PS4.6

Targeting the deployment of sustainable human and robotic exploration on the Moon by the end of this decade, there is a pressing need for better understanding the lunar water cycle and the availability of water for ISRU. The O-H isotope signatures in lunar water are key for determining the water origin in the Earth-Moon system and the mechanisms controlling water distribution and redistribution on the Moon. This has profound implications for understanding the Earth-Moon system’s history and the stability and renewability of water deposits.
Lunar volatiles are involved in a largely unconstrained and complex system of input, transport, trapping, recycling, and loss. The water origin on the Earth-Moon system remains poorly understood. The δD signatures from Apollo samples and meteorites suggest various contributing reservoirs of different origins for lunar water, and/or secondary processes [1], [2]. The different origins include: i) Magmatic (primordial) [3]; ii) asteroidal/cometary impacts [4], [5]; iii) solar wind H+ [1]; iv) mixed origin (solar wind H+/inclusion within meteorite impact glasses or volcanic glasses [6]).
The Roscosmos/ESA Luna 27 mission [7] is one of several international lunar polar missions for in-situ analyses of lunar surface, targeting pressing scientific and industrial knowledge gaps. To interpret the results derived from those polar missions it is critical to understand the extent and nature of any potential water ice loss and related isotope fractionation during the sampling chain.
Experimental studies on isotope fractionation during ice sublimation in nonequilibrium conditions are scarce. These studies concluded on different trends: i) no relevant isotope fractionation up to 40% ice mass loss [8], ii) relevant Rayleigh-like fractionation trend [9]. There is no kinetic isotope fractionation model (theoretical or experimental) for ice sublimation in low pressure systems at cryogenic temperatures, which considers the expected physical processes. Thus, the calculation of water ice isotope signatures remains highly uncertain, hindering the assessment of potential lunar water resources and the interpretation of scientific planetary data.
Here we present a theoretical isotope fractionation model derived from concepts developed by Criss (1999) [10] and adapted to the physical processes expected under lunar conditions, which will contribute to i) more robust interpretations of water ice behaviour in lunar environment and/or extra-terrestrial and/or extreme terrestrial environments; ii) mission operational planning, data processing, extraction/processing techniques; iii) exploration/exploitation roadmap, space mining business plan, natural resources management. [1] B. M. Jones et al., 2018. Geophys. Res. Lett., 45(20), 10,959-10,967; [2] F. M. McCubbin and J. J. Barnes, 2019. Earth Planet. Sci. Lett., 526; [3] A. E. Saal et al., 2013. Science, 340(6138), 1317–1320; [4] J. P. Greenwood et al., 2011. Nat. Geosci., 4(2), 79–82; [5] J. J. Barnes et al., 2016. Nat. Commun., 7(1), 11684; [6] C. I. Honniball et al., 2021. Nat. Astron., 5(2), 121–127; [7] D. J. Heather et al., 2021. Lunar Planet. Sci. Conf. LPI, Abstract #2111; [8] J. Mortimer et al., 2018. Planet. Space Sci., 158(Feb), 25–33; [9] R. H. Brown et al., 2012. Planet. Space Sci., 60(1), 166–180 [10] R. E. Criss, 1999. USA: Oxford University Press.

How to cite: López Días, V., Pfister, L., Hissler, C., and Barnich, F.: A more robust interpretation of water ice isotope signature from lunar polar missions: theoretical model for isotope fractionation during water ice sublimation in very low pressure systems at cryogenic temperatures., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8169, https://doi.org/10.5194/egusphere-egu22-8169, 2022.

The observation of an eclipse of the Moon at millimetre wavelengths makes it possible to investigate the electrical and thermal properties of the lunar surface to a depth of 10 cm without being influenced by deeper layers. Such measurements are usually carried out with radio telescopes on Earth. When microwave instruments on weather satellites use observations of deep space for their calibration, however, the whole lunar disk appears sometimes in their field of view as well. We identified such an event with the Advanced Microwave Sounding Unit-B on NOAA-15 that coincided with a total lunar eclipse. From this unique vantage point in a polar orbit around the Earth we could measure, once per orbit, the lunar radiance at 183 GHz - a frequency, where the atmosphere is not transparent.

We found a maximum temperature drop during the eclipse of 47±9 K at 183 GHz, corresponding to 16.6±2.1% of the flux density of full Moon, and of 17.3±6 K, corresponding to 6.4±2.1% of the flux density of full Moon, for the window channel at 89 GHz. The evolution in time of the global flux agrees well with the predictions from a new radiative transfer model simulating the global brightness temperatures. Our measurements are consistent with results reported in the past, except for two, which we consider erroneous. The temperature changes are similar everywhere on the lunar disc. The good agreement between the observations from a weather satellite and theoretical predictions demonstrates that the Moon is very useful as flux reference and for checking the reliability of climate data records from Earth observation.

How to cite: Burgdorf, M., Liu, N., Buehler, S. A., and Jin, Y.: Observation of a Total Eclipse of the Moon at 183 GHz, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1276, https://doi.org/10.5194/egusphere-egu22-1276, 2022.

