The geological, geochemical, and geophysical properties of the rocky inner Solar System worlds provide us with a basic set of rules for understanding rocky planets generally. Although many of the details differ, there are broad similarities between the inner Solar System worlds—including composition, interior structure, and geological evolution. Farther from the Sun, the icy satellites of the giant planets show clear similarities, even when subject to different orbital dynamical environments, with each other and in some regards with their inner Solar System neighbours. Some types of exoplanet, such as super-Earths and sub-Neptunes, are notably missing from the Solar System. Yet our planetary siblings are similar enough that we can begin to paint, at least in broad strokes, a picture of how rocky planetary bodies form and develop in planetary systems beyond our own.

How to cite: Byrne, P.: What Can the Solar System Teach Us About Rocky Exoplanets?, EPSC-DPS Joint Meeting 2025, Helsinki, Finland, 7–13 Sep 2025, EPSC-DPS2025-2075, https://doi.org/10.5194/epsc-dps2025-2075, 2025.

During Earth’s last supercontinent phase, Pangea, both the surface—including continental location, topography, and clustering—and its climate were markedly different from today. At least for its early tenure (End Permian, ~252 Ma), geological evidence indicates a greenhouse climate with elevated pCO₂, minimal polar ice, and an arid continental interior. It is predicted that, within the next 200–300 million years, our planet will once again transition into a new supercontinent phase. Given the gradual increase in solar irradiance as the Sun ages coupled with the substantial reorientation of continents, it is likely that the future supercontinent will experience a climate substantially different from the present.

Building upon previous results, we apply a novel metric of habitability which incorporates conditions for both temperature and water availability and has additionally been validated against the observed distribution of surface life on present day Earth. We first repeat the validation for a 'baseline' present day simulation to verify the ROCKE-3D model and metric validity at a coarse-scale resolution. This is followed by a comparison of the model-predicted surface habitability of Pangea (~252 Ma) against a set of lithological indicators, which we then use to inform upon the impact of future continental configuration and topography upon climate and habitability. Specifically, we investigate how Earth's capacity to support both complex and microbial life—both on land and within the upper ocean—may differ as continents assemble and fragment, offering insights into the evolution of habitability on a tectonically active planet over geological timescales.

How to cite: Woodward, H., Davies, H., and Way, M.: Investigating the influence of the supercontinent cycle on planetary habitability, EPSC-DPS Joint Meeting 2025, Helsinki, Finland, 7–13 Sep 2025, EPSC-DPS2025-948, https://doi.org/10.5194/epsc-dps2025-948, 2025.

The upcoming generation of extremely large ground-based telescopes and space observatories promises to transform our understanding of rocky exoplanets within the habitable zones of their stars. Observations from the James Webb Space Telescope are already challenging current models of exoplanetary atmospheres and interiors (e.g., Foley 2024). Conventionally, a habitable zone exoplanet orbits within a circumstellar region where liquid water could potentially exist on its surface (e.g., Hart 1979; Kasting et al. 1993). It is generally assumed that silicate weathering regulates atmospheric carbon dioxide (CO₂) to levels supporting liquid water, providing a stabilizing feedback on climate (Walker et al. 1981); otherwise, planetary habitability would be a matter of luck. This negative feedback underpins the concept of the circumstellar habitable zone (CHZ) and may play a critical role in climate regulation on water-bearing, tectonically active rocky exoplanets. Identifying evidence for a carbon cycle on exoplanets and verifying the validity of the habitable zone concept are key objectives for future research (e.g., Bean et al. 2017)—efforts that would benefit from a deeper understanding of the carbonate–silicate cycle. In particular, the interplay between global climate, atmospheric CO₂, and silicate weathering rates is not fully understood. While the role of continental weathering in this negative feedback has been extensively studied, seafloor weathering has received comparatively less attention despite its potential to be equally significant. For instance, during the Late Mesozoic—known for its hothouse climate state—seafloor weathering fluxes were comparable in magnitude to those of continental weathering (e.g., Coogan & Gillis 2013). Here, I explore the factors controlling basalt dissolution by applying the more mechanistic weathering model of Maher and Chamberlain (2014) to both the modern and Late Mesozoic upper oceanic crust.

