Publications.

Abstract Modeling the interior of a rocky or water-rich exoplanet is a thermodynamic closure problem: every layer’s density, temperature gradient, and phase must follow from an equation of state (EoS) that remains self-consistent across the pressure-temperature range from surface to core. Existing EoS span disciplines, use different formalisms, and rarely supply the full thermodynamic quantities needed by evolutionary models of interior phase transitions. We present PALEOS (Planetary Assemblage Layers: Equations of State), an open-source toolkit consolidating EoS for iron, magnesium silicate (MgSiO₃), and water (H₂O) into a unified, phase-aware, thermally responsive framework spanning 17 phases. PALEOS derives density, energy, entropy, heat capacities, thermal expansion, and the adiabatic gradient analytically via Maxwell relations, and is released as lookup tables on regular P-T grids. We validate it against the Preliminary Reference Earth Model, recovering Earth’s radius to 0.3% and lower-mantle densities to 3%, and compute 17,900 mass-radius relations from 0.1 to 100 M⊕ for rocky (Fe + MgSiO₃) and water-rich (Earth-like core + H₂O envelope) compositions at 300-4000 K. Continuous solid-to-melt EoS let thermal expansion span the fully-solid to magma-ocean regime: the radius offset exceeds 1% above 1500 K and reaches 16% at 4000 K for low-mass silicate planets, comparable to composition degeneracy and transit-radius uncertainties. We demonstrate this on two ultrashort-period super-Earths, WASP-47 e and TOI-1807 b: each admits two purely rocky solutions indistinguishable in mass and radius but in radically different states, one fully solid with no dynamo, the other hosting a deep magma ocean and a liquid iron core capable of sustaining a magnetic field. Phase-aware, thermally resolved EoS are essential for translating astronomical observations into exoplanetary geophysics.

At a glance To understand what rocky exoplanets are made of, we need accurate descriptions of how materials behave under extreme pressures and temperatures. PALEOS is an open-source toolkit that provides these descriptions for iron, rock, and water across 17 different material phases, from solid to fully molten. Applying it to observed exoplanets reveals that two planets with identical size and mass could be in completely different states: one frozen solid, the other hosting a deep magma ocean with an active magnetic field.

Abstract Static structure models, which map mass-radius constraints to bulk planet composition, are frequently used to categorise exoplanets due to their computational efficiency and the high-level insight they offer into planetary properties. However, static structure models typically have simplified atmospheric treatments, which may introduce systematic biases when interpreting the structures, and therefore the climates, of sub-Neptunes and super-Earths.We present a framework for recovering exoplanet properties using static structure models that accounts for necessary physical-chemical complexity in their atmospheres. We produce a comprehensive library of 504,000 exoplanet simulations that unify deep planetary interior structure with radiative-convective-chemical climate calculations. From these models we demonstrate that a planet’s envelope mass fraction, a critical parameter to infer, is frequently degenerate with its instellation flux and atmospheric metallicity, and sensitive to the treatment of gravitational acceleration at the mbar level. Such uncertainties have significant implications for inferring planetary processes, as our modelling shows that habitable-zone sub-Neptunes readily host supercritical surfaces or deep magma oceans, despite their temperate irradiation regime. To marginalise over these uncertainties, we introduce a Bayesian retrieval tool that uses our library of self-consistent models. By applying this Bayesian approach to case-studies of Pi Men c and TOI-421 b, we show that robust physical interpretations are achievable through whole-planet mass-radius retrievals. While new data from JWST, Ariel, and PLATO will expand our observational horizon, physically-consistent modelling provides the means to transition from categorical interpretations toward a comprehensive picture of the exoplanet continuum.

At a glance Traditional models classify exoplanets by mass and radius alone, but this study couples full atmospheric and interior physics to simulate planets spanning gas-rich sub-Neptunes to bare rocky worlds. It finds that volatile envelope fraction is strongly degenerate with stellar irradiation and atmospheric metallicity, and that even temperate sub-Neptunes in the habitable zone may host deep magma oceans beneath their gas envelopes.

