PS8.1 | Rocky planets and moons: Evolution, characterization and astrobiological implications
Rocky planets and moons: Evolution, characterization and astrobiological implications
Convener: Jean-Pierre Paul de Vera | Co-conveners: Dennis HöningECSECS, Francesca MiozziECSECS, Kaustubh Hakim, John Lee Grenfell, Lena Noack, Benjamin TaysumECSECS
Orals
| Wed, 26 Apr, 08:30–10:15 (CEST)
 
Room E2
Posters on site
| Attendance Thu, 27 Apr, 16:15–18:00 (CEST)
 
Hall X4
Orals |
Wed, 08:30
Thu, 16:15
In this session, we discuss the interior structure and evolution, surface and atmosphere, and possible conditions and habitats for the origin and persistence of life of planetary bodies. We cover planets and moons within the solar system including Earth, Mars, and icy moons, and exoplanets from the size of Earth to Super-Earths and sub-Neptunes. We are interested the mineraolgy and interior structure of these planetary bodies, mantle evolution, interior-atmosphere volatile exchange, the conditions for habitability, prebiotic chemistry, the origin of life, signatures of life, and the possible links between life and the evolution of planetary reservoirs.

To this interdisciplinary session, we invite contributions of relevance to the topic from all fields of Planetary Sciences, Geology, Geochemistry, Geophysics, Photochemistry, (Exo-)Biology and Astronomy. This includes the formation and structure of planetary bodies, interior dynamics and evolution, insights from high-pressure high-temperature laboratory experiments, volatile outgassing and recycling, atmospheres, impacts, geological evidence of habitability, abiotic and prebiotic chemistry, biogeochemical interactions, extremophiles and the limits of life, preservation and detection of biosignatures, as well as mission concepts for exploration of planetary atmospheres and habitability.

Orals: Wed, 26 Apr | Room E2

Chairpersons: Jean-Pierre Paul de Vera, Dennis Höning
08:30–08:35
08:35–08:45
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EGU23-3391
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solicited
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Virtual presentation
Caroline Dorn

There is a lot of enthusiasm in the exoplanet community for the detection and characterization of super-Earth and sub-Neptunes. These planets seem most abundant among observable planets, and yet we know little about their interiors. Indirect evidence implies that sub-Neptunes have thick H/He envelopes on top of massive magma oceans, while super-Earths have lost their H/He envelopes. There is a lack of similar planets in the Solar System and therefore their origin and atmospheric evolution represent an important challenge for our understanding of planets.

Moreover, the majority of current formation and evolution models suffer from simplified assumptions of chemically inert interiors and cold rocky interiors in solid-state, as well as the neglect of volatile-exchange at the rock-atmosphere interface. This prevailing view is shifting: (1) the majority of exoplanets are partly molten, i.e., they host global magma oceans; (2) redox reactions between magma and atmospheric volatiles affect bulk composition; and (3) magma oceans represent huge reservoirs for volatiles. The exoplanet community is just beginning to explore new dimensions of these complexities. I will give an overview of general and personal efforts on this front.

How to cite: Dorn, C.: Deep volatile reservoirs in super-Earths and sub-Neptunes, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3391, https://doi.org/10.5194/egusphere-egu23-3391, 2023.

08:45–08:55
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EGU23-5425
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solicited
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Highlight
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On-site presentation
Frank Postberg, Yasuhito Sekine, Fabian Klenner, Christopher R. Glein, Zenghui Zou, Bernd Abel, Kento Furuya, Jonathan K. Hillier, Nozair Khawaja, Sascha Kempf, Lenz Noelle, Takuya Saito, Jürgen Schmidt, Takazo Shibuya, Ralf Srama, and Shuya Tan

Enceladus’s subsurface global ocean (1) can be probed by sampling the gaseous and icy material the moon expels into its cryovolcanic plume and - even further out - into Saturn’s E ring (2,3,4,5). Hydrothermal outflows caused by tidal heating (4,5,6), together with rich organic chemistry (7,8) imply that the moon appears to be one of most habitable places in our solar system. Among the critical elements C, H, N, O, P and S that are considered to be essential for life, all except phosphorous have either been identified (5,7,8) or - in the case of sulfur - tentatively detected (9). Recent geochemical modelling claims that P will be severely depleted in ocean worlds and thus P could be a bottle neck for the emergence of life in subsurface oceans (10).

Here we present results from a re-analysis of mass spectrometric data from Cassini’s Cosmic Dust Analyzer (CDA), showing proof of sodium-phosphate salts in ice grains originating from Enceladus’s subsurface ocean. We found a small number of ice grains whose spectra clearly indicate the presence of at least two sodium orthophosphates: Na3PO4 and Na2HPO4. These CDA spectra have been subsequently reproduced in the laboratory which enables the quantitative evaluation of CDA spectra (11). We infer phosphate concentrations in the Enceladus ocean in the order of a few mM, at least 100-times higher concentrations than in Earth’s ocean.

We carried out geochemical experiments and calculations showing that such high phosphate abundances can be achieved in Enceladus, either at the cold seafloor or in hydrothermal environments with moderate temperatures. The driver enabling the abundant availability of phosphate is the high observed concentration of dissolved carbonate species, which shift phosphate-carbonate mineral equilibria toward dissolution of solid phosphates into Enceladus’ ocean. We show that interactions between chondritic rocks and CO2-rich fluids generally lead to conditions where dissolved phosphate concentrations tend to maximize. Therefore P-rich oceans would commonly occur in ocean worlds beyond in the outer Solar System beyond the CO2 snow line.

These results demonstrate that Enceladus has a high availability of dissolved P, which is thus likely not a limiting factor for development of putative life on Enceladus and probably on other ocean worlds in the outer Solar System. Since phosphate plays many roles in organic synthesis (12), Enceladus and other icy bodies could moreover serve as natural analogs of P-rich environments on early Earth, where chemical evolution might have been promoted.

1 Thomas et al., Icarus 264 (2016), 2 Postberg et al., Nature 459 (2009), 3 Postberg et al., Nature 474 (2011), 4 Hsu et al., Nature 519 (2015), 5 Waite et al., Science 356 (2017), 6 Choblet et al. , Nat Astron 1 (2017), 7 Postberg et al., Nature 558 (2018) , 8 Khawaja et al., MNRAS 489 (2019), 9 Postberg et al., ISBN: 9780816537075 (2018), 10 Lingam & Loeb, Astron. J., 2018., 11 Klenner et al., Rapid Commun Mass Spectrom 33 (2019), 12 Powner et al., Nature 459 (2009)

How to cite: Postberg, F., Sekine, Y., Klenner, F., Glein, C. R., Zou, Z., Abel, B., Furuya, K., Hillier, J. K., Khawaja, N., Kempf, S., Noelle, L., Saito, T., Schmidt, J., Shibuya, T., Srama, R., and Tan, S.: Detection of phosphate in Enceladus’ ocean with implications for geochemistry and habitability in the outer solar system, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5425, https://doi.org/10.5194/egusphere-egu23-5425, 2023.