The oceanic crust, through its formation, alteration, and subduction, is a key component of this geochemical cycle. Carbon is transferred from Earth’s mantle to surface reservoirs (e.g., the atmosphere and oceans) via volcanic outgassing. Concurrently, basalt dissolution and carbonate precipitation recapture dissolved carbon from seawater, storing it within the oceanic crust. Over geological timescales, subducted tectonic plates carry these carbonates back into the mantle reservoir, ultimately supplying carbon to volcanoes. Nonetheless, the primary controls on seafloor weathering rates remain debated. Most models have historically focused on the dependence of mineral dissolution kinetics on temperature and CO₂ concentrations, yet observational data suggest that both kinetic and thermodynamic factors govern global weathering fluxes, underscoring the need for models that can incorporate this dual control. Kinetic weathering models (e.g., Walker et al. 1981) fail to account for the changes in Earth’s weatherability through time (e.g., West et al. 2005). To address this, Maher & Chamberlain (2014) developed a solute transport model that integrates hydrological and tectonic influences and imposes a thermodynamic limit on weathering rates. However, this model has only occasionally been applied to continental weathering in exoplanet climate studies (e.g., Graham & Pierrehumbert 2020, 2024), and its relevance to seafloor weathering remains largely unexplored (Hakim et al. 2021).

In this work, I assessed the model’s sensitivity to key parameters by comparing its predictions with observed age-dependent carbon content in the upper oceanic crust (Gillis & Coogan 2011). I then extended the model into two dimensions to represent the evolving age distribution of Earth’s seafloor and examine its impact on global weathering fluxes. Simulations using this supply-limited seafloor weathering model successfully reproduce observed age-related trends in carbon content within Earth’s upper oceanic crust and provide further evidence that over 80% of carbonate formed within 20 Myr of crust formation (Gillis & Coogan, 2011; Albers et al. 2023). This model can also capture the higher CO₂ concentrations in Late Mesozoic crust compared to Cenozoic crust. Our results indicate that crustal age, permeability, porosity and fluid flow strongly influence weathering rates. These findings challenge the prevailing view that elevated temperatures primarily drove enhanced carbon uptake during the Late Mesozoic, emphasizing further the importance of incorporating geologic and hydrologic processes into climate models. Consequently, seafloor weathering emerges as a necessary process not only for understanding Earth’s past climate but also for interpreting future observations of potentially habitable rocky exoplanets.

How to cite: Fournier-Tondreau, M.: Crustal Controls on Seafloor Weathering and Climate Regulation, EPSC-DPS Joint Meeting 2025, Helsinki, Finland, 7–13 Sep 2025, EPSC-DPS2025-634, https://doi.org/10.5194/epsc-dps2025-634, 2025.

With more than 5,000 exoplanet detections confirmed, most of which are small planets below the size of Neptune, a population of ‘samples’ is now at our reach to assess the diversity of interior properties permitted in planetary systems and the impact on the atmospheric composition and climate. The formation of secondary atmospheres around rocky planets via volcanic outgassing is known to be controlled by key properties of the interior, i.e., the oxygen fugacity describing the bulk redox state of the mantle, and the volatile inventory. Observations of exoplanet atmospheres can provide crucial constraints on the relative abundances of molecular species including CO2, CH4, CO, NH3 and SO2 which encode crucial information on the interior properties. A clear ambitious direction is emerging in the field aiming to use the retrieved atmospheric properties to constrain the interior properties of rocky exoplanets and thus better understand the formation of secondary atmospheres in various planetary systems including our own.

Clear correlations between the relative abundances of these observable volatiles and the interior properties (oxygen fugacity and volatile budget) are required to draw reliable conclusions. The relative abundance CO2/CO for instance is a known reliable indicator of oxygen fugacity. This approach however relies on the assumption that the volatile composition outgassed in the atmosphere and observed with telescopes is not influenced by other atmospheric mechanisms. In the present work, we address the role of atmospheric thermochemistry and photochemistry to assess the induced change on the observed relative abundances of volatiles and the bias introduced on the interior properties such as oxygen fugacity. We explore a wide range of possible conditions for rocky exoplanets in terms of volatile budget, oxygen fugacity and surface pressure. We use a self-consistent chemistry-radiative model to consider the change of gases in the atmosphere and their influence on the climate.

We find that atmospheric thermochemistry is a key process changing the relative abundances of volatiles in the atmosphere following the decrease of temperature between the interior and the surface, a process referred to as atmospheric cooling. This mechanism alone can lead to strong biases on the inferred interior oxygen fugacity as it significantly modifies the CO2/CO ratio in the atmosphere. In addition, the decrease of temperature in the atmosphere can allow significant build-up of CH4 in reducing conditions. Co-existence of CH4 and CO2 at high abundances is possible in several conditions at high temperatures. In practice, it means that one needs to have reliable constraints on the surface temperature to use CO2-CH4 as a biosignature. In reducing conditions, the formation of methane by thermochemistry triggers a climate feedback given the strong greenhouse properties of methane. This mechanism should lead to observations with clear signatures of CH4 and CO2  which do not indicate habitable conditions but rather indicate reducing conditions and high surface temperature.