Lunar Laser Ranging (LLR) has been measuring the distance between the Earth and the Moon since 1969, where the measurements are provided by the observatories as Normal Points (NPs). The Institute of Geodesy (IfE) LLR model has (as of April 2021) 28093 NPs. Using the LLR observation equation, the LLR residuals (difference of observed and calculated values of the light travel time) are obtained for each NP. The LLR analysis procedure is an iteration of the calculation of ephemeris of the solar system followed by the calculation of residuals and the estimation of parameters using a Least-Squares Adjustment (LSA). The initial orbit of the Moon (Euler angles and angular velocity of the lunar mantle, Euler angles of the lunar core, and the position and the velocity of the selenocenter), amongst many other parameters, is estimated from the LSA. In our previous standard calculation, the initial orbit of the Moon was estimated for June 28, 1969 and ephemeris was calculated from this time until June 2022. In this study, we estimate the initial orbit of the Moon for Jan 1, 2000 to be able to benefit from the higher accuracy of the NPs over the timespan of LLR. The ephemeris is then calculated in forward and backward directions (until June 2022 and June 1969). When comparing the uncertainty obtained from a LSA of this study with the previous standard calculation, preliminary results show an improvement of over 50% in the initial position and the initial velocity of the Moon, a deterioration of about 20% in the Euler angles of the mantle and the core, and an improvement of over 15% in the angular velocity of the mantle. The changed analysis procedure will allow to compute a more accurate ephemeris for the upcoming years benefitting future lunar science. Recent results will be presented and major changes would be discussed.

Acknowledgement. This research was funded by Deutsche Forschungsgemeinschaft (DFG) under Germany’s Excellence Strategy EXC 2123 QuantumFrontiers-390837967.

How to cite: Singh, V. V., Biskupek, L., Mueller, J., and Zhang, M.: Estimation of Lunar Ephemeris from Lunar Laser Ranging, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2815, https://doi.org/10.5194/egusphere-egu22-2815, 2022.

Orbital magnetic field observations of the Moon show several magnetic anomalies distributed heterogeneously across its surface. These observations and results from paleomagnetic studies on lunar rocks corroborates that the lunar crust is locally magnetized. The origin of these magnetic field anomalies is still debated, as most of them are not related to known geological structures or processes. Some of the current suggestions to explain the origin of the anomalies sources include contamination from impactors that could deliver iron-rich material to the lunar surface, and heating associated with localized magmatic activity that could thermochemically alter rocks to produce strong magnetic carriers. Both hypotheses need however an inducing field to magnetize the lunar crust, and strong evidence from previous studies argues in favor of this being a global magnetic field generated by a core dynamo.

In this work, we aim to elucidate the origin of the magnetic anomalies by constraining the location and shape of the underlying magnetization. We do so by inferring the magnetization geometry from orbital magnetic field measurements using an inversion scheme that assumes unidirectional magnetization while making no a priori assumptions about its shape. This method has been used up to now to infer the direction of the underlying magnetisation but it has not yet been used to infer the geometry of the sources. We test the performance of the method by conducting a variety of synthetic tests using magnetized bodies of different geometries such as basins, dykes, and lava tubes, each corresponding to a different possible origin scenario for the observed magnetic anomalies.  Results from our synthetic tests show that the method is able to recover the location and shape of the magnetized volume. We explore how different input parameters, such as shape, depth, thickness, and field direction influence the method’s performance in retrieving the characteristics of the magnetized volume. Such an analysis can be performed on many lunar magnetic anomalies, including those which are not related to swirls or impact craters, i.e., the mechanisms that have been most studied up to now. This will help elucidate the geological history of the Moon and key features of the lunar dynamo evolution.

How to cite: Oliveira, J. S., Vervelidou, F., Wieczorek, M. A., and D. Michelena, M.: Constraints on the lunar magnetic sources location using orbital magnetic field data, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8651, https://doi.org/10.5194/egusphere-egu22-8651, 2022.

Understanding whether the Moon had a long-lived magnetic field is crucial for determining how the lunar interior and surface evolved, and in particular for assessing whether a paleomagnetosphere shielded the regolith. Magnetizations from some Apollo samples have been interpreted as records of a global lunar magnetic field between approximately 4.2 and 1.5 Ga that would have created shielding, but the inferred paleofields are too strong and continuous to be generated by the small lunar core. Moreover, vast areas of the lunar crust lack magnetic anomalies that should mark the past presence of a dynamo. New paleointensity data from an Apollo impact glass associated with a young 2 million-year-old crater records a strong Earth-like magnetization, providing evidence that impacts can impart intense signals to samples recovered from the Moon, and other planetary bodies (Tarduno, Cottrell, Lawrence et al., Science Advances, 2021). This observation provides motivation for future lunar collections to constrain impact size - magnetization scaling relationships. Moreover, new data from silicate crystals bearing magnetic inclusions from Apollo samples formed at 3.9, 3.6, 3.3, and 3.2, Ga are capable of recording strong core dynamo-like fields but do not, indicating the lack of a global magnetic field (Tarduno, Cottrell, Lawrence et al., Science Advances, 2021). Together, these new data indicate that the Moon did not have a long-lived core dynamo. As a result, the Moon was not sheltered by a sustained paleomagnetosphere, and the lunar regolith should hold buried 3He, water, and other volatiles resources acquired from solar winds and Earth’s magnetosphere over some 4 billion years. These findings highlight the opportunity to learn about the evolution of the solar wind and Earth’s earliest atmosphere during future lunar exploration. This could in turn provide key data to better understand how Earth evolved as a habitable planet despite the expected extreme solar forcing during its first billion years (Tarduno, Blackman, Mamajek, Phys. Planet Inter., 2014).