08:55–09:05
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EGU23-7267
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Highlight
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On-site presentation
Haje Korth, Robert Pappalardo, Bonnie Buratti, Kate Craft, Sam Howell, Rachel Klima, Erin Leonard, and Alexandra Matiella Novak

With a launch readiness date of late 2024, NASA’s Europa Clipper will set out on a journey to explore the habitability of Jupiter’s moon Europa. At the beginning of the next decade, the spacecraft will orbit Jupiter, flying by Europa more than 40 times over a four-year period to observe this moon’s ice shell and ocean, study its composition, investigate its geology, and search for and characterize any current activity. The mission’s science objectives will be accomplished using a highly capable suite of remote-sensing and in-situ instruments. The remote sensing payload consists of the Europa Ultraviolet Spectrograph (Europa-UVS), the Europa Imaging System (EIS), the Mapping Imaging Spectrometer for Europa (MISE), the Europa Thermal Imaging System (E-THEMIS), and the Radar for Europa Assessment and Sounding: Ocean to Near-surface (REASON). The in-situ instruments comprise the Europa Clipper Magnetometer (ECM), the Plasma Instrument for Magnetic Sounding (PIMS), the SUrface Dust Analyzer (SUDA), and the MAss Spectrometer for Planetary Exploration (MASPEX). Gravity and radio science will be achieved using the spacecraft's telecommunication system, and valuable scientific data will be acquired by the spacecraft’s radiation monitoring system. The project, flight system, and payload have completed their Critical Design Reviews, and the project has completed its System Integration Review, so that Europa Clipper is now formally in mission Phase D. The spacecraft and payload are currently under construction, as assembly, testing, and launch operations (ATLO) are well underway. Recent major milestones include the delivery to ATLO of the Propulsion Module and six instruments (E-THEMIS, Europa-UVS, EIS-WAC, PIMS, MASPEX, SUDA) and the assembly of the solar array wings. The integration of these instruments’ sensors on the spacecraft and its nadir-viewing deck and of the instrument electronics in vault has begun. The remaining instruments (ECM, EIS-NAC, MISE, REASON) are in mature stages of assembly and will be delivered in the next months. The science team is in the process of evaluating minor changes to the candidate tour, and is preparing a set of manuscripts describing the mission’s science and instruments for publication in the journal Space Science Reviews.

How to cite: Korth, H., Pappalardo, R., Buratti, B., Craft, K., Howell, S., Klima, R., Leonard, E., and Matiella Novak, A.: Europa Clipper Mission Update, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7267, https://doi.org/10.5194/egusphere-egu23-7267, 2023.

09:05–09:15
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EGU23-663
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ECS
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On-site presentation
Seda Işık, Mohit Melwani Daswani, and Emre Işık

The icy moons in the Solar System, such as Europa, Enceladus and Titan, are  of great interest to the astrobiological and biogeochemical communities, owing to their subsurface liquid oceans. These oceans are potential targets for deep explorations of biochemical processes in our cosmic neighbourhood.

In our study, we use the Deep Earth Water (DEW) model to calculate the thermodynamic properties of water and aqueous compounds. We employ DEWPython, a modular software interface, enabling access to both DEW and SUPCRT models, with the purpose of investigating the stability of organic molecules in ocean worlds. In particular, we model the equilibrium constant and Gibbs free energy (GFE) as a function of pressure and temperature for reactions involving metabolically essential amino acids, basic molecules possibly involved in the emergence of life (H2, NH3, CH4, etc.), as well as products of water-rock interaction such as serpentinization and abiotic methanogenesis. Considering the results from space missions such as Europa Clipper and Dragonfly, such molecular stability analyses can contribute to the search for conditions ideal for habitability and extraterrestrial life.

We map out reaction networks, by first calculating the individual equilibrium constants and GFE changes of the hydrothermal reactions that (i) form a given organic species from inorganics, and then (ii) decompose into other (in)organic molecules. In the final step, we obtain the net equilibrium constant as a measure of the stability of the species, by proportioning the total equilibrium constant of the reactions responsible for the formation of a particular species to those responsible for its destruction. At a given pressure and temperature, a value greater or less than unity indicates that the formation of a species is favourable or unfavourable, respectively.

Our current results suggest that alanine and glycine, two common and simple amino acids, can remain stable throughout the ocean columns, and just beneath the seafloors, of Titan and Europa, and thus could potentially be sampled by plumes or cryovolcanism.

In the next development phase of our model, we will further constrain the depths at which the species of interest can be found, by identifying and ruling out regions of high pressure ice stability, using the SeaFreeze model.

The research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration (80NM0018D0004). © 2022. Jet Propulsion Laboratory, California Institute of Technology. Government sponsorship acknowledged.

Fig 1 : Alanine stability (contours) through Europa’s ocean and ocean floor (colored lines). Positive (negative) regions indicate stable (unstable) conditions.

How to cite: Işık, S., Daswani, M. M., and Işık, E.: Stability of organic species in ocean world interiors with geochemical models, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-663, https://doi.org/10.5194/egusphere-egu23-663, 2023.

09:15–09:25
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EGU23-10768
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ECS
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On-site presentation
Fakhri Bintang, Tobias Keller, and Luke Daly

Collisions of planetesimals with pre-differentiated cores aided in the formation of the cores in the terrestrial planets in our Solar System. The differentiation of the interior of planetesimals from a primitive chondritic composition to differentiated metallic core and silicate mantle is therefore an important step in the development of the early Solar System, setting the initial conditions for collisional planetary growth. However, meteoritic evidence of the differentiation stage of planetesimals are rare and challenging to interpret. Therefore, mathematical models are necessary to constrain the timescales and elucidate the physics behind metal-silicate segregation in planetesimals. We present progress towards a new numerical model which models the thermo-chemical and fluid-mechanical evolution of silicate-metal planetesimals. The model is comprised of four material phases: solid and liquid silicates, and solid and liquid Fe-FeS metal. Hence, the model quantifies the different segregation rates of metal alloys at various stages of planetary melting. The thermo-chemical evolution quantifies the melting and chemical fractionation of the materials using two separate phase diagrams for the silicate and iron systems respectively and calibrated based on enstatite chondrite meteorites as the starting primitive material. The fluid mechanics represents conditions where the silicate liquid phase dominates and captures the settling of solid particles and immiscible liquid metal droplets by hindered Stokes settling. Our model will simulate core formation under a range of initial planetesimal compositions, nebular compositions, and planetesimal sizes. We also intend to implement compatible element partitioning into our model, in particular Hf-W isotope partitioning, to compare our model results with the meteoritic record. Results from our model will allow more robust estimations of the timescales for planetesimal core formation.

 
 

How to cite: Bintang, F., Keller, T., and Daly, L.: Four-phase modelling of metal-silicate differentiation in planetesimals, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10768, https://doi.org/10.5194/egusphere-egu23-10768, 2023.

09:25–09:35
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EGU23-6149
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ECS
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Highlight
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On-site presentation
Vera Palma, Nicasio Jiménez-Morillo, Francesco Sauro, Matteo Massironi, José M. De la Rosa, José A. González-Pérez, Bogdan Onac, Igor Tiago, Ana Teresa Caldeira, and Ana Z. Miller

The Selvagens Islands (Madeira, Portugal), located in the North Atlantic, are a small archipelago of volcanic origin formed by two main islands, which emerged in the Oligocene (25-29 Ma). These oceanic islands are recognized as a unique example of marine and terrestrial biodiversity, characterized by many endemic species. Still unblemished by civilization, this isolated and undisturbed ecosystem makes the volcanic caves from Selvagens a promising model system for investigating biosignatures preserved in the rock record valuable for astrobiology. 

The Inferno Cave, one of the three main terrestrial caves of the Selvagens Islands, has copious amounts of fine white powder crusts scattered throughout the cave. From the mineralogical point of view, the whitish powdery deposits are mainly composed of gypsum and minor amounts of clay minerals. Thermal analyses (TG/DTG-DsC) revealed the presence of labile and stable organic matter (OM), with contrasting relative abundances among the gypsum samples. The stable isotope composition of carbon was determined by elemental analysis coupled to isotope ratio mass spectrometry (EA/IRMS) to decipher the origin of the organic fraction preserved in the gypsum deposits. Two well-differentiated organic matter pools were distinguished: one comprising 𝛿13C values > –19 ‰ related to microbial activity (i.e., microbial degradation of fresh organic matter), and another with 𝛿13C < –20 ‰), which may suggest the preservation of recalcitrant biomarkers from aboveground vegetation. U-series results from the gypsum deposits were used to produce isochron ages needed to generate an age-depth model for the 1-m thick gypsum deposit.