For thinner atmospheres, we found that the low surface temperature make thermochemistry inefficient relative to photochemistry. Photochemistry can however also bias the CO2/CO abundance ratio as water vapor is dissociated by UV photons and oxidizes CO into CO2. This mechanism occurs over long timescales that may be compensated by the surface volcanic flux assuming that the targeted exoplanet is still volcanically active.

How to cite: Drant, T., Tian, M., Thompson, M., Bower, D., Sossi, P., Carrasco, N., and Heng, K.: Inferring interior properties of rocky exoplanets from observations of their atmospheres: evaluating the biases caused by atmospheric photochemistry and thermochemistry, EPSC-DPS Joint Meeting 2025, Helsinki, Finland, 7–13 Sep 2025, EPSC-DPS2025-1473, https://doi.org/10.5194/epsc-dps2025-1473, 2025.

Introduction: How the Earth and other terrestrial planets acquire their volatile element budgets (e.g., N, C, H, noble gases) remains a fundamental unanswered question. Large fractions of planetary volatiles are believed to have been acquired during the main stages of accretion (e.g., Halliday 2013; Marty 2012; Mukhopadhyay & Parai 2019). Therefore, the atmospheres and oceans of the planetary embryos from which terrestrial planets are built must have survived the giant impact phase – a period dominated by collisions between planet-sized bodies – for those volatiles to be retained to this day.  Accurately quantifying how much atmosphere is lost in different styles of impact and by what mechanisms is key to gaining a better understanding of the volatile evolution of planets. 

Early studies (e.g., Ahrens 1990; Melosh & Vickery 1989; Ahrens & O'Keefe 1987; Vickery & Melosh 1990) suggested that atmospheric loss during giant impacts can be driven primarily by air shocks, ejecta plumes, and shock-kick. Recent advances in numerical techniques have allowed such processes to be captured simultaneously in high-resolution 3D smoothed particle hydrodynamics (SPH) simulations (e.g., Kegerreis et al. 2020a,b; Denman et al. 2020, 2022), and have allowed scaling laws to be produced that can predict the expected loss outcome for a given set of impact parameters. However, these previous studies did not explore in detail the relative contributions of the different mechanisms driving loss and how they varied with impact parameters and atmospheric properties, which can lead to significant errors in the loss predicted by existing scaling laws (e.g., Kegerreis et al. 2020b).

The mechanisms of atmospheric loss: We conducted a suite of SPH giant impact simulations of collisions onto planets between 0.35–5.0 Earth masses (M_⊕) with 5% mass fraction H₂–He atmospheres. We de-convolve the total atmospheric loss (Fig.1) into its near- and far-field components and show conclusively that atmospheric loss is principally controlled by different mechanisms depending on location relative to the impact – ejecta plumes and air shocks in the near field and shock-kick in the far field (Fig.2). By parameterising these mechanisms independently, we derive a new scaling law that accurately approximates atmospheric loss and can readily be incorporated into models of volatile accretion during planet formation.

Figure 1: Atmospheric loss fraction as a function of impact parameter for different target planet masses (line style), mass ratios (panels), and velocities (colours/shapes) (Roche et al. 2025).

Figure 2: Illustrative time snapshots from an example SPH giant impact simulation with a resolution of 10⁶ particles (Roche et al. 2025).

Predicting loss from 1D–3D coupling: Lock & Stewart (2024) showed that hotter, lower mean molecular weight, and lower pressure atmospheres are much more easily lost during giant impacts. Such atmospheres can be difficult to model using SPH simulations due to the lack of high-quality, publicly available equations of state and the extremely high numerical resolutions required to model thin atmospheres. Here we investigate whether atmospheric loss can be predicted by combining the results of 3D simulations with less computationally expensive 1D calculations to help overcome these limitations. 

Atmospheric loss due to shock-kick has previously been investigated using 1D hydrodynamic simulations (Genda & Abe 2003, 2005; Lock & Stewart 2024), and  comparisons made to the loss calculated from SPH simulations (Genda & Abe 2003; Kegerreis et al. 2020a). We improve upon this previous work and calculate the far-field loss that would be predicted from coupling the shock field from our SPH simulations with 1D impedance match calculations of loss from shock-kick (Lock & Stewart 2024). 

We find excellent agreement between the 3D and coupled 1D–3D calculations (Fig.3), meaning that ground pressures sampled from existing SPH simulations  can be used to make first order approximations of loss for a given impact without needing to run additional high resolution SPH simulations. 

Figure 3: Mollweide projections of far-field loss fraction (upper hemisphere) from 3D SPH simulations and the far-field loss fraction predicted by coupled 1D–3D calculations (lower hemisphere) (Roche et al. 2025).

