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 (T_C,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: 'D¹⁷O_VSMOW) 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 T_C,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.

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.

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.

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 M_J (Jupiter’s mass) in the initial GJ 1148 system with initial orbital separations set to 3.5, 4, and 4.5 mutual Hill radii R_m,H respectively and initial semi-major axis of the innermost planet a_i,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 a_i,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 a_i,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 a_i,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.

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.

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.

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.

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.

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 SO₄^2- (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.

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.

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.

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.

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 M_Sun 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.

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.

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.

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).

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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

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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.

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.