Abstract Sub-Neptunes are the most common type of detected exoplanet, yet their observed masses and radii are degenerate with several interior structures. One possibility is that sub-Neptunes have silicate/iron interiors and H₂-dominated atmospheres (μ<3.8 g mol⁻¹), i.e., they are ‘gas dwarfs’. If gas dwarfs have molten interiors, interactions between their magma oceans and atmospheres will produce distinct observational signatures. These signatures may break the degeneracy in interior structure, while providing insight into their interior processes, history, and population trends. We expect all such planets are born molten, but under what conditions do they remain molten today? We use the coupled interior-climate evolution model, PROTEUS, to estimate the ‘solidification shoreline’: the instellation flux boundary (as a function of stellar Teff) that separates molten gas dwarfs from solidified ones. Our results show that 98% of detected sub-Neptunes occupy a region of parameter space consistent with their having permanent magma oceans, if they are gas dwarfs. While mantle fO2 and bulk volatile C/H ratio both influence magma ocean cooling, planets with oxidising mantles and carbon-rich atmospheres are likely to have high mean-molecular weight atmospheres (μ>3.8 g mol⁻¹) and are thus outside the scope of this study. Therefore, most detected sub-Neptunes, if they are gas dwarfs, have permanent magma oceans. This result motivates further research into the interactions between molten interiors and overlying atmospheres, and campaigns to identify unambiguous signatures of these interactions.

At a glance Sub-Neptunes are the most common type of exoplanet, yet their interiors remain mysterious. This study shows that most rocky sub-Neptunes with hydrogen-rich atmospheres have mantles hot enough to be fully molten, and maps the boundary where rocky interiors transition from liquid to solid across the exoplanet population.

Abstract Spectroscopic characterization of rocky exoplanets with the James Webb Space Telescope has brought the origin and evolution of their atmospheres into the focus of exoplanet science. Time-evolved models of the feedback between interior and atmosphere are critical to predict and interpret these observations and link them to the Solar System terrestrial planets. However, models differ in methodologies and input data, which can lead to significant differences in interpretation. In this paper, we present the experimental protocol of the Coupled atmospHere Interior modeL Intercomparison (CHILI) project. CHILI is an (exo-)planet model intercomparison project within the Climates Using Interactive Suites of Intercomparisons Nested for Exoplanet Studies (CUISINES) framework, which aims to support a diverse set of multi-model intercomparison projects in the exoplanet community. The present protocol includes the initial set of participating magma ocean models, divided into evolutionary and static models, and two types of test categories, one focused on Solar System planets (Earth & Venus) and the other on exoplanets orbiting low-mass M-dwarfs. Both test categories aim to quantify the evolution of key markers of the links between planetary atmospheres and interiors over geological timescales. The proposed tests would allow us to quantify and compare the differences between coupled atmosphere-interior models used by the exoplanet and planetary science communities. Results from the proposed tests will be published in dedicated follow-up papers. To encourage the community to join this comparison effort and as an example, we present initial test results for the early Earth and TRAPPIST-1 b, conducted with models differing in the treatment of energy transport in the planetary interior and atmosphere, surface boundary layer, geochemistry, and the in- and outgassing of volatile compounds.

At a glance Different research groups model what happens when a young rocky planet’s molten surface interacts with its early atmosphere, but they don’t agree with each other. CHILI is a community protocol that lets us run the same simulated planets through every model and compare the answers head-to-head. Once everyone’s models are calibrated against each other, we can interpret JWST observations of young rocky exoplanets with more confidence.

Abstract In the aftermath of the Moon-forming giant impact, the Hadean Earth’s mantle and surface crystallized from a global magma ocean blanketed by a dense volatile-rich atmosphere. While prior studies have explored the thermal evolution of such early-Earth scenarios under idealized, oxidizing conditions, the potential feedback between tidal heating driven by Earth─Moon orbital forcing and variable redox scenarios have not yet been explored in detail. We investigate whether tidal heating could have prolonged this early magma ocean phase and supported quasi-steady state epochs of global radiative equilibrium: periods of thermal balance between outgoing radiation and interior heat flux. Using the PROTEUS simulation framework, we simulate Earth’s early evolution under a range of plausible tidal power densities, oxygen fugacities, and volatile inventories. Our results suggest that feedback between tidal heating and atmospheric forcing can induce substantial variation in magma ocean lifetimes, from ∼30 Myr up to ∼500 Myr, sensitive to interior redox conditions. Global radiative equilibrium epochs commonly arise across this range, lasting from ∼2 to ∼320 Myr, and typically occur from 24 Myr after the Moon-forming impact. Under oxidizing conditions, late-stage H₂O degassing promotes melt retention and sustained heating due to its significant contribution to greenhouse forcing. Weak tides increase the atmospheric abundance of H₂S and NH₃ and deplete CO. Therefore, the feedback between tides and atmospheric forcing induces a disequilibrium signature in the magma ocean atmosphere.

