e.g., sample NR1 shown in Figure 4 contains ~66% of Plg).

   These results can be applied to the study of feldspathic rocks at the surface of rocky planets and more precisely of Mars. Indeed, recent detections of Plg [5, 6, 7] were made using the CRISM instrument (MRO) at the surface of Mars. The interpretation of these signatures, in terms of lithologies, is still under discussion given the variety of feldspathic rocks containing plagioclase [4, 5, 6, 7, 8] that exhibit the typical Plg absorption band. The construction of a reference library acquired on macroscopic rock fragments that we undertook should lead to a more accurate interpretation of Martian detections.

4. References

[1] J.B. Adams an L.H. Goullaud (1978). LPSC Conference, 9th, 3, 2901-2909 (A79-39253 16-91).

[2] D.A. Crown and C.M Pieter (1987). Icarus, 72(3), 492-506.

[3] L.C. Cheek et al. (2014). American Mineralogist, 99(10), 1871-1892.

[4] A.D. Rogers et H. Nekvasil (2015). Geophy.Res.Lett., 42, 2619-2626.

[5] J.J. Wray et al. (2013). Nature Geoscience, 6, 1013-1017.

[6] J. Carter et Poulet (2013). Nature Geoscience, 6, 1008–1012.

[7] J. Flahaut et al. (2020). EGU General Assembly (EGU2020-13377).

[8] A.D. Rogers et W.H. Farrand (2022). Icarus, 376, 114883.

How to cite: Barthez, M., Flahaut, J., Guitreau, M., Pik, R., and Ito, G.: Reflectance spectroscopy and optical microscopy laboratory analyses of terrestrial feldspathic rocks as analogs to Mars, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-467, https://doi.org/10.5194/epsc2022-467, 2022.

Abstract

Northwestern part of Terra Cimmeria displays a wide range of fluvial, lacustrine and glaciofluvial geomorphological features, indicative of presence of liquid water in this area early in the Martian history. These features were previously mapped as part of global studies, but not in relation to the area itself. Here we present our reconstruction of hydrologically correct model of northwestern Terra Cimmeria based on algorithm assisted mapping exercise of unprecedented precision. Based on our findings we are able to contextualize the geomorphological specifics of individual subbasins within the framework of Late Noachian Icy Highlands model and subsequent climatic transition towards the dry and cold state of the Amazonian period.

Physiographic Characteristic

Terra Cimmeria is an extensive region of the Martian southern highlands. Its northwestern portion (Northwestern Terra Cimmeria, NWTC) lies in the equatorial area of the planet and likely did so even before the Tharsis-induced true polar wander event (Bouley et al., 2016). It is nested between the volcanic province of Hesperia Planum to the southwest and the Utopia highland-lowland boundary to the north (Skinner and Tanaka, 2007). In the setting of the disputed Arabia Level ocean shoreline (Sholes et. al, 2021 and references therein) NWTC would stand out as the longest peninsula on Mars. The surface of NWTC is dominated by the Late Noachian highland unit with „undifferentiated impact, volcanic, fluvial and basin material“ (Tanaka et al., 2014). There are several open-basin lakes as mapped by Fassett and Head (2008), craters in different stages of degradation, and numerous valley networks which dissect the terrain (Carr, 1995; Hynek et al., 2010; Alemanno et al., 2018) and few on which terminate as deltaic deposits previously mapped by Achille and Hynek (2010). The variety and density of geomorphological features whose formation is tied to the presence of volatiles suggests a rich history of fluvial, lacustrine, and glaciofluvial activity and importantly fluvially dominated erosion and deposition. We incorporated available imagery and previously derived datasets in our algorithm assisted mapping exercise in order to contextualize the putative sources of the valley carving runoff within the local climatic background.

Methodology

NWTC valley networks were mapped several times in different level of detail starting with Carr (1995) who based his mapping on Viking imagery. This initial campaign was followed by Hynek et al. (2010) who utilized THEMIS daytime IR imagery and MOLA DEM and later by Alemanno et al. (2018) who in addition to THEMIS daytime IR and MOLA DEM used the ConTeXt (CTX) camera imagery to improve their recognition capability where the forementioned datasets lacked sufficient resolution.

Our mapping is based on the high resolution global CTX image mosaic rendered at 5 m/pixel (Dickson et al., 2018), THEMIS nighttime IR dataset, and MOLA DEM with the vectorized valley network dataset of Alemanno et al. (2018) serving as a baseline. We used Whitebox GAT surface flow accumulation model with hybrid breaching-filling sink removal capability (Lindsay, 2015) to digitalize the thalwegs as well as subbasins based on MOLA DEM. The algorithm-derived thalwegs and previously mapped valley networks were used to guide and double check the manual mapping which was based strictly on the CTX and THEMIS nighttime IR mosaics. Subsequently, digitalized subbasin borders were checked against the CTX mosaic and corrected based on the underlaying terrain. Notable geomorphological features were identified and marked as point features and putative headwater areas we delineated based on the previously logged data.

Results

We mapped an area spanning more than 8✕10⁵ km² and reconstructed 7 main valley networks. The valley networks were divided into over 80 subbasins based on manual correction of flow accumulation model. We managed to identify and connect seemingly isolated stretches of valleys and incorporate them into their respective networks thus creating a hydrologically correct reconstruction of the area. We identified several headwater-specific geomorphic features, pingos and paleolakes.

Discussion

In Noachian NWTC was situated between the equilibrium and terminus lines of a Late Noachian Icy Highlands (LNIH) ice sheet (Fastook and Head, 2015) and as such it would favor the formation of subglacial channels fed by meltwater (Galofre et al., 2020) and accumulation of ice (Wordsworth et al., 2013; Fastook and Head, 2015). The presence of developed dentritic networks which could have been carved by glavial meltwater is proven by our mapping exercise. Head et al. (2022) proposed that the climate of Mars underwent a transitional period during which a decrease in the atmospheric pressure induced a shift from altitude dependent temperature regime typical for the Noachian period (Wordsworth et al., 2013) towards latitude dependent temperature regime of the Amazonian period. This transition would start with ablation and melting of the lower altitude icy deposits and end with desiccation of equatorial ice reservoirs – both of which are in broader sense applicable to NWTC. In the beginning of this transitional period, meltwater released during the phases of peak temperatures would return to the highland cold traps in the time between these episodes. It is therefore plausible that given the specific combination of altitude, latitude, and location of NWTC, this area could sustain active surface or near-subsurface hydrology for an extended period of time up to 10⁶ -10⁸ years. This is supported by the variety of geomorphic features present in NWTC, but remains to be further tested with buffered crater counting and development of conceptual and hydrological models based on the newly created datasets.

Acknowledgements

VC & YM were supported by Czech Science Foundation (#20-27624Y).

References

Carr, Michael H. (1995), doi:10.1029/95je00260; Skinner, J. A., & Tanaka, K. L. (2007), doi:10.1016/j.icarus.2006.08.013; Fassett, C. I., & Head, J. W. (2008), doi:10.1016/j.icarus.2008.06.016; Achille, G. D., & Hynek, B. M. (2010), doi:10.1038/ngeo891; Hynek, B. et al. (2010), doi:10.1029/2009je003548; Wordsworth, R et al. (2013), doi:10.1016/j.icarus.2012.09.036; Tanaka, K. L. et al. (2014), doi:10.3133/sim3292; Fastook, J. L., & Head, J. W. (2015), doi:10.1016/j.pss.2014.11.028; Bouley, S. et al. (2016), doi:10.1038/nature17171; Lindsay, J. B. (2016), doi:10.1002/hyp.10648; Alemanno, G. et al. (2018), doi:10.1029/2018ea000362; Dickson, J. et al. (2018). A Global, Blended CTX Mosaic of Mars with Vectorized Seam Mapping: A New Mosaicking Pipeline Using Principles of Non-Destructive Image Editing; Galofre, A. G. et al. (2020), doi:10.1038/s41561-020-0618-x; Sholes, S. F. et al. (2021), doi:10.1029/2020je006486

How to cite: Cuřín, V. and Markonis, Y.: Reconstruction of Northwestern Terra Cimmeria Watersheds, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-549, https://doi.org/10.5194/epsc2022-549, 2022.

Introduction.

Earth's most-ancient crust has been recycled through plate tectonics processes making it unlikely that we will ever directly sample it (although, one can imagine finding ancient Earth meteorites one the Moon [1].) Mars, on the other hand, hosts ancient crustal outcrops on its surface. The uplifted massifs surrounding Argyre, Hellas, and Isidis – the three largest, well-preserved impact basins on Mars - formed in the chaotic aftermath of the basin-forming impacts due to normal faulting caused by crustal thinning from impact excavation [2]. Our goal is to understand the igneous minerals associated with uplifted massifs using the Compact Reconnaissance Imagining Spectrometer for Mars (CRISM) [3] around Argyre, Hellas, and Isidis (Fig. 1). Here, we present initial results in this effort for the north Hellas area and expect to present preliminary results for Argyre and Isidis, as well, at the conference.

Fig. 1 Context view of the study area. Squares outline 5°x5° CRISM tiles. Number of tiles is 100, covering an approximate 5% of the surface. CRISM coverage is >80 % over tiled areas. Inset shows a region at the map scale of 1:250,000 with CRISM spectra of uplifted massifs compared to library spectra. In the spectral parameter combination, red is consistent with olivine, yellow with plagioclase, and blue with low-calcium pyroxene.

Methods.

CRISM Data Processing. We used CRISM multispectral mapping data (MSP) and hyperspectral mapping data (HSP). The MSP mapping strips have 19 visible to near-infrared (VNIR, 0.4-1 µm) spectral channels and 55 short-wavelength infrared (SWIR, 1-4 µm) channels, and the HSP mapping strips contain 107 VNIR channels and 154 SWIR channels. Both mapping datasets have a ground sampling distance of approximately 180 m. The set of wavelength channels contained in the MSP dataset were chosen to sample more densely in wavelengths regions known to contain absorption features of minerals likely to be detected on Mars (primary rock-forming silicates, phyllosilicates, etc. [3]). For our study, HSP data were resampled to the MSP wavetable to increase the spatial coverage. Typical coverage of the MSP+HSP dataset is ~85%, with sufficient overlap to allow for mosaicking and radiometric reconciliation. We processed these data through a custom pipeline [4] that includes initial noise filtering, photometric and atmospheric corrections [5], [6], and an empirical correction for “spectral smile” [7]. The final products of this pipeline are 5°x5° mosaic tiles with improved inter-strip variability in atmospheric residuals [8].

A typical method for condensing the information contained in a CRISM image into an interpretable form is by calculating “spectral parameters”, i.e., mathematical summations of particular characteristics of the spectra [9]. Spectral parameters can be combined into 3-band RGB images that highlight specific, thematically-related, combinations of interest. Fore example, the MAF summary product combines indexes intended to highlight mafic mineralogy: olivine (OLINDEX3), low-calcium pyroxene (LCPINDEX2), and high-calcium pyroxene (HCPINDEX2). From the CRISM mapping tiles, we constructed summary products that are well-suited for compositional mapping over large areas [10] (e.g., Fig. 1).

Compositional Mapping. Regions of interest were identified with the map tile summary products in ArcGIS followed up by detailed spectral analyses in IDL/ENVI (specialized software for analyzing hyperspectral images) with custom add-on analysis tools. Point locations of compositions, confirmed through spectral analysis, were imported back into ArcGIS and “outcrops” were mapped using summary products. We define outcrop in the context of this work as a spatially contiguous region with an internally consistent spectral signature distinct from its surroundings (e.g., Fig. 2).  

Fig. 2 Example plagioclase-bearing massif north of Hellas basin. (A) CRISM browse product (same as in Fig. 1). Yellow tones are consistent with plagioclase. Black boxes indicate 8 regions over which spectra were taken and plotted in C. (B) CTX 5 m/pixel image of the same massif as in (A). White dashed lines denote outcrops mapped in this A and B. (C) Average CRISM ratioed I/F spectra from the 8 regions indicated in A and B.

Results and Discussion.

Thus far, we have mapped 12 high-calcium pyroxene-bearing outcrops, 97 plagioclase-bearing outcrops, 128 LCP-bearing outcrops, and 129 olivine-bearing outcrops (Fig. 3). Outcrops with distinct mineralogical signatures are often observed adjacent to each other on the same massif, or on massifs in close spatial proximity (relative to the size of the massifs, ~several kilometers). We also identified Fe-, Mg-, and Al-phyllosilicate minerals associated with the massifs and, more commonly, with impact crater ejecta along the northern Hellas rim.

The number and spatial extent of plagioclase-bearing outcrops was surprising and is described in [11]. The massifs pre-date Hellas (≥ 4.1 Ga) and are situated stratigraphically above putative mantle material. The north Hellas massif outcrops may expose the remains of an ancient large igneous complex, perhaps similar to terrestrial layered mafic intrusions. Preliminary results from the Argyre and Isidis uplifted massifs will be presented at the conference and compared to those from north Hellas.

Fig. 3 Summary of detections over north Hellas. (A) Red squares indicate all locations of plagioclase-rich outcrops discovered previous to our work. (B) Context map showing all mafic mineral outcrops mapped in our study. Arcs are 50-km interval bins measured radially from the center of Hellas. Geologic units are Noachian crater (Nc), Noachian highland (Nh) and Noachian massif (Nm) from Leonard and Tanaka, 2001. (C) %Area is the area of each mineral outcrop normalized to the area of the Nc, Nh, and Nm geologic units in each radial bin. Note the concentration of detections interior to the nominal radius of Hellas, highlighting the stratigraphically low position of the outcrops.

[1]       J. J. Bellucci et al. doi: 10.1016/j.epsl.2019.01.010.

[3]       G. J. Leonard and K. L. Tanaka, 2001.

[4]       S. L. Murchie et al. doi: 10.1029/2009je003344.

[5]       F. P. Seelos and S. L. Murchie, LPSC. p. 2325, 2018.

[6]     F. P. Seelos, et al.,  LPSC. p. 1783, 2016.

[7]     F. Morgan et al., LPSC. p. 2453, 2011.

[8]     F. P. Seelos et al., LPSC. p. 1438, 2011.

[9]     F. P. Seelos, et al., LPSC p. 2635, 2019.

[10]     C. E. Viviano‐Beck et al. doi: 10.1002/2014JE004627.

[11]     C. E. Viviano et al., LPSC, p. 1485, 2020.

[12]     Phillips, M. S., et al., Geology, accepted.

How to cite: Phillips, M., Viviano, C., Moersch, J., Rogers, A. D., and Seelos, F.: Mars uplifted massifs: unique and extensive samples of ancient crust., Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-736, https://doi.org/10.5194/epsc2022-736, 2022.

An upward transport of water via the Hadley cell has been suggested as one of the mechanisms to transport water vapor to the upper atmosphere [Shaposhnikov et al., 2019], which would enhance the hydrogen escape on Mars [cf. Chaffin et al., 2017]. Carbon monoxide is one of the tracers which can measure the dynamics in the Martian atmosphere because CO distribution is a combination of photochemistry and dynamics. Above ~60 km altitude, the CO mixing ratio increases with altitude due to the production from photodissociation of CO₂ and is further enhanced around the polar regions because of downwelling from the thermosphere [Daerden et al., 2019; Holmes et al., 2019; Olsen et al., 2021; Yoshida et al., accepted]. In the lower atmosphere, CO is recycled to CO₂ by the catalytic cycle by odd hydrogen. The photochemical lifetime of CO is too slow, and then its lifetime is ~6 years in the lower atmosphere [Krasnopolsky, 2007]. Thus, seasonal variation of CO in the lower atmosphere is a consequence of CO₂ sublimation/condensation at the polar cap [Encrenaz et al., 2006; Smith et al., 2009, 2021]. In addition, transport of rich CO atmosphere from southern to northern hemispheres during L_s = 90 – 180 has been measured by Smith et al. (2008, 2018) as predicted due to the breaking of the polar vortex by the GCM model. Although the vertical distribution of CO VMR is an index to determine the condensation of CO₂, photochemistry, and dynamics, there is no direct comparison between measurements and simulations because we did not obtain the CO vertical distribution before the Trace Gas Orbiter (TGO) ExoMars mission. To clarify the vertical and horizontal transport of CO in the Martian atmosphere, we investigate the CO VMR retrieved from the solar occultation (SO) channel of Nadir and Occultation for MArs Discovery (NOMAD) instrument aboard TGO [Vandaele et al., 2018].

The SO channel operates at wavenumbers from 2325.6 to 4347.8 cm^-1 with relatively high spectral resolution (R = 17,000). CO (2-0) band spectra features between 3970.7 and 4360.1 cm^-1 are measured regularly in orders 186 to 191 of the instrument. We retrieved CO number densities using CO spectra features in orders 186 to 191 and radiative transfer code, ASIMUT [Vandaete et al., 2006], based on the Optimal Estimation Method [Rogers, 2006]. ASIMUT was performed for each spectrum at each tangential altitude independently [e.g., Aoki et al., 2019]. The latest updated instrument calibrations [Villanueva et al., submitted; Thomas et al., 2022] have been applied. We used the GEM-Mars model temperature and CO₂ profiles [Neary et al., 2018; Daerden et al., 2019] to derive the CO VMR. The CO spectra were investigated from April 2018 to September 2021, corresponding from MY 34 L_s ~ 150 to MY 36 L_s ~ 105. The total number of dataset is 31,000.

Firstly, we found that the retrieved CO VMR in orders 187 to 191 does not correspond to that in order 186 below ~60 km altitude. The CO VMR derived from orders 187 to 191 is underestimated. The strongest 2-0 band of CO is located at 4288.3cm^-1, which corresponds to order 190, and it saturates around ~60 km. The saturation of CO lines would be related to the underestimation of CO VMR. When we tested the retrieval sensitivity of saturated lines in order 186, the underestimation of CO VMR also appears below 40 km altitude in the case that we perform the ASIMUT using the entire wavenumber range of order 186 (4179.0 – 4212.2 cm^-1) compared with using a partial wavenumber range, 4189.0 – 4198.0 cm^-1, of order 186. To avoid the underestimation of CO VMR, the retrieved CO VMR derived from CO spectra in the orders 187 – 191 is limited between 60 and ~110 km altitude, that from CO spectra in order 186 is limited between 40 and ~110 km, and that from CO spectra in 4189.0 – 4198.0 cm^-1 is limited between the near-surface to 40 km altitude.

The retrieved CO VMR distributes from 300 to ~5000 ppm. In the polar regions, the CO VMR increases above ~40 km and reaches 4000 ppm at 70 km, which is attributed to the production of CO from photodissociation of CO₂ and transport of CO-enriched air via meridional circulation [Daerden et al., 2019]. That is consistent with the results measured by the Atmospheric Chemistry Suite aboard TGO [Olsen et al., 2021]. In the lower atmosphere, the enriched CO VMR up to ~3500 ppm appears from 90 to 200 in L_s in the southern hemisphere, which would be attributed to the CO₂ condense in the southern winter season. We will report the CO distribution in more detail while distinguishing the dataset into season and latitude along with altitude.

How to cite: Yoshida, N., Aoki, S., Vandaele, A. C., Nakagawa, H., Thomas, I., Erwin, J., Daerden, F., Trompet, L., Murata, I., Terada, N., Neary, L., Lopez-Valverde, M., Modak, A., Villanueva, G., Liuzzi, G., Kasaba, Y., Patel, M., Ristic, B., Bellucci, G., and López-Moreno, J. J.: CO distributions retrieved from TGO NOMAD SO using multiple orders, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-753, https://doi.org/10.5194/epsc2022-753, 2022.

Introducction

JAXA’s MMX (Martian Moons eXploration) mission, to be launched in 2024, will study both Martian satellites, for several years, and will drop a small rover to Phobos, to explore its surface [1]. As part of this rover scientific payload, it will be placed a Raman spectrometer, the RAX Instrument (Raman Spectrometer for MMX). The RAX will be able to analyse the mineral composition of the Phobos regolithe surface with in-situ measurements, complementing the Japanese Sample Return mission, and helping to reveal the nature and distribution of materials on the Martian Moon’s surface, and ultimately its origin and evolution [2].

The RAX instrument [3] has been designed, manufactured, integrated and tested by an international consortium led by DLR (Germany), with significant contributions from JAXA & University of Tokyo (Japan), and INTA-CAB-UVa (Spain). One of the Spanish contributions to RAX, will be the instrument Verification Target, a small piece of PET (polyethylene terephthalate) attached to MMX spacecraft, to be used before launch, and during cruise; for spectral instrument performances verification on-ground and just before the rover release to Phobos.

Figure 1. RAX Verification Target design proposed by INTA-CAB-UVa

Experimental

Thanks to previous expertise of the UVa-INTA group with PET material, used on the Raman Laser Spectrometer (RLS) Calibration Target [4] for ESA’s ExoMars mission; and SuperCam Calibration Target [5] for NASA Mars2020; a newly design-deuterated PET material, decreasing the PET fluorescence background, and adding new Raman bands with respect to ordinary PET [6] has been developed, manufactured, characterized and space-qualified for MMX-RAX mission by INTA-CAB-UVa; so it was proposed as candidate the RAX Verification Target.

Figure 2. RAX Verification Target Flight batch for qualification/acceptance

Results and discussion

During the session, a detailed description of different tests carried out for the space qualification of the deuterated material, will be shown. And how the final performances with respect to other commercial PETs have been improved; and so, how the final verification-calibration of the Raman instrument has been optimized.

Acknowledgements

INTA’s internal I+D+I project IDMats; and MICINN grants PID2019-107442RB-C32 & PID2019-107442RB-C31

References

[1]       Michel P. et al. (2022) Earth, Planets and Space 74, 2.

[2]       Hagelschuer, T. et al. (2019) 70th Int. Astronautical Congress, 2019.

[3]       Hagelschuer, T. et al. (2022) 73th Int. Astronautical Congress.

[4]       López-Reyes, G. et al. (2020) Journal of Raman Spectroscopy, 1-13

[5]       Manrique, J.A. et al. (2020) Space Sci Rev, 216:138

[6]       Mora, J. et al (2020) Acta Astronaut. 167 (2020) 360–373

How to cite: Moral, A. G., Mora, J., Prieto-Ballesteros, O., Fernández Sanpedro, M., López-Reyes, G., Ercilla, O., Sanz Arranz, J. A., Herrera, A., Pérez, C., Rull, F., Böttger, U., Cho, Y., Schöder, S., and Hübers, H.-W.: Improving the Polyethylene Terephtalate (PET) perfomances, for the RAX Verification Target for MMX mission, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-784, https://doi.org/10.5194/epsc2022-784, 2022.

Introduction

The detection of anomalous bright reflections beneath the Martian SPLD by MARSIS radar has sparked a vast debate on the characterization of the basal material. The source of the reflections has been interpreted by someone as an evidence of basal liquid salty water [1, 2], while by others as clay sediments or volcanic rocks [3, 4]. Though it has been demonstrated that clays cannot be the responsible of the strong reflections [5], it has not yet been well understood if the dielectric permittivity of the volcanic rocks can be so high as to cause the reflectivity seen by MARSIS. Furthermore, although there are in literature several attempts to demonstrate a correlation between the dielectric properties of volcanic rocks and their whole-rock compositions [6], these data can hardly be compared with each other, since every work employs different experimental setup and procedures. Therefore, a definitive dataset of the permittivity of such samples and planetary simulants does not yet exist, especially at the operating frequencies of planetary radar sounders ( 1 MHz - 1 GHz). The present work aims to be a first step towards a reliable dataset of electromagnetic measurements of volcanic rocks, investigating the relation between their geochemical and their electric and magnetic properties.