Implications for the volatile evolution of planets: We apply our new scaling law to the results from existing N-body simulations of solar system formation (Carter et al. 2015; Carter & Stewart 2022) to gain insight into the role that loss during giant impacts could play in the volatile evolution of planets (Fig.4). We find that individual loss events that substantially change atmosphere mass fraction (by >10%) are not uncommon for small planet masses (<0.6 M_⊕) but are generally rare for larger planet masses (>0.8 M_⊕). Despite this, the cumulative effect of multiple giant impacts during accretion can lead to much greater atmospheric loss (40–70%) for planets approaching ~1.0 M_⊕ with an initial 5% mass fraction H₂–He atmosphere. Given that we have neglected the fact that lower pressure atmospheres are more easily eroded (Lock & Stewart 2024) and have also not considered the presence of surface oceans which are known to strongly control atmospheric loss (Genda & Abe 2005; Lock & Stewart 2024), these results represent a lower limit and likely a significant underestimate of the amount of loss driven by giant impacts during accretion. Giant impacts therefore likely play a key role in controlling the volatile budgets of planets.

Figure 4: Atmospheric loss fraction experienced from individual giant impacts (a) and the combined effect of loss through accretion (b) in N-body simulations for four different solar system formation scenarios (colours/shapes) (Roche et al. 2025).

Conclusion: We have gained critical insight into the mechanisms of atmospheric loss during giant impacts which has allowed us to develop new tools for better understanding the role of giant impacts in the volatile evolution of planets. Our results suggest that atmospheric loss due to giant impacts plays a considerable cumulative role in shaping the volatile budgets of terrestrial planets. Future work will seek to quantify differences in the efficiency of atmospheric loss depending on the atmospheric and surface properties, as well as quantifying the delivery of volatiles by the impactor as well as the target.

How to cite: Roche, M., Lock, S., Dou, J., Carter, P., Kegerreis, J., and Leinhardt, Z.: Atmospheric loss during giant impacts: mechanisms and scaling of near- and far-field loss, EPSC-DPS Joint Meeting 2025, Helsinki, Finland, 7–13 Sep 2025, EPSC-DPS2025-1501, https://doi.org/10.5194/epsc-dps2025-1501, 2025.

Mars is thought to have formed rapidly within the first 4 million years of the solar system's history (Dauphas & Pourmand, 2011), while the solar nebula was still present (Wang et al. 2017) . Isotopic analyses of heavy noble gases suggest that Mars acquired its early atmosphere directly from this solar reservoir (Ott et al. 1988; Conrad et al. 2016; Avice et al. 2018). In contrast, the krypton isotopic composition of the Martian mantle is consistent with a chondritic source (Peron et al. 2022). This is consistent with the scenario in which Mars' mantle rapidly formed from chondritic material, before accreting its atmosphere from the solar nebula.

After solar nebula dispersal, a dynamical instability among the giant planets scattered comets into the inner solar system (Gomes et al. 2005; Nesvony 2018). The lack of a detectable cometary xenon signature in the present-day Mars' atmosphere - in contrast to Earth's (Marty et al. 2017) - is therefore surprising, and suggests that the capture of solar nebular gas was significant enough to dilute later cometary contributions.

In this study, we combine geochemistry and solar system dynamics to quantify the mass of cometary material efficiently retained on Mars, thereby placing a lower bound on the mass of its primordial atmosphere. To test the robustness of our conclusions, we use cometary bombardment data from two independent studies (Joiret et al. 2024; Ribeiro et al. 2025). Our results indicate a minimal atmospheric pressure of a few bars at the Martian surface.  This estimate is compatible with recent findings showing that heavier molecular species from outgassing can substantially increase nebular gas retention (Pahlevan et al. 2025).

How to cite: Joiret, S., Morbidelli, A., de Sousa Ribeiro, R., and Avice, G.: The primordial atmosphere of Mars was massive, EPSC-DPS Joint Meeting 2025, Helsinki, Finland, 7–13 Sep 2025, EPSC-DPS2025-9, https://doi.org/10.5194/epsc-dps2025-9, 2025.

The Earliest Solar System Materials and Solar System Formation.  Sun-like TTauri stars (TTS) grow in their final stages via magnetically focused mass flows from a circumstellar accretion disk (CAD) [1-2; Fig.1]. The CAD is also the site of formation of the first planetesimals, from asteroids to KBOs, but the processes by which CAD dust particles grow into planetesimals is not well understood. Some planetesimals may form through slow collisional aggregation of dust particles, while others form quickly through stochastic gravitational instabilities in dense regions of the CAD. Processing of CAD dust at high-temperatures, like the 1250-1650K temperatures of the CAD inner disk wall [3], is also required [4-5] to form the oldest known solid constituents of these planetesimals, refractory inclusions (RIs) and chondrules. The formation mechanisms for these oldest solid constituents are hotly debated, with model mechanisms ranging from stellar flare events to shock heating to CAD lightning to giant impacts [6-10].