At a glance After the Moon-forming impact, Earth was covered in a global magma ocean beneath a thick atmosphere. We show that tidal heating from the young Moon, combined with greenhouse warming from outgassed volatiles, could have kept Earth’s surface molten for anywhere from 30 to 500 million years depending on the chemistry of the mantle. The interplay between tides and atmospheric composition also produces distinctive chemical signatures that could help constrain the early conditions that led to habitability.

Abstract We investigate how well the Large Interferometer for Exoplanets (LIFE) mission concept can detect habitable conditions on exoplanets through the presence of atmospheric water vapor as a proxy for surface oceans. We model the atmosphere of a pre-biotic Earth-like planet across a range of water concentrations, from water-poor to water-rich, with surface partial pressures from 10⁻⁷ to 1 bar of H₂O. We simulate LIFE-like noise at spectral resolutions R = 50 and 100 using LIFEsim and perform Bayesian atmospheric retrievals to determine the technical requirements for LIFE to confirm habitability. We model three vertical water distributions: a vertically constant profile, a Manabe-Wetherald based Earth-like profile, and a diffusion and photochemistry profile to test how the assumed vertical structure influences the retrieved abundances. Clouds are not modeled. We find the ability for LIFE to detect water strongly depends on the vertical profile assumed. LIFE is unable to constrain the highest water cases and provides upper limits on low water planets. For the highest water abundances, absorption features saturate and reduce sensitivity to characterize precise H₂O levels. Water vapor is not detectable in any profile modeled for ≤10⁻⁶ bar in surface water, comparable to Mars. For an Earth-like profile, LIFE could constrain H₂O concentrations from 10⁻³ to 1 bar, spanning below and above present-day Earth concentrations of 10⁻² bar. Detectable atmospheric water may imply surface oceans, as water is highly reactive and rapidly removed by surface mineral reactions. Thus, LIFE can characterize water abundances indicative of habitable surface conditions.

At a glance Detecting water vapor in exoplanet atmospheres could indicate habitable surface conditions, but too much or too little water makes detection unreliable. This study quantifies the sensitivity of the planned LIFE space telescope to water vapor on Earth-like planets and identifies the range of atmospheric water abundances it can reliably measure.

Abstract Small, low-density exoplanets are sculpted by strong stellar irradiation, but their primordial compositions and subsequent evolution are still unknown. Two often-considered scenarios hold that they formed with rocky interiors and H₂-He atmospheres (gas dwarfs') or alternatively with bulk compositions dominated by H₂O phases (water worlds’). Here we constrain the possible range of evolutionary histories linking the birth conditions of low-density super-Earth L 98-59 d to recent observations using a coupled atmosphere-interior evolutionary model. We find that the observations can be explained by in situ photochemical production of SO₂ in an H₂ background, indicative of a chemically reducing mantle and substantial (>1.8 mass%) early sulfur and hydrogen content, inconsistent with both the gas-dwarf and water-world scenarios. L 98-59 d’s interior comprises a permanent magma ocean, allowing long-term retention of volatiles within its mantle over billions of years, consistent with California-Kepler Survey trends. Our analysis reveals an evolutionary pathway in which planets host volatile-rich atmospheres sustained by long-term magma-ocean degassing, shaped by secular cooling, atmospheric erosion and photochemistry. Internal and environmental processes contribute to the observed diversity of super-Earth and sub-Neptune exoplanets.

At a glance The exoplanet L 98-59 d is surprisingly large for its mass, suggesting it holds substantial volatiles, but whether it is a miniature gas planet or a water world has been unclear. By simulating its evolution from birth to present day, we find neither scenario fits; instead, its atmosphere is sustained by a permanent magma ocean releasing sulfur and hydrogen over billions of years. This points to a new evolutionary pathway in which long-lived magma oceans drive the atmospheric diversity we observe among super-Earths.