A detailed study of the organic fraction preserved in the gypsum deposits was conducted by pyrolysis gas chromatography/ mass spectrometry (Py-GC/MS) and by GC-MS after extraction of total lipids. Preliminary results show the presence of n-alkanes of low molecular weight (<C21). In addition, long-chain n-alkanes (C>21) were also observed, which indicates a direct contribution of plant biomass from the overlying surface. Interestingly, the Py-GC/MS analysis also shows relatively large contents of mid-chain branched alkanes associated with a direct biological source focused on microorganisms since they are known to biosynthesize such alkanes. A predominance of chemolithotrophic microbial communities was found based on the 16S rRNA gene analysis, which is consistent with the biological origin of the mid-chain branched alkanes. 

The mineralogical, biogeochemical, and microbiological characterization of the gypsum samples from the pristine Selvagens Islands is thus a reliable way to infer the biogenicity of cave mineral deposits, recognize biosignatures, and determine paleoenvironmental changes from a natural environment, free from anthropogenic influence. Considering the analogies with Mars, the Selvagens Islands are also suitable for space research, including astronaut training and rover testing for future planetary missions.

Acknowledgements: This work received support from the Portuguese Foundation for Science and Technology (FCT) under the MICROCENO project (PTDC/CTA-AMB/0608/2020). The financial support from the Spanish Ministry of Science and Innovation (MCIN) under the research project TUBOLAN PID2019-108672RJ-I00 funded by MCIN/AEI/ 10.13039/501100011033 is also acknowledged. A.Z.M. was supported by the CEECIND/01147/2017 contract from FCT, and the Ramón y Cajal contract (RYC2019-026885-I) from the MCIN.

 

How to cite: Palma, V., Jiménez-Morillo, N., Sauro, F., Massironi, M., De la Rosa, J. M., González-Pérez, J. A., Onac, B., Tiago, I., Caldeira, A. T., and Miller, A. Z.: Looking for biosignatures in a pristine Mars analogue environment on Earth, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6149, https://doi.org/10.5194/egusphere-egu23-6149, 2023.

09:35–09:45
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EGU23-4382
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Highlight
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On-site presentation
Taras Gerya and Rbert Stern

It is often assumed that quest for intelligent life is equivalent to quest for any life in general. In particular, the Drake Equation predicts that there should be many exoplanets in our galaxy hosting active, communicative civilizations (ACCs) but the Fermi Paradox notes that there is no evidence that any others exist. The paradox may be explained by recognizing that advanced complex life is only likely to develop on a very small fraction of planets hosting any life. Here, we suggest that ACCs can only develop on a convecting silicate body with life, prolonged plate tectonics and significant expanses of oceans and continents, and that meeting all three of these requirements may be extremely difficult to achieve.  Continents and oceans are required because early life evolution must happen in water but late evolution capable of creating technology must happen on slowly but continuously evolving land masses due to the critical influence of landscape and habitat diversity in space and time for accelerating the evolution of complex species. We further suggest that oceanic-continental plate tectonic environments of the modern Earth have formed only very recently at 1.0-0.5 Ga and accelerated the evolution of complex life in five ways: 1) increased nutrient supply; 2) increased free oxygen in the atmosphere and ocean; 3) climate amelioration; 4) accelerated habitat formation; and 5) moderate sustained environmental pressure.  The absence of comparable factors on the other possible types of global tectonic environments (such as squishy lid, stagnant lid, volcanic heat pipe) characteristic for silicate bodies (e.g., early Earth, Mars, Venus, Mercury, Moon, Io) makes the emergence of both complex life and ACCs on such bodies unlikely.  The Fermi Paradox may therefore be resolved if: 1) two additional terms are added to the Drake Equation: foc (the fraction of exoplanets with significant continents and oceans) and fpt (the fraction of habitable planets that have had plate tectonics operating for at least 500 Ma; and 2) the product of foc and fpt is very small.  The lack of evidence for extraterrestrial civilizations in our galaxy may reflect the scarcity of long-lived oceanic-continental plate tectonic environments in particular requiring goldilocks condition in term of the stable surface water volume allowing for long-term coexistence of both dry lands and oceans. 

How to cite: Gerya, T. and Stern, R.: The Key Role of Plate Tectonics for Accelerating the Evolution of Complex Life: Quest for the Missing Extraterrestrial Civilizations, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4382, https://doi.org/10.5194/egusphere-egu23-4382, 2023.

09:45–09:55
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EGU23-13456
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Highlight
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On-site presentation
Sascha P. Quanz and The LIFE collaboration

One of the major goals - and possibly the most challenging one in 21st century exoplanet research - is the investigation of the atmospheric properties for a large number of terrestrial exoplanets. On the one hand, a statistically significant dataset is invaluable for understanding the diversity of planetary bodies, but on the other hand, this is driven the motivation to search for habitable conditions and identify potential biosignatures, i.e., indications of biological activtity, outside our Solar System. First steps in this direction will be taken in the coming 10-15 years with funded or selected ground- and space-based projects and missions. In addition, the US astrophysics decadal recommended a UV-optical-NIR space telescope (the Habitable Worlds Observatory) with an aperture diameter of at least 6 meters as next flagship mission for the 2040s. This telescope shall be sensitive enough to survey dozens of Earth-sized exoplanets. A highly synergistic approach to this mission, which focuses on the reflected light of the exoplanets, is to directly detect the exoplanets’ thermal emission in the mid-infrared by means of a space-based nulling interferometer. In this contribution, we summarize the current status of the European-led LIFE initiative, which has the goal to develop the science, the technology and a roadmap for such an ambitious space mission that will allow humankind to detect and characterize the atmospheres of hundreds of nearby extrasolar planets including dozens that are similar to Earth. Given the outcome of ESA’s "Voyage 2050" process and the corresponding recommendations from the ESA Senior Committee, the direct detection of the thermal emission of temperate terrestrial exoplanets is given very high scientific priority in ESA future science program and is considered as a candidate theme for a future L-class mission. The unique discovery space for a mid-infrared mission, in particular for the detection of atmospheric biosignatures in exoplanets, will be discussed, the international scope of the inititiative (including contributions from the US, Japan and Australia) will be highlighted, and synergies between LIFE and the NASA's future Habitable Worlds Observatory mission will be emphasized.

How to cite: Quanz, S. P. and collaboration, T. L.: The LIFE initiative - establishing a space mission to search for biosignatures in exoplanet atmsopheres in the mid-infrared, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13456, https://doi.org/10.5194/egusphere-egu23-13456, 2023.

09:55–10:05
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EGU23-15501
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ECS
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On-site presentation
Marrick Braam, Paul Palmer, and Leen Decin

Interpreting atmospheric spectra of exoplanets requires understanding the underlying atmospheric physics and chemistry. Studies have previously shown that for tidally locked, Earth-like exoplanets that orbit M-dwarf stars, photochemistry supports a highly structured 3-D ozone distribution, including a stratospheric ozone layer. We use a 3-D coupled Climate-Chemistry model (CCM), the Met Office Unified Model with the UK Chemistry and Aerosol framework, to describe the atmosphere of Proxima Centauri b. The chemical network includes the Chapman ozone reactions and the hydrogen oxide and nitrogen oxide catalytic cycles. We find that ozone is mainly produced on the dayside of the planet, initiated by the incoming stellar radiation. The ozone is then advected to the nightside, where it descends at the locations of permanent Rossby gyres that result in localised ozone hotspots. We will show that a stratospheric dayside-to-nightside circulation drives this nightside ozone distribution. This finding illustrates the 3-D nature of exoplanetary atmospheres and the potential impact on spectroscopic observations.