Figure 1 – Infant T Tauri star schematic. Accretion occurs from an ~0.1M_sun (CAD), driven by ionized material at the inner CAD wall focused by magnetic fields onto the protostar surface [1-2]. Outflow jets are sourced near the inner CAD wall. The inner wall, at T >1000K, occurs where the Keplerian period of orbiting CAD material matches the protostar’s rotation period.

Spectral Evidence that RWAurA harbors abundant amounts of chondrules and CAI-like material. The TTS system RWAurA (K1Ve, d=165 pc, 1.4M_sun,~3Myr) is known to host an extended, active CAD [11-18]. Spitzer/IRS observations taken during the system’s quiescent phase ([19]; Fig. 2a) show the CAD’s 0.7–35 um spectrum can be described as the sum of a protostellar photosphere at ~4000K, the inner accretion disk wall at T~1300K, a CAD gap at ~2 au with apparent temperature T_gap~190K, and a very faint, cold (T~40K) component most likely due to the outer CAD envelope.

Figure 2 – (a) Combined 0.7-35 um RWAurA “quiescent” SED formed from 2006-2007 IRTF/SpeX  0.8–5.2 um spectra of (aqua,blue; [18]) plus a 2005 Spitzer/IRS spectrum [19] (black). Also shown are modified blackbody fits to the underlying continua from the protostellar surface (4000K), the inner CAD wall (1300K), a CAD gap (190K), and the CAD envelope sensed by ALMA (~40K; [16]). Assuming T_wall ~217K/r[AU]^0.57 [21] then T_{inner wall}=1300K at 0.06 AU and a T_gap =190K gap located at ~1.7AU from the primary.

(b) Spectral-compositional fit to the hot inner CAD wall emissivity of (a), showing evidence for impact silica, SiO gas, alumina, crystalline olivines, crystalline pyroxenes, phyllosilicates, and amorphous carbon. None of the low temperature amorphous silicates and magnesium sulfides typically seen in unprocessed ISM and cometary dust SEDs [22-24] are present, having been replaced by materials consistent with rapid high temperature processing of rocky materials (c.f. [25] & references therein).

Emission features due to a combination of ferromagnesian silicate and alumina/silica materials at 8–11 and 17–25 um as well as alumina at 12–14 um are seen from the hot (T~1300 K) inner system dust (Fig.2b). This compositional mineralogy is lacking in the amorphous silicates and metal sulfides found in molecular clouds and protosolar nebulae; instead it is rich in alteration products like high temperature glassy silicas, alumina oxides, crystalline silicates, and phyllosilicates[3, 20]. This dust has been heavily processed and altered to produce products akin to RIs and chondrules, and new higher resolution JWST spectra verify these findings.

 A Dynamic, Rapidly Evolving System. RWAurA is a uniquely special laboratory to study RI and chondrule formation because recent work [3, 26-27] has demonstrated that energetic planetesimal collisions in the hot inner disk wall region have occurred there within the last decade. A tremendous drop in RWAurA’s normal visible (Fig. 3) and soft XUV emission was reported in 2014–2017, due to a “huge increase in a neutral extinctor” in the protostar’s atmosphere [26-27]. Coupled with an concomitant large increase in Fe K-shell X-rays [26-27], this suggests that huge amounts of obscuring gaseous iron (Fe) and fine “neutral” refractory rocky dust able to withstand prolonged temperatures > 1600K (= RIs) was created around the central protostar.

Figure 3 – (a) Optical lightcurve of RW Aur A for 2005–2025, showing relatively stable behavior from 2005 – 2010, a strong, short dip in 2011, more stable behavior in 2012–2014, a large unusual event/stochastic upset 2014-2020, and the onset of a new event in early 2025.