Abstract The interaction between a magma ocean and a primordial atmosphere is increasingly recognized as a key process in shaping planetary envelope compositions. This coupling should strongly influence gas accretion, yet its role during the disk-embedded stage remains poorly constrained. We develop a time-dependent model that couples solid accretion, nebular gas accretion, and water enrichment and partitioning through magma─atmosphere interactions, along with post-disk thermal evolution and escape. We find that, for super-Earth-mass planets, water production is generally limited by the magma oxygen budget and typically ceases before disk dispersal. Subsequent nebular gas accretion dilutes the envelope toward hydrogen-dominated compositions, largely independent of the initial magma redox state. This establishes an upper bound on the envelope water fraction—the oxygen exhaustion limit—primarily set by the reactive oxygen inventory and the planet mass. After disk dispersal, degassing increases the water fraction only in Earth-mass planets undergoing strong escape, while super-Earths exhibit little change because surface pressures are hardly affected by escape. Magma─atmosphere coupling alone therefore cannot maintain water-rich envelopes in sub-Neptunes and produces a strong mass─composition relation imposed by the oxygen exhaustion limit. Highly enriched sub-Neptunes would therefore imply additional mechanisms such as late volatile delivery or post-disk giant impacts. The relation between planetary radius and envelope composition offers a means to infer magma properties, providing a pathway to connect present-day observables with early formation histories.

At a glance When a young planet’s magma ocean interacts with its atmosphere, it can produce water vapor by reacting hydrogen with oxygen from the rock. We find that this process runs out of available oxygen surprisingly quickly, setting an upper limit on how water-rich a sub-Neptune’s atmosphere can become through magma chemistry alone. Sub-Neptunes with very water-rich atmospheres would therefore need additional water delivered later, for instance by icy impacts.

Abstract Ultra-short period lava worlds offer a unique window into the coupled evolution of planetary interior and atmospheres under extreme irradiation. In this study, we investigate the mantle dynamics, nightside volcanism, and volatile outgassing on lava world K2-141 b (1.54 R⊕, 5.31 M⊕) using two-dimensional convection models with tracer-based volatile tracking. Our simulations explore a range of interior configurations, including models with and without plastic yielding, basal versus mixed heating, core cooling, and melt intrusion. In models without plastic yielding (i.e. with a strong lithosphere), we find that mantle upwellings form at the substellar and antistellar points, while downwellings form near the day-night terminators at the boundary between the magma ocean and cold, solid nightside. These downwellings facilitate the recycling of crustal material, representing a form of asymmetric, single-lid tectonics. The resulting magma ocean thickness varies from 200 to 300 km depending on the model parameters, corresponding to about 2-3% of the planet’s radius. Continuous nightside volcanism produces a basaltic crust and gradually depletes the mantle of volatiles. We find that over a billion years, volcanic eruptions can outgas tens of bars of CO₂ and H₂O. We show that even relatively large volcanic eruptions on the nightside produce thermal emission signals of no more than 1 ppm, remaining below the current detectability threshold in thermal phase curves. However, for most models, outgassing rates are increased near the day-night terminators and future studies should assess whether such localised outgassing could lead to atmospheric signatures in transmission spectroscopy.

At a glance Ultra-hot lava worlds like K2-141 b have permanent dayside magma oceans and cooler nightsides. This study models how internal mantle convection driven by extreme surface temperature contrasts can sustain nightside volcanism and outgassing, connecting the planet’s interior dynamics to potentially observable atmospheric signatures.

Abstract Sub-Neptunes with substantial atmospheres may possess magma oceans in contact with the overlying gas, with chemical interactions between the atmosphere and magma playing an important role in shaping atmospheric composition. Early JWST observations have found high abundances of carbon- and oxygen-bearing molecules in a number of sub-Neptune atmospheres, which may result from processes including accretion of icy material at formation or magma-atmosphere interactions. Previous work examining the effects of magma-atmosphere interactions on sub-Neptunes has mostly been limited to studying conditions at the atmosphere-mantle boundary, without considering implications for the upper atmosphere which is probed by spectroscopic observations. In this work, we present a modeling architecture to determine observable signatures of magma-atmosphere interactions. We combine an equilibrium chemistry code which models reactions between the core, mantle and atmosphere with a radiative-convective model that determines the composition and structure of the observable upper atmosphere. We examine how different conditions at the atmosphere-mantle boundary and different core and mantle compositions impact the upper atmospheric composition. We compare our models to JWST NIRISS+NIRSpec observations of the sub-Neptune TOI-270 d, finding that our models can provide a good fit to the observed transmission spectrum with little fine-tuning. This suggests that magma-atmosphere interactions may be sufficient to explain high abundances of molecules such as H₂O, CH₄ and CO₂ in sub-Neptune atmospheres, without additional accretion of icy material from the protoplanetary disk. Although other processes could lead to similar compositions, our work highlights the need to consider magma-atmosphere interactions when interpreting the observed atmospheric composition of a sub-Neptune.

At a glance JWST observations of the sub-Neptune TOI-270 d have revealed unexpectedly high abundances of carbon- and oxygen-bearing molecules. This study shows that chemical reactions between a hydrogen-rich atmosphere and an underlying magma ocean can naturally explain these observations, without requiring exotic compositions.