Methodology

Sample characterization

We studied the granular samples of three different volcanic rocks that are plausibly representative of the overall surface compositions of the terrestrial planets [7]. In the following, the samples are named as: St. Augustine (2006), Etna (1991-1993) and Etna (Holocene). The St. Augustine (2006) sample is a lava rock coming from the 2006 eruption of the St. Augustine stratovolcano in Alaska [8]. Sample Etna (1991-1993) comes from the Piana del Trifoglietto lava field at SE of Etna summit craters generated by the eruption started on December 1991 and stopped on March 1993 [9]; the rock is characterized by a potassic geochemical signature. Sample Etna (Holocene) is a mugearite from Pizzi Deneri Formation and it comes from an ancient eruption (57000-15000 years ago), representing the more sodic volcanic activity [10]. In Fig. 1 and Tab. 1 are shown respectively the TAS diagram of the samples and their geochemical composition.

The samples exhibit different grain densities: ρ_{St. Augustine(2006)} = (2.736± 0.001) g/cm3, ρ_Etna(91-93)= (2.961 ± 0.001) g/cm³ and ρ_{Etna(Holocene)}= (2.787 ± 0.001) g/cm³.

Table 1. Whole-rock compositions of the samples.

Figure 1. Total Alkali vs. Silica diagram of the samples.

Electromagnetic measurements and mixing formulas

The electromagnetic measurements were carried out with a two port Vector Network Analyzer (VNA), employing a cage coaxial cell and using the experimental procedure and setup described in [11]. The complex permittivity ε and magnetic permeability µ were estimated by using the Nicholson-Ross-Weir algorithm and the equations slightly modified in [12]:

where F_g is a factor related to the geometry of the cell, Γ and Ψ are the reflection and transmission coefficients, l_e = 5 cm is the electrical length of the cell, c is the velocity of the light in a vacuum and ν is the frequency. The complex effective permittivity of the two phases granular rock-air was studied using Lichtenecker and Bruggeman mixing formulas:

where ε_i and ε_eare respectively the permittivity of the environment (the solid grains) and inclusions (air) and f = 1- Φ is the volume fraction of the grainsin the sample, with Φ the porosity.

Results and conclusions

Measurements with the VNA were performed on the granular samples at room temperature, for percentage porosities ranging from 31% to 55%.  The magnetic permeability µ is not reported because the three samples do not show a magnetic behavior (and then we can consider µ ≃ 1). Fig. 2 illustrates the complex dielectric permittivity as a function of frequency and at Φ = 0.36. Gray areas in the plots show values that are not reliable since at high frequencies the NRW algorithm diverges because of the cell resonances. Data have larger uncertainties at low frequencies due to VNA instrumental limits. The two Etna samples show a similar dielectric behavior, instead the St. Augustine sample has lower values of both real and imaginary part of permittivity. In the end, we fitted at 80 MHz the complex permittivity as a function of porosity using eqs. 3 and 4. In Tab. 1 we show the measurements at Φ = 0.36 and the values obtained with the mixing formulas at Φ = 0. The St. Augustine sample has the lower values of the solid complex permittivity, probably due to its lower iron abundances and higher abundances of SiO_2, while the two Etna samples show a similar dielectric behavior. Further measurements will be required in the future in order to identify the relation between the electromagnetic properties and the geochemical compositions of volcanic rocks that can be accounted as good simulants of the surface and subsurface of terrestrial planets, such as Mars and Venus.

Figure 2. Complex permittivity frequency spectra of the samples.

Table 2. Complex permittivity measured at Φ = 0.36 and fitted at Φ = 0 with eqs. 3 and 4.

References 

• Orosei R. et al. (2018) Science, 361(6401), 490-493
• Lauro S. E. et al. (2020) Nat. Astron., 5(1), 63-70
• Smith I. B. et al. (2021) Geophys. Res. Lett. 48, 15
• Grima C. et al. (2022) Geophys. Res. Lett. 49.2, e2021GL096518.
• Mattei, E. et al. (2022). Earth and Plan. Sci. Lett. 579, 117370.
• Rust A. C. (1999) Jour. of Volc. and Geoth. Res. 91.1: 79-96.
• McSween Jr et al (2009) Science, 324.5928: 736-739.
• Larsen J. F. et al. (2010). Rapp. tecn. US Geological Survey.
• Calvari S. et al. (1994) Acta Vulcan., 4: 1-14.
• Vona A. et al. (2017) Chem. Geol., 458: 48-67.
• Brin A. et al. (2021) Icarus 114800.
• Mattei E. et al. (2013). IEEE trans. on instr. and meas., 62(11), 2938–2942.

How to cite: Brin, A., Salari, G., Lauro, S. E., Cosciotti, B., Mattei, E., and Pettinelli, E.: Electromagnetic and geochemical characterization of volcanic rock samples in the framework of radar exploration of terrestrial planets, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-956, https://doi.org/10.5194/epsc2022-956, 2022.

The Nadir and Occultation for Mars Discovery (NOMAD) is one of the four instruments on board the 2016 ExoMars Trace Gas Orbiter. The instrument is a suite of three spectrometers, mainly designed to study minor atmospheric species at high spectral resolution (A.C. Vandaele et al., 2015; E. Neefs et al., 2015). Nevertheless, Oliva et al. (2022) demonstrated the capability of NOMAD infrared nadir channel to investigate surface ice composition in the 2.3 – 2.6 μm wavelength range. Ice signatures have been also observed at mid/equatorial latitudes suggesting, after analysis, the first detection of CO₂ ice clouds through the study of the narrow 2.35 μm absorption band.

In this work, we also use observations of the NOMAD infrared LNO channel in order to evaluate its capability to detect H₂O ice clouds. We present a technique taking advantage of the 2.7 µm strong ice absorption band. For this study, we select LNO spectral orders 167, 168, 169 and combine them to derive a spectral index for H₂O ice detection, namely the Frost and Clouds Index (FCI). The acquisition of data during Mars Year 34 and 35 (March 2018 to February 2021) allows us to construct seasonal maps for H₂O ice clouds. The results appear in agreement with previous studies focused on Mars Express SPICAM/UV and OMEGA data analysis (Willame et al., 2017; Olsen et al., 2021). FCI is sensitive to the Polar Hood clouds, although the full structure is not detected. Moreover, detections in the Aphelion Cloud Belt (ACB) are limited. This is consistent with previous OMEGA spectrometer observations (Olsen et al, 2021) showing different physical properties between the two main Martian atmospheric structures and making the ACB less detectable in the infrared. We hence derive the LNO channel sensitivity limit for these clouds detection.

Acknowledgements

ExoMars is a space mission of the European Space Agency (ESA) and Roscosmos. The NOMAD experiment is led by the Royal Belgian Institute for Space Aeronomy (IASB-BIRA), assisted by Co-PI teams from Spain (IAA-CSIC), Italy (INAF-IAPS), and the United Kingdom (The Open University). This project acknowledges funding by the Belgian Science Policy Office (BELSPO), with the financial and contractual coordination by the ESA Prodex Office (PEA 4000103401, 4000121493), by Spanish Ministry of Science and Innovation (MCIU) and by European funds under grants PGC2018-101836-BI00 and ESP2017-87143-R (MINECO/FEDER), as well as by UK Space Agency through grants ST/V002295/1, ST/V005332/1 and ST/S00145X/1  and Italian Space Agency through grant 2018-2-HH.0. This work was supported by the Belgian Fonds de la Recherche Scientifique – FNRS under grant number 30442502 (ET_HOME). The IAA/CSIC team acknowledges financial support from the State Agency for Research of the Spanish MCIU through the ‘Center of Excellence Severo Ochoa’ award for the Instituto de Astrofísica de Andalucía (SEV-2017-0709). US investigators were supported by the National Aeronautics and Space Administration. Canadian investigators were supported by the Canadian Space Agency. SR thanks BELSPO for the FED-tWIN funding (Prf-2019-077 - RT-MOLEXO).

References

A.C. Vandaele, et al., 2015. Optical and radiometric models of the NOMAD instrument part I: the UVIS channel. Optics Express, 23(23):30028–30042.

Neefs, et al., 2015. NOMAD spectrometer on the ExoMars trace gas orbiter mission: part 1—design, manufacturing and testing of the infrared channels. Applied optics, 54(28):8494–8520.

Oliva, F., et al., 2022. Martian CO2 Ice Observation at High Spectral Resolution With ExoMars/TGO NOMAD. Journal of Geophysical Research: Planets, 127, e2021JE007083.

Willame, Y., et al., 2017. Retrieving cloud, dust and ozone abundances in the martian atmosphere using spicam/uv nadir spectra.Planetary and SpaceScience, 142:9–25.

K.S. Olsen, et al., 2021 Retrieval of the water ice column and physical properties of water-ice clouds in the martian atmosphere using the OMEGA imaging spectrometer, Icarus, Volume 353, 2021, 113229, ISSN 0019-1035.

How to cite: Ruiz Lozano, L., Karatekin, Ö., Dehant, V., Bellucci, G., Oliva, F., D'Aversa, E., Altieri, F., Carrozzo, F. G., Willame, Y., Thomas, I., Daerden, F., Ristic, B., Patel, M., López Moreno, J. J., and Vandaele, A. C.: Evaluation of the capability of ExoMars-TGO NOMAD infrared nadir channel for water ice clouds detection on Mars, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-946, https://doi.org/10.5194/epsc2022-946, 2022.

The Interior Exploration using Seismic Investigations, Geodesy and Heat Transport (InSight) mission has discovered over thirteen hundreds seismic events since landing on Mars in 2018, shedding the light on the internal structure of Mars (InSight Marsquake Service, 2022). These events have been applied in various Martian seismology studies such as interiors determination and scattering estimation (Lognonné et al., 2020). Site effect study, which is commonly conducted on Earth to estimate the seismic hazard and invert the surficial subsurface structure, has been implemented to Martian ambient noise and event records (Carrasco et al., 2022; Xiao et al., 2022). Nevertheless, a recently detected big event S1222a that reach the magnitude of about 5.0 would further aid to the site effect study beneath the landing site. The amplification of ground accelerations is thought to be related to the subsurface layers and mostly event-independent. Therefore, site effects from different events are expected to share similar features and help to obtain a better result with lower uncertainty compared to result from single event.

The main focus of this study is to investigate the subsurface resonances excited by seismic events in high frequencies above 1.0 Hz. We adopted the classical horizontal to vertical spectral ratio (HVSR) method (Nakamura, 1989) and coherency analyses and explored the optimal parameters for these time-frequency analyses in order to balance both time and frequency resolutions. We used the ambient noise to serve as a baseline in order to distinguish the effects of seismic events and environmental contaminations. Results from ambient noise show that the HVSR spectrogram and coherogram are consistent to each other and both show diurnal variation controlled by the local meteorological conditions. Several H/V peaks are found in the averaged H/V curve, most likely originating from the wind-induced lander vibrations. In contract, we calculated the H/V curves within the P-wave and S-wave windows provided by InSight Marsquake Service (2022) to compare with the results from ambient noise. S1222a stands out to exhibit abundant high frequency content well above the noise level, while other events present energy close to noise level for frequencies above 5.0 Hz. Besides, we identified the excitation of lander modes by seismic events, which is most obvious for the magnitude ~5 S1222a event perhaps due to its very high signal-to-noise ratio. All the analyses above indicate the existence of site effects and both subsurface and lander mechanical resonances could be excited. It is thus important to study how to separate the subsurface resonances and further use them for sublayer inversion.

Previous studies from InSight hammering experiments and jointly seismic-geodetic inversion obtained the physical properties of surficial regolith (Lognonné et al., 2020). Together with these results, it is possible to better constrain the very shallow layers beneath the landing site. Since the site effects would basically have influence on all observation of InSight seismic data, this study also has implication to environmental contamination removal, sublayer velocity inversion, and any other seismic studies that could be affected by strong site effects.

References

[1] Carrasco, S., et al. (2022). Empirical H/V spectral ratios at the InSight landing site and implications for the martian subsurface structure. Geophysical Journal International, submitted.

[2] Lognonné, P., et al. (2020). Constraints on the shallow elastic and anelastic structure of Mars from InSight seismic data. Nature Geoscience, 13(3), 213-220. https://doi.org/10.1038/s41561-020-0536-y

[3] InSight Marsquake Service (2022). Mars Seismic Catalogue, InSight Mission; V10 2022-04-01. ETHZ, IPGP, JPL, ICL, Univ. Bristol. https://doi.org/10.12686/a16

[4] Nakamura, Y. (1989). A method for dynamic characteristics estimation of subsurface using microtremor on the ground surface. Railway Technical Research Institute Quarterly Report, 30(1), 25–33.

[5] Xiao, W., et al. (2022). Characteristics of Horizontal to Vertical Spectral Ratio of InSight Seismic Data from Mars. Journal of Geophysical Research, under review.

How to cite: Xiao, W., Lognonné, P., Kawamura, T., Xu, Z., Carrasco, S., and Knapmeyer-Endrun, B.: Site Effect Study based on Magnitude 4~5 InSight Marsquakes, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-816, https://doi.org/10.5194/epsc2022-816, 2022.

The Apollo Passive Seismic Experiments recorded more than 13000 events on the Moon during 1969-1977 [1]. However, not all of these events were used in our previous studies on the Moon due to the degradation of the quality of the recorded data (Figure 1A). To make better use of Apollo seismic data, we propose several new methods to reprocess it. First, since Apollo seismic records sometimes contain invalid data in every station and component (including the short period component), we removed these invalid data from raw Apollo records using time and ground station number. Then we removed several special spikes with the help of amplitude histogram. This enables us to compute the envelopes for a larger number of moonquake events. Acceleration and displacement step responses are used to fit glitches using the Lagrange multiplier method. The ‘glitches’ we term here are artifact one-sided pulses in the raw data. We find that the instrument response parameters vary with time. So, we determined the instrument response parameters with the calibration signal and removed it near the event. Finally, we used the smoothed envelope to detect the single spike (spike with only one point) and removed it when exceeds the envelope. These new processing steps lead to considerably cleaner Apollo data (Figure 1B), yield a more accurate arrival time reading, and result in an envelope that reflects more realistic waveform characteristics. We expect that additional moonquake records will become available with these methods for future research. Further study of the instrument response variations of the Apollo seismometer will also provide a reference for the new lunar seismometers to be deployed in upcoming space missions.

Figure 1. An example of a comparison plot before (A) and after (B) Apollo moonquake data processing.

Reference:

[1] Nunn, C., Garcia, R. F., Nakamura, Y., Marusiak, A. G., Kawamura, T., Sun, D., et al. (2020), Lunar seismology: A data and instrumentation review. Space Science Reviews, 216(5), 89. doi:10.1007/s11214-020-00709-3

How to cite: Zhang, X., Lognonné, P., Kawamura, T., Samuel, H., Xu, Z., Sainton, G., Froment, M., and Onodera, K.: Reprocessing Apollo seismic data, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-846, https://doi.org/10.5194/epsc2022-846, 2022.

Introduction

Most spacecraft missions to small bodies provide the gravity field of their targets. As the extended gravity field is an expression of the mass distribution within the body, it can provide information about its interior structure, and that in turn can constrain its origin and history.

We present a method to detect density anomalies within a small body from the global gravitational potential. As is well known, such an inverse problem is ill-posed [1], and requires regularization. Our main assumption, which mitigates the non-uniqueness of the problem, is that the interior of the body is composed of a finite number of domains, in which the density is uniform. The boundary of each domain is therefore a surface, that we describe as the level-set of a function. This approach, known as the level-set method, has been extensively used in local inversions of Earth’s gravity measurements [2]. It simplifies the manipulation of complex shapes, which in our case delimit the density anomalies.  

In order to reduce the dimensionality of the problem, we employ parametric expressions for the level-set functions. The aim is then to determine the parameters of each level-set function, which describe the location and size of the anomalies, along with the density within each anomaly and the bulk density of the body.

Methods

We model the gravity field of the body through a mascons approach [3]. The observables we consider are the coefficients of the spherical harmonic expansion of the potential. By implementing a continuous approximation for the unit step function, the partials derivatives of the measurements with respect to the level-set function parameters can be computed via the chain rule [4]. Then, the function parameters and the densities can be estimated via non-linear least-squares inversion of the gravity data.

However, the problem is generally non-convex, which means that in order to converge to a global optimum the a priori values for the unknowns should be close to this solution. Since we assume no initial knowledge of the distribution to retrieve, a preliminary step is needed for the definition of an a priori model. To this end, we generate a Voronoi partition of the interior from randomly sampled points within the body. The domains are now fixed, and only the densities within each Voronoi cell are estimated from the data. This inversion problem is linear, but the solution will depend on the partition of the body. However, averaging solutions from many of such random partitions can provide a good approximation of the true model [5]. This averaged solution is then used to initialize the values of the level-set algorithm.

Discussion and outlook

We have tested the ability of our level-set implementation to retrieve interior models from simulated gravity data. 

Figure 1 shows an example of the inversion results for a Bennu-shaped body. In this case, the level-set functions are chosen so that the anomalies they describe are cuboids. The model in Figure 1a is the ground truth, used to simulate gravity coefficients up to degree 11. Figure 1b shows the density retrieved from the noise-free data, and Figure 1c the results when the data are perturbed by 1% Gaussian noise. The method can retrieve the location and density of the anomalies with good approximation, even in the perturbed case. For anomalies where the density and the size cannot be estimated simultaneously, such as with nearly-spherical shapes, the method can usually still correctly determine the total mass and the position of the center-of-mass. The size could then be constrained by independent observations from other instruments or by theoretical models.

In a more realistic scenario, the resolution of the gravity would be lower, and the noise profile would be increasing with the degree of gravity. This could aggravate the non-uniqueness problem, since having fewer and less precise measurements could lead to different models fitting the data equally well. Current work is focused on improving the robustness of our approach and on better defining its limitations in its application to real gravity measurements. 

Figure 1. Interior density models, shown via sections along 3 planes perpendicular to the body axes and containing the origin: a) Ground truth; b) Solution from noise-free data; c) Solution from data with 1% noise

Acknowledgements

This work was financially supported by the French community of Belgium within the framework of a FRIA grant, and by the Belgian PRODEX program, managed by the European Space Agency in collaboration with the Belgian Federal Science Policy Office.

References

[1]  V. Isakov. Inverse Source Problems. American Mathematical Soc., 1990. 

[2]  J. Giraud, M. Lindsay, and M. Jessell. Generalization of level-set inversion to an arbitrary number of geologic units in a regularized least-squares framework. GEOPHYSICS, 86(4):R623–R637, July 2021. 

[3]  S. Le Maistre, A. Rivoldini, and P. Rosenblatt. Signature of Phobos’ interior structure in its gravity field and libration. Icarus, 321:272–290, March 2019.

[4]  A. Aghasi, M. Kilmer, and E. L. Miller. Parametric Level Set Methods for Inverse Problems. SIAM Journal on Imaging Sciences, 4(2):618–650, January 2011. 

[5]  L.-I. Sorsa, M. Takala, P. Bambach, et al. Tomographic inversion of gravity gradient field for a synthetic Itokawa model. Icarus, 336:113425, January 2020.

How to cite: Caldiero, A., Le Maistre, S., and Dehant, V.: A parametric level-set approach to the global gravity inversion of small bodies, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-1118, https://doi.org/10.5194/epsc2022-1118, 2022.

Introduction: The dating of geological surfaces on the Moon is crucial for understanding its geological history and evolution. The measurement of Crater Size-Frequency Distributions (CSFDs) can be used for determining relative and absolute ages of surfaces. Older surfaces reflect more and larger craters than younger geological units [1-4]. To determine the relative surface ages, a production function (PF) is constructed to which the CSFD is fitted. One frequently used PF was empirically-derived by measuring craters on reference surfaces using Apollo era data (Neukum, 1983 [1]), which was revised in 2001 [5], and is valid for crater diameters of 10 m - 300 km and 10 m - 100 km, respectively. With increased image resolution of more recent missions [e.g., 6], it has been possible to measure CSFDs for crater diameters down to a few meters. Therefore, it would be beneficial to be able to extend the PF to smaller crater diameters, which would allow the determination of relative and absolute ages for young/small geological units.

A crucial influence on small craters formed in the strength regime are target properties, which has been investigated in several studies [e.g., 7, 8, 9]. Therefore, we aim to perform the crater counts exclusively on continuous ejecta blankets. Secondary craters [e.g., 10-12] influence the CSFD as well and can contaminate the count area, causing a steeper CSFD-slope [e.g., 10, 13, 14]. To avoid this effect and obtain the cleanest PF possible, we selected ejecta areas derived from young Copernican-aged craters. This minimizes the number of field secondary craters on the ejecta and also avoides major degradation of the small craters [15, 16]. However, the identification of self-secondary craters remains problematic, since they occur irregularly distributed on the ejecta blankets and often have morphologies similar to primary craters [e.g., 12, 13].

Method: We used Lunar Reconnaissance Orbiter Narrow Angle Camera (NAC) images [6] including M180509194LE, M1122929850LE and M103831840LE/RE at Giordano Bruno (GB), M1107052575RE and M1112971104RE at Moore F, M129187331LE/RE  at North Ray (NR), M119754107RE at South Ray (SR) and M114064206LE at Cone. The resolutions vary between 1.6 m/px and 0.5 m/px, the incidence angles are from 54° to 78°. The CSFDs were measured in ArcGIS with the CraterTools add-in of [18] and displayed in CraterStats with pseudo-log binning [19].

Two areas were investigated at Cone, three at GB, Moore F and SR, respectively. Four areas were investigated by [17] at NR. The selected counting areas are all on the ejecta blakets of the named craters.

Results: Similar to [17] we combined the statistics from the separate count areas into one file and display these CSFDs in a cumulative plot in Figure 1.

Figure 1: Display of the combined CSFDs at GB (green), Moore F (blue), NR (violet), SR (red) and Cone (orange), respectively. The vertical lines of individual data points represent the error bars.

The comparison between the individual CSFD-slopes at GB, Moore F, NR, SR and Cone generally show slightly steeper slopes than the nominal -3 slope of [1] for crater diameters between 10 m and 23 m (in our case 20 m, see Table 1).

Table 1: Display of the considered crater diameter range and the respective CSFD-slopes.

Discussion: We found that the CSFD-slopes on the ejecta blakets of the investigated craters show a tendency regarding the crater diameter. Considering only diameters ≤10 m the slope is marginally shallower than Neukum’s [1] -3 slope, except at GB, which might be explained through secondary cratering. This trend was also observed by [15] (and references therein) and [20] who investigated NR, Cone, Copernicus and Tycho. This might suggest that CSFDs of young Copernican craters have actually a slightly shallower slope at smaller crater diameters. Another possible explanation is the faster degradation of smaller craters [e.g., 21]. Further effects might be the coverage of ejecta material of nearby craters; NR (52.3 Ma [20]), might be influenced by the ejecta of SR (2 Ma [22]), SR by Baby Ray. Moreover, larger craters in two areas at NR and Cone probably penetrated through the ejecta blanket, which can lead to mixed target propertie effects.

Further investigations are required to quantify the effects of secondary cratering, target properties, crater degradation or impactor flux on the determination of our CSFDs. Additional investigation is necessary to determine at which crater diameter the slope becomes shallower or if a transition zone is present.

Acknowledgments: This Project is funded by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) – Project-ID 263649064 – TRR 170.