How to cite: Tarduno, J.: Absence of a long-lived lunar paleomagnetosphere and opportunities for future exploration, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10400, https://doi.org/10.5194/egusphere-egu22-10400, 2022.

The lunar cratering record is used to constrain the bombardment history of both the Earth and the Moon. However, it is suggested from different perspectives, including impact crater dating, asteroid dynamics, lunar samples, impact basin-forming simulations, and lunar evolution modelling, that the Moon could be missing evidence of its earliest cratering record. Here we report that impact basins formed during the lunar magma ocean solidification should have produced different crater morphologies in comparison to later epochs. A low viscosity layer, mimicking a melt layer, between the crust and mantle could cause the entire impact basin size range to be susceptible to immediate and extreme crustal relaxation forming almost unidentifiable topographic and crustal thickness signatures. Lunar basins formed while the lunar magma ocean was still solidifying may escape detection, which is agreeing with studies that suggest a higher impact flux than previously thought in the earliest epoch of Earth-Moon evolution.

How to cite: Miljkovic, K., Wieczorek, M. A., Laneuville, M., Nemchin, A., Bland, P. A., and Zuber, M. T.: Large impact cratering during lunar magma ocean solidification, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2214, https://doi.org/10.5194/egusphere-egu22-2214, 2022.

Tidal response of the Moon provides crucial insight into the structure and rheology of the lunar interior (Williams et al. 2013). The body deformation subject to forces raised by external objects, most evidently Earth and the Sun, induces a variability of the gravitational field, which is characterized by the Love number, k. This effect may, in turn, manifest itself over time in the perturbed motion of orbiting spacecraft (Konopliv et al. 2013; Lemoine et al. 2013).

For an elastic body the response to the periodic excitation is instantaneous and relaxation times resulting in phase lags of the response are thus neglected. In reality, the lunar interior exhibits a degree of viscosity and dissipates energy through friction, in which case k not only varies with frequency but also comprises an imaginary part that represents a phase lag in tidal response (Williams et al. 2013).

Here, we investigate the signatures of the frequency-dependent Love number in the motion of a lunar orbiter. We formulate the problem following Williams & Boggs (2015), and focus on the variability of five Stokes' coefficients of the second degree effected by k2. The time-varying components are expanded at given characteristic frequencies associated with (linear combinations of) the Delaunay arguments. We make use of the Technical University Delft Astrodynamics Toolbox (Dirkx et al., 2019; https://tudat-space.readthedocs.io/) to investigate the orbit evolution of lunar orbiters, e.g., the Lunar Reconnaissance Orbiter (Mazarico et al. 2018), subject to the time-varying lunar gravitation. Meanwhile, we leverage the analytic theory of Kaula (1966) to illuminate the impact of such specific yet minute perturbations, especially non-short-period variations of the spacecraft orbit (Kaula 1964; Lambeck et al. 1974; Felsentreger et al. 1976).

A particular interest here is in the potential estimability of the frequency-dependent phase lag. Following Dirkx et al. (2016), we conduct a preliminary study of the sensitivity of spacecraft orbit adjustment to the said tidal effects. That is, we investigate if, under which conditions, and to what degree, the signals in question will be absorbed by the adjustment of initial states or other parameters, a consequence that will effectively prohibit the detection of the tidal effects. The outcome is expected to shed light on the minimum criteria of their estimation and thus instructive to real-world data analysis in the future.

Reference

Dirkx, D., et al. (2016), PSS, 134, 84-95
Dirkx, D., et al. (2019), Astrophysics and Space Science, 364:37
Kaula W.M. (1964), Reviews of Geophysics, 2, 661-685
Kaula W.M. (1966), Theory of Satellite Geodesy, Dover Publications, Inc.
Konopliv, A.S., et al. (2013), GRL, 41, 1452-1458 
Lambeck, K., et al. (1974), Reviews of Geophysics and Space Physics, 12, 412-434
Felsentreger, T.L. et al. (1976), JGR, 81, 2557-2563
Lemoine, F.G., et al. (2013), JGRP, 118, 1676-1698
Mazarico, E., et al. (2018), PSS, 162, 2-19
Williams J.G., et al. (2013), JGRP, 119, 1546-1578
Williams J.G., and Boggs, D.H. (2015), JGRP, 120, 689-724

How to cite: Hu, X., Stark, A., Dirkx, D., Hussmann, H., Fienga, A., Fayolle-Chambe, M., Melini, D., Spada, G., Mémin, A., Rambaux, N., and Oberst, J.: Sensitivity analysis of frequency-dependent visco-elastic effects on lunar orbiters, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9722, https://doi.org/10.5194/egusphere-egu22-9722, 2022.

Many moons of the Solar System, e.g. the Galilean satellites or Earth’s Moon, are subject to strong tidal deformations. Measurements of the tidal Love number h2 by laser altimeters from orbiting spacecraft may provide crucial constraints on their interior structures and rheology. Using precise observations by laser altimeters estimates for h2 were obtained for the Moon (Mazarico et al. 2014, Thor et al., 2021) and Mercury (Bertone et al., 2021), and are planned for Ganymede (Steinbrügge et al., 2015). Typically, height differences at crossing points of laser profiles, so called crossover points, are used for such measurements (Mazarico et al. 2014, Bertone et al., 2021). However, a new method based on simultaneous inversion of tidal deformations and global topography has recently been demonstrated (Thor et al. 2021) using data from the Lunar Orbiter Laser Altimeter (LOLA) on board the Lunar Reconnaissance Orbiter (LRO).