Abstract Ultrashort-period (USP) exoplanets, with R_p ≤ 2 R⊕ and periods ≤1 day, are expected to be stripped of volatile atmospheres by intense host star irradiation, which is corroborated by their nominal bulk densities and previous eclipse observations consistent with bare rock surfaces. However, a few USP planets appear anomalously under-dense relative to an Earth-like composition, suggesting an exotic interior structure (e.g., core-less) or a volatile-rich secondary atmosphere increasing their apparent radius. Here we present the first dayside emission spectrum of the low-density (4.3±0.4 g cm⁻³) USP planet TOI-561 b, which orbits an iron-poor, alpha-rich, 10 Gyr old thick disk star. Our 3-5 μm JWST/NIRSpec observations demonstrate the dayside of TOI-561 b is inconsistent with a bare-rock surface at high statistical significance, suggesting instead a thick volatile envelope that is cooling the dayside to well below the 3000 K expected in the bare-rock or thin-atmosphere case. These results reject the popular hypothesis of complete atmospheric desiccation for highly irradiated exoplanets and support predictions that planetary-scale magma oceans can retain substantial reservoirs of volatiles, opening the geophysical study of ultrahot super-Earths through the lenses of their atmospheres.

At a glance Ultra-short-period rocky planets orbiting extremely close to their stars are expected to be stripped of any atmosphere. New JWST observations of super-Earth TOI-561 b challenge this picture by revealing evidence for a thick volatile atmosphere, suggesting some close-in rocky worlds can retain or regenerate atmospheric gases.

Abstract Rocky exoplanets accessible to characterization often lie on close-in orbits where tidal heating within their interiors is significant, with the L 98-59 planetary system being a prime example. As a long-term energy source for ongoing mantle melting and outgassing, tidal heating has been considered as a way to replenish lost atmospheres on rocky planets around active M-dwarfs. We simulate the early evolution of L 98-59 b, c, and d using a time-evolved interior-atmosphere modelling framework, with a self-consistent implementation of tidal heating and redox-controlled outgassing. 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’. Our coupled 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 time-scales. Comparisons with a semi-analytic model demonstrate that this negative feedback is a robust mechanism which can probe a given planet’s initial conditions, atmospheric composition, and interior structure. The orbit and instellation of the sub-Venus L 98-59 b likely place it in a regime where tidal heating has kept the planet molten up to the present day, even if it were to have lost its atmosphere. For c and d, a long-lived magma ocean can be induced by tides only with additional atmospheric regulation of energy transport.

At a glance Rocky exoplanets on tight orbits experience internal tidal heating, similar to how Jupiter’s gravity keeps Io volcanically active. We discovered a self-regulating feedback: as tidal heating melts the mantle, the softened rock dissipates tidal energy less efficiently, capping the heating rate far below previous estimates. Despite this self-limitation, tidal heating in the L 98-59 system can still sustain magma oceans for billions of years.

Abstract The search for extraterrestrial life in the Solar System and beyond is a key science driver in astrobiology, planetary science, and astrophysics. A critical step is the identification and characterization of potential habitats, both to guide the search and to interpret its results. However, a well-accepted, self-consistent, flexible, and quantitative terminology and method of assessment of habitability are lacking. Our paper fills this gap based on a three year-long study by the NExSS Quantitative Habitability Science Working Group. We reviewed past studies of habitability, but find that the lack of a universally valid definition of life prohibits a universally applicable definition of habitability. A more nuanced approach is needed. We introduce a quantitative habitability assessment framework (QHF) that enables self-consistent, probabilistic assessment of the compatibility of two models: First, a habitat model, which describes the probability distributions of key conditions in the habitat. Second, a viability model, which describes the probability that a metabolism is viable given a set of environmental conditions. We provide an open-source implementation of this framework and four examples as a proof of concept: (a) Comparison of two exoplanets for observational target prioritization; (b) Interpretation of atmospheric O₂ detection in two exoplanets; (c) Subsurface habitability of Mars; and (d) Ocean habitability in Europa. These examples demonstrate that our framework can self-consistently inform astrobiology research over a broad range of questions. The proposed framework is modular so that future work can expand the range and complexity of models available, both for habitats and for metabolisms.

At a glance Assessing whether a planet could support life requires a consistent framework, but existing terminology around habitability is used inconsistently across the scientific community. This paper proposes a standardized quantitative framework and terminology for evaluating the habitability of both Solar System and extrasolar worlds.