References: [1] Neukum (1983), NASA TM-77558. [2] Öpik (1960), RAS 120(5), 404-41. [3] Shoemaker et al. (1970), Science, 167 (3918), 452-455. [4] Baldwin (1971), Icarus, 14, 36-52. [5] Neukum et al. (2001), Space Sci. Rev., 96, 55. [6] Robinson et al. (2010), Space Sci. Rev. 150, 81-124. [7] van der Bogert et al. (2010), LPSC 41, #2165. [8] Wünnemann et al. (2011), Proceedings of the 11th hypervelocity impact symposium., Vol. 20. [9] van der Bogert et al. (2017), Icarus, 298, 49-63. [10] McEwen and Bierhaus (2006), Annu. Rev. Earth Planet. Sci. 34, 535-567. [11] Xiao and Strom (2012), Icarus 220, 254. [12] Zanetti et al. (2017), Icarus 298, 64-77. [13] Plescia et al. (2010), LPSC 41, #2038. [14] Plescia and Robinson (2011), LPSC 42, #1839. [15] Moore et al. (1980), Moon and Planets, 23, 231-252. [16] Fassett and Thomson. Journal of Geophysical Research: Planets 119.10, 2255-2271. [17] Hiesinger et al. (2012), JGR 117, E00H10. [18] Kneissl et al. (2011), PSS 59, 1243-1254. [19] Michael et al. (2016), Icarus 277, 279-285. [20] Williams et al. (2014), Icarus 235, 23-36. [21] Mahanti et al. (2018), Icarus, 299, 475-501. [22] Stöffler and Ryder (2001), Space Sci. Rev., 96, 9-54.

How to cite: Oetting, A., Hiesinger, H., and van der Bogert, C.: Refinement of the Lunar Production Function - The CSFD-Slope of Small Crater Diameters on Ejecta Blankets, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-828, https://doi.org/10.5194/epsc2022-828, 2022.

 Phyllosilicate minerals have been detected at Oxia Planum, the ExoMars landing site, which indicate this area has been subject to aqueous activity during the Noachian [1,2,3]. The aim of the ExoMars rover mission is to search for signs of past or present life at Oxia Planum and to characterise the geochemical environment [1]. Evidence of past life may include physical biosignatures such as fossilised cells or stromatolites, or chemical biosignatures, such as biominerals and organic molecules produced by biological activity (biomarkers) [1,4,5]. The rover will be equipped with a suite of instruments, such as Multispectral Panoramic cameras (PanCam), Close-up imager (CLUPI), Raman Laser Spectrometer (RLS), and Mars Organic Molecule Analyser (MOMA), the latter of which includes gas chromatography-mass spectrometry (GC-MS) and laser desorption/ionisation-mass spectrometry (LDI-MS) capable of detecting biomarkers [6,7,8,9].

Mineralogy plays a vital role in the preservation of organic molecules [10]. Phyllosilicate minerals have been shown to adsorb organic compounds on and between their layered structures [11,12], protecting them from degradation by radiation and oxidation [13]. Given the identification of phyllosilicate mineralogy at Oxia Planum, detecting biomarkers there is plausible. However, alteration of biosignatures may have occurred at Oxia Planum through a range of geological processes, such as impacts.

Geomorphological data of Oxia Planum indicates that extensive impact cratering has occurred, which would have altered the surface mineralogy, and may have modified any biomarkers present in the sediments [14]. However, organic molecules detected in impact craters on Earth have been shown to have survived the impact process [15] and impact experiments have shown impact energy, angle of ejection and mineralogy will influence the decomposition rate of organic molecules [16]. In addition, glasses formed by impact processing have been shown to trap organic components and aid their preservation [17, 18]. However, the elevated temperatures and pressures experienced during impact events can cause the modification of organic molecules, such as bond breaking and formation, thermal oxidation and racemization [19,20].  Depending on the reaction dynamics of these changes, these modifications may differ according to particular mineral hosts [20]. 

In this study, we perform laboratory impact experiments using the all-axis light gas gun (LGG), at the Open University, to understand the effects of impacts on the local mineralogy at Oxia Planum. These experiments use a mineralogical simulant for Oxia Planum, which is composed of a mixture of unaltered basaltic minerals, a phyllosilicate component, iron oxides and an amorphous component, representing the possible mineral assemblage at Oxia Planum[21].The LGG will expose the simulant to the high pressures and temperatures associated with planetary impacts at a range of velocities relevant to impacts at Oxia Planum. Samples taken of the simulant will be analysed using Near-IR, Raman and XRD analysis to assess the changes to its mineralogy. Here, we will present the preliminary results from these experiments, and will outline their application to understanding the survival of biomarkers at the Oxia Planum landing site.

[1] Vago et al., Astrobiology Vol 17 No. 6 and 7, 2017 [2] Carter et al., LPSC abstract Vol. 47 No. 2064 [3] Quantin-Nataf et al., Astrobiology Vol. 21 No. 3, 2021 [4] Parnell et al., Astrobiology Vol. 7 No. 4, 2007 [5] Simoneit et al., Origins of Life and Evolution of the Biosphere Vol.28 p. 475–483, 1998 [6]Coates et al., Astrobiology, Vol. 17 No. 6-7, 2017[7]Rull et al., Astrobiology, Vol. 17 No 6-7[8] Goesmann et al., Astrobiology, Vol. 17 No 6-7 [9]Josset et al., Astrobiology, Vol. 17 No 6-7[10] Wiseman et al., Geoderma Vol. 134 p. 109–118, 2006 [11]Kleber et al., European Journal of Soil Science Vol. 56 No. 717–725, 2005 [12] Pearson et al., Meteoritics & Planetary Science Vol. 37, p.1829-1833 (2002) [13] dos Santos et al., Icarus Vol. 277 p. 342–353, 2016[14] Roberts et al., Journal of Maps, Vol. 17 No. 2, 2021[15]Burchell et al., Astrobiology Vol. 14 No. 6, 2014[16] Bowden et al., Astrobiology Vol. 8 No. 1, 2009[17]Sapers et al., Earth and Planetary Science Letters Vol. 430 p.95–104, 2015 [18]Edwards et al., LPSC Vol. 40 No. 2524 [19] Bowden et al., Journal of Analytical and Applied Pyrolysis Vol. 82, p.312–314 (2008) [20] Furukawa  et al., Orig Life Evol Biosph,  Vol. 48 p.131–139. 2018[21] Dugdale et al., LPSC (2020)

How to cite: Dugdale, A., Ramkissoon, N., Fawdon, P., Patel, M., and Pearson, V.: Impact generated modification of the mineralogy at Oxia Planum, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-851, https://doi.org/10.5194/epsc2022-851, 2022.

1. Introduction

Asteroid impacts, ranging from small-scale cratering events to catastrophic disruption, have played a crucial role in the formation and evolution of asteroids (Jutzi et al., 2015). Thanks to the increasing performance of computers, shock-physics numerical codes have become commonly used in the field of hypervelocity impacts, to extrapolate experimental results and help us be better prepared for space missions devoted to asteroid deflection using the kinetic impactor techniques, such as the NASA DART (Rivkin et al. 2020) and ESA Hera missions (Michel et al. 2022), and evaluate the outcomes.

Past numerical studies showed us that it is possible to divide the asteroid impact process into two stages that occur at very different time scales, the early stage of fragmentation of the asteroid and the late stage of gravitational reaccumulation of the fragments (e.g, Michel et al. 2001). For the early stage, various numerical methods have been developed to solve this short but extreme physical process, such as the Smooth Particle Hydrodynamics (SPH) technique used in codes like the Bern SPH and grid techniques used in codes like CTH or iSALE. Each method has its unique advantages, but they share a common challenge that the contact and the boundary condition are not well handled (El Mir et al., 2019).

In this study, we exploit the Material Point Method (MPM) framework, an extension of the particle-in-cell method, to simulate the early stage of impact in order to offer a new approach and solutions to the above problems.

2. Methods

MPM is a meshfree method, characterizing the material domain by a group of points. These Lagrangian material points carry all state variables. Meanwhile, a predefined regular background grid is used. In each timestep, material information is mapped to grid nodes, to solve the momentum equations, and material points deform with the grid. Then the information is mapped back to the points to update their positions and velocities, discard the deformed grid, and reset a new one to calculate the next timestep (Zhang et al., 2013). MPM framework combines the advantage of both Lagrangian description and Eulerian description, which not only avoids the undesirable mesh tangling caused by large deformations, but also eliminates the difficulties in solving contact and boundary conditions.

As such, MPM is well used in simulating impacts, explosions, and metal forming of on-earth situation (Zhang et al., 2013). So far, it has not been commonly used to model hypervelocity impacts on asteroids (El Mir et al., 2019). Hence, we start with building material models that are applicable to asteroids made of porous and brittle materials.

The material models include Drucker-Prager strength model that describes cohesion and pressure-dependent strength effect. We also use the Tillotson equation of state for basalt coupled with the P-alpha model which accounts for porosity, and as stress-based failure criterion consistent with Weibull distribution. The framework is thus similar to that used by other studies using the SPH numerical method (Raducan and Jutzi, 2021). Our MPM model is then validated by comparing with laboratory impact experiments and the simulations using the SPH method.

3. Results

We compare our simulations with SPH simulations (Benz & Asphaug, 1994) and the impact experiments (Nakamura et al., 1991) on non-porous basalt sphere used to validate them. Our result shows that our material model under the MPM framework can successfully characterize the shell-like propagation of the failure zone (Fig 2.c2). However, a concentration of stresses reflected back from the boundary subsequently occurres, resulting in a severe secondary failure in the nuclear region. (Fig 2.c3) This stress concentration may cause by the unsmooth discrete boundary and the lack of energy dissipation. The analysis of large fragments reveals this problem too: although with a similar mass distribution, the velocity of the largest fragment in MPM simulation is significantly higher (Fig 3.a). Apart from that, the simulation results are otherwise in good agreement with the previous studies, especially the shape of the largest fragment of MPM simulation (Fig 3.b) versus a recent experiment (Fig 3.c). Noting the usual spreading in experimental outcomes using same conditions, the MPM method can thus be considered valid.

Further research will be centered on verifying the P-alpha model and the correct treatment of porosity (Jutzi et al., 2009).

4. Conclusion and Discussion

The MPM framework can complement of other shock-physics code to balance the accuracy and efficiency of calculation. Furthermore, the mentioned features of solving contact and boundary conditions with MPM broadens the application of the simulation algorithm in the hypervelocity impact stage, and may make it easier than SPH models to combine with the Soft-Sphere Discrete Element Method (SSDEM) code (Fig 4) to simulate the two-stage impact process (SPH-SSDEM method refers Zhang et al., 2021).

All these studies will offer a glimpse into the active processes from the early formation of the solar system to the current epoch, and contribute to planetary defense.

Acknowledgements:

We acknowledge support from the Université Côte d’Azur. X.Y. acknowledges support from Tsinghua University, funding from the Chinese Scholarship Council, and the National Natural Science Foundation of China (No. 11872223). P.M. acknowledges funding from CNES, from the European Union’s Horizon 2020 research and innovation program under grant agreement No. 870377 (project NEO-MAPP) and from the CNRS through the MITI interdisciplinary programs.

References:

Arakawa, M. et al. (2020) Science, 368, 67–71.

Arakawa, M. et al. (2022) Icarus, 373, 114777.

Benz, W., & Asphaug, E. (1994) Icarus, 107(1), 98–116.

El Mir, C. et al. (2019) Icarus, 321, 1013–1025.

Raducan, S.D. & Jutzi, M. (2021) 52nd LPSC, #1900.

Jutzi, M. et al. (2009) Icarus, 201(2), 802–813.

Jutzi, M. et al. (2015) In: Asteroids IV (Michel P. et al., eds.) 679–699.

Michel et al. (2001) Science, 294, 1696-1700.

Michel et al. (2022) Planetary Science Journal, accepted.

Nakamura, A., & Fujiwara, A. (1991). Icarus, 92, 132–146.

Rivkin, A. et al. (2020) Planetary Science Journal, 2, 173.

Zhang, X. et al. (2013) Beijing: Tsinghua University Press.

Zhang, Y. et al. (2021) 52nd LPSC, #1974.

How to cite: Yan, X., Liu, Y., Zhang, Y., Michel, P., and Li, J.: Hypervelocity impact simulation on asteroids with MPM framework, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-1064, https://doi.org/10.5194/epsc2022-1064, 2022.

Introduction

A lunar impact flash (LIF) is a rapid burst of light caused by a hypervelocity impactor hitting the moon, releasing a fraction of its energy as light. They are observable though moderately sized (0.4m) telescopes, and are therefore observable by both amateur and professional astronomers.

LIF observations are typically performed in visible or NIR, and can only take place when the lunar phase is between 10-50%, during local night, and are only observable against the lunar night-side; the most commonly observed LIFs are faint, approximately Mag_I = 9, Mag_R = 10 [1], making them indistinguishable against the illuminated lunar background. This limits potential observations of LIFs to ~30h per month on average, with weather limiting this further.

In order to increase the average number of observable hours that LIF observations can be made, and thereby increase the number of observed LIFs, we have developed new techniques to perform LIF observations at all local times, and all lunar illuminations. This technique theoretically only requires clear weather and a visible moon.

Theory

LIFs have been shown to behave as black bodies, releasing energy according to Planck's law [2]. The temperature of LIFs observed by NELIOTA is between 1300-5800 k, with average temperature, T_avg = 2800k [3]. This average has peak wavelength of λ_peak = 1.035 μm. The illuminated portion of the lunar surface is reflecting light from the sun (T = 5778 k, λ_peak = 0.5 μm). In R-band and I-band, the ratio of energy radiated by the sun is greater by a factor of 57 in R-band, and 28 in I-band. My observing in wavelengths closer to the λ_peak of the flash, we can improve this ratio greatly.

_{Figure 1:The Planck curve for the sun (5778k) and the average LIF (2750k), R, I, and J-band regions are highlighted in orange, red, and grey respectively.}

As illustrated in Fig. 1, by observing in J-band the irradiance of the sun is lowered, being only 10 times greater than the 2800 k LIF. This effective dimming of the background leads to an increase in the signal-to-noise ratio (S/N) of the LIF against the sun-illuminated background.

The S/N ratio is a measure of how detectable a signal is above the background, and can be defined as:

S/N = S" / (σ × √A_pix)

Where S" is the total count of the signal, σ_B is the standard deviation of the background, and A_pix is the area of the background measurement. A S/N ratio above ≈10 is generally required for a signal to be considered detectable.

Observations

Observations were performed on 2022-02-23 from the Observatoire de la Côte d'Azur, using a 0.5 m diameter, 2 m focal length telescope with Ninox 640 II camera and J-band filter attached. For the first set of observations, high gain mode was used, for the second set of observations low gain mode was used. A 30 μm exposure time was used for both sets of observations.

The star HD137463 was observed, which has Mag_J = 5.423, obtained by Simbad [4] Observations began during the night, and continued until after sunrise in order to measure the brightness of the sky during daytime. 

By performing A-B subtraction to remove the dark current and background of the observed frames, as shown in Fig. 2, a pixel count for the clean star signal, S", can be obtained. As it is constant, an average for the star signal can be used as ground truth in order to calculate the S/N ratio for the daytime sky brightness, as well as the illuminated lunar surface.

_{Figure 2: The A-B subtraction of two observations of HD137463. The subtraction removes any dark current or background to leave only a clean positive and negative signal.}

Results

The S/N ratio for the a Mag_J = 5.423 star are shown in Fig. 3. A sharp decrease in S/N ratio is observed as air-glow begins around solar altitude = -5. The S/N continues to decrease, slowly levelling off around S/N = 15 as the sun reaches solar altitude = 5. This puts the mag_J = 5.423 star well above the detectable threshold, and would correspond to a Mag_R = 6.7 LIF. 

_{Figure 3: Left: The S/N ratio in high gain mode, of HD137463 against the sky background between solar altitudes -10 & -1. Right: The S/N ratio in low gain mode, of HD137463 against the sky background between solar altitudes -1 & -5.}

By taking measurements of the lunar background brightness, we can verify the S/N ratio we would expect from these LIF when observed on the lunar surface. Table 1 contains the results from count-averaged observations of the background, and the S/N of the Mag_J star if observed against the background, emulating a flash. Again, even against the illuminated bright limb, the S/N ratio is above the detectable threshold, and shows that with this system, we would be able to detect LIFs of Mag_J ≥ 5.423, with the possibility of even fainter magnitudes under more favourable conditions.

_{Table 1:  The S/N ratio of the reference star used against different regions on the lunar surface, from darkest to brightest.}

References
[1] Liakos et al (2019) A&A, 633, 29 pp.
[2] Eichhorn (1975) P&SS, 23, 11, 1519-1525
[3] Avdellidou & Vaubaillon (2019) MNRAS, 484, 5212-5222
[4] Wegner et al (2000) A&A, 143, p.9-22  

How to cite: Sheward, D., Delbo, M., Avdellidou, C., Cook, A., and Lognonne, P.: J-Band Measurements for All-Hours Lunar Impact Flash Observations, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-1077, https://doi.org/10.5194/epsc2022-1077, 2022.

Introduction

The survivability of bacteria in planetary impacts has previously been investigated using a two-stage Light Gas Gun (as seen in Figure 1). During these experiments, projectiles were doped with bacteria (Rhodococcus erythropolis) and fired at hypervelocity into rock [1,2], metal [2], water-ice [3,4] and agar [4,5] targets. These experiments were designed to investigate the feasibility of the panspermia theory, which details how indigenous life forms may be spread beyond their host body via the ejecta created by hypervelocity impacts and go on to seed neighbouring bodies. These studies showed that bacteria do survive hypervelocity impact; however, the methods do not accurately quantify the survival rate on the target compared to the initial cell load on the projectile, nor do they quantify or characterise any sub-lethal effects.

Figure 1: The Light Gas Gun impact facility at the University of Kent.

Creating A Successful Target

Attempts have been made to develop new methods that give greater quantitative insights into both survival and sub-lethal effects of hypervelocity impacts. As well as investigating the survival rate of the bacterial population, we are looking at whether the transient extremes of pressure which occur as a result of hypervelocity impact modulate phenotypic change amongst the surviving bacteria, and thus could be a factor in the evolution of life.

The bacteria (in this case Escherichia coli) in our experiments have been placed inside the target instead of the projectile. This decision was made in order to remove the potential issues of the loss or death of cells as a result of the acceleration of the projectile. Several different target designs were trialled, largely involving the use of agar as a medium for housing the bacteria. These attempts led to a set of criteria being defined for a successful target, including efficient propagation of the shock wave through the sample to ensure that the bacteria are experiencing the intended conditions, and clean recovery of the majority of the sample with little or no contaminants.

The Liquid Target Setup

Following much experimentation, a liquid target setup was created, as seen in Figure 2. A 50 ml liquid sample containing the bacteria is housed inside a thin polythene bag and placed inside a steel tube, which upon impact collects the liquid and allows for ease of recovery and analysis. The impacted plastic bag produces a large amount of debris within the collected sample, which interferes with some of the optical data gathered during post-impact analysis of the bacteria. Also, there is concern that the entirety of the sample is not experiencing the full force of the impact. To address these issues, we are designing a secondary tube with a much smaller diameter which can be inserted and secured inside the primary steel tube; this should mean that more of the sample volume will experience higher shock pressures in the range of several GPa, which can be verified by simulating the impacts using Autodyn modelling. To replace the polythene bag, and thus attempt to minimise the quantity of debris entering the system, the liquid sample will be sealed directly inside the secondary tube with an extremely thin foil.

Impacts have been completed across the velocity range of 1-5 km/s using this setup. The following analysis methods have been applied to the recovered samples post-impact:

• OD₆₀₀ (optical density) recordings to understand changes in whole cell numbers by measuring the number of particles within a given sample
• Protein assays to understand the amount of physical damage or lysis to the cells
• Growth on agar plates to understand how the viability of the population has changed via the counting of colony forming units (CFUs)
• Oxygen electrode analysis to see if the metabolic pathways of the cells have been affected by measuring cellular respiration in the presence of glucose

So far, no significant changes to the survival rate or the phenotype of the population have been observed following these impacts using the analysis methods described.

Figure 2: The liquid target setup within the target chamber of the Light Gas Gun.

Influence of Exposure Time to Impact Conditions

The results from the liquid target impacts have raised the question of whether the extremely short duration of the shock pressure is insufficient to lead to any meaningful change in the bacterial population. To investigate this, E. coli samples prepared in the same manner as for the impacts are instead placed inside a sonicator, where the sound waves generate pressures within the sample of around 200 MPa, compared to the impact shock pressures of several GPa created in the Light Gas Gun. The sonication exposure times were varied, using 4 bursts of 0, 5, 10, 30 and 60 seconds, compared to the milliseconds or less that the peak shock pressures are applied to the sample in the Light Gas Gun.

A steady decline of surviving bacteria and a significant increase in cell lysis was observed as the exposure time was increased, supporting the idea that time is the key factor in generating populational changes. At burst exposure times of 30 seconds or more, an unusual phenotype emerges following growth of the sonicated samples in the form of a new colony type displaying a concentric ring pattern of growth, as shown in Figure 3. This is currently being investigated further with repeat experiments, antibiotic testing and 16S rRNA sequencing to confirm that this is indeed a change in phenotype and not a result of a separate factor such as contamination.

Figure 3: An agar plate spread with a sample of E. coli cells following 4 30-second bursts of sonication.

References

[1] Burchell et al. (2000) In Gilmour I., Koeberl C. (eds) Impacts and the Early Earth. Lecture Notes in Earth Sciences, vol 91.

[2] Burchell et al. (2001) Adv. Space. Res. 28(4), 707-712.

[3] Burchell et al. (2003) Origins of Life and Evolution of the Biosphere 33, 53-74 (2003).

[4] Burchell et al. (2004) Mon. Not. R. Astron. Soc. 352, 1273-1278 (2004).

[5] Burchell et al. (2001) Icarus 154, 545-547 (2001).

How to cite: Wilkinson, R., Wozniakiewicz, P., and Robinson, G.: Exploration of Methodologies to Investigate Bacterial Survival in Planetary Impacts, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-121, https://doi.org/10.5194/epsc2022-121, 2022.

Introduction

A planet that harbor water in a liquid state becomes as a study subject for its habitability evaluation. Water is the only known solvent in which the reactions for life as we know it take place, while is also a sink of molecules that include bio-essential elements such as carbon.

On Earth, oceans are reservoirs of CO₂ and CH₄ and, along with other molecules (H₂S, N₂, etc.) may be encapsulated in minerals of clathrate hydrates (thereafter clathrates) under high pressure and low temperature conditions [1]. Water molecules begin to arrange in space and join through hydrogen bonds, constructing a tridimensional crystal network that host gases inside by the van der Waals interaction forces [2]. This physical and chemical conditions required for clathrate deposits formation are found on Earth in continental margins and polar regions [3].

On Europa and Enceladus moons, clathrate deposits would not only be found in the seafloor, but also floating into oceans [4, 5, 6]. On Titan, as well as on Europa, they might form part of the composition of water-ice crust [7, 8], whereas on Ganymede and Pluto they may constitute some global layers of its internal structure [9, 10].

Clathrate formation and dissociation would play a role in geological processes and, above all, in (bio)-geochemical cycles of these planetary bodies. As clathrates are sinks of carbon and other chemical elements essential for life, the dissociation of these minerals by changes in physical chemical conditions would release gases into Europan and Enceladus´ oceans, enabling to promote favourable conditions for development of a hypothetical chemolithoautotrophic life [11]. However, gases could also be sequestrated again as carbonates or another salts due to reactions between them and rocky core in the water-rock interphase.