Here we propose the refined “self-registration” method, which makes use of an accurate reference digital terrain model (DTM) constructed from the laser profiles themselves. This DTM is obtained by iteratively co-registering random subsets of laser profiles to an intermediate DTM produced by the other profiles. With our method we are not limited to profiles that are actually crossing themselves and can obtain height difference between all available profiles. Moreover, we can overcome the interpolation error at the crossover points as we use the entire profile with all its data points to measure the relative height differences. This method was recently successfully applied to measure the seasonal change of the ice/snow level in polar regions of Mars using Mars Orbiter Laser Altimeter (MOLA) data (Xiao et al., 2021).

In order to validate our method and assess its performance we perform a simulation of a tidal signal in the LOLA data with an assumed value for the tidal Love number h2 of the Moon. Thereby the height measurement at the location of the LOLA footprint is derived from a DTM and an artificial tidal signal applied on it. Thereby, we consider viscoelastic effects on the tidal deformation and different tidal frequencies. With the help of these simulations we assess the accuracy of the h2 measurement and check the sensitivity to the measurement of the tidal phase lags.

References:

Mazarico et al. (2014). Detection of the lunar body tide by the Lunar Orbiter Laser Altimeter. GRL, 41(7), 2282-2288. doi:10.1002/2013GL059085

Thor et al. (2021). Determination of the lunar body tide from global laser altimetry data. JoG, 95(1). doi:10.1007/s00190-020-01455-8

Bertone et al. (2021). Deriving Mercury Geodetic parameters with Altimetric Crossovers from the Mercury Laser Altimeter (MLA). JGR-Planets, 126(4), e2020JE006683. doi:10.1029/2020JE006683

Xiao et al. (2021). Prospects for Mapping Temporal Height Variations of the Seasonal CO2 Snow/Ice Caps at the Martian Poles by Co-registration of MOLA Profiles. Under review in PSS, https://arxiv.org/abs/2109.04899

How to cite: Stark, A., Xiao, H., Hu, X., Fienga, A., Hussmann, H., Oberst, J., Rambaux, N., Mémin, A., Briaud, A., Baguet, D., Spada, G., Melini, D., and Saliby, C.: Measurement of tidal deformation through self-registration of laser profiles: Application to Earth’s Moon, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10626, https://doi.org/10.5194/egusphere-egu22-10626, 2022.

We are studying the transient lunar phenomena (TLP) as an indicator of lunar tectonics. Seismic events can be used as a direct indicator of some tectonic activities of the planets. The Moon-Earth gravitational interaction has been studied extensively as a triggering mechanism for earthquakes. However, this is a controversial topic. Our present study investigated the reverse Earth-Moon interaction concerning the TLP activities. The lunar outgassing is potentially the leading source of TLP activities. We have investigated both Earth venting and earthquakes and have found that radon was frequently activated before significant seismic events due to the Moon-Sun interaction with the Earth (Ouzounov et al., 2018). Earthquake lights, an associated phenomenon reported before some major earthquakes, are analogous to TLP activities on the Moon. In 1972, N. Kozyrev suggested a possible lunar response to the significant seismic events on the Earth. To understand whether TLP's have any possible connection with earthquakes, we performed a statistical review between significant earthquakes, using the NEIC catalog and TLPs during 1907-1977, for four lunar areas: Aristarchus, Plato, Gassendi, and Alphonsus. We used TLP catalogs published by Middlehurst et al. 1968; Cameron, 2006; and Crotts, 2008.  Our results revealed a causal relationship between significant earthquakes and TLP events. However, the strength of this relationship varies from the location and depth of the earthquakes. Deformation on the Moon triggers the degassing process, and TLPs are indicators for those underlying activities. Our work can provide new information about the origin of TLP and the existence of a possible relationship between the tectonic processes of Earth and the Moon. The Earth causes crustal tides on the Moon, and the Moon produces tides on the Earth.

How to cite: Ouzounov, D., Taylor, P., Kafatos, M., and Cutchins, K.: Lunar TLP's and the tectonic processes of the Earth and the Moon, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12932, https://doi.org/10.5194/egusphere-egu22-12932, 2022.

While the origin of lunar polar volatiles remains an open question, their most likely sources are volcanic outgassing or volatile-rich impactors. Both such sources are sporadic in nature and are characterized by release of large amounts of volatiles over a short period of time and long periods of repose between such events. If a sufficient amount of volatiles was generated in such a delivery event, a transient collisional atmosphere could form. Such an atmosphere, if it persists for a long enough time, would protect certain volatiles (like water) from photodissociation and escape to space and would promote their transport to the polar cold traps where they could be stored and preserved for billions of years. Hence, such transient atmospheres could have a significant impact on the distribution and abundance of volatiles currently observed on the Moon. Here we study such a hypothetical atmosphere that could have been formed due to volcanic outgassing during the peak of lunar volcanic activity at ~3.5 Ga and investigate its longevity, climatology and effect on volatile transport.