Our near-infrared (NIR) imaging and spectral monitoring observations of RWAurA [3, 28] over the last decade have shown evidence for a highly excited system with a bright, hot, asymmetric CAD, numerous hot atomic emission lines from the protostar’s atmosphere, and a new stochastic emission event in its high-speed focused outflow jets moving away at 100 – 200 km/s (Fig. 4). The hot (T~20,000K) bifurcated RWAurA jet spectral signature was seen to decay back to its normal pre-event level over the course of ~7 years, suggesting that Vesta-sized amounts of excess hot Fe+S+C+Si, common planetesimal core materials, had just blown out of the system’s jets. Conspicuously absent in the RWAurA jet spectral signatures were traces of any lithophilic elements that 

Figure 4 – IRTF/SpeX 0.7–5.0 µm spectroscopic monitoring from 2006 to 2020 found a huge increase, circa 2018, in line emissions like the FeII 1.2557um line shown here, bifurcated by huge new jet outflows. By late 2020 the jets had subsided and the lines had returned to near-normal [3].

occur in the rocky mantles of differentiated planetesimals. These species remained in the solid phase, producing the “large amounts of reported new “neutral extinctors” in the protostar’s atmosphere [26-27]. Thus it is likely that the observed 2015 dimming event involved the catastrophic disruption of a primitive planetesimal, with easily vaporized Fe delivered into the jets and onto the protostar in the gas phase, while more refractory rocky materials melted and recondensed into highly refractory solid state materials like RIs and Chondrules.

References: [1]Armitage+2001,MNRAS324:705[2]Armitage2007,arXiv:astroph/0701485[3]Lisse+2022,ApJ928:189[4]Connelly+2012,Science338:651[5]Weiss+2013,Annu.Rev.EarthPlanet.Sci.41:529[6]Johnson+2015,Nature517:33[7]Horanyi+1995,Icarus114:175[8]Alexander+2012,MAPS47:1157[9]Desch+2012,MAPS47:1139[10]Hood+2012,MAPS47:1715[11]Valenti+1993,AstronJ.106:2024[12]Hartigan+1995,ApJ452:736[13]White+2001,ApJ556:265[14]Alencar+2005,A&A440:595[15]Facchini+2016,A&A596:A38[16]Rodriguez+2018,ApJ859:150[17]Dai+2015,MNRAS449:1996[18]Koutoulaki+2019,A&A625:A49[19]Furlan+2011,ApJSuppl195:3[20]Lisse+2009,ApJ701:2019[21]Osterloh&Beckwith1995,ApJ439:288[22]Kemper+2004,ApJ609:826[23]Harker+2005,Science310:278[24]Lisse+2007,Icarus187:69[25]MacPherson2003,inTreatiseonGeochemistry1,pp.711[26]Günther+2018,AJ156:2[27]Gárate+2019,ApJ871:53 [28]Takami+2020,ApJ 901:24

How to cite: Lisse, C., Sitko, M., Wolk, S., Günther, H.-M., Brittain, S., Green, J., Steckloff, J., Johnson, B., Koutoulaki, M., Espaillat, C., and Jackson, A.:  Evidence for Ongoing Core Expulsion & Refractory Inclusion/Chondrule Formation in the RW Aurigae T-Tauri System  , EPSC-DPS Joint Meeting 2025, Helsinki, Finland, 7–13 Sep 2025, EPSC-DPS2025-448, https://doi.org/10.5194/epsc-dps2025-448, 2025.

Neutral sodium is a geological beacon in our solar system, representative of rocky meteors in the Earth's atmosphere, regolith sputtering and desorption at the Moon and Mercury, volcanic outgassing at Jupiter's moon Io, and saltwater ascent at Enceladus and Europa. Due to the favorable cross section of sodium (NaD) and potassium (KD) to probe tenuous gases, indirect inferences of active, rocky exomoons can be made in the optical by carefully monitoring Doppler shifts at common alkali exoplanet systems. Notably, we present new Keck Planet Finder (KPF) observations of WASP-49 A b characterizing the sodium exosphere of WASP-49 A b, a hot Saturn exoplanet, and its putative satellite WASP-49 A b I. Based on new KECK observations, we present 3-D numerical gas tori and cloud models of the orbiting sodium with SERPENS, comparing also to candidate exomoon systems HD-189733 b II and WASP-39. The indirect sodium (and volcanic gas) spectroscopy method described here is directly applicable to the search for active exoplanets in general as, similar to Jupiter-Io, volcanic and sputtered sodium gas is readily ionized undergoing a series of plasma processes affecting the lifetime and morphology of neutral sodium.  Previous HARPS/3.6-m and KECK/HIRES observations suggest an exomoon orbit near the Roche limit at ~1.2 Rp, which is also consistent with recent dynamical studies. However, dozens more observations are needed to build a sodium radial velocity curve, to constrain an exomoon orbital period with reasonable accuracy, should the cloud indeed be bound to the exomoon. 

How to cite: Oza, A., Unni, A., Meyer zu Westram, M., Sorate, A., Fisher, C., and Gebek, A.: Sodium Evidence of a Rocky Exomoon, EPSC-DPS Joint Meeting 2025, Helsinki, Finland, 7–13 Sep 2025, EPSC-DPS2025-1797, https://doi.org/10.5194/epsc-dps2025-1797, 2025.