On Earth, encapsulated gases into clathrate structure may be metabolized by organotrophs [15] and/or by a consortium of methanotrophic archaea and sulfate-reducing bacteria after its dissociation [11, 16]. As a consequence carbonate precipitates, known as clathrite [17] because it records the past presence of these deposits. The aim of this study is to simulate the abiotic clathrite formation process under ocean-world-environmental-conditions when there are calcium saturation during clathrate formation and dissociation.

Methodology

For the experiments, we used a high-pressure simulation chamber made of stainless steel (volume capacity 67 ml) which is connected to a tank of CO₂ (gas). It is coupled with a thermocouple and pressure sensor to monitor temperature and pressure parameters and with a Raman spectrometer to analyse phase changes. We filled the high-pressure cell with crushed ice made of 7.4 wt% Ca(OH)₂ dissolution. The chamber was pressurized at 30 bar and then temperature was reduced down to 260 K. Once CO₂ clathrates were formed, the chamber was heated slowly up to 284 K. We studied the synthesis process of clathrite, taking in situ Raman spectra with a 532 nm laser at every pressure and temperature change.

Results

Carbonate precipitation occurred since CO₂ was injected to the chamber. The final product phase obtained was calcite. Nevertheless, during experiment of clathrate formation and dissociation, carbonate structure took diverse polymorphs of calcium carbonate different from pure calcite, aragonite and vaterite structures. This was evidenced by the spectral signature within the ranges of 1069.42-1087.75 cm^-1 and 709.26-731.94 cm^-1 for stretching and bending vibration of the CO₃^2- ion respectively and 150.30-160.62 cm^-1, 194.17-211.97 cm^-1 and 280.03-289.94 cm^-1 for lattice modes.

Acknowledgments

We thank project PID2019-107442RB-C32 funded by MINECO. Ana de Dios is supported by the AEI pre-doctoral contract under the project MDM-2017-0737-19-1.

References

[1] Rajput and Thakur (2016) in Geological Controls for Gas Hydrates and Unconventionals, Elsevier. [2] Sloan (1998) in Clathrate hydrates of natural gases, CRC Press. [3] Ruppel and Kessler (2017) Rev. Geophys., 55, 126-168. [4] Bouquet et al. (2015) Geophys. Res. Lett., 42, 1334-1339. [5] Prieto-Ballesteros et al. (2005) Icarus, 177, 491-505. [6] Boström et al. (2021) Astron. Astrophys. 650:A54. [7] Choukroun et al. (2010) Icarus, 205, 581-593. [8] Bouquet et al. (2019) ApJ, 855 (14). [9] Izquierdo-Ruiz et al. (2020) ACS Earth Space Chem., 4 (11), 2121-2128. [10] Kamata et al. (2019) Nat. Geosci., 12, 407-410. [11] Carrizo (2022) Astrobiology, 22 (5), DOI:10.1089/ast.2021.0036. [12] Choukroun et al. (2010) Icarus, 205, 581-593. [13] Fagents (2003) J. Geophys. Res., 108, 5139. [14] Bouquet et al. (2015) Geophys. Res. Lett., 42, 1334-1339. [15] Snyder et al. (2020) Sci. Rep., 10, 1876. [16] Bohrmann et al. (2002) Proc. Fourth Int. Conf. Gas Hydrates, Yokohama, Japan, 102-107. [17] Kennet and Fackler-Adams (2000) Geology, 28, 215-218. [18] Wehrmeister et al. (2007) J. Gemmol., 37(5/6), 269-276. [19] Eaton-Magaña et al. (2021) Minerals, 11, 177. [20] Chen et al. (2015) Chem. Eng. Sci., 138, 706-711.

How to cite: de Dios Cubillas, A., Muñoz Iglesias, V., and Prieto Ballesteros, O.: Abiotic clathrite synthesis from CO2-clathrate under ocean world conditions, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-544, https://doi.org/10.5194/epsc2022-544, 2022.

Laboratory studies of the radiation chemistry occurring in astrophysical ices have sought to better understand the dependence of this chemistry on a number of experimental parameters, such as the temperature of the ice or the energy of the incident radiation. One experimental parameter which has received significantly less attention from the research community is that of the phase of the solid ice under investigation. Our research group based at the Institute for Nuclear Research (Atomki) in Debrecen, Hungary has therefore made use of the custom-built Ice Chamber for Astrophysics-Astrochemistry (ICA) [1,2] to conduct experiments aimed at providing a better understanding of the role of the solid phase of an ice in determining the outcome of its radiation (astro)chemistry.

We have performed a series of systematic and comparative 2 keV electron irradiations of the amorphous and crystalline phases of various pure astrophysical ice analogues, including N₂O, CH₃OH, and H₂O, at 20 K [3,4]. The radiation-induced decay of these ices and the concomitant formation of products were monitored in situ using FT-IR spectroscopy. A direct comparison between the irradiated amorphous and crystalline CH₃OH ices revealed a significantly more rapid decay of the former compared to the latter. Interestingly, a significantly smaller difference was observed when comparing the decay rates of the amorphous and crystalline N₂O ices (Figure 1).

The extent of the similarity between the radiolytic decay curves of the amorphous and crystalline phases of these ices has been quantified by applying the weighted Jaccard coefficient, J_w (also sometimes referred to as the Tanimoto coefficient). This coefficient measures the similarity between two real, non-zero functions and varies between 0-1, with the 0 indicating no statistical similarity whatsoever and the 1 indicating identical functions. In the case of the radiolytic decay curves for the amorphous and crystalline CH₃OH ices, J_w = 0.40, while in the case of the investigated N₂O ices this was much higher at J_w = 0.80.

Figure 1: Electron-induced decay of CH₃OH (above) and N₂O (below) ice phases with increasing 2 keV electron fluence. Reproduced from Mifsud et al. (2022) with permission of the Royal Society of Chemistry [3].

These results have been interpreted in terms of the strength and extent of the intermolecular forces of attraction present in each molecular ice. The strong and extensive hydrogen-bonding network that exists in the crystalline CH₃OH – but not in the amorphous phase – is thought to add a significant stabilizing effect to this phase which makes it more resistant to radiation-induced decay. On the other hand, although the alignment of the molecular dipole of N₂O is expected to be more extensive in the crystalline phase, its weak attractive potential does not significantly stabilize the crystalline phase against radiation-induced decay compared to the amorphous phase as in the case of CH₃OH.

Experiments were also performed on various phases of H₂O ices using 2 keV electrons. Irradiated amorphous solid water (ASW), restrained amorphous ice (RAI), cubic crystalline ice (Ic), and cubic hexagonal ice (Ih) were found to demonstrate different responses upon the onset of electron irradiation (Figure 2). For example, the compaction of ASW ice was noted to occur fairly quickly. The ordered phases, on the other hand, all underwent amorphization as a result of their irradiation by energetic electrons. Interestingly, the amorphization of Ih was noted to require a higher electron fluence compared to those of RAI and Ic (Figure 3). This is perhaps not unexpected, as these latter phases are only meta-stable with respect to Ih.

Large variations in the appearance and shape of the mid-infrared absorption bands between the crystalline and amorphous H₂O ices made the use of the weighted Jaccard coefficient difficult and inappropriate. As such, the difference in the radiolytic decay rates of these ices was gauged indirectly by measuring the yield of H₂O₂ observed after electron irradiation of each phase. The ASW ice was found to be the most chemically productive in this way, with 0.32% of the H₂O being converted to H₂O₂. On moving to more ordered phases, however, the H₂O₂ yield was found to progressively decline, with 0.21, 0.16, and 0.14% of the H₂O being converted to H₂O₂ as a result of the irradiation of the RAI, Ic, and Ih phases, respectively.

Our results have important implications for radiative astrochemistry of interstellar and outer Solar System ices, as it is clear that the radiolytic decay and, by extension, the potential chemical productivities of these ices are greater when they are in the amorphous state rather than the crystalline phase. Given that most astrophysical ices undergo cycles of thermally induced crystallization and space radiation induced amorphization, our results suggest that the formation of new molecules (including those complex molecules of relevance to biology and the emergence of life) as a result of the processing of these ices by galactic cosmic rays, the solar wind, or giant planetary magnetospheric plasmas is most productive in those astrophysical regions where the amorphization process is more efficient. This is not an unreasonable conclusion, particularly in light of the recent spate of discoveries of complex organic molecules in the pre-stellar cloud TMC-1 [e.g., 5,6].

Figure 3: Structured H₂O stretching modes were observed to broaden as a result of electron-induced amorphization of the ices; which is suggested to be slower in the Ih phase.

The authors all gratefully acknowledge funding from the Europlanet 2024 RI which has been funded by the European Union Horizon 2020 Research Innovation Programme under grant agreement No. 871149.

References:
[1]  P. Herczku, et al. Rev. Sci. Instrum. 92, 084501 (2021)

[2]  D.V. Mifsud, et al. Eur. Phys. J. D. 75, 182 (2021)

[3]  D.V. Mifsud, et al. Phys. Chem. Chem. Phys. 24, 10974 (2022)

[4]  D.V. Mifsud, et al. Eur. Phys. J. D. 76, 87 (2022)

[5]  B.A. McGuire et al. Science 371, 1265 (2021)

[6]  K.L.K. Lee et al. Astrophys. J. Lett. 908, L11 (2021)

How to cite: Mifsud, D., Hailey, P., Herczku, P., Juhász, Z., Kovács, S., Sulik, B., Kumar Kushwaha, R., Rácz, R., Biri, S., Ioppolo, S., Kaňuchová, Z., Paripás, B., McCullough, R., and Mason, N.: The Effect of the Solid Phase Adopted by Astrophysical Ices on their Radiation Chemistry and Physics: Implications for the Synthesis of Prebiotic Molecules, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-832, https://doi.org/10.5194/epsc2022-832, 2022.

Introduction: Planets that retain a primordial, H-He dominated atmosphere can have hydrogen act as a greenhouse gas: the collision induced absorption (CIA) of infra-red light increases with pressure. This mechanism could replace regular greenhouse gasses in exoplanets to allow warm enough temperatures for a liquid water layer. Prior work[1, 2] demonstrated that either stellar insolation or intrinsic heat could be a sufficient energy source. In the case of the latter, a ‘habitable zone’ for such planets could extend up to infinity[3, 4]. In this work we aim to study the long-term potential for habitability of planets with hydrogen-dominated atmospheres. We simulate planets with varying properties to investigate how these influence the likeliness of habitable conditions. Importantly, we include for the first time long-term temporal evolution of both the planet and the host-star, to estimate how long liquid water could remain.

Methods: We model the thermal structure of a silicate-iron planet with a H-He-dominated atmosphere and vary the core mass, initial envelope mass, and semimajor-axis. An evolution model for the host-star's luminosity is included, as well as a model for the evolution of the planet's intrinsic heat and radius. The intrinsic heat model includes a radiogenic component based on Earth's abundance of radioactive materials as well as cooling and contraction of both the silicate-iron core and the gaseous envelope. We furthermore include a thermal XUV-driven atmosphere loss model. By comparing the pressure and temperature at the bottom of the atmosphere with the water phase diagram, we determine when liquid water can exist.

Results: We find that terrestrial and super-Earth planets with masses of about 1 - 10 Earth masses can maintain liquid water conditions for more than 9 billion years at radial distances larger than 2 AU. The required surface pressures are typically between ~100 bar (as on Venus) and 1 kbar (as in the oceanic trenches on Earth). Hydrodynamic escape can reduce this duration significantly for planets with a smaller envelope than 10-5 Earth mass within 10 AU, while planets with an envelope larger than 10-3 Earth mass remain mostly unaffected by this mechanism. Planets that receive a negligible amount of stellar radiation can maintain the conditions as long as the internal heat source is sufficient, which is at maximum 80 billion years in our simulation.

Conclusions: Under the assumptions of our model we show that there is a wide range of conditions under which liquid water can exist and remain on the order of 10 billion years. This raises the question whether most potentially habitable planets are very different from Earth. Our model is simplified and future work should investigate the formation and retention of a liquid water ocean in more detail. The pathway and the conditions towards planets with the right initial conditions should be studied in the future as well. This will enable us to better predict the occurence rate of such a planet and the chances of observing them at the current age of the universe.

References: [1] Stevenson D. J. (1999) Nature 400:32. [2] Pierrehumbert R. & Gaidos E. (2011). The Astrophysical Journal Letters 734:L13. [3] Seager S. (2013) Science, 340:577-581. [4] Madhusudhan, N. et al. (2021) The Astrophysical Journal, 918:1.

How to cite: Mol Lous, M., Helled, R., and Mordasini, C.: Potential long-term habitable conditions on planets with primordial H-He atmospheres., Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-1139, https://doi.org/10.5194/epsc2022-1139, 2022.

Introduction:

The interest for the Moon has risen with many missions being planned for the Moon surface culminating to the Artemis missions, spearheading a new era of human presence on the lunar surface. At the same time a recent paper (1) provided an overview of the current state of Martian research and understanding. A common theme on both of these endeavors is the requirement of extensive research across the fields of astrobiology, the frontier of ISRU technologies and habitability research under simulated conditions of those environments. A large number of Lunar and Martian Simulants has been developed over the past decades, often though produced rapidly with lower fidelity to satisfy demand  (2). Towards this purpose, our group made an effort to develop such materials, since in Greece only potentially analogue locations for simulated research exists. This research was initiated with the introduction of a new simulant classification system, after having highlighted a number of issues that pertain on the facet of Martian Simulants. We here report on the development of new simulants we produced for the Lunar and Martian surfaces.

Methodology:

Initially, we scrutinised the literature focusing on three focal points of research to collect data on the composition of Lunar and Martian surface location, the Lunar Curator Facility, the Analyst’s Notebook and the respective publications on simulant production, in order to identify which datasets have been already utilised. Based on these data, we selected one Lunar and two Martian locations to produce simulants. For the Moon we selected the 15260 Apollo Sample which has been extensively studied. (3) For Mars, we opted for the Rocknest and Gobabeb targets, which are 2 of the most cited and compared sites for simulant production. More specifically, for Moon we utilised the chemical analysis provided by (3) and for Mars those provided by (4).

For the simulant development we collected a number of igneous rock samples from the field, and acquire a number of pure mineral phases, for use as individual components, presented in table 1. All of the materials utilised by our team in the synthesis of the simulants have been firstly crushed and grounded to a grain fraction of under 1 mm. A portion of the material was further crushed in under 250 μm, and later refined for XRD analysis. Each sample was then scanned in three random locations via SEM-EDS and the average analysis was taken as the sample’s chemistry. Thus, via those two analytical techniques, the background of the chemical and mineralogical make up of our inventory of materials was established.

In order to establish the quality of our simulants we utilised the Figure of Merit (FOM) proposed by (5) and applied by (6). By using this system you can deduce the accuracy of your simulant based on how close the percentages of chemical oxides are to the reference sample.

Simulants:

Up to the point of writing, our team has produced a total of four simulants, two for the Moon and two for Mars. Initially a production of two prototypes for a Lunar and Martian simulant, Simulant #1 and #2 respectively, were made by mixing three individual mineral and rock components to verify the method of synthesis and correct any mistakes. However, even at that stage the theoretical FOM of our Simulant #1 was above 95% when compared to the Apollo 15260 sample, and Simulant #2 for Mars had FOM 90,7% and 89% for the Rocknest and Gobabeb targets respectively. (Table 1) 

Based on the preliminary results we produced refined simulants, Simulant #3 and #4 for Moon and Mars respectively, using additional components materials as showed in table 1. Thus, Simulant #3 for the Apollo 15260 sample reached FOM of almost 96% and Simulant #4 for Mars reached FOM of 94,6% and 91,6% for the Rocknest and Gobabeb targets, respectively. (Table 1) 

Future Goals:

The goal of this project is to try and make simulant materials for Moon and Mars more accessible to the scientific community, but also provide materials of higher fidelity and accuracy. Based on their chemistry, the FOM values on the martian simulants are higher than those presented in (6), suggesting that our endeavor has significant prospects compared with the fidelity of other simulants and providing the confidence that higher accuracy simulants can be synthesised. Furthermore, an additional number of analytical techniques will be used to verify their fidelity. Additionally, by the acquisition of additional mineral phases and rock samples we are targeting to increasing the FOM values. A short term requirement is also the availability of well-known simulants in order to be used in the OxR ESA project (7).

References:

• H. G. Changela et al., Mars: new insights and unresolved questions. International Journal of Astrobiology, 1-33 (2021).
• G. H. Peters et al., Mojave Mars simulant—Characterization of a new geologic Mars analog. Icarus 197, 470-479 (2008).
• A. Duncan et al. (1975) Interpretation of the compositional variability of Apollo 15 soils. in Lunar and Planetary Science Conference Proceedings, pp 2309-2320.
• C. Achilles et al., Mineralogy of an active eolian sediment from the Namib dune, Gale crater, Mars. Journal of Geophysical Research: Planets 122, 2344-2361 (2017).
• C. Schrader et al. (2009) Lunar regolith characterization for simulant design and evaluation using figure of merit algorithms. in 47th AIAA Aerospace Sciences Meeting Including the New Horizons Forum and Aerospace Exposition, p 755.
• L. E. Fackrell, P. A. Schroeder, A. Thompson, K. Stockstill-Cahill, C. A. Hibbitts, Development of Martian regolith and bedrock simulants: Potential and limitations of Martian regolith as an in-situ resource. Icarus 354, 114055 (2021).
• ESA (2022) https://www.esa.int/Enabling_Support/Space_Engineering_Technology/Moon_and_Mars_superoxides_for_oxygen_farming.

Table 1. Simulant components and Figure of Merit percentages.

How to cite: Stavrakakis, H.-A., Argyrou, D., and Chatzitheodoridis, E.: Introducing the First Greek Martian and Lunar Simulants, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-611, https://doi.org/10.5194/epsc2022-611, 2022.

The identification of novel terrestrial sites that are analogous for other planetary bodies is an active area of research within astrobiology, because of the logistical and financial difficulties in obtaining extraterrestrial samples for analysis. Characterisation of potential analogue sites is undertaken to assess how accurately they represent a specific extraterrestrial environment. Analysing their physicochemical conditions and microbial communities are key components of these studies to understand what metabolisms would be viable in such environments.

One such novel analogue environment is the salt plains of Western Sahara. Western Sahara is one of the driest regions on Earth. It is located on the northwest coast of West Africa and is characterised by high UV exposure, low annual precipitation and water activity, subsurface water and high annual temperatures. These features make Western Sahara a potential analogue site for Mars during the Noachian-Hesperian transition period (3.5 – 3.8 Ga), when the atmosphere began to thin and surface water started evaporating (Warner et al., 2010), similar to other terrestrial deserts, such as the Atacama Desert and the McMurdo Dry Valleys.

The hypersalinity, aridity and high UV radiation levels of the Western Sahara salt plains would also be appropriate to study whether dissimilatory sulfur metabolisms would be viable in a Noachian-Hesperian Mars analogue environment. Dissimilatory sulfur cycling refers to the use of inorganic sulfur compounds for energy conservation and it has been recognised as a metabolic strategy of interest for putative martian life (Macey et al., 2020). On Earth, evidence from stable sulfur isotope fractionation has suggested this metabolism emerged early in the history of life (~3.5 Ga). During this period, the conditions on Mars were predicted as being more habitable than present-day, with an active magnetic field, thicker atmosphere and liquid water on the surface.

In this study, molecular and geochemical techniques were used to give first insights into the potential of the Western Sahara salt plains to serve as an analogue of Mars during the Noachian-Hesperian transition period. The microbiology was investigated through cultivation-independent and culture-dependent analyses of salt crystals, sediment and water samples obtained at three sites near Llaayoune (Fig. 1). The chemical nature of the samples was analysed through ion chromatography (IC) and inductively coupled plasma - optical emission spectrometry (ICP-OES).

The geochemical characterisation confirmed the high salinity of the samples and identified that sodium, potassium, magnesium and sulfur were the most enriched elements within all samples. Cultivation-dependent work resulted in the enrichment of a wide range of metabolic strategies from the samples including aerobic heterotrophs, phototrophs and sulfate-reducers. The enrichments from the salt were dominated by strains of Bacillus, whereas sulfate-reducing strains of Clostridium were isolated from the sediment samples. Microscope analysis of phototroph-selective media also indicated that algae and Cyanobacteria were successfully enriched from the samples. 16S rRNA amplicon sequencing results will also be presented to gain further in-depth understanding of the microbial community composition. Additionally, results from quantitative polymerase chain reaction (qPCR) experiment targeting sox and dsr genes will be presented to identify the abundance of genes specific for dissimilatory sulfur metabolisms within the samples.

Preliminary data shows that sulfur cycling is occurring in Western Sahara salt plains. Future characterisation of this environment will involve metagenomic analysis of the samples and genome sequencing of the isolates to identify the key metabolisms underpinning the survival and viability of the microbial community. Comparative studies with other Mars analogue environments will then be undertaken to identify metabolisms that may have been thermodynamically viable in ancient martian aqueous environments.

Figure 1. Location of the sample collection sites. Images were generated with Google Earth Pro.

References

Macey, M. C., Fox-Powell, M., Ramkissoon, N. K., Stephens, B. P., Barton, T., Schwenzer, S. P., . . . Olsson-Francis, K. (2020). The identification of sulfide oxidation as a potential metabolism driving primary production on late Noachian Mars. Scientific Reports, 10(1), 10941. https://doi.org/10.1038/s41598-020-67815-8

Warner, N., Gupta, S., Lin, S.-Y., Kim, J.-R., Muller, J.-P., & Morley, J. (2010). Late Noachian to Hesperian climate change on Mars: Evidence of episodic warming from transient crater lakes near Ares Vallis [https://doi.org/10.1029/2009JE003522]. Journal of Geophysical Research: Planets, 115(E6). https://doi.org/https://doi.org/10.1029/2009JE003522

How to cite: Ilieva, V., Stephens, B., Goodall, T., Ori, G., Read, D., Pearson, V., Olsson-Francis, K., and Macey, M.: Western Sahara salt plains as a potential novel Mars analogue, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-1043, https://doi.org/10.5194/epsc2022-1043, 2022.

Global dust storms at Mars engulf the entire planet in a dusty haze, causing increases in temperature and ion escape as dust is lifted up to 80 km in altitude. The two most recent storms occurred in 2007 (Mars Year (MY) 28) and 2018 (MY34), and have been observed by spacecrafts such as Mars Express (MEx). MEx has been operating at Mars since 2004, and has produced a long time-base of plasma measurements from as low as 250 km. Using MEx, we investigate whether the 2007 dust storm has influenced the magnetosphere of Mars by looking at the position of the bow shock and induced magnetospheric boundary, compared to the expected position provided by 3D magnetohydrodynamical models. To identify boundary positions, we use data from the ASPERA-3 instrument (Analyser of Space Plasma and EneRgetic Atoms) onboard MEx, which contains an electron spectrometer (ELS), ion mass analyser (IMA), neutral particle imager (NPI) and neutral particle detector (NPD). For this study, we use data from ELS and IMA. We consider a number of influences on the boundary position, including the solar wind conditions and the crustal fields. Our study period includes time before, during, and after the MY28 global storm, and we expected the bow shock and induced magnetospheric boundary to increase in altitude due to the storm. Out results show that the system is more complex, and multiple influences need to be distinguished to leave any change due to the dust storm itself.

How to cite: Regan, C., Coates, A., Wellbrock, A., Haythornthwaite, R., Jones, G., Sánchez-Cano, B., Holmström, M., Frahm, R., and Garnier, P.: Investigating the Global Dust Storm in Mars Year 28 with Mars Express, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-527, https://doi.org/10.5194/epsc2022-527, 2022.