How to cite: Braam, M., Palmer, P., and Decin, L.: Stratospheric dayside-to-nightside circulation responsible for nightside ozone hotspots on tidally-locked exoplanets, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15501, https://doi.org/10.5194/egusphere-egu23-15501, 2023.

10:05–10:15
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EGU23-11789
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ECS
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Highlight
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On-site presentation
Andreas Bartenschlager, John Lee Grenfell, Konstantin Herbst, Miriam Sinnhuber, Ben Taysum, and Fabian Wunderlich

The launch of the James Webb Space Telescope (JWST) in December 2021 opens up the possibility of studying the composition of exoplanetary atmospheres in habitable zones, such as TRAPPIST-1e, in the near future. With the help of numerical models of the exoplanetary atmospheres, the observations and the processes behind them can be better understood and interpreted (Herbst et al., 2022). We investigate the influence of stellar energetic particles (SEPs) and galactic cosmic rays (GCRs) on the atmospheric chemistry of exoplanets around a very active M-star using the ion chemistry model ExoTIC. In collaboration with the University of Kiel and DLR Berlin, we perform model experiments with different N2 or CO2 dominated atmospheres, depending on the initial CO2 partial pressure, as well as humid and dry conditions (Wunderlich et al., 2020), taking into account the ionization rates for such events. A further specification regarding the scenarios results from the distinction between dead and alive atmospheres, whose atmospheric composition is characterized by a lower or higher oxygen fraction in the initial conditions. Within ExoTIC we can calculate the impact of the ionization events on these atmospheres both as a single and as a series of events with different strengths. Preliminary results show a significant impact of SEP events on the chemical composition of the atmosphere, including biosignatures such as O3 . The strength and structure of these impacts depend on the composition of the starting atmosphere, in particular on the availability of oxygen as well as nitrogen and water vapour.

How to cite: Bartenschlager, A., Grenfell, J. L., Herbst, K., Sinnhuber, M., Taysum, B., and Wunderlich, F.: Investigation of the Influence of Stellar Particle Events and Galactic Cosmic Rays on the Atmosphere of TRAPPIST-1e, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11789, https://doi.org/10.5194/egusphere-egu23-11789, 2023.

Posters on site: Thu, 27 Apr, 16:15–18:00 | Hall X4

Chairperson: Lena Noack
Planet formation and composition
X4.348
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EGU23-5257
Stephen Mojzsis, Robert Spaargaren, and Ramon Brasser

Abundance patterns ranging from (ultra-)refractory (e.g. W, Zr, Al, Ca and Rare Earth Elements), to moderately volatile (e.g. Li, K and Na) and highly volatile (e.g. Zn, Cl, Br, I and In) lithophile elements show a broadly ‘hockey stick’ element depletion trend for Earth and Mars [1,2]. This is because refractory element abundances relative to solar composition and normalized to Mg or Al [3] are weakly affected by devolatilization processes but the moderately volatile elements describe a devolatilization depletion factor with a particular slope (α). Volatile elements with 50% condensation temperatures (TC,50%) 750-500 K (Zn) are unfractionated with respect to one another [4]. This pattern is recapitulated in some carbonaceous chondrite meteorite groups (CM, CV and CR). Such secular trends in lithophile element abundances potentially yield useful clues regarding the parameter space of planetary accretion such as localization of feeding zones, supply of volatile species to the planets and the degree to which orbital architecture may have changed due, for example, to migration. Nucleosynthetic isotopic tracers (e.g. 50Ti, 54Cr, 62Ni), as well as mass-independent oxygen isotopes (expressed in the conventional notation as: 'D17OVSMOW) of the sampled terrestrial planets, deviate from the volatile-rich carbonaceous chondrites (CC). The terrestrial planets instead show affinities with the non-carbonaceous feedstocks (NC) that are poorer in volatiles than CC. Here, we show that Earth and Mars, along with best estimates of the bulk compositions of Mercury and Venus inferred from geochemical models coupled with remote and in situ analysis, display both a hockey stick element depletion pattern and systematically different devolatilization depletion factors of the moderately volatile lithophiles (slope, α). We further find that the degree of devolatilization in TC,50% as a function of depletion trend (α) plotted against total stellar irradiance (S0 in in Wm-2) correlates with heliocentric distance (au) and thus, stellar luminosity, following a power law . This relationship accounts for the bulk compositions and volatile inventories of the inner planets, and strongly implies that they formed locally, in agreement with recent studies [7-9]. We also find that some NC achondrite meteorite groups (e.g. angrites, ureilites) record extreme lunar-like depletion trends (α) that we interpret to be from a special origin (i.e. colossal impacts with re-condensation). To lowest order, these observations reveal information about complex processes in planet formation scenarios while considering the already-assembled planet. Finally, imminent data (e.g. JWST spectra) for ionized lithophile elements in the atmospheres of ultra-short period exoplanets will allow us to quantitatively assay formation models that are too simple and/or seem to indicate an unwitnessed process in the history of a planet such as migration.

 

References: [1] Carlson et al. Space Sci. Rev. 214:121 (2018); [2] Vollstaedt et al. ApJ 897:82 (2020); [3] Wang et al. Icarus 328:287-305 (2019); [4] Braukmuller et al. Nat. Geosci. 12:564-568 (2019); [5] Sossi et al. Nat. Astro. 6:951-960 (2022); [6] Yoshizaki & McDonough. Geochem. 81:125746 (2021); [7] Mah et al. MNRAS 511, 158–175 (2022); [8] Mah et al., A&A 660, A36; [9] Brasser & Mojzsis. Nat. Astro. https://doi.org/10.1038/s41550-019-0978-6.

How to cite: Mojzsis, S., Spaargaren, R., and Brasser, R.: Total stellar irradiance and lithophile element devolatilization trends for the terrestrial planets, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5257, https://doi.org/10.5194/egusphere-egu23-5257, 2023.

X4.349
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EGU23-17577
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ECS
Maximilian Zimmermann and Elke Pilat-Lohinger

We show the distribution of collision parameters of planetesimals and planetary embryos in an evolving protoplanetary disk for various binary star–giant planet configurations. This statistical study provides an overview which and how many of the mutual disk object collisions have to be studied in more detail with SPH (smooth particle hydrodynamics) simulations and which can be approximated by a “corrected“ perfect merging process. In all configurations the gas has been already depleted and thus, only gravitational interactions are
taken into account.The binary star systems (with M = 1 M ⊙ for both) have seperations of 50 au or 100 au and eccentricities of 0.0 or 0.3. In the 50 au binary star the giant planet (with M ≈ MJ ) is placed at 3 or 5 au and in the 100 au binary systems at 4.5 or 6 au. In all configurations the planetsimal/embryo disk consists of about 1500 objects which move in nearly circular and planar orbits between the host-star and the giant planet. In the different simulations the disk objects have masses either from Ceres to Moon mass in case of planetesimals or from Moon to Mars mass in case of planetary embryos. To study the gravitational interactions of the whole system our recently developed GPU N-body integrator GANBISS is used, which is able to simulate some thousand (massive) disk objects in binary star systems.

How to cite: Zimmermann, M. and Pilat-Lohinger, E.: N-body interactions in proto-planetary disks: A study of collision velocities and impact angles, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-17577, https://doi.org/10.5194/egusphere-egu23-17577, 2023.