We employ the ROCKE-3D [1] planetary climate model to simulate processes in a volcanically-induced lunar atmosphere. We use orbital and radiation parameters corresponding to conditions at 3.5 Ga (17.8 days rotation period and a solar constant 75% of the modern value). For most experiments we use zero obliquity, though we investigate the effect of non-zero obliquity on atmospheric stability and volatile transport. We assume a CO₂-dominated atmosphere in accordance with predictions of our chemistry model [2]. For the atmospheric thickness we follow the argument of Head et al. [3] that due to long periods of repose between the volcanic events the atmosphere would not accumulate above the pressure of a few microbars, and thus we limit our parameter space to a range of 1 microbar to 1 mb surface pressures. To investigate the ability of such an atmosphere to transport volatiles we set up a typical volcanic eruption experiment [4] and follow the fate of the outgassed water.

In most of our experiments the atmosphere was stable, though in some cases a small non-zero obliquity (a few degrees) was needed to prevent a collapse due to CO₂ condensation at the poles. We found that even very thin atmospheres were efficiently transporting volatiles to the poles. The efficiency of transport sometimes was higher for thinner atmospheres, most likely due to a stronger circulation cell. We also found that water transport efficiency depended on initial conditions at the surface. A water-free dry surface suppressed re-evaporation, thus reducing the total flux of outgassed water to the poles. But even in the case of dry soil, water transport was efficient with 19% of outgassed water delivered to the poles in just a few months (for the 10 microbar atmosphere).

References: [1] Way M. J. et al. (2017) ApJS, 231, 12. [2] Aleinov I. et al.  (2019) GRL, 46, 5107–5116. [3] Head J. W. et al. (2020) GRL, 47, e2020GL089509. [4] Wilson L. and Head J. W. (2018) GRL, 45, 5852-5859.

How to cite: Aleinov, I., Way, M., Head, J., Tsigaridis, K., Harman, C., Wolf, E., Gronoff, G., Varnam, M., and Hamilton, C.: Effect of Volcanically-Induced Transient Atmospheres on Transport and Deposition of Lunar Volatiles., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10764, https://doi.org/10.5194/egusphere-egu22-10764, 2022.

Lunar Gravitational-wave Antenna (LGWA) proposes to deploy an array of high-end seismometers on the surface of the Moon. The LGWA network will measure the lunar surface displacement excited by Gravitational waves (GWs) with a targeted observation band of 1mHz – few Hz.   Seismic noise in that frequency band is very low due to the absence of atmosphere and oceans, representing the main inherent advantage that makes the Moon an ideal target for a GW detection experiment. 

The scientific and technical challenges of LGWA are diverse.  Since its initiation, LGWA has relied on experts from fundamental physics, astrophysics, geophysics, engineering, and planetary science. 

The collaboration is currently organized in working groups (WGs) to cover five key themes: GW science, lunar science, payload, deployment, and operations.  

At the beginning of 2022, we started the activities of WG2 to assess the current knowledge of the lunar environment. We aim to characterize and develop models of deployment scenarios suitable for LGWA sensors, via a multi-pronged approach of data analysis and on-field experiments probing terrestrial analogs of lunar terrains. 

Besides characterizing the lunar seismic background noise, other goals of the group are related to modeling the lunar interior structure as well as Moon’s normal modes. These will be further used to develop a model of the interaction between the Moon and GWs. The knowledge about the displacement level of this excitation and the background noise will be used to define novel techniques for background noise reduction.

For this purpose, WG2 is composed of physicists, engineers, geophysicists, and geologists. For our activities, we chose an interdisciplinary approach that requires initial communication efforts to create a common ground that will evolve into a crucial baseline activity for the whole LGWA project.

Here we will report our progress in the first months of the activity of our collaboration.     

How to cite: Frigeri, A., Olivieri, M., Harms, J., Bonforte, A., Giunchi, C., Komatsu, G., Majstorović, J., Massironi, M., and Melini, D.: The Moon Science Working Group of the Lunar Gravitational-Wave Antenna Project, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10171, https://doi.org/10.5194/egusphere-egu22-10171, 2022.

Mons Hansteen Alpha is a lunar ‘red spot’ that is now considered to be of non-mare volcanic origin. In addition to being characterized by an evolved silicic composition, Mons Hansteen Alpha is also of interest because of the presence of Mg-spinel exposures in association with the siliceous lithology, as detected by the Moon Mineralogy Mapper on board the Chandrayaan-1 mission. The Compton-Belkovich volcanic complex on the Moon is the only other established example of this kind. The origin of Mg-spinel exposures on the lunar surface is considered to be either impact related or endogenic. Models have been proposed in earlier studies to explain the spinel exposures on anorthosites, and spinel in association with other mafic minerals such as olivine and orthopyroxene. However, the origin of Mg-spinel exposures within an evolved siliceous body that has very limited associated mafic minerals is yet to be fully explored. In this study, the Mg-spinel exposures on Mons Hansteen Alpha were analyzed using high resolution LROC NAC images and correlated with topographic information from the SLDEM data. These investigations suggest that in most cases, the spinel exposures on Mons Hansteen are not related to any impact related structures. The exposures are often found on elevated features such as ridges, or around irregular-shaped pits. The distribution of the exposures is mostly limited to the Pitted unit, the youngest unit in the volcanic structure; this favours an endogenic origin instead of one related to impact as otherwise, the exposures would also have been distributed in the other units. On the bases of these observations, it is suggested that the Mg-spinel exposures on Mons Hansteen Alpha are endogenic in nature. A model is proposed for the origin of endogenic Mg-spinel exposures on silicic volcanic structures. For this, model reactions were considered between a lunar picritic basaltic magma and two types of crustal protoliths- (i) a mixture of silica and anorthosite and (ii) a lunar monzogabbro. The modelling has been done using the alphaMELTS 2 software. The proposed model combines the crustal melting model for the genesis of silicic volcanic structures with a genetic model for the Mg-spinel exposures. The mixture of silica and anorthosite has been considered as a possible crustal protolith consistent with recent experimental lunar magma ocean (LMO) crystallization models that crystallized silica as one of the end stage products. On the other hand, earlier studies have proposed monzogabbro as a possible protolith composition for lunar silicic lithology. The models demonstrate the possible pathways of forming silicic compositions similar to the lunar granite samples collected during the Apollo missions, with simultaneous crystallization of Mg-spinel.