1.  Introduction

Titan is the only moon in our solar system with a substantial atmosphere. It comprises 98% Nitrogen (Niemann et al., 2005), and is rich in hydrocarbon (C_xH_y) and nitrile (C_xH_yN_z) species. Such species photochemically react to produce organic aerosols which compose a thick orange haze suspended in Titan’s middle atmosphere.

Global Circulation Models (GCMs) predict the meridional circulation in Titan’s stratosphere and mesosphere is dominated by a single pole-to-pole circulation cell for most of the Titan year (Hourdin et al., 1995; Newman et al., 2011; Lebonnois et al., 2012), and observations are broadly consistent with this prediction (Teanby et al., 2012, Vinatier et al., 2015). These models suggest circulation across the stratospheric equator, but this is not entirely consistent with what is observed. Existing studies show a North-South asymmetry in stratospheric haze abundance (Lorenz et al., 1997; de Kok et al., 2010), suggesting a mixing barrier near the equator. Here, we present a radiance ratio method for approximating latitudinal distributions of stratospheric HCN. We apply this to the region +/-30 degN and use HCN as a tracer to investigate the evolution and behaviour of the equatorial mixing barrier over the Cassini mission.

2.  Observations

The Cassini spacecraft explored Saturn and its moons from 2004 to 2017. Throughout its 13-year exploration, Cassini performed 127 close flybys of Titan, observing at infrared, visible and ultra-violet wavelengths. One of Cassini’s twelve instruments, the Composite Infrared Spectrometer (CIRS) (Flasar et al., 2004; Jennings et al., 2017; Nixon et al., 2019) collected almost 10 million Titan spectra in the mid and far-infrared ranges (10 – 1500 cm^-1), at a varied spectral resolution between 0.5 – 15.5 cm^-1. In this study, we analyse low spectral resolution (~15 cm^-1) observations collected by two CIRS focal planes, sensitive to wavenumber ranges 600 – 1100 cm^-1 (FP3) and 1100 – 1500 cm^-1 (FP4). Generally, low spectral resolution observations require shorter scan times so can be performed at a closer approach distance to Titan, hence achieving higher spatial resolution. This allows small spatial variations in atmospheric constituents to be resolved. Low-resolution observations also have good coverage of Titan’s equatorial region throughout the entire Cassini mission (Figure 1).

Figure 1: Mission coverage for the Cassini CIRS low spectral resolution nadir mapping observations.

3.  Optimising Line-by-Line Retrieval Efficiency

Line-by-line (LBL) inversions in spectral analysis are computationally expensive. The correlated-k approximation (Lacis and Oinas, 1991) is often used to decrease the computation time of retrievals, but we found that it is not sufficiently accurate for these low spectral resolution and high signal-to-noise ratio observations (Figure 2c, d). In LBL modelling, a key parameter is the underlying spectral grid spacing. Finer grid spacing improves the forward model accuracy, but at a greater computation cost. To improve the efficiency of LBL runs, we determine a maximum grid spacing (Figure 2a, b) for which a LBL inversion will produce a sufficiently accurate spectrum in the shortest computation time. Typically, a single forward model run takes 2 hours for LBL, compared to 2 seconds for k-tables.

Figure 2: Comparison of spectra produced using a correlated-k (k-table) method and a line-by-line (LBL) method at varied spectral grid spacing. Maximum radiance difference (MRD) (a, b, blue line) between spectra produced at varied (0.1 – 0.0001 cm^-1) and fine (0.0001 cm^-1) grid spacing is assessed against a level of sufficient accuracy (a, b, grey area). The grid spacing determined to be optimal (0.001 cm^-1 for FP3, 0.005 cm^-1 for FP4) produces an almost identical spectrum to very fine (0.0001 cm^-1) grid spacing (c, d) but at a significantly reduced runtime (a, b). A spectrum produced using a coarse grid spacing (0.1 cm^-1) is shown for comparison. The spectrum retrieved using k-tables is not sufficiently accurate for these low-resolution observations (c, d).

4.  Estimating Stratospheric HCN with a Radiance Ratio

We construct a radiance ratio formula for approximating HCN abundance from CIRS spectra, such that a greater number of observations can be analysed rapidly. Radiance ratios can be a useful tool for approximating gas contributions to a spectrum. They do not have the reliability of full spectral retrievals but require significantly less computation time. We compare the radiance ratio latitude dependence to full LBL retrievals of HCN, for a subset of our observations, to assess the reliability of our ratio method. LBL retrievals are performed using the Nemesis radiative transfer and retrieval code (Irwin et al., 2008) with our pre-determined optimal grid spacing. We calculate the radiance ratio for a set of approximately 20 low spectral resolution mapping observations (3 are shown in Figure 3).

There appears to be a sharp change in HCN abundance near the equator (Figure 3). This hints at a potential mixing barrier in Titan’s stratosphere. Furthermore, the position of this potential barrier appears to migrate over time. We use the results of this study to investigate dynamic processes in the equatorial region of Titan’s stratosphere and its evolution over the entire Cassini mission.

Figure 3: Our radiance ratio calculated for observations acquired on 08/2005 (a), 05/2006 (b) and 07/2012 (c). The radiance ratio is smoothed by fitting splines (Teanby, 2007). The gradient of each smoothed fit is also shown (bottom).

Acknowledgements

This research was funded by the UK Sciences and Technology Facilities Council.

References

de Kok, R., et al. (2010). https://doi.org/10.1016/j.icarus.2009.10.021

Flasar, F. M., et al. (2004). https://doi.org/10.1007/s11214-004-1454-9

Hourdin, F., et al. (1995). https://doi.org/10.1006/icar.1995.1162

Irwin, P., et al. (2008). https://doi.org/10.1016/j.jqsrt.2007.11.006

Jennings, D. E., et al. (2017). https://doi.org/10.1364/AO.56.005274

Lacis, A. A., & Oinas, V. (1991). https://doi.org/10.1029/90JD01945

Lebonnois, S., et al.  (2012). https://doi.org/10.1016/j.icarus.2011.11.032

Lorenz, R. D., et al. (1997). https://doi.org/10.1006/icar.1997.5687

Newman, C. E., et al. (2011). https://doi.org/10.1016/j.icarus.2011.03.025

Nixon, C. A., et al. (2019). https://doi.org/10.3847/1538-4365/ab3799

Niemann, H. B., et al. (2005). https://doi.org/10.1038/nature04122

Teanby, N. A. (2007). https://doi.org/10.1007/s11004-007-9104-x

Teanby, N. A., et al.  (2012). https://doi.org/10.1038/nature1161

Vinatier, S., et al.  (2015). https://doi.org/10.1016/j.icarus.2014.11.019

How to cite: Wright, L., Teanby, N. A., Irwin, P. G. J., Nixon, C. A., and Mitchell, D. M.: Stratospheric HCN and Evolution of a Mixing Barrier in Titan’s Equatorial Region from Low-Resolution Cassini/CIRS Spectra, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-463, https://doi.org/10.5194/epsc2022-463, 2022.

The grand appearance of Jupiter’s banded atmosphere, coloured with many shades from white to red, whose cloud structure currently remains elusive with no clear single cloud model responsible for this varied appearance. With a general pattern of alternating bright cloudy zones and darker belts, as well as unique regions such as the Great Red Spot, finding a way to model all of these differing appearances with a single model has proven difficult. Jupiter’s atmosphere provides continual challenges when attempting to characterise its cloud structure due to its frequently varying appearance. This leads to differences between every observation meaning that models are constantly having to adapt to be explain these changes. Such changes can be seen in Figure 1, both of these spectra have been extracted for the same region of the Equatorial Zone (EZ) but are not identical due to the changes in appearance over the 3 years. 

Recent works [1,2,3,4] have all attempted to model Jupiter’s atmosphere using a universal chromophore (cloud colouring compound), combined with a deeper conservatively-scattering cloud and also a stratospheric haze layer. These works have all been able to model the atmosphere successfully but it has currently not been possible to determine between these differing solutions to find the most likely representation of the atmosphere. As all the different sets ups have several ways to vary cloud structure and chromophore properties among other parameters, they have been able to fit the changes in the observations. Therefore keeping each set up viable even as the atmosphere changes. The current inability to conclude on a favoured cloud structure highlights the highly degenerate nature of this problem.

Utilising new observations and techniques to analyse the data highlights the delicacy of these results as the previous set ups have to be altered in order to produce the desired fit to the new observations once the input have varied slightly. An unchanged fit is shown in Figure 1, where the ideal fit of the EZ in 2018 has been used for 2021 data and is unable to model the spectra as well as for the spectra which it was derived from. Furthermore introduction of a limb viewing technique, as used in [2], has been done for this data. Here we attempt to fit multiple viewing angles simultaneously, which also begins to question the robustness of these results, due to an inability of nadir derived set ups to reproduce the multiple observations as successfully. 

Therefore in this work we have begun to attempt to reduce the degeneracy of the problem before utilising the Non-linear optimal Estimator for Multi-variatE spectral analySIS (NEMESIS) radiative-transfer retrieval algorithm [5], to fit to our observations. From this we want to find a vertical cloud structure which is more reproducible using different observations and techniques. It is hoped that reducing one of the degenerate parameters before fitting will allow us to constrain the atmospheric structure more decisively. Furthermore combining this with the limb darkening technique will hopefully allow us to rule out some of the solutions to this highly degenerate problem to find more confidence in the proposed models. 

In this work we will present the preliminary results taken from the application of these methods to observations to derive a new atmospheric model which can be compared with past work. Additionally we will present the use of new techniques to determine the ability of previous models to adapt to new observations to see if they are still viable. 

Figure 1: Spectra of the Equatorial Zone in both 2018 and 2021 and the spectral fit using the model from [1] derived for the 2018 data. 

[1] Braude, A. S., Irwin, P. G., Orton, G. S., and Fletcher, L. N. (2020). Colour and tropospheric cloud structure of jupiter from muse/vlt: Retrieving a universal chromophore. Icarus, 338:113589. 

[2] Pérez-Hoyos, S., Sánchez-Lavega, A., Sanz-Requena, J., Barrado-Izagirre, N., Carrión-González, O., Anguiano-Arteaga, A., Irwin, P., and Braude, A. (2020). Color and aerosol changes in jupiter after a north temperate belt disturbance. Icarus, 352:114031.

[3] Dahl, E. K., Chanover, N. J., Orton, G. S., Baines, K. H., Sinclair, J. A., Voelz, D. G., Wijerathna, E. A., Strycker, P. D., and Irwin, P. G. J. (2021). Vertical structure and color of jovian latitudinal cloud bands during the juno era. The Planetary Science Journal, 2(1):16. 

[4] Baines, K., Sromovsky, L., Carlson, R., Momary, T., and Fry, P. (2019). The visual spectrum of jupiter’s great red spot accurately modeled with aerosols produced by photolyzed ammonia reacting with acetylene. Icarus, 330:217–229.

[5] Irwin, P. G. J., Teanby, N. A., de Kok, R., Fletcher, L. N., Howett, C. J. A., Tsang, C. C. C., Wilson, C. F., Calcutt, S. B., Nixon, C. A., and Parrish, P. D. (2008). The NEMESIS planetary atmosphere radiative transfer and retrieval tool. , 109:1136–1150 

How to cite: Alexander, C. and Irwin, P.: Comparing atmospheric models of Jupiter, can we reduce the degeneracy of this problem?, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-632, https://doi.org/10.5194/epsc2022-632, 2022.

How to cite: Smirnova, M., Galanti, E., and Kaspi, Y.: Studying the dynamics of Jupiter using a 3D general circulation model constrained by radio occultation measurements, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-932, https://doi.org/10.5194/epsc2022-932, 2022.

Helium ions, He⁺, react only slowly with molecular hydrogen. A consequence of this is that He⁺ ions produced by, for example, photoionization of He in H₂-dominated ionospheres, such as those of Jupiter and Saturn, can have principal loss mechanisms other than through reactions with molecular hydrogen even if the other reactants prevail in rather small volume mixing ratios. The Ion and Neutral Mass Spectrometer (INMS) onboard the Cassini mission operated in open-source ion mode during a few of the passages through Saturn’s upper atmosphere throughout the proximal orbits in 2017. Due to the high spacecraft velocity, exceeding 30 km/s, the retrieval of ion number densities was limited to light ion species with masses (for singly charged species) of < 8 Da. The retrieval of number densities of volatiles like H₂O, CH₄, NH₃, N₂ and CO were in part complicated by adsorption effects.

We seek to make an independent estimate of the mixing ratios of volatiles other than H₂ and He by making use of a simple model focusing on the production and loss balance of helium ions. We first consider two models to estimate the local production rate of He⁺ from the measured density profiles of He and H₂ and show that these give estimates in reasonable agreement with each other. Then we show that the calculated concentration of He⁺ exceeds the observed values by up to two orders of magnitude if we only account for the loss of He⁺ ions through reactions with molecular hydrogen. We take this as a strong indicator that the principal loss mechanism of He⁺ in Saturn’s ionosphere is through reactions with other species than H₂. We proceed with a brief survey of chemical reaction databases highlighting that it seems reasonable to consider an effective rate constant of k₁ ≈ (1.0 ± 0.5)*10^-9 cm³ s^-1 for reactions involving the neutralization of He⁺ in reactions with H₂O, CH₄, NH₃, N₂ and CO. This allows us to estimate the mixing ratio of these molecules across an altitude profile. Our results are compatible with the average values reported by Miller et al. (2020) and show indications of enhanced mixing ratios towards lower altitudes and/or near equatorial latitudes.

How to cite: Dreyer, J. and Vigren, E.: Deriving mixing ratios of heavier neutral species in Saturn's ionosphere from light ion measurements, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-1053, https://doi.org/10.5194/epsc2022-1053, 2022.

We combine the electromagnetic fields from a hybrid model with a particle-tracing code to calculate the time-varying spatial distribution of magnetospheric ion flux onto the surface of Jupiter’s moon Europa. The electromagnetic fields at Europa are perturbed by the sub-alfvénic interaction of the moon’s ionosphere and induced dipole with the magnetospheric plasma. These perturbations substantially modify magnetospheric ion trajectories at all energies. We calculate spatially resolved surface flux maps of thermal and energetic ions for various distances between Europa and the center of Jupiter’s magnetospheric plasma sheet. The upstream ion distributions are constrained through in-situ particle data from the Galileo and Juno spacecraft. These maps are then combined to obtain the average distribution of magnetospheric ion surface flux over a full synodic rotation. Our results show that the draping and pileup of the magnetic field reduce ion flux onto Europa’s trailing hemisphere by several orders of magnitude, while a significant number of the incident ions are deflected onto the leading hemisphere. Taking into account the deflection of energetic ions in the draped electromagnetic fields shifts the region of minimum energetic ion surface flux from Europa’s wakeside equator to its ramside equator. This generates an “inverted bullseye” pattern of energetic ion flux centered at the trailing apex. Despite drastic changes to the morphology of the ion surface flux when the alfvénic plasma interaction is included, we still find a strong correlation between variations of sulfuric acid concentration observed across Europa’s surface by Galileo and our modeled sulfur influx pattern.

How to cite: Addison, P., Liuzzo, L., Arnold, H., and Simon, S.: Influence of Europa’s Time-Varying Electromagnetic Environment on Magnetospheric Ion Precipitation and Surface Weathering, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-1, https://doi.org/10.5194/epsc2022-1, 2022.

Io is the innermost galilean satellite of Jupiter and object to extreme tidal forces. As a result of these forces Io is the most volcanically active body in our solar system. Its large volcanic plumes can rise up to several hundred kilometres above the surface and are one known source of Io's SO₂ atmosphere. Additionally, the surface of the moon is covered with surface frost which sublimates in sunlight and condenses during the night or when Io enters eclipse behind Jupiter. Therefore, Io’s atmosphere is a result of the combination of volcanism and sublimation, but it is unknown exactly how these processes work together to create the observed atmosphere. That is why we want to present an approach on modelling Io’s atmosphere and provide a better understanding of the ongoing dynamic processes.

Both, the gas flow of the plume and the sublimation atmosphere, are modelled using the Direct Simulation Monte Carlo (DSMC) method first utilised by G. A. Bird [1]. The DSMC method is the most suitable for this case because the gas dynamics can be modelled over a great range of gas densities which is especially important for rarefied gas flows at high altitudes and on the night side of Io. It is a particle-based method which returns a 3D gas flow field as a result. While we currently focus on single species simulations, our DSMC code is designed to support multiple species enabling us to study the gas emission of other volcanic features as for example lava lakes in the future. This allows us to investigate the influence and contributions of different processes to the atmosphere. The idea of our work is based on simulations done by McDoniel et al. [2].

In a first case, we are investigating the flow of SO₂ gas from the source of a plume, into the umbrella-shaped canopy and eventually back onto the surface locally. Additionally, we also study the interaction of the plume with an ambient sublimation atmosphere. In a second case, data obtained by the Galileo SSI experiment is used to create a surface albedo map of Io which enables us to calculate a more precise global thermal model for the sublimation atmosphere. We can then place plumes on the surface and study the interaction of volcanic and sublimation effects globally. Finally, we are also able to implement dust particles in the plume and analyse the effect for different dust sizes. From these results we can calculate images of the column density and the reflectance which in a next step could be used to compare to observational data.

Overall, our goal is to gain a better understanding of the plume structure, the interaction with the ambient atmosphere and the overall contribution of different processes to Io's atmosphere in preparation for future missions such as JUICE, Europa Clipper and a possible future Io Volcano Observer.

[1] Bird, G. A. (1994). Molecular Gas Dynamics and the Direct Simulation of Gas Flows.

[2] McDoniel, W. et al. (2019). Simulation of Io’s plumes and Jupiter’s plasma torus. Phys. Fluids 31, 077103. DOI: 10.1063/1.5097961.

How to cite: Klaiber, L., Thomas, N., Marschall, R., and Milazzo, M.: DSMC Simulations of Io’s atmosphere, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-931, https://doi.org/10.5194/epsc2022-931, 2022.

Evidence of explosive volcanism on the surface of Mercury has been identified in the form of vents and pyroclastic deposits using images and spectral data acquired by the MESSENGER mission (Goudge et al. 2014, Thomas et al. 2014, Jozwiak et al. 2018, Pegg et al. 2021). Understanding the history of the volcanic eruptions forming these features provides an insight in the geological and thermal evolution of the planet. To this end, it is important to constrain the characteristics of each vent and, correlating them with the environment, classify the features according to their age and geological conditions. An individual analysis of a selection of vents has been carried out by Barraud et al. 2021 and Besse et al. 2015, providing new insights on the size, volcanic content and spectral properties of these features. However, performing a global analysis presents further challenges.  The collection of volcanic features identified presents a wide variety of characteristics in terms of morphology (simple vent, pit vent, vent-with-mound etc.), shape (circular, elliptical, curved), location (crater centre, crater rim, inter-crater plain), distribution (isolated or compound) and spectral properties of the pyroclastic deposit. This introduces a large number of variables that complicate the characterisation and timing of volcanic eruptions. 

The vast amount of data returned by the MESSENGER mission offers both a challenge and an opportunity in the methodology to solve this problem. While the combination of a large number of observations from different instruments can complicate the physical interpretation of a given process, it opens the door to the use of machine learning techniques. These methods rely on the identification of patterns on the input data without considering the associated physics, with the aim to reveal underlying correlations that can then be related to physical and chemical phenomena. This technique has been applied to the entire dataset collected by the Mercury Atmospheric and Surface Composition Spectrometer (MASCS), to classify the visible-near-infrared reflectance spectra into three categories (D'Amore et al. 2022). 

In this work, we investigate the application of machine learning to explore the differences amongst the pyroclastic deposits and volcanic vents, with the aim of improving the understanding on the evolution of explosive volcanism in Mercury. In this methodology we combine data from the MASCS and the Mercury Laser Altimeter (MLA) instruments with other properties of the vent surroundings (e.g., crustal thickness). By treating unrelated physical variables together as components of the same input vector, the outcome is a set of dimensions that have no direct physical meaning but can uncover underlying structures to be later physically or chemically interpreted. 

How to cite: Leon-Dasi, M., Besse, S., and Doressoundiram, A.: Exploring the diversity in pyroclastic deposits and volcanic vents on Mercury with machine learning techniques, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-680, https://doi.org/10.5194/epsc2022-680, 2022.

InSight seismic data and marsquake catalogue

NASA's InSight seismometer has been recording the seismicity of Mars for over 3 years and to date, over 1300 seismic events were found by the Marsquake Service (MQS) [1,2]. Marsquakes usually have a low signal-to-noise ratio (SNR) and are consequently often hidden or contaminated by the background noise, making their detection and analysis challenging. Local winds interact with the lander and seismometer system and generate noise levels that fluctuate throughout the Martian day and regularly exceed typical event amplitudes. Additionally, extreme temperature changes cause transient high-amplitude spikes [3]. Conventional tools, such as the STA/LTA detectors, perform poorly on this dataset, as the various noise signals often share a common bandwidth and can be similar in duration to marsquakes [3]. Therefore, MQS detects events by manual data review and discriminates them from wind noise [4] by comparing the seismic data to onboard wind measurements if available, or otherwise, to the excitation of wind-driven lander modes. MQS classifies events by their frequency content into low- (<10%) and high-frequency (>90%) event families and assigns a quality based on their locatability (A: highest to D: lowest quality) [1].

Marsquake detection with convolutional neural network

Deep learning methods, and in particular convolutional neural networks (ConvNet) are nowadays routinely used for complex tasks such as speech or visual object recognition [5]. Here, we use a ConvNet architecture designed for image segmentation [6] to detect marsquake energy in the time-frequency domain. We train the ConvNet to predict segmentation masks that pixel-wise identify event and noise energy based on the time-frequency representation of a given waveform. We use the method to detect marsquakes and to decompose their signal in event and noise components. This allows us to estimate the marsquake duration, frequency content, and SNR.  We use the ConvNet to extend the MQS catalogue and further highlight its value in removing noise contamination from marsquakes [7]. Since the MQS catalogue is much smaller than typically labelled datasets used in deep learning [7], we create a training set with synthetic events with stochastic waveform modelling [8]. Synthetic events mimic the different MQS event types in terms of frequency content and duration and are combined with recorded InSight noise to include all types of noise.

Results

We run our ConvNet-based detector on the complete 20 samples-per-second dataset (over 900 Martian days) and compare our results to the careful manually curated MQS catalogue: we can detect all high-quality events and the majority of low-quality events - in addition to these, we find many additional low SNR events. We extend the catalogue by ~50% more events, of which the majority belongs to the high-frequency event family. An overview of the MQS events and our new detections is given in Figure 1. Similar to the MQS catalogue, we find many events in the quiet evening periods during the spring and summer of the Martian year 1 and 2, and further increase the number of events during the nights when noise levels are elevated. During the high noise periods (day time and winter), when noise amplitudes are orders of magnitudes above typical event amplitudes, we do not confidently detect events apart from a few that fall into short quieter periods. Our results suggest that the MQS catalogue is essentially complete for high SNR events and further support previous findings [9] on the seasonality of high-frequency events and their increased activity in Martian year 2 compared to year 1.

Figure 1: Overview of seismic noise, catalogued MQS events and new detections from ConvNet: the background of the main figure represents the broadband, vertical component seismic noise level (data gaps shown in white). The symbols indicate different event types belonging to the low frequency (LF, BB) or high frequency family (2.4, HF, VF), and colours indicate the qualities in the MQS catalogue; new detections found with our ConvNet detector are shown with their predicted event family type. The panel on the left side shows the cumulative event count using MQS events (blue) and MQS events and new detections (red). The event numbers are dominated by the high frequency events (corresponding to over 90% of events).