X4.350
|
EGU23-17428
|
ECS
Terrestrial Planet formation Simulations: Homogeneous Comparison between Methods.
(withdrawn)
Samuele Crespi and Ian Dobbs-Dixon
X4.351
|
EGU23-16508
Nader Haghighipour and Jeffrey Sudol

We have developed the currently most comprehensive and self-consistent approach to realistically simulate the formation of terrestrial planets in our solar system including the formation of Mars. Our approach begins with simulating the collisional growth of planetesimals and continues with resolving giant impacts and the full formation of terrestrial planets. It takes into account the dynamical friction due to the debris and planetesimal disks, migration of planetesimals and embryos, and the perturbation as well as possible migration of giant planets. As the most important step toward a fully comprehensive and realistic model, our approach incorporates SPH simulations into N-body integrations in real time allowing, for the first time, collisions to be simulated accurately as they occur. Results point to several important findings. For instance, in the context of our solar system, almost all simulations produced an Earth-analog. They also demonstrated that the similarities between the size and mass of Earth and Venus are a natural outcome of the formation process, and Mars-sized planets appear in systems where the mass distribution in the planetesimal disk is non-uniform. When studying the effects of giant planets, results showed that secular resonances are the main reason that our solar system does not have Super-Earths. They are also the reason that terrestrial planets form interior to 2.1 AU. Simulations also show that the capture into resonance of migrating giant planets does not play a significant role on the formation of terrestrial planets, and while giant planets may affect the inventory of planet-forming material and water-carrying objects, especially when they migrate, they play no role in the mechanics of the formation of terrestrial planets and the transfer/transport of water to them. Formation and water delivery is merely due to the mutual interactions of planetary embryos, a process that occurs even when no giant planet exists. We will present the results of our study and discuss their applications to extrasolar planets. 

How to cite: Haghighipour, N. and Sudol, J.: A Comprehensive and Self-consistent Model of Terrestrial Planet Formation, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16508, https://doi.org/10.5194/egusphere-egu23-16508, 2023.

X4.352
|
EGU23-9390
Terrestrial Planet Formation in Systems with Three Giant Planets
(withdrawn)
Farhang Habibi and Nader Haghighipour
X4.353
|
EGU23-16843
|
ECS
Longhui Yuan and Man Hoi Lee

GJ 1148 is an M-dwarf star, which has two well-separated Saturn mass planets with an orbital period ratio of around 13 and eccentricities of around 0.375 at the current epoch. A plausible scenario for producing the orbital architecture of the GJ 1148 system is planet-planet scattering. To test this scenario, we perform scattering experiments, assuming the third planet of 0.1 MJ (Jupiter’s mass) in the initial GJ 1148 system with initial orbital separations set to 3.5, 4, and 4.5 mutual Hill radii Rm,H respectively and initial semi-major axis of the innermost planet ai,1 in the range of 0.10-0.50 AU. The majority of scattering results in planet-planet collisions, followed by planet ejections, and planet removals as its distance to the star are smaller than a critical value of 0.02 AU. Among them, only the post-ejection two-planet systems have similar properties to the GJ 1148 system, and when ai,1 is around 0.21 AU, the semi-major axis of the inner planet GJ 1148 b can be reproduced. We further perform simulations with ai,1 in a narrower range between 0.16 and 0.30 AU, and found one system with similar orbital properties to the GJ 1148 system. Therefore, the simulation results suggest that the GJ 1148 system may have lost a giant planet. The two-sample Kolmogorov–Smirnov (KS) test on simulations with and without GR apsidal precession shows that it does not affect the ejection outcomes. When setting the mass of the third planet to 0.227 MJ of GJ1148 c, the optimal ai,1 move to about 0.29 AU.

How to cite: Yuan, L. and Lee, M. H.: Scattering of Giant Planets Around M-dwarf: The Implication for the Origin of the Hierarchical and Eccentric Two-planet System like GJ 1148, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16843, https://doi.org/10.5194/egusphere-egu23-16843, 2023.

X4.354
|
EGU23-11015
Paolo Sossi, Lukas Carmichael, and Kaustubh Hakim

To date, more than 5000 exoplanets have been discovered, of which roughly 1800 are thought to be rocky on the basis of mass and radius measurements. However, the resulting densities are degenerate with respect to the compositions of these planets, necessitating other constraints. Of these, the most readily available is the composition of the host star (e.g. Adibekyan et al. 2021). On this basis, the compositions of rocky exoplanetary mantles are expected to be similar to those found in our own Solar System (e.g. Putirka and Rarick, 2019; Spargaaren et al. 2022). Here, we evaluate this conclusion by examining stellar compositions in the system Fe-O-Mg-Si-Ca-Al for F- and G-type stars in the Hypatia and GALAH databases. In reducing the multidimensionality of the dataset, we apply a Principal Component Analysis (PCA) to identify the prevailing chemical trends among the stellar population. We find that the first principal component describes the positive correlation among major element abundances, though O abundance increases less markedly with Fe than those of metals. Therefore, increasing metallicity (as defined by Fe/H) results in an increase in the metal/oxygen ratio of the star. Consequently, the core mass fraction of rocky planets around such stars cannot be treated as a free parameter. Instead, we predict compositions of hypothetical Earth-like planets (i.e., assuming planet/star chemical fractionation equivalent to Earth/Sun) and show that planets around low metallicity stars can be coreless, while those orbiting high metallicity stars should have Fe-free mantles and abundant Si in their cores.

How to cite: Sossi, P., Carmichael, L., and Hakim, K.: Extreme compositional diversity among rocky exoplanets, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11015, https://doi.org/10.5194/egusphere-egu23-11015, 2023.

X4.355
|
EGU23-11232
|
ECS
Ron Maor and David Goldsby

The planetary Love number is a dimensionless parameter representing the deformation response of a planet
to stress (Love, 1927). In its original formalism, the Love number was defined for pure elastic deformations,
but this definition was later extended to linear viscoelastic deformations using the Correspondence Principle
(Peltier, 1974). Currently, there are multiple methods for calculating planetary Love numbers that can
incorporate advanced rheological models (Henning and Hurford, 2014; Renaud and Henning, 2018; Melini
et al., 2022), yet all of these methods require that the rheology will be limited to linear viscoelasticity.
On the other hand, laboratory studies of attenuation on different geological materials suggest a nonlinear
viscoelastic behavior due to the movement of dislocations within the lattice (Gueguen et al., 1989; McCarthy
and Cooper, 2016). At high enough stresses, dislocations can escape pinning points and interact with
each other (Gremaud, 2009), leading to permanent deformations and attenuation that is dependent on
the amplitude of the oscillations. In this work, we are taking the first step into incorporating nonlinear
viscoelasticity in the calculation of planetary Love numbers. Assuming a homogeneous, incompressible,
self-gravitating sphere with nonlinear rheology, we are using a numerical scheme to calculate the complex
Love number. The results of the numerical model are then compared to the known analytical solutions for
the linear case.

How to cite: Maor, R. and Goldsby, D.: The Effect of Nonlinear Viscoelasticity on Planetary Love Numbers, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11232, https://doi.org/10.5194/egusphere-egu23-11232, 2023.

Long-term evolution of planets and habitats
X4.356
|
EGU23-14069
|
ECS
Tobias G. Meier, Dan J. Bower, Tim Lichtenberg, Paul J. Tackley, Mark Hammond, and Brice-Olivier Demory

Many super-Earths are very close-in to their host star and are therefore likely to be tidally locked. Tidally locked super-Earths experience intense solar heating on their permanent dayside, whereas the nightside surface can reach extremely cold temperatures. For the case of super-Earth LHS 3844b, a bare-rock super-Earth with a radius around 1.3 Earth radii, we have shown that this strong contrast between the dayside and nightside surface temperature can lead to a so-called hemispheric tectonic regime. Such a regime is characterised by a strong downwelling on one hemisphere and upwellings that rise on the other side. We further define hemispheric tectonics as a special case of degree-1 convection (one upwelling and one downwelling), where the downwelling gets pinned to either the dayside or nightside and upwellings are preferentially on the other hemisphere.  