How to cite: Moitra, H. and Gupta, S.: Investigating the origin of Mg-spinel exposures on Mons Hansteen Alpha, an evolved silicic volcanic structure on the Moon, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10274, https://doi.org/10.5194/egusphere-egu22-10274, 2022.

   Chang’E-4 was the first mission to land a human object on the far side of the Moon. The landing site was at the Von Kármán (VK) crater at the South-Pole Aitken (SPA) basin, one of biggest craters in the solar system. SPA is believed that was created by a huge impact that penetrated the lunar crust and uplifted mantle materials. Evidence of these materials are expected to be found by the Yutu-2, the rover of the mission that is still active to this day, having covered more than 1km on the lunar’s surface. Yutu-2 is equipped with a stereo camera, visible/near-infrared imaging spectrometer, alpha particle x-ray spectrometer and Ground-Penetrating Radar (GPR). In-situ GPR is a powerful geophysical methodology with a uniquely wide range of applications to civil engineering, archaeology and geophysics. In planetary science, it was first used in 2013 during the Chang’E-3 mission. Since then, GPR has become a very popular instrument in planetary missions, and has been included in the scientific payload of Chang’E-4, E-5, Tianwen-1, and Perseverance. It is also planned to be used in the future missions Chang’E-7 (2024) and ExoMars (September 2022).

   Yutu-2 rover is equipped with three different GPR systems. One low frequency and two high frequency antennas. Unfortunately, due to interferences between the antenna and the metallic parts of the rover, the low frequency data have very low signal to clutter ratio making the interpretation of these data unreliable. On the other hand, the signal from the high frequency antennas is very clear, probably due the lack of ilmenite in the area, which results to low electromagnetic losses (compared to the Chang’E-3 landing site). This resulted to good quality radagrams that provided new insights into the structure and composition of the top ejecta layers at the VK crater.

    In the current paper, we introduce a complete processing scheme, tuned for high frequency lunar penetrating radar.  The first step of the proposed framework is an advanced hyperbola fitting (AHF) capable of inferring previously unseen layers due to their smooth boundaries. Subsequently, the reconstructed layered structure is used in a Reverse-Time Migration (RTM) coupled with Finite-Differences Time-Domain (FDTD) method. Via this approach, the radagram is focused subject to a 1D model, avoiding homogeneity constrains that often deviate from reality. Lastly, an un-supervised thresholding is applied to cluster the migrated image into two categories i.e. A) the background host medium and B) rocks/boulders. The suggested scheme is applied to the high frequency data collected by the Yutu-2 rover at the first 100 meters of the mission. A layered structure is inferred at the top 12 meters, similar to the results presented in [1]. Moreover, using the proposed RTM, an abundance of rocks/boulders was revealed. The distribution of the rocks/boulders correlates with the permittivity/density profile, indicating the reliability of the proposed scheme.   

References

[1] Giannakis, I., Zhou, F., Warren, C., & Giannopoulos, A. (2021). Inferring the shallow layered structure at the Chang’E-4 landing site: A novel interpretation approach using lunar penetrating radar. Geophysical Research Letters, 48, e2021GL092866

How to cite: Giannakis, I., Martin-Torres, J., Zorzano, M.-P., Warren, C., and Giannopoulos, A.: GPR Reverse-Time Migration for Layered Media: A Case Study at the Chang’E-4 Landing Site, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7634, https://doi.org/10.5194/egusphere-egu22-7634, 2022.

China’s first lunar sample return mission, Chang’E-5, has collected 1.731 kg samples from one of the youngest mare basalt units in the northern Oceanus Procellarum. In this study, we conducted a systematical analysis on regolith properties at the landing site using optical, multispectral, thermal infrared and radar observations, and then traced regolith provenance using ejecta deposition models.

The CE-5 landing site is within a flat (< 5° in slope), young (˜1.3 Ga), intermediate titanium (4.6 wt.%) mare basalt unit, named P58/EM4, which is surrounded by several older, low titanium mare basalt units. In the Kaguya Multiband Imager TiO₂ map, some impact craters have low titanium ejecta blankets (e.g., Mairan G), indicating that they have excavated the underlying low titanium materials. Size and spatial distribution of these craters suggest that the basalt is thicker in the center of unit P58 and thinner around the perimeter with thickness from ˜15 to ˜50 m. Morphologies of small fresh craters identified in high-resolution optical images show that regolith thickness varies from ˜1.5 to ˜8 m with a median value of ˜5 m. A comparison between Mini-RF radar image and Lunar Reconnaissance Orbiter Diviner surface rock abundance (RA) map indicates that subsurface rocks play a significant role in producing the observed radar backscatter. Further analysis of the radar echo suggests that subsurface RA is ˜0.47%–0.88% if the effective size is 3 cm, which can explain the shallow sampling depth (˜0.9 m) of the CE-5 drilling device.