References:

[1] Clinton et al. (2021), 10.1016/j.pepi.2020.106595

[2] InSight Marsquake Service (2022), doi.org/10.12686/a16

[3] Ceylan et al. (2021), 10.1016/j.pepi.2020.106597

[4] Charalambous et al. (2021) 10.1029/2020JE006538

[5] LeCun et al. (2015), 10.1038/nature14539

[6] Ronneberger et al. (2015), 10.1007/978-3-319-24574-4_28

[7] Zhu et al. (2019), 10.1109/TGRS.2019.2926772

[8] Boore (2003), 10.1007/PL00012553 

[9] Knapmeyer et al. 10.1016/j.epsl.2021.117171

How to cite: Dahmen, N., Clinton, J., Meier, M.-A., Stähler, S., Kim, D., Stott, A., and Giardini, D.: A Deep Marsquake Catalogue, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-1066, https://doi.org/10.5194/epsc2022-1066, 2022.

Mutual impedance experiments are active electric instruments that provide in situ diagnostic in space plasmas, such as the plasma density and electron temperature. The instrumental technique is based on the coupling between electric antennas embedded in the plasma, and characterizes the local properties of the plasma dielectric. 

Different versions of mutual impedance instruments are present onboard past and future planetary missions, such as Rosetta, BepiColombo, JUICE, and Comet Interceptor. Recently, the interest of the scientific community is shifting from large satellite platforms with single-point measurements concepts to small satellite platforms, to enable multipoint measurements for the spatial mappings of planetary outer environments. Therefore, instruments previously designed for large platforms are now miniaturized and adapted to small satellites. In this context, instrumental efforts are devoted to adapting mutual impedance experiments to small satellites, such as in the case of the CIRCUS CubeSat or the SPEED SmallSat missions projects. 

Current state-of-the-art quantitative instrumental models of mutual impedance experiments are based on the assumption of an unmagnetized plasma. However, for planetary environments within which the magnetic field is not negligible, such as intrinsic planetary magnetospheres (e.g. Mercury, Ganymede) significant modifications of mutual impedance measurements are expected. 

The goal of this work is twofold: (i) support the preparation of mutual impedance instruments for small satellites and (ii) extend current mutual impedance instrumental models to take into account the effects of the magnetic field on the plasma diagnostic. 

This investigation is performed by combining two complementary approaches. First, numerical simulations are used to quantify the impact of the plasma magnetization on the mutual impedance measurements and, therefore, improve its diagnostic. In particular, we have developed and validated a new instrumental model, based on the numerical calculation of the electric potential emitted by an electric antenna in a magnetized, homogeneous, collisionless, Maxwellian plasma. This new instrumental model is used to compute synthetic mutual impedance spectra and assess the impact of electron magnetization on the instrumental response. Using this new model, we provide diagnostics for the plasma density, electron temperature, and magnetic field amplitude. Second, laboratory experiments are used to test and validate our numerical model. We use the controlled plasma environment of the PEPSO plasma chamber at LPC2E laboratory in Orléans. This plasma chamber offers the possibility to test the performances of space plasma instruments and CubeSats in realistic planetary ionospheric conditions. A model of CubeSat is present inside the plasma chamber, and is equipped with a set of electric antennas that are used to perform mutual impedance measurements in the same configuration as a CubeSat. The measurements obtained by this setup are compared with the instrumental model, to validate the plasma diagnostic of the instrument prototype on a CubeSat. 

How to cite: Dazzi, P., Henri, P., Bucciantini, L., Lavorenti, F., Wattieaux, G., and Califano, F.: Mutual impedance experiments as a diagnostic for magnetized space plasmas, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-1091, https://doi.org/10.5194/epsc2022-1091, 2022.

How to cite: Tan, H. and Durech, J.: Models and physical properties of asteroids from optical and infrared data, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-958, https://doi.org/10.5194/epsc2022-958, 2022.

The aim of this project is to derive reference phase functions and their parameters using data from the ATLAS survey. The reference phase function corrects for the observation geometry by removing the influence of the asteroid shape by normalizing it to a sphere. (Muinonen et al. 2020)

The ATLAS survey performed photometric observations in two filters: cyan (420-650 nm) and orange (560 - 820 nm) for over 180 000 asteroids at phase angles even below 1 deg (Heinze et al. 2018). Mahlke et al. (2021) derived over 1270 000 phase curve parameters using the ATLAS photometry, but they were corresponding to different viewing geometries, so they cannot be directly compared with each other.

Traditional phase curves are derived based on lightcurve brightness maximum (or mean) values at a given phase angle. When using sparse photometry (e.g., Gaia, ATLAS), the observational geometry can substantially change between observations and objects. As a result, it is challenging to compare phase curves obtained for different asteroids (even if they were observed at the same epoch). If enough photometry is available, one can account for brightness changes due to shape, rotation, and aspect changes by moving to a reference phase function, which can be directly compared with the phase functions of other objects. (Muinonen et al. 2020, Martikainen et al. 2021, Wilawer et al. 2022)

We derive the reference phase functions for ~2750 asteroids with models derived by Ďurech et al. (2020) using ATLAS photometric data. As a result, for each object, we will derive two  reference phase functions: one for each ATLAS filter.

This work has been supported by grant No. 2017/25/B/ST9/00740 from the National Science Centre, Poland.

References

Ďurech, J., J. Tonry, N. Erasmus, L. Denneau, A. N. Heinze, H. Flewelling, and R. Vanco. ‘Asteroid Models Reconstructed from ATLAS Photometry’. Astronomy & Astrophysics 643 (November 2020): A59. https://doi.org/10.1051/0004-6361/202037729.

Heinze, A. N., J. L. Tonry, L. Denneau, H. Flewelling, B. Stalder, A. Rest, K. W. Smith, S. J. Smartt, and H. Weiland. ‘A First Catalog of Variable Stars Measured by the Asteroid Terrestrial-Impact Last Alert System (ATLAS)’. The Astronomical Journal 156, no. 5 (November 2018): 241. https://doi.org/10.3847/1538-3881/aae47f.

Mahlke, Max, Benoit Carry, and Larry Denneau. ‘Asteroid Phase Curves from ATLAS Dual-Band Photometry’. Icarus 354 (January 2021): 114094. https://doi.org/10.1016/j.icarus.2020.114094.

Martikainen, J., K. Muinonen, A. Penttilä, A. Cellino, and X.-B. Wang. ‘Asteroid Absolute Magnitudes and Phase Curve Parameters from Gaia Photometry’. Astronomy & Astrophysics 649 (May 2021): A98. https://doi.org/10.1051/0004-6361/202039796.

Muinonen, K., J. Torppa, X.-B. Wang, A. Cellino, and A. Penttilä. ‘Asteroid Lightcurve Inversion with Bayesian Inference’. Astronomy & Astrophysics 642 (October 2020): A138. https://doi.org/10.1051/0004-6361/202038036.

Wilawer, E, D Oszkiewicz, A Kryszczyńska, A Marciniak, V Shevchenko, I Belskaya, T Kwiatkowski, et al. ‘Asteroid Phase Curves Using Sparse Gaia DR2 Data and Differential Dense Light Curves’. Monthly Notices of the Royal Astronomical Society 513, no. 3 (May 2022): 3242–51. https://doi.org/10.1093/mnras/stac1008.

How to cite: Wilawer, E., Oszkiewicz, D., Kryszczyńska, A., Muinonen, K., MacLennan, E., and Uvarova, E.: Asteroid reference phase functions from the ATLAS photometry, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-1000, https://doi.org/10.5194/epsc2022-1000, 2022.

So far all the comets that have been visited by a spacecraft were short period comets and as such their surfaces have been altered by sublimation processes. Comet Interceptor is a new F-class mission developed by the European Space Agency. The objective of the Comet Interceptor mission is to observe a dynamically new comet or an interstellar object. Comets are thought to be relicts from the formation of our solar system and as such observing a more pristine object could give new insight in the planet formation process. Comet Interceptor will be build and potentially launched before the target object has been found, because the warning times of the arrival of such objects would be too short to intercept them otherwise. For this reason the dust environment around the nucleus is difficult to constrain during the development of the mission [1].
As described in several publications ([2],[3],[4]) the dust hazard assessment will be crucial for the success of the Comet Interceptor mission. The goal of the presented work is to develop a tool that models the dust environment of a comet and can estimate the total amount of impacting particles and the total mass of the impacting particles along a chosen trajectory. We build our model to be flexible enough to enable further usage in future cometary missions. To allow for an efficient information of the user we are aiming to keep the running time of the model as low as possible, while providing an accurate estimation of the dust hazard for a wide range of scenarios. Our model is accounting for solar radiation pressure based on the scattering properties of the dust particles, emission angle dependent dust production rates and outflow velocities and variability in the dust production rate with the rotation of the nucleus. The size distribution of the particles will be treated by using logarithmic size bins and calculating the number densities of each bin. Our model will also be able to derive an Afρ value based on the scattering properties and the dust number densities, which then can be compared to ground based observations. Using a simplified case we can show, that our model is in good agreement with an analytical fountain model (see [5]). Further, we will compare our model with measurements made during the Giotto mission [6] and the engineering dust coma model [3].

Acknowledgement
This work has been carried out within the framework of the National Centre of Competence in Research PlanetS supported by the Swiss National Science Foundation. The authors acknowledge the financial support of the SNSF.

References
[1] Colin Snodgrass & Geraint H. Jones, The European Space Agency’s Comet Interceptor lies in wait. Nat Commun 10, 5418 (2019). https://doi.org/10.1038/s41467-019-13470-1
[2] Nico Haslebacher, Selina-Barbara Gerig, Nicolas Thomas, Raphael Marschall, Vladimir Zakharov \& Cecilia Tubiana, A numerical model of dust particle impacts during a cometary encounter with application to ESA’s Comet Interceptor mission, Acta Astronautica, Volume 195, 2022, Pages 243-250, ISSN 0094-5765, https://doi.org/10.1016/j.actaastro.2022.02.023.
[3] Raphael Marschall, Vladimir Zakharov, Cecilia Tubiana, Michael S. P. Kelley, Carlos Corral van Damme, Colin Snodgrass, Geraint H. Jones, Stavro L. Ivanovski, Frank Postberg, Vincenzo Della Corte, Jean-Baptiste Vincent, Olga Muñoz, Fiorangela La Forgia, Anny-Chantal Levasseur-Regourd and the Comet Interceptor Team, Determining the dust environment of an unknown comet for a spacecraft fly-by: The case of ESA's Comet Interceptor mission, Astronomy & Astrophysics, under review, 2022
[4] Valentin Preda, Andrew Hyslop & Samir Bennani, S. Optimal science-time reorientation policy for the Comet Interceptor flyby via sequential convex programming. CEAS Space J 14, 173–186 (2022). https://doi.org/10.1007/s12567-021-00368-2
[5]  Neil Divine, H. Fechtig, T. I. Gombosi, M. S. Hanner, H. U. Keller, S. M. Larson, D. A. Mendis, Ray L. Newburn, JR., R. Reinhard, Z. Sekanina & D. K. Yeomans, The comet Halley dust and gas environment, Space Science Reviews (ISSN 0038-6308), vol. 43, Feb. 1986, p. 1-104., 1986
[6] P. Edenhofer, M. K. Bird, J. P. Brenkle, H. Buschert, E. R. Kursinki, N. A. Mottinger, H. Porsche, C. T. Stelzried, and H. Volland. Dust Distribution of Comet p/ Halley’s Inner Coma Determined from the Giotta Radio Science Experiment. Astronomy and Astrophysics, 187:712, November 1987

How to cite: Haslebacher, N., Thomas, N., and Marschall, R.: Time efficient modelling of cometary dust environments to support future cometary mission planning and operations, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-783, https://doi.org/10.5194/epsc2022-783, 2022.

Introduction:

The properties of icy surfaces in the Solar System evolve under the effect of numerous processes either external, internal or induced by the climate. Thanks to spaceborne remote sensing data, we have access to the current microphysical and compositional state of ices (see for instance Cruz Mermy et al 2022, EPSC [1]) but quantifying the numerous mechanisms involved remains challenging. To study these surfaces hard to access, our goal is to build a one-dimensional numerical model of planetary ices evolving over time.

This task consists in creating an unprecedented innovative tool general to many icy surfaces in the solar system, similar to what the SNOWPACK model does for Earth snow evolution (Tuzet et al., 2017 [2]). These simulations would predict ice microphysics within a depth of a few meters evolving on multiple seasons. They will integrate multiple physical processes (heat transfers, phase changes, surface energy balance, ice grains metamorphism and spatial weathering) acting on the ice layers and couple them with each other.

The numerical scheme will be designed to be versatile enough to activate/deactivate each physical process parametrization. When possible, several approximations of each process will be designed in order to better control numerical efficiency versus realism. Several pieces are already present in the literature, but the novelty and extremely promising nature of the present approach is to encompass them all, since they all contribute to the evolution of ices with potentially similar time and length scales.

We would like to present the thermic module which gives the evolution of the temperature profile of the ice for different layers of variable properties. Previous models have been designed to estimate the thermal transfer in the subsurface, such as LMD 1D (Forget et al, 1999 [3]), KRC (Kieffer et al., 2013 [4]), THERMPROJRS (Spencer et al. 1989 [5]). Among them, some have been designed to model Earth snow evolution, such as SNTHERM (Jordan, 1991 [6]) and SNOWPACK (Tuzet et al., 2017 [2]). Here, we propose to follow the standard heat equation but solve it numerically for non-constant heat properties, especially with time and depth dependent thermal inertia.

Methods:

In this model, the boundary condition is given by the energy equilibrium at the surface: the incoming absorbed solar flux is balanced by the black body emission and the heat flux from the ground. The thermic properties of the materials can be depth and time dependent. We have discretized the heat equation in these conditions and solved the system of equations with an implicit solver.

The spatial grid representing space is discretized as a vector which starts at the planet’s surface and ends such that the zero-flux condition at the bottom is respected. In terms of time discretization, we run the algorithm several sideral days, with a thousand timesteps each. The aim is to validate the algorithm by comparing with analytical and standard numerical solutions.

Results

Validation of our algorithm by comparison with well-known analytic solutions of the heat equation is possible in specific conditions. For a material of constant conductivity, density and heat capacity, the one-dimensional heat equation can be solved analytically for a given set of initial and boundary conditions. In particular, for an initial step function profile bounded in a box with no flux at the boundaries, the solution can be expressed as a Fourier Series which is obtained through separation of variables. Results show a perfect fit between the numerical and analytical solutions which proves that our model works well for a material with constant properties (see figure 1).

Figure 1:  Comparative evolution of the temperature profiles.

In more complex cases, in particular when the heat conductivity is depth dependent, analytical solutions of the heat equation do not exist. In these cases, validation of the model comes from comparison with experimental data or from other previously well-established numerical algorithms. Here we choose to compare our method with Spencer’s explicit algorithm for realistic planetary surface conditions (Spencer et al. 1989).

To compare these two models, one must make sure that the initial conditions are the same. Notably, the solar flux responsible for the temperature evolution must be equal. In this fairly simple insolation model Spencer chose to approximate the heating of a planet surface by the Sun throughout a sidereal day by a sinusoidal function. The resulting total surface flux is the equilibrium between the solar flux and the surface black body emission. Results show that the two flux are identical (see figure 2).

Figure 2: Evolution of the surface flux during multiple days (Blue).

For the sake of validation, values of density, heat capacity and conductivity were varied as a function of depth by the largest scales allowed by Spencer’s explicit scheme stability criteria (see figure 3).

Figure 3: Depth dependant properties profiles.

These results show that our implicit model is fully compatible with Spencer’s explicit algorithm, without the restrictions of stability (see figure 4). Using an implicit model will greatly help us to choose our own set of parameters.

Figure 4: Comparative evolution of Spencer’s temperature profile (Blue
lines), and our implicit scheme temperature profiles (Red lines).

Conclusion and Perspectives

We implemented an implicit numerical scheme in Python to solve the heat transfer equation in a layered medium. It has been validated by comparison with analytical solutions and a reference numerical implementation. Our implicit scheme solver of the heat equation has the advantage of ensuring stability and convergence regardless of the material’s properties.

Now we plan to extend our simulation by coupling other processes acting on ice microphysics like ice grains metamorphism. We also plan to use this algorithm to retrieve surface properties in infrared and radar wavelength.

References:

[1] Cruz-Mermy et al., 2022, EPSC 2022

[2] Tuzet et al., 2017, The Cryosphere, 11

[3] Forget et al, 1999, JGR, 104

[4] Kieffer et al., 2013, JGR, 118

[5] Spencer et al. 1989, Icarus, 78

[6] Jordan, 1991, Documentation SNTHERM, 89

How to cite: Mergny, C. and Schmidt, F.: Numerical modeling of thermal wave in layered icy surface, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-592, https://doi.org/10.5194/epsc2022-592, 2022.

• Introduction

The characterization of the complex magnetic susceptibility (real and imaginary parts) of rocks is an unexplored tool to constrain the composition, structure and geological history of rocks in surface planetary exploration. We propose the NEWTON susceptometer for the determination of the complex magnetic susceptibility, to provide valuable information about the regolith and surface rocks in rocky bodies of the solar system, to be used as a selection criterion of rocks for sample return missions or for the in-situ scientific studies of the magnetic properties during planetary missions [1]. The instrument is based on AC - inductive methods, and its dynamic range of the real susceptibility covers magnetic susceptibility values for rocks from the Earth, Moon and Mars [2, 3, 4]. The sensor is suitable to be placed on board rovers, or to be used as a portable device during field campaigns and by astronauts in manned space missions. This sensor provides a great advantage compared to available commercial susceptometers due to its robustness, compatibility with the planetary environments and that it does not require sample preparation, but only minimum sample dimensions (~50 x 20 x 20 mm). 

The aim of this work is to test the capability of the instrument in two different scenarios with distinct types of samples representative of a wide susceptibility range: 1) the in-situ real magnetic susceptibility determination in Cerro Gordo volcano, considered as a terrestrial analogue [5]; and 2) the characterization of meteorites from the collection of the Museo Geominero (Madrid, Spain).

The first study case consists of an intraplate volcano, with potential similar composition and structure of volcanoes from Mars. The second study case comprises various meteorite samples of different origins. 

2.1 Terrestrial analogue: Cerro Gordo volcano

Cerro Gordo volcano was proposed as a Martian analogue due to its structural similarities with Martian volcanoes. It lies to the SW of Almagro (38°49’13”N/3°44’37”W), within the Campo de Calatrava volcanic region in Spain [6], and is emplaced among Paleozoic host rocks where the Armorican quartzite yields the topographic heights.

Cerro Gordo is part of a volcanic lineation, all of olivinic nefelinite composition and thought to have erupted coevally (1.5 ± 0.3 Ma [7]), that follows a NNE-SSW fracture [8]. Its eruptive style varied with time from phreatomagmatic to strombolian and phreatomagmatic again to end with an effusive phase [9]. For this reason the deposits found in the field (pyroclastic surge deposits, lahar facies, scoria and pyroclastic deposits, a lava flow, tuffs, breccias and spatter deposits) are varied in composition and structure, and therefore comprise a large range of magnetic susceptibility values,  making Cerro Gordo an excellent scenario for a demonstration campaign of the susceptometer prototype.

2.2 Meteorites

A total of 16 meteorites of different compositions, and therefore varied susceptibility ranges, have been measured for this work, 10 aerolites and 6 siderites. The criteria followed was that their volume accomplished the minimum size stated in the introduction. The samples were divided into faces and measured twice in each of them. In the case of the siderites showing a flat polished face with Widmanstätten structures, the polished face was measured in two orthogonal directions to test the possible influence of the internal structural ordering.

• Conclusions

Previous results from Cerro Gordo showed the capability of the magnetic susceptibility results to distinguish between different rock deposits. The ongoing work on the collected samples analysis and geological description of the study location is intended to relate the magnetic susceptibility values with the mineral composition of the rocks, enhancing the comprehension of the susceptibility measurements and the structure of the volcano. The measurements on meteorites are currently under analysis, and aim to classify the measured samples as a function of their magnetic susceptibility [10].

Acknowledgements:

This work has been funded by the Spanish Programme for Research, Development and Innovation under the grants of references ESP2017-88930-R and PID2020-119208RB-I00: MagAres and MINOTAUR, respectively, as well as the European Union Project NEWTON, of grant agreement 730041. JSO is funded by the European Union’s Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement SIGMA no 893304.

References:

[1] Díaz Michelena et al. 2017, Sensor Actuat A-Phys, vol. 263, pp. 471-479

[2] Rochette et al. 2005, Meteoritic and Planetary Science, 40 (4): 529–540

[3] Rochette 2010, Earth Planet. Sci. Lett., 292: 383–391.

[4] Hunt et al. 2013, Wiley. Online Library. DOI: 10.1029/RF003p0189.

[5] Monasterio et al. 2021, Terrestrial Analogs Conference (LPI Contrib. No. 2595)

[6] Becerra-Ramírez et al. 2020, Geosciences, 10, 441.

[7] Ancoechea & Huertas 2021, J. Iberian Geology (47): 209-223.

[8] Ancoechea 1999, Enseñanza de las Ciencias de la Tierra (73): 237-243.

[9] González et al. 2010, Aportaciones Recientes en Volcanología 2005-2008: 57-65.

[10] Rochette et al. 2003, Meteoritics & Planet. Sci., 38: 251-268.

How to cite: Mesa Uña, J. L., Losantos, E., Oliveira, J. S., G. Monasterio, Ó., and Díaz Michelena, M.: Testing the applicability of NEWTON Susceptometer for fast and in-situ determination of the magnetic susceptibility, in meteorite samples and a Martian terrestrial analogue., Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-827, https://doi.org/10.5194/epsc2022-827, 2022.

In this abstract we discuss a proposal for a microgravity flight campaign within which we will investigate penetrometry in a microgravity environment. Understanding the mechanical properties of solar system minor bodies is essential for understanding their origin and evolution. Past missions such as Hayabusa-2 and OSIRIS-REX have landed on asteroids and taken samples to discover what these bodies are made of. However, there has been conflicting evidence and reports into the physical properties of the granular surface material of these bodies. With future missions such as JAXA’s MMX mission travelling to Phobos to take a sample of the body the results from this campaign will be very important to that and future missions. Penetrometry, i.e. the determination of the reaction force an object experiences as it penetrates into a surface, can help to understand the essential properties regarding regolith such as grain size, grain shape, cohesion and bulk density. The usage of penetrometry however has mostly been limited ground-based studies such as soil sciences or even cheese maturation. Very little is known about the underlying physics of penetrometry. Results of penetrometry experiments are largely analysed based on empirical models, which presents us with a challenge if we want to apply the same parameters to understand granular materials on asteroid surfaces. Obviously, gravity cannot be eliminated in the laboratory. Hence, it is essential to verify penetrometry as a method and validate penetrometry instrument designs in microgravity.

For this purpose, we propose a parabolic flight campaign. Our experiment will test the use of penetrometry in asteroid-analogue environments by investigating samples with varying properties such as grain size and shape. The microgravity aspect of the experiment is one of the most important factors because it enables us to correlate laboratory experiments at 1g with identical setups in a gravity regime relevant to asteroids. The proposed experimental setup will include a variety of samples with varying grain sizes, grain shapes, porosities and grain size distributions. The penetrometer used will also have varying properties such as the diameter, shape, and velocity of penetration. A robotic arm will push a penetrometer into the samples to measure the reaction force which can then be used to determine the mechanical properties of the samples. By varying the samples and penetrometer properties it will be possible to better understand the relevant parameters affecting reaction force. The suitability of the setup will also be reviewed to understand its usage and applicability in microgravity environments such as the robotic arm that will be used. All of the experiments carried out during the parabolic campaign will also be done at 1g to compare the tests in varying gravity levels. With a better understanding of the science behind penetrometry and the effects of microgravity, future missions will be better prepared and be able to use penetrometry more effectively to understand small-body surfaces.