Here, we focus on super-Earth GJ 486b, which has also a radius around 1.3 Earth radii, but for which it is unknown whether it was able to retain an atmosphere. We investigate how different surface temperature contrasts affects the likelihood of hemispheric tectonics.  
For this, we run 2D geodynamic simulations of the interior mantle flow using the mantle convection code StagYY. The models are fully compressible with an Arrhenius-type viscosity law where the mantle is mostly composed of perovskite and post-perovskite. The lithospheric strength is modelled through a plastic yielding criterion and the models are basally heated. We use general circulation models (GCMs) of potential atmospheres to constrain the surface temperature assuming different efficiencies of atmospheric heat circulation. We find that degree-1 convection is a consequence of the strong lithosphere, while hemispheric tectonics is favoured for strong surface temperature contrasts between the dayside and nightside, and higher surface temperatures. 

Our results show that hemispheric tectonics or degree-1 convection could operate on super-Earth GJ 486b (or other tidally locked super-Earths), even if the surface temperature contrast between the dayside and nightside is not as strong as for LHS 3844b. Upwellings that rise preferentially on one hemisphere could lead to generation of melt and subsequent outgassing of volatiles on that side. Imprints of such outgassing on the atmospheric composition could possibly be probed by current and future observations such as JWST, ARIEL, or the ELT. 

How to cite: Meier, T. G., Bower, D. J., Lichtenberg, T., Tackley, P. J., Hammond, M., and Demory, B.-O.: Exploring hemispheric tectonics on tidally locked super-Earths, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14069, https://doi.org/10.5194/egusphere-egu23-14069, 2023.

X4.357
|
EGU23-5578
|
Alexander Grayver, Dan Bower, Joachim Saur, Caroline Dorn, and Brett Morris

Many stars of different spectral types with planets in the habitable zone are known to emit flares. Until now, studies that investigated the long-term impact of stellar flares and associated Coronal Mass Ejections (CMEs) assumed that the planet's interior remains unaffected by interplanetary CMEs, only considering the effect of energetic particles interactions on the atmosphere of planets. Here, we show that the magnetic flux carried by flare-associated CMEs results in planetary interior heating by ohmic dissipation and leads to a family of new interior–exterior interactions. We construct a physical model to study this effect and apply it to the TRAPPIST-1 and Proxima Centauri stars whose flaring activity has been constrained by Kepler and TESS observations. We pose our model in a stochastic manner to account for uncertainty and variability in major input parameters. Our results suggest that the heat dissipated in the silicate mantle is both of sufficient magnitude and longevity to drive geological processes and hence facilitate volcanism and outgassing particularly for the innermost planets. Furthermore, our model predicts that Joule heating can further be enhanced for planets with an intrinsic magnetic field compared to those without. The associated volcanism and outgassing may continuously replenish the atmosphere and thereby mitigate the erosion of the atmosphere caused by the direct impact of flares and CMEs.

How to cite: Grayver, A., Bower, D., Saur, J., Dorn, C., and Morris, B.: Interior heating of rocky exoplanets from stellar flares with application to Trappist-1 and Proxima Centauri, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5578, https://doi.org/10.5194/egusphere-egu23-5578, 2023.

X4.358
|
EGU23-15709
Kaustubh Hakim, Meng Tian, Dan J. Bower, and Kevin Heng

The carbonate-silicate cycle is thought to play a key role in maintaining temperate climates on Earth via continental silicate weathering and seafloor carbonate precipitation. Present-day carbonate precipitation on Earth’s seafloor is mainly attributed to calcium carbonates. However, observations of refractory element ratios in stellar photospheres and planet formation models suggest a large diversity in exoplanet bulk composition and thereby the near-surface composition. In this work, we compute exoplanet ocean pH and carbonate compensation depth (CCD). We find that ocean pH exhibits a limited range of values as a function of ocean temperature and partial pressure of CO2, where the limits are given by the absence and presence of carbonates. The CCD increases with ocean temperature and partial pressure of CO2. If the CCD is above the seafloor, the carbonate-silicate cycle ceases to operate and therefore high ocean temperature and partial pressure of CO2 favor the carbonate-silicate cycle. With the help of pure carbonate systems of key divalent elements, we show that magnesium, calcium and iron carbonates produce an increasingly wider parameter space of deep CCDs, suggesting that chemical diversity promotes the carbonate-silicate cycle. This work motivates the inclusion of more chemically diverse targets than Earth twins in the search for life in exoplanets.

How to cite: Hakim, K., Tian, M., Bower, D. J., and Heng, K.: Carbonate Compensation Depth in Exoplanet Oceans and Ocean pH, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15709, https://doi.org/10.5194/egusphere-egu23-15709, 2023.

X4.359
|
EGU23-11114
|
ECS
Aleksandra Puławska, Magdalena Kowalewicz-Kulbat, Jolanta Kalinowska, Gabriela Arciszewska, Dominika Drzewiecka, and Maciej Manecki

Underground salt mines represent the most extreme environments which combine low nutrient availability, darkness, and hypersaline conditions. Halophilic (“salt-loving”) microorganisms are known to constitute the natural microbial communities of hypersaline ecosystems around the world (salt rocks, underground brines, saline lakes, etc.). For the first time halophilic microorganisms were detected in the air of the Bochnia Salt Mine, Poland. 

The purpose of this study was to determine the impact of various abiotic factors of the atmosphere on the presence and abundance of halophilic microbial communities present in mine air. Samples of aerosol components were collected at four different locations: one on the surface (at the air intake) and three underground at increasing distances from the intake. The inorganic aerosol was collected by dry (filter-based) and wet (scrubber-based) sampling method using portable air pumps. Besides microclimatic conditions, the content of water-soluble constituents, trace elements, carbon, and minerals were determined in aerosols. Simultaneously, the airborne cultivable microorganisms were collected by MAS-100 sampler. Mesophilic microorganisms were cultivated as a control, on general tryptic-soya (TSA) media, at 37°C and 28°C for up to one month. Halophilic ones were grown on a specific HBM medium containing 20% and 25% of NaCl concentration, at 37°C and 28°C for up to three months.

The primary component of aerosol was NaCl (1000-3000 µg·m-3). It enters the air mainly in the form of a solution droplets due to the deliquescence of rock salt in humid air (up to 80% of relative humidity). The wet aerosol in salt mine is also composed of SO42- (110-300 µg·m-3), Ca2+ (90-280 µg·m-3), K+ (50-190 µg·m-3), Mg2+ (15-40 µg·m-3), and Fe3+ (10-50 µg·m-3). The dry fraction of aerosol does not exceed 200 µg m-3 and is composed of fragments of natural rock salt (halite), anhydrite, gypsum, and clay minerals. The maximum indoor concentrations of airborne halophilic microorganisms cultivated at 37°C or 28°C reached 1910 CFU (colony-forming units) ·m-3 and 1210 CFU·m-3, respectively. Moreover, the content of halophilic microorganisms increased with the increase of the water-soluble constituents and NaCl concentrations. Our results suggest that airborne salt-saturated droplets may be a major factor influencing the abundance of live halophilic microorganisms in the atmosphere while the presence of mesophilic microorganism (which are associated with the outdoor environment) and the presence of humans seem to have no effect on the presence of halophilic microbial community.

Our research indicates that halophilic microorganisms can survive in the air of the underground Bochnia Salt Mine. Abiotic factors, like high moisture content in the air and saline aerosol in liquid form may play an important role in their survival in the air. This way some extremophile microorganisms, given favorable environmental conditions, can survive even in such a hostile environment as the atmosphere in the underground mine. This could be important for astrobiology research, since various extremophiles, including halophiles, are considered excellent candidates for life beyond our planet.

The study was supported by the Polish National Science Center (NCN) grant No. 2021/41/N/ST10/02751.