Rocky planets can host two distinct types of surface magma oceans. First, post-accretion magma oceans, sustained by the residual heat from accretional impacts [1]. The planet’s surface can remain molten for extended periods depending on the planet’s volatile content and the atmospheric properties. Second, permanent magma oceans, maintained by intense stellar irradiation, possibly combined with a strong greenhouse effect. For Earth and Venus, early evolution likely involved both mechanisms, with their large water inventories (at least 0.01 % of the planetary mass) making a dense steam atmosphere unavoidable during these phases.

In both cases, a classic approach to modelling these hot, dense atmospheres has been to assume that they are entirely convective from the surface to the photosphere, where most of the planet’s thermal emission is radiated to space. This assumption, first formalized by Kasting [3], greatly simplifies the problem, the atmospheric profile follows an adiabatic lapse rate, and the outgoing longwave radiation becomes independent of the surface temperature over a wide range [350-2000 K] triggered by the runaway greenhouse threshold near 270 W/m^2. If the combined internal and stellar heat flux exceeds this limit, complete vaporization of the water reservoir occurs, and the surface temperature rises above 2000 K, leading to the formation of a magma ocean.

This approximation has been systematically applied to hot, thick terrestrial atmospheres. For example, to estimate magma ocean lifetimes [4, 6], to describe Venus's past [2], Earth's future, or to model the mass-radius relationships of highly irradiated rocky planets  [8, 9] and to predict or interpret JWST observations of hot terrestrial exoplanets like TRAPPIST-1b, c, and d.

However, recent work [3] has shown that this assumption is generally invalid for hot and dense atmospheres, where radiative zones may develop and break the fully convective structure. For thick atmospheres the assumption of full convection breaks down, radiative processes dominate over convection in large portions of the atmosphere. This invalidates the widely used inverse climate modeling method, where a prescribed atmospheric profile is coupled to radiative transfer in order to determine equilibrium fluxes. Instead, a consistent radiative-convective equilibrium must be solved for each atmospheric layers.

In this study, we present an improved coupling model between the magma ocean evolution and a consistent 1D radiative-convective atmospheric model using the Exo_k framework [5]. This code allows efficient computation of radiative transfer and convective adjustment, including effects such as dry and moist convection, condensation, precipitation and turbulent diffusion. Importantly, it can handle the wide range of radiative timescales-spanning seconds to tens of thousands of years-that arise in thick steam atmospheres.

Focusing on Venus, we reassess its early thermal evolution. Classical models predict that its steam atmosphere, maintained by insolation, kept the surface in a molten state for hundreds of millions of years-long enough for hydrodynamic escape to remove the planet’s water [2]. In summary, our work demonstrates the critical importance of using consistent radiative-convective atmospheric models to accurately capture magma ocean lifetimes and volatile evolution. These insights have many implications not only for the early histories of Venus and Earth but also for exoplanet characterization and the interpretation of future observations with the James Webb Space Telescope (JWST) and other missions.

References
[1] L. Elkins-Tanton. Linked magma ocean solidification and atmospheric growth for Earth and Mars.Earth and Planetary Science Letters, 2008.  
[2] K. Hamano, Y. Abe, and H. Genda. Emergence of two types of terrestrial planet on solidification  of magma ocean. Nature, 2013.
[3] J. F. Kasting. Runaway and moist greenhouse atmospheres and the evolution of Earth and Venus. Icarus, 1988.  
[4] T. Lebrun, H. Massol, E. Chassefi.re, A. Davaille, E. Marcq, P. Sarda, F. Leblanc, and  G. Brandeis. Thermal evolution of an early magma ocean in interaction with the atmosphere. Journal of Geophysical Research: Planets, 2013
[5] J. Leconte. Spectral binning of precomputed correlated-k coefficients. Astronomy & Astrophysics, 2021.
[6] H. Massol, A. Davaille, and P. Sarda. Early Formation of a Water Ocean as a  Function of Initial CO2 and H2O Contents in a Solidifying Rocky Planet. Journal  of Geophysical Research: Planets, 2023
[7] F. Selsis, J. Leconte, M. Turbet, G. Chaverot, and E. Bolmont. A cool runaway greenhouse without  surface magma ocean. Nature, 2023
[8] M. Turbet, E. Bolmont, D. Ehrenreich, P. Gratier, J. Leconte, F. Selsis, N. Hara, and C. Lovis. Revised mass-radius relationships for water-rich rocky planets more irradiated than the runaway  greenhouse limit. Astronomy & Astrophysics, 2020
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How to cite: Pelissard, H., Selsis, F., Leconte, J., Turbet, M., Massol, H., and Milcareck, G.: Revisiting rocky planets cooling phase and magma ocean occurrence with a consistent atmospheric model, EPSC-DPS Joint Meeting 2025, Helsinki, Finland, 7–13 Sep 2025, EPSC-DPS2025-1568, https://doi.org/10.5194/epsc-dps2025-1568, 2025.