To study sample provenance, deposition history and stratigraphy of landing site, we established a catalogue of 1896 craters that can deposit materials to the landing site. Our analysis shows that 80% of the primary ejecta (˜0.6 m) sampled by CE-5 comes from 12 craters within 1 km range from the landing site, and that XuGuangqi crater (46–90 Ma) contributes about 50%. There are four major source craters outside P58 unit, and their primary ejecta contribution is less than 10%. The detailed locations and depths of ejecta at landing site are given by using Maxwell Z-model (e.g., for XuGuangqi crater, 18.7–43.7 m depth and 112.3–123.0 m from crater center). Based on the age of the major craters, we further simulated the deposit thickness and composition profile of the regolith at landing site using the Monte Carlo and ballistic sedimentation model. The results show that the craters totally produced ˜1.1 m thick ejecta deposits, and the uppermost ˜0.46 m consists of primary ejecta from XuGuangqi and a smaller crater near landing site. The model predicts that FeO and TiO₂ abundances decrease with depth, to a minimum value at ˜0.1 m, and then increase and become constant with depth. This can provide a feasible way to identify the provenance of single sample by using FeO and TiO₂ abundances.

This study provides key information about geological context, regolith property, sample provenance and stratigraphy of landing site, which is critical for explaining laboratory measurements of CE-5 samples.

How to cite: Jia, B. and Fa, W.: Properties and provenance of the lunar regolith at Chang’E-5 landing site: Constraints from remote sensing observations and ejecta deposition models, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10988, https://doi.org/10.5194/egusphere-egu22-10988, 2022.

ESA and ROSCOSMOS’ Luna 27 mission will explore the south polar region of the Moon and will sample the lunar surface. To ensure the best samples are collected, which yield the greatest scientific return eight potential landing sites are being investigated using remote sensing methods. We have studied the safety of the eight potential landing sites by creating slope maps using the LOLA (30m/px) digital elevation model and classified slopes into safe areas (slopes <10°) and unsafe areas (slopes >10°). Additionally, we created slope maps classified in 2° intervals from 0-14° and greater than 14°, to further investigate which areas have the lowest slopes and therefore potentially the safest landing sites.

      We found that each of the eight landing sites contain areas that are safe for landing (slopes <10°) and sites 1, 2, 4, 6 and 8 contain large areas (>500 km²) that are classified as safe for landing. Site 3 has large craters with steep crater walls, which may present a hazard to landing. At site 5 there is a large crater (~20 km diameter) to the bottom right of the site, which has a steep crater walls and rim, which creates a topographic ridge in the south east of the landing site and should be avoided as a landing site. Site 7 also has a steep topographic ridge which again should be avoided as a landing area. In comparison site 8 contains a large area with shallow slopes in the center with slopes of 0-2°, which would be an ideal landing site. Site 1 covers a large crater (~40 km diameter), and the center of the crater floor has shallow slopes with less than 4°. Site 2 similarly has a large crater floor with slopes less than 4°. Both the crater floors of site 1 and site 2 could be a safe landing site.

     This initial investigation into the potential landing sites has identified areas which could be safe for landing Luna 27. Future work will use multiple datasets to explore the scientific potential of the landing sites including investigating the surface roughness, identifying craters and boulders, which could present a hazard to the lander, using thermal maps to measure the thermal stability, and exploring the illumination conditions and Earth visibility at each of the landing sites.

How to cite: Boazman, S., Heather, D., Sefton-Nash, E., Orgel, C., Houdou, B., Lefort, X., and Lunar Lander Team, T.: Investigating Potential Safe Landing Sites for ESA/ROSCOSMOS' Luna 27 Mission, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5452, https://doi.org/10.5194/egusphere-egu22-5452, 2022.

The study and investigation of local scale geological features (boulders and boulder fields) of planetary/asteroid surfaces can provide insight on the evolution of the regolith and the contribution of various processes to their formation. Numerous studies have employed photometric modelling to study the surface properties of the lunar regolith on a regional and local scale (e.g., [1], [2], [3])

In this study we employ photometric methods to study the properties of boulder fields/rock fragments in a multiscale approach from resolved (meter scale) to sub pixel (cm scale). In our approaches we use the Hapke model [4] on LROC NAC data [5]. The retrieved properties of boulders, in particular their shape, can in turn shed light on the boulder material strength and surface exposure time [6].

Usually, photometric studies (e.g., [2]) consider the Hapke parameters SSA (single scattering albedo), b, c, theta_bar (roughness) as unknown and estimate them by inversion. Here we take a different approach and strongly constrain the possible combinations of the four parameters. The constraint is facilitated by the knowledge of the geological context of the surface either above (sub pixel approach) or below (resolved boulder field approach) the image resolution, visually inferred with images.

We are interested in the relative probability of each geologic context for a given region. This information is sufficient reveal information about the possible micro-scale geology of a region, namely the shape, and thus degradation, of rocks. We apply these techniques to the boulder fields in the vicinity of the Apollo 16 landing site at North Ray crater.