How to cite: Moore, A., Hagermann, A., Kaufmann, E., Granvik, M., Barabash, V., Murdoch, N., Sunday, C., Miyamoto, H., Ogawa, K., and Soria-Salinas, A.: Penetrometry in Microgravity- From Brie to Bennu, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-178, https://doi.org/10.5194/epsc2022-178, 2022.

The impact processes are ubiquitous in the solar system, as one of the fundamental mechanisms driving the evolution of asteroids and comets^[1]. From small meteorite impacts to gigantic Moon-forming collisions^[2], the impact cratering formation holds key insights pointing out the dynamic history of our solar system from 4.5 billion years ago. Thanks to the rapid progress in numerical modeling and computational resources, high-resolution numerical models offer a powerful framework for expanding our knowledge of the impact cratering phenomena. Meanwhile, planetary defense missions have steeply advanced in characterizing Near-Earth Objects (NEO), such as NASA's upcoming DART mission^[3], which will deflect the orbit of Dimorphos through a kinetic impactor. A few years after the DART impact, the Hera mission by European Space Agency (ESA)^[4] will rigorously portray the consequences of the collision, from cratering to exploring the interior and dynamics. Several numerical efforts have recently provided significant insights on impact cratering and ejecta dynamics in response to the DART impactor. Raducan et al. (2019)^[5], for example, have comprehensively reported several factors that affect the Dimorphos' response, from target layering and strength^[6] to the projectile obliquity^[7]. In the present study, after verifying our results using the impactor/target constraints^[5-7], we have further examined the consequences of DART impact, focusing more on the impact-generated porosity and gravity anomalies. To accomplish this, we performed hypervelocity impact simulations by the iSALE2D shock physics code^[8-10] set up for a variety of target scenarios, ranging from low-cohesion gravity-dominated to high-cohesion stress-dominated regimes. Our simulation results shed new light on the detailed picture of cratering formation in the aftermath of the DART impact.

Figure 1: DART impact-generated gravity and density distribution on asteroid Dimorphos.

References

^[1] Holsapple, K. A. (1993). The scaling of impact processes in planetary sciences. Annual review of earth and planetary sciences, 21(1), 333-373.

^[2] Wada, K., Kokubo, E., & Makino, J. (2006). High-resolution simulations of a Moon-forming impact and postimpact evolution. The Astrophysical Journal, 638(2), 1180.

^[3] Michel, P., Küppers, M., & Carnelli, I. (2018). The Hera mission: European component of the ESA-NASA AIDA mission to a binary asteroid. 42nd COSPAR Scientific Assembly, 42, B1-1.

^[4] Cheng, A. F., Rivkin, A. S., Michel, P., ... & Thomas, C. (2018). AIDA DART asteroid deflection test: Planetary defense and science objectives. PSS, 157, 104-115.

^[5] Raducan, S. D., Davison, T. M., Luther, R., & Collins, G. S. (2019). The role of asteroid strength, porosity and internal friction in impact momentum transfer. Icarus, 329, 282-295.

^[6] Raducan, S. D., Davison, T. M., & Collins, G. S. (2020). The effects of asteroid layering on ejecta mass-velocity distribution and implications for impact momentum transfer. PSS, 180, 104756.

^[7] Raducan, S. D., Davison, T. M., & Collins, G. S. (2022). Ejecta distribution and momentum transfer from oblique impacts on asteroid surfaces. Icarus, 374, 114793.

^[8] Amsden, A., Ruppel, H., and Hirt, C. (1980). SALE: A simplified ALE computer program for fluid flow at all speeds. Los Alamos National Laboratories Report, LA-8095:101p. Los Alamos, New Mexico: LANL.

^[9] Collins, G. S., Melosh, H. J., and Ivanov, B. A. (2004). Modeling damage and deformation in impact simulations. Meteoritics and Planetary Science, 39:217--231.

^[10] Wünnemann, K., Collins, G., and Melosh, H. (2006). A strain-based porosity model for use in hydrocode simulations of impacts and implications for transient crater growth in porous targets. Icarus, 180:514--527.

How to cite: Senel, C. B. and Karatekin, O.: Hypervelocity impact simulations of DART on asteroid Dimorphos: Impact-generated porosity and gravity anomalies, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-404, https://doi.org/10.5194/epsc2022-404, 2022.

Asteroids have inhabited the Solar System since its formation, and some of them may pose risks to life on Earth due to the possibility of collision with our planet. The most emblematic case of a catastrophic impact, with very significant implications for life, is the asteroid that struck the Earth 66 million years ago, forming the Chicxulub crater in the Gulf of Mexico, and causing the extinction of about 75% of all life forms on Earth. But despite this and several other events that continue to occur on smaller scales, this theme is rarely addressed by sciences, especially in Brazil. When approached by the press, it is usually under an alarmist and poorly grounded from the point of view of science. 

This research aimed to analyze the level of awareness related to the importance of planetary defense among university students, as well as on ways to properly communicate the characteristics and risks related to this phenomenon to society. Besides searching for ways to defend the Earth from a possible future cosmic impact, one of the main goals of Planetary Defense is to make the population aware of its characteristics, frequency of occurrence, risks and consequences. 

We focused on this subject using Science communication strategies, such as the creation of an Instagram page, where it was sought and perfected to put together posts about Planetary Defense in a simple way to reach non-specialist audiences. Thus, forms and languages have been sought to convey the facts surrounding meteoritic impacts in a way that they can be understood by the population, thus attracting the necessary attention and avoiding possible misinformation and/or panic. 

We employed a semi-quantitative methodology that begins by presenting what asteroids and comets are, showing simulations of large impact events, and detailing physical phenomena arising from encounters between asteroids and the Earth. Measures to protect the planet were also analyzed and how institutions such as NASA (National Space Agency, United States) and ESA (European Space Agency, European Community) have contributed with research and equipment for planetary defense.

In addition, we combined this methodology with a semi-structured survey questionnaire. The survey was aimed at investigating society's perception of the potential risks of impacts of celestial bodies against the Earth, using students enrolled at the State University of Campinas (Unicamp, Brazil). as a sampling population. 

The survey´s results refer to a total 150 responses, Fig. 1 shows that the large majority of the UNICAMP’ students don’t have previous knowledge of the concept of Planetary Defense, and that they also do not consider the topic as relevant. This shows the need for awareness dissemination regarding the risk of asteroid impacts, the only natural disaster that can be predicted in advance.

Figure 1: Survey questionnaire about society's perception of the potential risks of impacts of celestial bodies against the Earth.

As part of the study, a series of activities were developed at the University of Campinas to mark Asteroid Day 2022, celebrated annually on June 30th. During two days, a number of guest speakers presented topics related to Planetary Defense to an audience comprising Unicamp´s students and faculty members, as well as the general public, mostly high-school students and school teachers. The results contributed significantly for raising the awareness about planetary defense and for disseminating the scientific knowledge on asteroid impacts and their risk to Earth and to humankind.

Still part of Asteroid Day 2022, a series of interactive activities were developed with children at the city of Campinas Planetarium. These included workshops on rocket launching towards "asteroids", for transmitting the concept of the DART Mission to the kids and their parents. Presentations were also made on general themes about planetary sciences, as well as an astrophotography workshop held at the Campinas Municipal Observatory.

Although the study is still in progress, our preliminary conclusions are that there is very scarce knowledge of what Planetary Defense is, or recognition of its importance, even among higher education students of one of the most prestigious universities in Brazil. This shows how much Planetary Sciences are undervalued, and particularly, the theme of Planetary Defense. We expect that, by the end of this study, adequate ways will be exploited for disseminating knowledge on these topics.

How to cite: Mistro, M. E. T., Crosta, A. P., Costa, J. O. P., and Schmidt, S. C.: Planetary Defense: Public Perception and How to Communicate, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-682, https://doi.org/10.5194/epsc2022-682, 2022.

The size distribution of solids in the protoplanetary disk is still ill constrained [1] but is a vital parameter that influences planetary growth [2]. The typical size and spatial distribution of solids evolves throughout the planet formation process via collisions and radial drift. As the planets grow, they excite the mutual random velocities among planetesimals making their mutual collisions destructive which leads to fragmentation, reducing their typical size. This effect of self-interacting planetesimals has been found to inhibit or favor the formation of planets due to competing effects of easier accretion of smaller fragments and depletion by gas-drag induced drift [3-4]. However, previous studies have either focused on single planets and systems or have neglected concurrent effects like migration.

Therefore, we run planet formation simulations with the generation III Bern model [5] with a Eulerian 1D solid disks. The model tracks the growth and evolution of several planetary embryos from oligarchic growth to the final planetary system. We added to it a fragmentation toy model [6] to see the impact fragmentation has on planet formation. To see its influence on the diverse types of exoplanets we make use of a population synthesis approach to investigate larger parts of the parameter space [7]. This allows us to have a more complete picture of what influence the collisional evolution of planetesimals has on planet formation and to study the effects that arise from its interplay with the formation of multiple planets in the same system.

In figure 1, we show two exemple synthetic planet populations of 1000 systems with (right) and without (left) the added fragmentation model. We find multiple interesting features in our synthetic populations that arise from the fragmentation of planetesimals. The fragmentation lends more importance to specific locations in the disk where growth is enhanced like the ice line and the inner disk. In addition, it enhances the formation of giants.

In conclusion, there are significant differences in synthetic populations when including or neglecting fragmentation. This suggests that the addition of fragmentation to global planet formation models is important as a self-consistent solid disk description is vital to understand planet formation.

In figure 1. Comparison of a synthetic exoplanet population without (left) the added fragmentation model and one with (right).  The semi major axis (in AU – log scale) is plotted on the x-axis and the planetary mass (in Earth masses – log scale) on the y-axis. Both populations are shown at an age of 5 Gyr. The Red points refer to planets with more envelope than core mass, the blue ones are icy planets (ice mass fraction larger than 1%) and the green points are rocky planets (ice mass fraction smaller than 1%).

References:

[1] Helled, R. & Morbidelli, A. 2021, in ExoFrontiers (IOP Publishing)

[2] Fortier, A., Alibert, Y., Carron, F., Benz, W., & Dittkrist, K.-M. 2012, A&A, 549, A44

[3] Guilera, O. M., de Elía, G. C., Brunini, A., & Santamaría, P. J. 2014, A&A, 565, A96

[4] Chambers, J. 2008, Icarus, 198, 256

[5] Emsenhuber, A., Mordasini, C., Burn, R., et al. 2021, A&A, 656, A69

[6] Ormel, C. W. & Kobayashi, H. 2012, The Astrophysical Journal, 747, 115

[7] Emsenhuber, A., Mordasini, C., Burn, R., et al. 2021b, A&A, 656, A70

How to cite: Kaufmann, N. and Alibert, Y.: A population level study on the influence of planetesimal fragmentation on planet formation, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-135, https://doi.org/10.5194/epsc2022-135, 2022.

The protoplanetary disk (PPD) is a complex structure. It is the birth place of protoplanetary systems. The interaction of growing planets and its surrounding PPD is also complex and not fully understand by now. The many different physical processes going on in the PPD over its life time, like accretion, outbursts, planet formation, etc. impact its evolution and structure. The evolution of such a PPD with a growing planet, implemented as a sink term, is simulated by the TAPIR code.  It is an 1+1D implicit code. Due to the fact that TAPIR is an implicit code the time steps are not restricted by the CFL-conditions, therefore it is able to simulate over the whole lifetime of a PPD and examine the evolutionary behaviour of the protoplanetary disk and the influence of a forming protoplanet on it. The results show the gap formation due to mass accretion onto the planet and impact of this sink term on the total disk mass, disk lifetime and accretion rat onto the star. Also the impact of accretion bursts on the accretion rate of the planet is discussed. If the planet is placed in the dead zone the presence of outbursts leads to a quite faster planet growth since the bursts rearranges the disk structure.

How to cite: Ringseis, I.: Impact of growing planets on the evolution of protoplanetary disks, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-1104, https://doi.org/10.5194/epsc2022-1104, 2022.

Observing dynamical interactions between planets and disks is key to understanding their formation. Two protoplanets have recently been observed within PDS 70's transition disk, along with an extended signal towards the north-west of the star. In this contribution, I will present a temporal analysis of the PDS 70 disk morphology with the aim of assessing whether it could trace a spiral arm caused by the dynamical interaction between the planet PDS 70 c and the disk - or rather be the footprint of a vortex, which can mimic a spiral-arm in an inclined disk. I will show the PDI and ADI images obtained with SPHERE-IRDIS spanning 6 years of observations. We reduced PDI datasets through the IRDAP polarimetric data reduction pipeline (for PDI data) and a novel algorithm that we developed (MUSTARD, for ADI data). I will explain the principle of our inverse-problem based MUSTARD algorithm. I will then show the trace of the potential spiral that we inferred by identifying local radial maxima in azimuthal slices of the disc in each dataset. I will then compare the measured traces with the expected motion of a spiral launched by planet c - i.e. in rigid-body motion. I will show how the traces seem to perfectly align in all datasets, and will finally discuss the implications of our results on the nature of this extended feature.

How to cite: Juillard, S., Christiaens, V., Absil, O., and Benisty, M.: A Spiral arm or a Vortex in the outer disk of PDS-70 ?, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-942, https://doi.org/10.5194/epsc2022-942, 2022.

The Habitable Zone (HZ) can be considered plainly as a measure of the potential of planetary habitability or as the parametric region about a star in which surficial water is deemed to be stable on a planet. This potential stability is a direct result of host star flux and effective radiative cooling mechanisms in accordance with the atmospheric greenhouse effect of orbiting planets. This stellar flux varies in conjunction with the temporal evolution of the host star.

Hence, we conduct the modelling of the Main Sequence (MS) and pre-MS phases of HZ evolution in order to characterise the habitability of 6 exoplanetary systems with FGK-Type host stars. In addition to this, 1 M⊙ hypothetical stars were modelled with fluctuating albedo and metallicity values to characterise the relationship of certain stellar and planetary parameters on temporal HZ evolution, to better calibrate the characterisation of exoplanet habitability in general for a diverse range of planets. This is a tool to allow us to make predictions about when or if these planets modelled are potentially habitable now, have previously been or will be in the future.

Our model simulations allow us to recommend certain exoplanets for further characterisation due to their potential current (or previous) orbit within their respective HZ, assuming they are currently considered or found to be rocky planets. These planets include Tau Ceti e, HD 40307g, Kepler 62f and e. Techniques that could be used to investigate these planets may be characterisation of their atmospheres for biosignatures using modelling of atmospheric composition to evaluate their habitability further, as situation within the HZ does not necessarily mean a planet is habitable. HZ planets, in relatively close proximity to the Earth and situated far enough from their host star to be resolved, should be probed using direct imaging to investigate surface environments, critical near-surficial conditions that may influence the stability of liquid water.

Potential future telescopes suitable for these recommendations would be the Habitable Exoplanet Imaging Mission (HabEx) and the Large Ultraviolet Optical Infrared Surveyor (LUVOIR) (Arney et al., 2018).

A major conclusion from the investigation of a 1 M⊙ hypothetical star reveals the potential for a closer inner HZ edge than formerly estimated (0.325 AU from the host star when albedo (A) = 0.9 in this work). The repercussions of this updated estimate imply that if a closely orbiting planet with a high albedo is found to orbit its host star, it may still be habitable and should not be neglected in terms of its habitability prospects. This also extends the frequency of habitable exoplanets if the inner edge of the HZ truly can exist at close proximity to the host star in question, having repercussions on exoplanet characterisation as a whole if these HZ distances can be replicated in subsequent works or verified by rocky exoplanet observations.

Furthermore, our results reinstate that a tidal-locking scenario is likely to shorten the width of the HZ significantly and draw it closer to the host star – introducing constraints for rocky bodies that may be considered habitable. This is significant when considering planets orbiting beyond the inner edge of the HZ and re-evaluation of their habitability may be necessary once atmospheric, albedo and other orbital data for exoplanetary systems can be determined.

Previous HZ publications have centred around MS habitability (Kasting et al., 1993; Kopparapu et al., 2013), yet the temporal evolution of the HZ is becoming more widely recognised as fundamental in evaluating habitability as a whole (Ramirez and Kaltenegger, 2014; Danchi and Lopez, 2013). Pre-MS evolution is a deciding factor as to whether planets are still habitable during the MS phase – planets within the pre-MS HZ are unchartered targets in the search for habitable worlds or even as tools to decipher habitable planet diversity and early water delivery mechanisms. Such results should be utilised as a first order estimation of exoplanetary habitability.

To summarise, there is still significant progress left to be made in calculating reliable HZ boundaries and to then characterise the habitability of planets orbiting within them. Nevertheless, these HZ boundaries serve as a critical basis for the assessment of the habitability of modelled exoplanetary systems. Such works are beneficial as they may result in the detection of habitable exoplanets suitable for observational follow-ups, or even to the eventuality of discovering evidence for extra-terrestrial life.

References:

• Arney, G., Batalha, N., Cowan, N., Domagal-Goldman, S., Dressing, C., Fujii, Y., Kopparapu, R., Lincowski, A., Lopez, E., Lustig-Yaeger, J. and Youngblood, A., 2018. The Importance of Multiple Observation Methods to Characterize Potentially Habitable Exoplanets: Ground-and Space-Based Synergies. arXiv preprint arXiv:1803.02926.
• Danchi, W.C. and Lopez, B., 2013. Effect of Metallicity on the Evolution of the Habitable Zone from the Pre-main Sequence to the Asymptotic Giant Branch and the Search for Life. The Astrophysical Journal, 769(1), p.27.
• Kasting, J., Whitmire, D. and Reynolds, R., 1993. Habitable Zones around Main Sequence Stars. Icarus, 101(1), pp.108-128.
• Kopparapu, R., Ramirez, R., Kasting, J., Eymet, V., Robinson, T., Mahadevan, S., Terrien, R., Domagal-Goldman, S., Meadows, V. and Deshpande, R., 2013. HABITABLE ZONES AROUND MAIN-SEQUENCE STARS: NEW ESTIMATES. The Astrophysical Journal, 765(2), p.131.
• Ramirez, R.M. and Kaltenegger, L., 2014. The habitable zones of pre-main-sequence stars. The Astrophysical Journal Letters, 797(2), p.L25.

How to cite: Hogan, J.: Characterising the Potential for Planetary Habitability: A Study of the Temporal Evolution of Exoplanet Habitable Zones, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-369, https://doi.org/10.5194/epsc2022-369, 2022.

Convective mantle flow of terrestrial planets is governed by a temperature- and pressure-dependent rheology. This results in a stagnant-lid regime observed on most terrestrial planets. Plastic deformation can lead to breaking of the strong upper lithosphere, which resembles plate tectonics on Earth.

Most efforts to model mantle convection with self-consistent plate tectonics combine Newtonian power-law with a stress-dependent pseudo-plastic rheology.
In the uppermost mantle, where stresses are high, deformation is thought to be driven partly by dislocation creep. This is often neglected in viscoplastic consideration, which employ purely diffusion-creep-driven flow combined with a yield criterion.

In our models we employ an effective viscosity law combining both Newtonian and Non-Newtonian power laws with a pseudo-plastic model. We study the influence of rheology in combination with grain size and different yield stress parameterizations on the likelihood of the on-set of plate tectonics in a 2D-spherical annulus geometry. We compute common diagnostic values related to the characterization of a mobilized surface. With this model we aim at identifying key planetary factors for the occurrence or absence of plate tectonics. 

How to cite: Henke-Seemann, O. and Noack, L.: Critical factors for plate tectonics on rocky planets, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-585, https://doi.org/10.5194/epsc2022-585, 2022.

Benzene is the simplest organic compound with a 6-carbon aromatic ring. As such, it was used as a first order representative of aromatic compounds in planetary atmospheres. These compounds can be brought by asteroid impacts into rocky planetary atmospheres, where they can serve as precursors for further synthesis. Our experiments show that benzene vapours in nitrogen-dominated atmospheres subjected to asteroid impacts (modelled by laboratory laser shots) lead to the formation of acetylene and hydrogen cyanide. Both these products appear in many proposed mechanisms of prebiotic chemistry.

How to cite: Knížek, A. and Petera, L.: The stability of benzene in planetary atmospheres, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-830, https://doi.org/10.5194/epsc2022-830, 2022.

The ICAPS experiment (Interactions in Cosmic and Atmospheric Particle Systems) was part of the Texus-56 sounding rocket flight in November of 2019. ICAPS studies the agglomeration of 1.5 µm-sized, monomeric silica grains under microgravity conditions, as would be present in the early stages of dust growth in protoplanetary disks, which our study aims at describing.

For this, a cloud of dust was injected into a vacuum chamber with ~7000 monomer grains per mm³. A thermal trap was then utilized to stabilize the dust cloud against any external disturbances during the flight. Two overview cameras and a long-distance microscope with a high-speed camera were used for the in-situ observations of the particles (see Figs. 1 and 2).

This talk focuses on the data analysis and results of ICAPS, in particular with respect to Brownian motion and aggregate growth. From the total experiment time of six minutes of almost perfect weightlessness, we extracted the masses and translational friction times of 414 dust aggregates from their translational Brownian motion. For a subset of 69 of these particles, we were also able to derive their moments of inertia and rotational friction times from their Brownian rotation. With these data, we derived a fractal dimension close to 1.8 for the ensemble of dust aggregates. We compared this unambiguous physical method for the determination of the fractal dimension with an optical approach, in which the mass is derived through the particle extinction and the moment of inertia is derived from the microscopic images.

The combination of both methods then facilitates the growth analysis, for which the overview cameras were also used. We observed an initial rapid, charge-induced growth of aggregates, which was followed by a slower growth rate, which was dominated by ballistic cluster-cluster agglomeration. As a surprise, around 100 seconds into the flight, clear indication for runaway growth (or the onset of gelation) was observed.

Fig. 1: Examples of dust aggregates from the long-distance
microscope images.

Fig. 2: Image from one of the overview cameras after 100 s of experiment time (1024 x 768 pixels, about 12 x 9 mm²).

How to cite: Schubert, B., Molinski, N., Blum, J., Glißmann, T., Pöppelwerth, A., von Borstel, I., Balapanov, D., Vedernikov, A., Houge, A., and Krijt, S.: ICAPS: Dust aggregate properties and growth derived from Brownian translation and rotation from the ballistic to the diffusive limit, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-581, https://doi.org/10.5194/epsc2022-581, 2022.