Recent characterisations of exoplanet atmospheres with the JWST, including especially the potential detection of CO as a dominant gas in the atmosphere of a rocky exoplanet (55 Cnc e, Hu et al. 2024), are in contrast to theoretical predictions from volcanic outgassing studies. Here we focus on the diverse atmospheres that can theoretically form at the end of the magma ocean stage of rocky planets by assuming different volatile concentrations in the magma ocean as well as redox states.
By using a first-principles magma ocean crystallization model considering redox-dependent partitioning of volatiles between the magma ocean and the solidifying mantle, gas speciation of volatiles, their solubility in the magma, as well as atmospheric chemical equilibrium, we model the redox- and composition-dependent formation of the primary outgassed atmosphere towards the end of the magma ocean stage.
We find that due to the low solubility of carbon species in melts, atmospheres in equilibrium with a magma ocean under low oxygen fugacity conditions would quickly become dominated in CO (even without photochemistry), which is in contrast to what we find for secondary atmospheres forming by long-term volcanic outgassing (Brachmann et al., 2025). In addition, we show that the often discussed catastrophic outgassing phase of a solidifying magma ocean only appears for oxidized magma oceans, whereas under reducing conditions the atmospheric pressures gradually increase during the crystallization, affecting also the storage capacity of volatiles in the solid mantle.
We show, that it is not only possible to explain recent potential findings of CO-dominated atmospheres around rocky planets by a low oxygen fugacity of the magma ocean and later rocky mantle, but also that the primordial outgassed atmosphere can differ strongly from secondary outgassed atmospheres, in contrast to what is often assumed in the astronomical community. We also plan to study the formation and destruction of CO by photochemistry and chemical reactions in the atmosphere in more depth using the 1D-TERRA climate-chemistry coupled model.

How to cite: Noack, L., Baumeister, P., Brachmann, C., Taysum, B., and Grenfell, J. L.: CO-dominated atmospheres during the magma ocean stage, EPSC-DPS Joint Meeting 2025, Helsinki, Finland, 7–13 Sep 2025, EPSC-DPS2025-1896, https://doi.org/10.5194/epsc-dps2025-1896, 2025.

Larger-than-Earth exoplanets are sculpted by strong stellar irradiation, but it is unknown whence they originate. Two propositions are that they formed with rocky interiors and hydrogen-rich envelopes (‘gas-dwarfs’), or with bulk compositions rich in water-ices (‘water-worlds’) . Multiple observations of super-Earth L 98-59 d have revealed its low bulk-density, consistent with substantial volatile content alongside a rocky/metallic interior, and recent JWST spectroscopy evidences a high mean molecular weight atmosphere. Its density and composition make it a waymarker for disentangling the processes which separate super-Earths and sub-Neptunes across geological timescales. We simulate the possible pathways for L 98-59 d from birth up to the present day using a comprehensive evolutionary modelling framework. Emerging from our calculations is a novel self-limiting mechanism between radiative cooling, tidal heating, and mantle rheology, which we term the 'radiation-tide-rheology feedback'. Coupled numerical modelling yields self-limiting tidal heating estimates that are up to two orders of magnitude lower than previous calculations, and yet are still large enough to enable the extension of primordial magma oceans to Gyr timescales. Our analysis indicates that the planet formed with a large amount (>1.8 mass%) of sulfur and hydrogen, and a chemically-reducing mantle; inconsistent with both the canonical gas-dwarf and water-world scenarios. A thick atmosphere and tidal heating sustain a permanent deep magma ocean, allowing the dissolution and retention of volatiles within its mantle. Transmission features can be explained by in-situ photochemical production of SO2 in a high-molecular weight H2-H2S background. These results subvert the emerging gas-dwarf vs. water-world dichotomy of small planet categorisation, inviting a more nuanced classification framework. We show that interactions between planetary interiors and atmospheres shape their observable characteristics over billions of years.

How to cite: Nicholls, H., Lichtenberg, T., Chatterjee, R. D., Guimond, C. M., Postolec, E., and Pierrehumbert, R. T.: Super-Earth lava planet from birth to observation: photochemistry, tidal heating, and volatile-rich formation, EPSC-DPS Joint Meeting 2025, Helsinki, Finland, 7–13 Sep 2025, EPSC-DPS2025-1929, https://doi.org/10.5194/epsc-dps2025-1929, 2025.