Our approach consists of the construction of a set of digital terrain models (DTMs) representative of the most possible geologic contexts. The contexts are described by the rock and debris apron shape and reflect the abrasion stage of the rock – Non-Abraded (flat top), Non-Abraded (angular), Mildly and Highly Abraded. The size-frequency distribution of the rocks follows a power-law [1]. The rock abundance is either measured (resolved scale analysis) or set as a free parameter (unresolved scale analysis). The size and spatial resolution of the DTM is defined by the scale of the analysis, either resolved or unresolved by LROC NAC. The Hapke reflectance model [4] is then used to illuminate these DTMs. Direct comparison of the reflectance at two phase angles as well as the Normalized Log Phase Ratio Difference value is carried out for the unresolved and resolved scale analysis, respectively.

References:

[1] Watkins R.N. et al. (2019) JGR-Planets, 124, 2754–2771 [2] Sato et al. (2014) JGR-P, 119,1775-1805 [3] Lin et al. (2020) A&A,638 [4] Hapke (2012) Theory of Reflectance and Spectroscopy [5] Robinson M.S. et al. (2010) SSR,150,81-124 [6] Rüsch and Wöhler (2021) submitted to Icarus arXiv:2109.00052v1

How to cite: Marshal, R. M., Rüsch, O., Wöhler, C., and Wohlfarth, K.: Estimating Lunar Rock Abrasion Stage using Photometric Studies, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12217, https://doi.org/10.5194/egusphere-egu22-12217, 2022.

The model for the catastrophic rupture of rocks on the lunar surface [1] is revisited by considering new functions describing rock shattering by impacts and size-frequency distributions of meteoroids. The input functions are calibrated by comparing the model block size–frequency
distributions with the measured size–frequency distribution of ejecta blocks around Tycho crater, which formation age is known. We find that the evolution of lunar block size–frequency distribution in the range 1–50 m is as follow: For young (≤ 50
Myr) population, the size–frequency distribution is best approximated by a power law, whereas for older populations, the extrapolation at small diameters is best performed by an exponential
distribution. New destruction rates are in better agreement with recent measurements [2,3] compared to the original model. For rocks above ~5 cm the survival time increases with increasing size, whereas for rocks below ~5 cm the survival time slightly increases with decreasing size. The updated model allows the estimation of both the exposure age and the initial abundance of a block field using the measurement of a block size–frequency distribution from LROC/NAC images.

References: [1] Hoerz et al., 1975, The Moon 13, 235–258. [2] Basilevsky et al., 2013, PSS, 89 (118–12). [3] Ghent et al., 2014, doi:10.1130/G35926.1.

How to cite: Ruesch, O., Marshal, R. M., Iqbal, W., Pasckert, J. H., van der Bogert, C. H., and Patzek, M.: The evolution of lunar rock size-frequency distributions: An updated model, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13240, https://doi.org/10.5194/egusphere-egu22-13240, 2022.

The ArtMoonMars programme of   cultural and artistic activities was started in 2010 by ILEWG Lunar Explorers Group in collaboration with ESA ESTEC and number of partner institutions, with more than 45 events (workshops, space artscience classes, public events, sessions at international conferences) and exhibitions.

What payload for an Artscience Museum on the Moon ?  For prototype ExoGeoLab lander in 2009. the team looked at possibility to host cultural or artscience  payload. Some joint ArtMoonMars events between space science, technology and art communities were organized, such as MoonLife Academy in 2010 .

ArtMoonMars organised classes of Artscience & Space at Royal Academy of Fine Arts in the Hague KABK –ESTEC. Artscience students participated to workshops at ESTEC & KABK and developed projects inspired by space and the Moon. These ArtScience classes were conducted 3 years with different themes. Some 50 ArtScience & Space projects were developed by students. Artists demos with scientists and engineers, including visual, electronic, VR artefacts and art performances.

ITACCUS The Committee for the Cultural Utilisation of Space (ITACCUS, created in 2006) https://www.iafastro.org/about/iaf-committees/technical-committees/committee-for-the-cultural-utilisation-of-space-itaccus.html

MoonGallery Foundation: The MoonGallery idea and concept was developed from 2010, to send an expanded gallery of artscience artefacts to the Moon on possible landers. on Gallery will launch 100 artefacts to the Moon within the compact format of 10 x 10 x 1cm plate on a lunar lander exterior panelling as early as 2022. .

A MoonGallery project team was formed in 2018 to issue a call for the community of artists. For these activities, ILEWG established ArtMoonMars grants to MoonGallery curators, and to some artists or temporary team members.

MoonMars Foundation : A new effort with external partner building on previous ArtMoonMars and EuroMoonMars programmes led to the definition of a new MoonMars foundation with broader objectives to develop opportunities and funding, to various groups including space artists.

Space Renaissance and Art: Space Renaissance International (SRI) is a global organisation dedicated to getting humanity off-world, not just astronauts engaged in pioneering exploration. The early Space Renaissance concept was founded on a pragmatic form of the humanist philosophy, with its roots here on Earth, and with its destiny among the stars. The founders took the historical Renaissance era with its focus on patronage of the arts and sciences as a model for a New Renaissance, a Space Renaissance. SRI runs a number of programs, projects and activities in support of its mission. It has started a Space Renaissance Art chapter.

How to cite: Foing, B. and team, I. L. E. and the ArtMoonMars collaboration team: ArtMoonMars Science, Cultural and Artistic programme: towards an Artscience Museum on the Moon  , EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13340, https://doi.org/10.5194/egusphere-egu22-13340, 2022.