 

How to cite: Puławska, A., Kowalewicz-Kulbat, M., Kalinowska, J., Arciszewska, G., Drzewiecka, D., and Manecki, M.: Abiotic factors affecting the presence of airborne halophilic microorganisms in the extreme atmospheric conditions of an underground salt mine, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11114, https://doi.org/10.5194/egusphere-egu23-11114, 2023.

X4.360
|
EGU23-2787
|
ECS
Youcef Sellam, Salome Gruchola, Matteo Reghizzi, Stefano Lugli, Andreas Riedo, and Peter Wurz

The search for evidence of extant and extinct life on Mars is of big interest for future robotic and human exploration missions. The properties and characteristics of evaporites such as gypsum make them an easily accessible target in the search for biosignatures of extraterrestrial life. On Earth, a diverse microbial community inhabits gypsum in modern brines. These microbes are easily entombed within gypsum due to its fast precipitation. Studies of primary lower gypsum deposits, accumulated in the Mediterranean Basin during the Messinian salinity crisis (5.97 – 5.33 Ma), revealed a well-preserved and prominent archive of diverse microbial life. Similar archives might exist on Mars considering the desiccation of large bodies of water there, representing a promising target for exploring the possibility of life on Mars. The recent imaging mapping and analysis done by orbiters and rovers on the surface of Mars led to the discovery of abundant gypsum and evaporite minerals suggesting the evaporation of large lakes and lacustrine systems and as the surface of Mars dried out, hypersaline lakes would have filled the ancient lake system. A similar scenario happened on Earth when thick layers of gypsum were deposited during the Messinian salinity crisis when the Mediterranean was turned into the youngest salt giant in Earth’s history.

Previous chemical and molecular laser mass spectrometry analyses done on microfossils preserved in different rock records showed these instruments’ ability to detect biosignatures related to ancient life. In this study, we successfully investigated the chemical composition of fossil filaments interpreted to be benthic microbial assemblages dominated by chemotrophic sulfide-oxidizing bacteria, sulfate-reducing bacteria, and planktonic cyanobacteria. This study demonstrated the efficiency of a miniaturized next-generation Laser based Mass Spectrometer (LMS) designed for future space explorations in the detection of microbial chemical biosignatures trapped in Messinian gypsum, shading light to the potential application to the search for life on Mars.

 

 

 

 

Literature

 

Natalicchio, M., Birgel, D., Dela Pierre, F., Ziegenbalg, S., Hoffmann-Sell, L., Gier, S., & Peckmann, J. (2022). Messinian bottom-grown selenitic gypsum: An archive of microbial life. Geobiology, 20, 3– 21. https://doi.org/10.1111/gbi.12464.

Bayles, M., Belasco, B.C., Breda, A.J., Cahill, C.B., Da Silva, A.Z., Regan, M.J., Jr., Schlamp, N.K., Slagle, M.P. and Baxter, B.K. (2020). The Haloarchaea of Great Salt Lake as Models for Potential Extant Life on Mars. In Extremophiles as Astrobiological Models (eds J. Seckbach and H. Stan-Lotter). https://doi.org/10.1002/9781119593096.ch4.

Lukmanov, RA., Tulej, M., Ligterink, NFW., et al. ( 2021). Chemical identification of microfossils from the 1.88-Ga Gunflint chert: Towards empirical biosignatures using laser ablation ionization mass spectrometer. Journal of Chemometrics, 35 ( 10):e3370. doi:10.1002/cem.3370.

How to cite: Sellam, Y., Gruchola, S., Reghizzi, M., Lugli, S., Riedo, A., and Wurz, P.: Chemical identification of fossil filament entrapped in Messinian gypsum using space Laser Mass Spectrometry, application for Mars astrobiology., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2787, https://doi.org/10.5194/egusphere-egu23-2787, 2023.

Atmospheres, observations, detections
X4.361
|
EGU23-16709
Lena Noack and Caroline Brachmann

The long-term evolution of the atmospheres or rocky planets depends on several different factors, including (but not limited to) volcanic outgassing by partial melting of the rocky interior. Uprising melt may contain different assembladges of volatiles (CHONS) depending on the general mantle composition and redox state, the local volatile inventory, as well as melting depth. All these factors are assumed to vary for mobile-lid planets with an active surface recycling mechanism (e.g. plate tectonics or convective mobile resurfacing) when compared to stagnant-lid planets. 

In addition, the strength of volcanic activity varies for stagnant-lid and mobile-lid planets, with stronger activity and hence volcanic outgassing expected for the latter case. Atmospheres with pressures above Earth values also severely influence which volatiles will be further outgassed into the atmosphere depending on the solubility of the individual gas species. The outgassing fluxes therefore strongly depend on the evolution of the atmosphere, including atmosphere losses to space or by condensation or weathering. Ultimately, different atmospheric compositions will evolve for planets with low-pressure atmospheres (i.e. low-mass planets, planets without an active surface mobilization process, or planets with efficient atmosphere sinks/losses) and high-pressure atmospheres.

Our studies allow us to predict ranges of likely atmospheric properties depending on planet mass and the surface mobility regime, that can then be compared to observations (i.e. with JWST or in the more distant future with the proposed LIFE mission).

How to cite: Noack, L. and Brachmann, C.: Outgassing efficiency and atmopsheric composition should differ for mobile-lid and stagnant-lid planets, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16709, https://doi.org/10.5194/egusphere-egu23-16709, 2023.

X4.362
|
EGU23-15078
|
ECS
Filip Elekes, Joachim Saur, and Alexander Grayver

Trappist-1 is an extraordinary planetary system with 7 confirmed terrestrial exoplanets, some of which may lie in the habitable zone around the central M dwarf star. M dwarfs are magnetically very active and probably emit a stellar wind that interacts with the planets. Stellar winds and their interaction with planetary atmospheres and magnetospheres, if the planets are magnetized, affect the energy budget of their surroundings and ultimately the habitability of those planets. During coronal mass ejections (CMEs) intersecting the planets the exposure to increased stellar wind pressure, density and velocity might result in significant heating of the planets surroundings and interior (Grayver et al. 2022)[1]. We aim to better understand the space environment around the Trappist-1 planets and their interaction with the surrounding stellar wind. We perform magnetohydrodynamic simulations to study the interaction of the planets with the stellar wind. We also study the effect of CMEs on the energy budget of planetary atmospheres and magnetospheres, their heating, and possible effects on exoplanet habitability.

References

  • A. Grayver et al., The Astrophysical Journal Letters 941, L7 (2022)

How to cite: Elekes, F., Saur, J., and Grayver, A.: Space environment and Poynting fluxes around the Trappist-1 exoplanets and effects of coronal mass ejections on their habitability, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15078, https://doi.org/10.5194/egusphere-egu23-15078, 2023.

X4.363
|
EGU23-15340
Manuel Scherf, Helmut Lammer, and Laurenz Sproß

The existence of an Earth-like Habitat (defined as a rocky exoplanet within the Habitable Zone of Complex Life that hosts an N2-O2-dominated atmosphere with minor amounts of CO2) is depending on a certain set of known (and, potentially, unknown) astrophysical and geophysical requirements that have to be met to allow for its evolution and environmental stability. A few of these requirements are already quantifiable to a certain extent by our current scientific knowledge while others are still under debate. One crucial factor that has to be taken into account when estimating the prevalence of Earth-like Habitats within the galaxy is a planet’s host star. Its radiation and plasma environment may affect the stability of an Earth-like atmosphere to such an extent that it can even render its stable existence unlikely around highly active stars. A star’s metallicity and location within the galactic disk may pose further restrictions on the prevalence of Earth-like Habitats within the Milky Way. Taking these factors into account, we will, based on current quantifiable scientific knowledge, derive that only a certain fraction of stars within the galaxy will in principle be able to host planets with Earth-like atmospheres. Interestingly, K dwarfs with a stellar mass around 0.8 MSun may constitute a particularly interesting environment for the existence of Earth-like Habitats. M stars, on the other hand, exhibit several different problems; planets suitable for life as we know it may therefore be a rare occasion around the smallest, but most abundant, stars within the galaxy.