Exoplanet observations with ground-based instruments are subject to climate conditions on Earth. Therefore, one important aspect in site selection for ground-based telescopes is the study of current climate conditions to optimise observing time. Since anthropogenic climate change is leading to a significant increase in global mean surface temperature, consequences for ground-based telescopes are likely [1], yet remain mostly unknown. The timescale needed to select the site and build a large telescope until its first light can easily take up more than a decade. In the case of the European Extremely Large Telescope, this process takes approximately 20 years. Together with a typical lifetime of 30 years for large telescopes, climate change  potentially degrades site conditions assessed during the site selection process noticeably until end of lifetime.
We present a study of eight sites around the world where ground-based telescopes are already in operation. The selected sites are namely Mauna Kea on the island of Hawaii (USA), San Pedro Mártir in Baja California in Mexico, the three Chilean sites Cerro Paranal, Cerro Tololo and La Silla, La Palma on the Canary Islands (Spain), Sutherland in South Africa and Siding Spring in Australia. From the observatories hosting these telescopes, we collect in situ measurements of temperature, specific and relative humidity, precipitable water vapour, cloud cover and astronomical seeing. We compare these in situ measurements to the fifth generation atmospheric reanalysis (ERA5) of the European Centre for Medium-Range Weather Forecasts and score the agreement. A reanalysis is a global and continuous assimilation of observations combined with weather and climate modelling and provides a connecting link between measurements and global climate models (GCMs). 
For a more holistic comparison and to study future trends, we use an ensemble of six of the highest resolution GCMs available with a horizontal grid spacing of 25-50 km. These GCMs are provided by the High-Resolution Model Intercomparison Project and developed as part of the EU Horizon 2020 PRIMAVERA project. We compare ERA5 climate output against historical GCM simulations and score their agreement. With this evaluation, we gain insights into the trustworthiness of future GCM simulations that were run up to 2050. Finally, we perform a Bayesian analysis of future trends. 
We find that ERA5 provides a good representation since it agrees well with in situ measurements over most sites. The comparison between ERA5 and PRIMAVERA shows a good agreement for temperature, specific humidity and precipitable water vapour, for which we find increasing future trends leading to a deteriorating quality of astronomical observations. For relative humidity, cloud cover and astronomical seeing, the confidence in future trends projected by the GCMs is low, due to an inadequate representation of climate conditions in comparison to ERA5. Also, the trends found for these variables are not significant.
With this study, we show that climate change should be considered an important aspect of instrumentation design for ground-based telescopes, especially for high-contrast imaging observations.

References:

[1] Cantalloube, F., Milli, J., Böhm, C. et al. The impact of climate change on astronomical observations. Nature Astronomy 4, 826–829 (2020).

How to cite: Haslebacher, C., Demory, M.-E., Demory, B.-O., Sarazin, M., and Vidale, P. L.: Climate change drives degradation of future observations with ground-based telescopes, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-791, https://doi.org/10.5194/epsc2022-791, 2022.

A central question in exoplanetary research is the characterisation of the composition and internal structure of exoplanets. However, the observable parameters of an exoplanet are scarce and generally limited to the planet’s mass and radius and the properties of its host star. This means that it is not possible to fully constrain the internal structure parameters of an exoplanet, such as the iron core mass fraction, the presence of a water layer or the amount of gas, from these observations: The problem is intrinsically degenerate [1,2].

To overcome this difficulty, a Bayesian inference scheme is used, which is an inverse method based on Bayes’ theorem. It updates the previously assumed probability of the internal structure parameters (the prior) based on the probability of the observation given the same parameters (the likelihood), returning the posterior distribution of these parameters.

In our case, the likelihood is determined based on an internal structure model, which calculates the radius of a planet with a given mass and composition based on the planetary structure equations as described in [6]. This calculated radius and the transit depth it implies are then compared to the observed transit depth of the real planet. For the internal structure model, we use the BICEPS code as described in [4] and based on [2,3] to model the core, mantle and water layers of the planet; the atmosphere is modelled separately according to [5]. For the composition, we assume that the planetary composition matches the one of the star exactly [7].

We developed a full grid approach that has multiple advantages over the traditionally used scheme based on Markov chain Monte Carlo methods. To compensate for the higher number of sampling points that such a brute force approach requires, we trained a deep neural network to replace the internal structure model, which significantly reduces the computation time of the model. Additionally, we take into account that the measured masses and radii of the planets in the same system are correlated, since they were measured relative to the same star. This allows for an increase in computation time that is only linear when adding an additional planet. The full approach including the internal structure model is described in more detail in [8].

This method has already been used to characterise the internal structure of various exoplanets observed by the CHEOPS mission, e.g. [8] and [9] (and more submitted). As an example, Figures 1 – 4 show the internal structure of TOI-561 b, c, d and e, calculated using the planetary and stellar parameters published in [9]. Note that the corresponding figures in [9] showing the posteriors of the internal structure parameters unfortunately do not use the published stellar parameters, see [10] for more details.

Figure 1. Posterior distribution of the most important internal structure parameters of TOI-561 b using the planetary and stellar parameters published in [9]. The shown parameters are the core and water mass fractions of the solid planet, the molar fractions of Si and Mg in the mantle and Fe in the core and the gas mass of the planet in Earth masses in a logarithmic scale. The dashed lines show the 5 and 95% quantiles, while in the titles the median and the 5 and 95% quantiles are shown.

Figure 2. Same as Figure 1 but for planet TOI-561 c.

Figure 3. Same as Figure 1 but for planet TOI-561 d.

Figure 4. Same as Figure 1 but for planet TOI-561 e.

References:

[1] Rogers, L. & Seager, S. 2010, The Astrophysical Journal, 712, 974

[2] Dorn, C., Khan, A., Heng, K., et al. 2015, A&A, 577, A83

[3] Dorn, C., Venturini, J., Khan, A., et al. 2017b, A&A, 597, A37

[4] Haldemann, J., et al. (in prep.)

[5] Lopez, E. D. & Fortney, J. J. 2014, ApJ, 792, 1

[6] Kippenhahn, R., Weigert, A. & Weiss, A. 2012, Stellar Structure and Evolution, 2nd edn., Astronomy and Astrophysics Library (Berlin Heidelberg: SpringerVerlag)

[7] Thiabaud, A., Marboeuf, U., Alibert, Y., Leya, I., & Mezger, K. 2015, A&A, 580, A30

[8] Leleu, A., Alibert, Y., Hara, N.C., et al. 2021, A&A, 649, A26

[9] Lacedelli, G., Wilson, T.G., Malavolta, L., et al. 2022, MNRAS, 511, 4551–4571

[10] Piotto, G., et al. (in prep.)

How to cite: Egger, J. A., Alibert, Y., Haldemann, J., and Venturini, J.: A Neural Network Based Approach to Modelling the Internal Structure of Transiting Exoplanets and Its Application to Planets Observed by the CHEOPS Mission, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-320, https://doi.org/10.5194/epsc2022-320, 2022.

Detecting exoplanets via the transit method is inherently biased towards short-period planets. Due to the nature of its observing strategy, the Transiting Exoplanet Survey Satellite (TESS) is particularly susceptible to this detection bias; only 12% of planets confirmed by TESS have orbital periods longer than 20 days. It’s crucial that we expand this sample of long-period planets to gain a more complete view of the exoplanet population. One way to do this is using duotransits - planet candidates with two observed transits separated by a large gap, typically two years. The true period of the duotransit is unknown, instead they have a discrete set of possible period aliases. We use these aliases to perform targeted follow-up of the duotransit with the CHaracterising ExOPlanets Satellite (CHEOPS), to recover the true period and ultimately confirm the planet. This allows us to find longer-period planets than are typically found by the TESS mission alone. To select the optimal targets for our CHEOPS follow-up we have developed a specialised pipeline that searches for duotransits in the TESS data. We will present this duotransit pipeline and the results from our CHEOPS follow-up program so far. We have discovered 10 long-period exoplanets, including two planets in the TOI-2076 system, all of which have P > 21 days, R_P < 5 R_Earth and Gaia magnitude < 12. Previously there were only 8 exoplanets discovered by TESS in this exciting parameter space, so our work has more than doubled the sample. These small, long-period transiting exoplanets are amenable to radial velocity follow-up and future atmospheric characterisation with the recently launched James Webb Space Telescope (JWST).

How to cite: Tuson, A. and the CHEOPS Consortium: A Search for Long-Period Transiting Exoplanets with TESS and CHEOPS, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-499, https://doi.org/10.5194/epsc2022-499, 2022.

Martian regolithic soil is considered an inhospitable environment to life as we know it with low availability of nutrients and the presence of powerful oxidants, namely perchlorate salts. Extreme microorganisms such as cyanobacteria of the genus Chroococcidiopsis dominate rock-dwelling communities in extreme deserts resembling the actual Martian environment. The strain Chroococcidiopsis 029, extremely tolerant to desiccation, ionizing, and UV radiation, can thrive in Mars-like conditions in a dried state. In the present work, we investigated the response of Chroococcidiopsis 029 when grown for a 3-week period using Martian regolith simulant containing 2.4 mM perchlorate anions. The growth either in the planktonic cells or biofilm life style was monitored following the in chlorophyll a content. The cellular and molecular responses to 2.4 mM perchlorate anions was studied following cell viability according to: i) PCR-PMA assay, ii) changes in gene expression of three SOD-coding genes (soda 2.1, soda.2, and sodC), and iii) production of intracellular ROS as revealed by CLSM. Results suggested that perchlorate did not compromise cell viability and that a significant over-expression of three SOD isoforms occurred after the one-week exposure with a greater expression of the membrane-bound MnSOD (sodA 2.1) in comparison to the cytoplasmic isoforms MnSOD (sodA 2.2) and Cu/ZnSOD (sodC). The accumulation of ROS within the cells was observed after 1-day exposure to perchlorate. Future investigations on the effect of Mars-like conditions in hydrated biofilms with 2.4 mM ClO4- and Martian regolith simulant will be carried out supported by the Europlanet scholarship 2024. These results are relevant for the habitability of Mars and the development of In-situ Resource Utilization.

How to cite: Gallego Fernandez, B., Mosca, C., Fagliarone, C., and Billi, D.: Responses of a desert cyanobacterium to prolonged exposure to perchlorate: implications for the habitability of Mars and In-Situ Resource Utilization, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-537, https://doi.org/10.5194/epsc2022-537, 2022.

Introduction

All known terrestrial life forms require liquid water to survive and grow. Therefore, under the conditions present on Mars today, sub-zero brines might be one of few environments allowing for microbial life to persist. These brines likely contain perchlorates which have been found in martian regolith (Hecht et al. 2009). Whilst their hygroscopicity as well as their potential to lower the freezing point of water support the presence of liquid water, ion-specific toxic characteristics such as chaotropicity may be detrimental for many organisms.

An organism thriving under very high salt concentrations is the halophilic archaeon Haloferax volcanii isolated from the Dead Sea (Mullakhanbhai and Larsen, 1975). Whilst halophilic archaea require salt, most importantly sodium chloride (NaCl), to survive, they only tolerate limited amounts of sodium perchlorate (Oren et al. 2014).

Here we present the concept and preliminary results of experiments investigating the stress responses of H. volcanii growing in medium containing sodium perchlorate (NaClO₄). To determine stress caused specifically by NaClO₄, and not by general ionic or oxidative stress or low water activity, results are compared to stress responses caused by NaCl and glycerol.

Methods

H. volcanii was grown at 40°C in altered DSMZ medium #97, where MgSO₄ was replaced by MgCl₂ and the concentration of NaCl was lowered from 4 to 1.7 mol/kg, in order to allow the addition of different amounts of NaClO₄, glycerol, or additional NaCl (up to NaCl saturation). Growth was tracked by measuring the optical density at 600 nm and regularly verified by colony forming unit (CFU) counts. Morphology was observed by light microscopy. Additional methods such as proteomics will be applied in upcoming experiments for analysing the stress responses in cells grown under the highest possible stress conditions.

Preliminary Results

H. volcanii is able to grow in medium containing 1.7 mol/kg of NaCl up to saturating concentrations, as was expected based on the very high tolerated NaCl range already described by Mullakhanbhai and Larsen (1975). Although visibly reduced, growth occured also in medium containing up to at least 0.6 mol/kg NaClO₄, which was achieved by letting the cells adapt to incrementally increasing NaClO₄ concentrations.

Fully substituting NaCl by NaClO₄ did not support any growth and resulted in complete death of the cell culture, as suggested by lack of CFUs. Hence, it is likely that the ClO₄^- anion cannot provide the necessary conditions for cell metabolism accomplished by Cl^- and possibly exhibits additional stress factors like chaotropic destabilization of biomacromolecules, as observed recently in the halotolerant yeast Debaryomces hansenii (Heinz et al. 2022). Although the NaCl tolerance of H. volcanii is higher, the tolerance for NaClO₄ is much lower than that of D. hansenii. Unlike the yeast, H. volcanii has no cell wall and, as a prokaryote, no cell compartmentalisation in general, which might cause increased susceptibility towards the destabilizing properties of perchlorate. Various cell morphologies, ranging from coccoid to rod shaped as well as varied sizes were observed under the different stress conditions, calling for additional research.

Outlook

Further experimentation is needed to confirm the abovementioned results and to determine the maximum solute concentrations at which H. volcanii can grow. Stress responses of cells grown under these conditions will be determined thereafter. By generating this data, we aim to better understand microbial responses to perchlorate stress and thereby further elucidate the habitability of martian brines and possibly can propose potential biomarkers for upcoming life detection missions on Mars.

References

Hecht MH, Kounaves SP, Quinn RC, West SJ, Young SMM, Ming DW, Catling DC, Clark BC, Boynton W V., Hoffman J, DeFlores LP, Gospodinova K, Kapit J, Smith PH (2009) Detection of perchlorate and the soluble chemistry of martian soil at the phoenix lander site. Science 325:64–67 . doi: 10.1126/science.1172466

Heinz J, Doellinger J, Maus D, Schneider A, Lasch P (2022) Perchlorate-Specific Proteomic Stress Responses of Debaryomyces hansenii Could Enable Microbial Survival in Martian Brines. 1–25, preprint available at bioRxiv, doi: 10.1101/2022.05.02.490276.

Mullakhanbhai MF, Larsen H (1975) Halobacterium volcanii spec. nov., a Dead Sea halobacterium with a moderate salt requirement. Archives of Microbiology 104:207–214 . doi: 10.1007/BF00447326

Oren A, Elevi Bardavid R, Mana L (2014) Perchlorate and halophilic prokaryotes: Implications for possible halophilic life on Mars. Extremophiles 18:75–80 . doi: 10.1007/s00792-013-0594-9

How to cite: Gries, A., Heinz, J., and Schulze-Makuch, D.: Perchlorate stress responses of Haloferax volcanii and implications on the habitability of Mars, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-550, https://doi.org/10.5194/epsc2022-550, 2022.

Putative Martian microorganisms could have adapted to the dry, subzero environment of present-day Mars by resorting to hygroscopic salts that might ensure, at least temporarily, the existence of near-surface liquid brines¹. Of relevance for this are perchlorates (ClO₄^-), which are widespread on Mars² and can absorb atmospheric water in a process called deliquescence while at the same time lowering its freezing point³. However, they might impair microbial life due to the reduction of water activity and ion-specific characteristics harmful to cells such as chaotropicity. As chaotropic agents, perchlorates disrupt the hydrogen bonding network between water molecules and thus the cellular biochemistry by promoting the denaturation of macromolecules.

Within the scope of this study, we aim to identify the perchlorate-specific stress response of the well-established model organism Escherichia coli by exposing the bacterium to sodium perchlorate (NaClO₄) while additionally examining other solutes (e.g. glycerol, NaCl, guanidine hydrochloride, and hydrogen peroxide) separately that induce osmotic, ionic, chaotropic, and oxidative stress and comparing the individually occurring cellular responses.

The growth medium DMSZ #1 (0.5% peptone, 0.3% meat extract, pH ~ 7.0) is being used as the basis for aerobic growth of E. coli in liquid cultures at a temperature of 35 °C and is supplemented with the additional solutes of interest for stress induction. E. coli is iteratively adapted to higher solute concentrations to quantify the various solute tolerances of the bacterium which guide further experiments. Cell growth and death are monitored by spectrophotometric measurement of the optical density at a wavelength of 600 nm (OD₆₀₀), as well as counting colony forming units (CFUs) and changes in cell morphology are observed by light microscopy.

Based on our preliminary results and minimal inhibitory concentrations described in the literature^4,5, it seems like E. coli can withstand higher concentrations of NaCl (up to 1 mol/kg) than NaClO₄ (up to 0.15 mol/kg). This reduced salt tolerance for NaClO₄ compared to NaCl has already been described for other organisms such as the halotolerant yeast Debaryomyces hansenii and could possibly be linked to the chaotropicity of perchlorates, causing macromolecule destabilization⁶. While final solute tolerances are still being determined, preliminary results suggest that E. coli exhibits a filamentous cell structure at increasing NaClO₄ concentrations, with cells clustered together lengthwise in a chain-like arrangement of varying lengths. This change in morphology could potentially be attributed to incomplete cell division⁷ and is in stark contrast to that of control cells in optimal growth medium, which dominantly appear as individual, rod-like cells. Cell filamentation triggered by NaClO₄ exposure has already been observed for the thermophilic and desiccation-tolerant organism Hydrogenothermus marinus⁸.

We are progressing to more precisely identify the biochemical processes involved in perchlorate-specific stress responses via proteome analysis. In addition, cell filamentation prompts further examinations, such as statistical chain-length evaluation, scanning electron microscope (SEM) imaging and testing for morphological reversibility upon NaClO₄-stress removal. Collectively, these results will help us understand the effects of perchlorate-induced stress and thereby allow us to further identify cellular processes critical for life to thrive in and adapt to perchlorate-rich environments like Martian brines.

References

1. Davila AF, Schulze-Makuch D. The Last Possible Outposts for Life on Mars. Astrobiology. 2016;16(2):159-168. doi:10.1089/ast.2015.1380

2. Clark BC, Kounaves SP. Evidence for the distribution of perchlorates on Mars. International Journal of Astrobiology. 2016;15(4):311-318. doi:10.1017/S1473550415000385

3. Zorzano M-P, Mateo-Martí E, Prieto-Ballesteros O, Osuna S, Renno N. Stability of liquid saline water on present day Mars. Geophys Res Lett. 2009;36(20). doi:10.1029/2009GL040315

4. Cebrián G, Arroyo C, Mañas P, Condón S. Bacterial maximum non-inhibitory and minimum inhibitory concentrations of different water activity depressing solutes. Int J Food Microbiol. 2014;188:67-74. doi:10.1016/j.ijfoodmicro.2014.07.011

5. Díaz-Rullo J, Rodríguez-Valdecantos G, Torres-Rojas F, et al. Mining for Perchlorate Resistance Genes in Microorganisms From Sediments of a Hypersaline Pond in Atacama Desert, Chile. Front Microbiol. 2021;12:723874. doi:10.3389/fmicb.2021.723874

6. Heinz J, Doellinger J, Maus D, et al. Perchlorate-Specific Proteomic Stress Responses of Debaryomyces hansenii Could Enable Microbial Survival in Martian Brines. preprint available at bioRvix.org. 2022. doi:10.1101/2022.05.02.490276

7. Nguyen K, Kumar P. Morphological Phenotypes, Cell Division, and Gene Expression of Escherichia coli under High Concentration of Sodium Sulfate. Microorganisms. 2022;10(2). doi:10.3390/microorganisms10020274

8. Beblo-Vranesevic K, Huber H, Rettberg P. High Tolerance of Hydrogenothermus marinus to Sodium Perchlorate. Front Microbiol. 2017;8:1369. doi:10.3389/fmicb.2017.01369

How to cite: Kloss, L. D. F., Heinz, J., and Schulze-Makuch, D.: Perchlorate-induced stress responses of Escherichia coli and their implications for the habitability of Mars, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-692, https://doi.org/10.5194/epsc2022-692, 2022.

Energy from active serpentinization processes potentially fuelled the origin of life on Earth, thus, if serpentinite-impacted sites facilitate microbial habitability, it is important to understand the source and retention of biological signatures in serpentine rocks. Investigating biological signatures in terrestrial analogues of serpentinite-impacted environments is also essential for interpreting molecular signature preservation on extra-terrestrial bodies.

To expand knowledge on the types of biological signatures directly derived from living microorganisms (intact polar lipids, IPLs), and both living and dead microorganisms (core lipids), mass spectrometry analysis was performed on Chimaera serpentinite rocks from Antalya Province, Turkey. Brucite rocks were dominated by IPLs from fungal, eukaryotic origin but in contrast, travertine samples had IPL profiles consistent with a mixed fungal, archaeal and bacterial community. The abundance and diversity of archaeal IPLs was significantly higher in the travertine compared to the brucite, and the abundance of archaeal IPLs inside the travertine rock was highest. Archaeal specific core lipids identified inside the brucite rock were not observed as IPL counterparts, suggesting the presence of a non-viable or fossil archaeal community. Comparing IPL profiles with core lipids can discriminate between living microbial communities, necromass, and fossils to combine as a promising molecular tool for identification and interpretation of bio-signatures in serpentinite-impacted sites. Continuing survey of serpentinization samples on Earth can act as analogue environments and provide valuable insight into microbial habitability on Mars and other planetary objects.

How to cite: Zetterlind, A., Rattray, J. E., Smittenberg, R. H., Potiszil, C., ten Kate, I. L., and Neubeck, A.: Lipidomics Based Microbial Ecology Snapshot of Ophiolitic Rocks, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-952, https://doi.org/10.5194/epsc2022-952, 2022.

CC is now expanding to provide resources to meet the needs of CfW and the Welsh language. CfW was first implemented in September 2021, shifting the educational focus from content-based learning to skills-based learning, giving teachers more freedom regarding the contents of their lessons. This brings in novel complications, like the difficulty of preparing educational and stimulating lessons while also including the required skills. CC aims to solve these problems by supplying teachers with a variety of easy-to-follow lesson plans, encompassing a range of required key skills.

As part of CC, students can experience the whole ‘astronomical research process’, from planning when to obtain observations, to requesting the capture of images using the Faulkes Telescope Project (FTP) to access the Las Cumbres Observatory robotic telescope network, to analysing their images and plotting the results. The data are also used by pro-am astronomers to analyse the objects for their own research. CC schools will then be included in any subsequent publications that utilise data obtained by students - an inspiring and exciting opportunity. Over 100 children from 4 primary schools in South Wales were involved in the CC pilot, and 3 of these schools were included on a 2021 ApJ paper, Physical Characterization of Main-belt Comet (248370) 2005 QN₁₇₃ [1], with another publication under review. 

Student feedback:

“It is amazing and cool that our little school in Mid Wales can control a big telescope in Australia from our classroom”.

“Amazing, I can’t explain how cool and inspiring [it is]”.

Teacher feedback:

“We have learnt so much about astronomy. But the activities cover so many other parts of the curriculum too!”

“It has been fantastic. I’ve enjoyed it and the children have absolutely loved it. I wish we had more time each week as there was so much great material.”

Teacher guides, videos and worksheets for students have been produced, explaining the core concepts behind comets, space, light, how to collect data, and how to measure data, in addition to guiding schools through all the processes needed to obtain and analyse images. Web-based tools are being developed to assist in these processes. This exposes pupils to real scientific research and procedures, helping to nurture a deeper interest and understanding of current science.

All resources and tools will be available in Welsh to expand CC to involve Welsh language schools throughout the country. Welsh language STEM projects are uncommon, which can lead to a decrease in STEM engagement in this population. Providing Welsh language resources gives new and exciting opportunities for students in what are often under-performing schools [2]. Student results in Welsh language schools are marked lower than students in English language schools, suggesting Welsh resources may not be of high enough quality. CC aims to ensure that our resources put Welsh and English language schools on a level playing field, giving equal opportunities and successes in the project for all schools.

The main aim of CC for the future is expansion, both geographically and in participant ages. This will include schools outside of Wales, to share our knowledge, tools, and materials with other partners. Translation of resources into languages other than Welsh or English will be encouraged. CC also intends to involve older school children (ages 14-18) where more emphasis can be put on the science in addition to conducing more complex data analysis.

How to cite: Stoddard-Jones, C., Roche, P., Usher, H., Miles, R., Angel, T., Wooding, B., and Wooding, S.: Chasing Comets in the Land of Dragons/Chwilotwyr Comedau yn Wlad y Dreigiau: Pro-Am-Schools collaboration to engage students in STEM in Wales., Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-1172, https://doi.org/10.5194/epsc2022-1172, 2022.