How to cite: Scherf, M., Lammer, H., and Sproß, L.: The host star as a crucial factor for the prevalence of Earth-like Habitats, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15340, https://doi.org/10.5194/egusphere-egu23-15340, 2023.

X4.364
|
EGU23-17476
Nicolas Iro, John Lee Grenfell, Konstantin Herbst, Miriam Sinnhuber, Benjamin Taysum, and Andreas Bartenschlager

M-dwarf stars have been preferred targets of exoplanet search due to the favourable parameters of the system for remote characterisation. However, planets in the habitable zones of these stars are expecting to experience intense radiation.

We present the INCREASE project (INfluence of strong stellar particle Events and galactic Cosmic Rays on Exoplanetary AtmoSpherEs), aiming at modelling the effect of energetic particles on the atmosphere of terrestrial exoplanets. The INCREASE model suite is an almost self-consistent simulation chain coupling the state-of-the-art magnetospheric and atmospheric propagation and interaction models PLANETOCOSMICS (Desorgher et al. 2006) and AtRIS (Banjac57 et al. 2019) with the atmospheric chemistry and climate models 1D-TERRA (e.g., Wunderlich et al. 2020) and ExoTIC. Finally, spectral characterisation is done using the GARLIC line by line radiative transfer model.

By combining these models, we are able to constrain the habitability of such planets, the stability of their atmosphere as well as simulating observational features.

How to cite: Iro, N., Grenfell, J. L., Herbst, K., Sinnhuber, M., Taysum, B., and Bartenschlager, A.: Effect of energetic particles on the atmosphere of terrestrial exoplanets, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-17476, https://doi.org/10.5194/egusphere-egu23-17476, 2023.

X4.365
|
EGU23-15251
Dave Brain and the MACH Team

Atmospheric escape from exoplanets is a topic of great interest for the exoplanet community since atmospheric retention is an important component of surface habitability. While atmospheric escape has been detected from large exoplanets, it remains difficult to measure for smaller (rocky) planets. Indeed, for rocky planets orbiting active stars it is thought that it may be difficult for atmospheres to be retained at all. In the absence of detailed observations, one option is to leverage observations and models for planets in our own solar system.

Here we consider atmospheric escape from Mars – if it orbited an M Dwarf star similar to Barnard’s star. Our analysis considers five escape processes: hydrodynamic escape, thermal escape, photochemical escape, ion escape, and sputtering. To estimate the escape rate via each process from our hypothetical “ExoMars”, we employ models for escape that have either been validated using observations or verified against other models. We provide escape rate estimates for important species in the Martian upper atmosphere: O, O2, H, and CO2, and use them to estimate the lifetime of the Martian atmosphere.

How to cite: Brain, D. and the MACH Team: Atmospheric lifetime from a hypothetical Mars-sized planet orbiting Barnard’s Star, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15251, https://doi.org/10.5194/egusphere-egu23-15251, 2023.

X4.366
|
EGU23-13634
|
ECS
Tim Lichtenberg and Sascha P. Quanz and the LIFE collaboration

LIFE (www.life-space-mission.com) is an initiative to develop the science, technology and a roadmap for an ambitious space mission that will allow humankind to detect dozens of warm, terrestrial exoplanets and hundreds of exoplanets overall at mid-infrared (MIR) wavelengths (Quanz et al., 2018, 2022). For most of the detected exoplanets direct estimates of their effective temperature and radius will be available, and a for a significant subset the atmospheric composition will be investigated including the search for potential biosignatures (Des Marais et al., 2002; Léger et al., 2019). Characterizing exoplanet atmospheres using their thermal emission at MIR wavelengths — compared to studies at optical/near-infrared wavelength looking at planets in reflected light — offers the possibility to study a broader set of molecular features (Schwieterman et al., 2018) and get a better understanding of the atmospheric structure (Line et al., 2019). Hence, in particular for questions related to the habitability of exoplanets, a mission like LIFE offers unprecedented scientific potential.

The current baseline design of LIFE features a 4-aperture interferometer array with a 6:1 baseline ratio to reduce the impact of instability noise (Lay, 2006). A beam combiner spacecraft is located at the center of the array. The size of the individual apertures is currently under study, but based on detection yield simulations including all relevant astrophysical noise sources, diameters of 2–3.5 m are under consideration. The aperture size is primarily driven by the number of detectable planets and the time-on-target required for in-depth atmospheric characterization. The current wavelength range requirement is 4–18.5 μm, but additional studies are underway for further verification. A spectral resolution of at least R=30, but better R=50, seems required in order to reliably quantify the abundance ratios of main molecular species in the atmosphere of an Earth-twin planet at several pc distance. The minimum mission lifetime is 5-6 years in order to have sufficient time for both a dedicated search phase, to identify the most interesting and promising targets, and a characterization phase for in-depth investigations of a subset of those. LIFE shall be launched to the Earth-Sun L2 point.

While the general feasibility of the required null-depth and stability was demonstrated in the context of Darwin and TPF-I (Martin et al., 2012), a corresponding experiment under cryogenic conditions is underway in the form of the Nulling Interferometric Cryogenic Experiment (NICE) at ETH Zurich (Gheorghe et al., in prep.). A more general overview of the readiness of key technologies for a space mission like LIFE was presented in Defrère et al. (2018).

 

Defrère, D., et al. 2018, Exp. Astron., 46, 475

Des Marais, D. J.,  et al. 2002, Astrobiology, 2, 153

Lay, O. P. 2006, in SPIE Astronomical Telescopes + Instrumentation (SPIE), 62681A-14

Léger, A., et al. 2019, Astrobiology, 19, 797

Line, M., et al. 2019, BAAS, 51, 271

Martin, S., et al. 2012, Appl. Opt., 51, 3907

Quanz, S. P., et al. 2018, SPIE Conf. Ser., 10701, 107011I

Quanz, S. P., et al. 2022, A&A, 664, A21

Schwieterman, E. W., et al. 2018, Astrobiology, 18, 663

 

How to cite: Lichtenberg, T. and Quanz, S. P. and the LIFE collaboration: Large Interferometer for Exoplanets (LIFE): characterizing the mid-infrared thermal emission of terrestrial exoplanet atmospheres, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13634, https://doi.org/10.5194/egusphere-egu23-13634, 2023.

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EGU23-8065
Therese Encrenaz, Athena Coustenis, Billy Edwards, Karan Molaverdikhani, Marc Ollivier, and Giovanna Tinetti

In 2018 and 2022, we have published an analysis about the observability of temperate planets (with an equilibrium temperature of about 350-500 K) with Ariel. This presentation is an update of this analysis which aims at using new targets identified in particular from the TESS database and analysing their observability with Ariel. Using the parameters of these new targets, we give an estimate of the number of transits needed for these objects to be observed in the Tier 2 mode of the space mission, and we define the information which could be derived about their atmospheric composition. We have identified about 15 targets which could be observable with ARIEL in the Tier 2 mode, which allows an identification of the main atmospheric absorbers. This list includes a gas giant, a few big Neptunes and several super-Earths/small Neptunes. This study is a follow-up of Encrenaz et al., Exp. Astr. 46, 31 (2018) and Exp. Astr. 53, 375 (2022).

How to cite: Encrenaz, T., Coustenis, A., Edwards, B., Molaverdikhani, K., Ollivier, M., and Tinetti, G.: Temperate exoplanets observable with Ariel : an update with new targets from TESS, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8065, https://doi.org/10.5194/egusphere-egu23-8065, 2023.