Abstract Climate transitions on exoplanets offer valuable insights into the atmospheric processes governing planetary habitability. Previous pure-steam atmospheric models show a thermal limit in outgoing long-wave radiation, which has been used to define the inner edge of the classical habitable zone and guide exoplanet surveys aiming to identify and characterize potentially habitable worlds. We expand upon previous modelling by treating (i) the dissolution of volatiles into a magma ocean underneath the atmosphere, (ii) a broader volatile range of the atmospheric composition including H₂O, CO₂, CO, H₂, CH₄, and N₂, and (iii) a surface-temperature- and mantle-redox-dependent equilibrium chemistry. We find that multicomponent atmospheres of outgassed composition located above partially or fully molten mantles do not exhibit the characteristic thermal radiation limit that arises from pure-steam models, thereby undermining the canonical concept of a runaway greenhouse limit, and hence challenging the conventional approach of using it to define an irradiation-based habitable zone. Our results show that atmospheric heat loss to space is strongly dependent on the oxidation and melting state of the underlying planetary mantle, through their significant influence on the atmosphere’s equilibrium composition. This suggests an evolutionary hysteresis in climate scenarios: Initially molten and cooling planets do not converge to the same climate regime as solidified planets that heat up by external irradiation. Steady-state models cannot recover evolutionary climate transitions, which instead require self-consistent models of the temporal evolution of the coupled feedback processes between interior and atmosphere over geologic time.

At a glance The ‘runaway greenhouse’ concept defines the inner edge of the habitable zone: the distance from a star where a planet’s oceans would boil away irreversibly. We show that this thermal limit, derived from pure-steam atmosphere models, vanishes when we account for the complex chemistry of atmospheres above magma oceans. Whether a planet retains habitable conditions depends not just on how much starlight it receives, but on the composition and melting state of its interior.

Abstract A wide variety of scenarios for the origin of life have been proposed, with many influencing the prevalence and distribution of biosignatures across exoplanet populations. This relationship suggests these scenarios can be tested by predicting biosignature distributions and comparing them with empirical data. Here, we demonstrate this approach by focusing on the cyanosulfidic origins-of-life scenario and investigating the hypothesis that a minimum near-ultraviolet (NUV) flux is necessary for abiogenesis. Using Bayesian modeling and the Bioverse survey simulator, we constrain the probability of obtaining strong evidence for or against this ``UV Threshold Hypothesis’’ with future biosignature surveys. Our results indicate that a correlation between past NUV flux and current biosignature occurrence is testable for sample sizes of 50 planets. The diagnostic power of such tests is critically sensitive to the intrinsic abiogenesis rate and host star properties, particularly maximum past NUV fluxes. Surveys targeting a wide range of fluxes, and planets orbiting M dwarfs enhance the chances of conclusive results, with sample sizes 100 providing 80% likelihood of strong evidence if abiogenesis rates are high and the required NUV fluxes are moderate. For required fluxes exceeding a few hundred erg/s/cm², both the fraction of inhabited planets and the diagnostic power sharply decrease. Our findings demonstrate the potential of exoplanet surveys to test origins-of-life hypotheses. Beyond specific scenarios, this work underscores the broader value of realistic survey simulations for future observatories (e.g., HWO, LIFE, ELTs, Nautilus) in identifying testable science questions, optimizing mission strategies, and advancing theoretical and experimental studies of abiogenesis.

At a glance The conditions under which life originates may leave detectable patterns in the distribution of biosignatures across exoplanet populations. This study models how UV-driven origin-of-life scenarios would imprint on observable biosignature statistics and shows how future surveys could test these hypotheses.

Abstract Understanding the physics of planetary magma oceans has been the subject of growing efforts, in light of the increasing abundance of solar system samples and extrasolar surveys. A rocky planet harboring such an ocean is likely to interact tidally with its host star, planetary companions, or satellites. To date, however, models of the tidal response and heat generation of magma oceans have been restricted to the framework of weakly viscous solids, ignoring the dynamical fluid behavior of the ocean beyond a critical melt fraction. Here we provide a handy analytical model that accommodates this phase transition, allowing for a physical estimation of the tidal response of lava worlds. We apply the model in two settings: the tidal history of the early Earth–Moon system in the aftermath of the giant impact, and the tidal interplay between short-period exoplanets and their host stars. For the former, we show that the fluid behavior of the Earth’s molten surface drives efficient early lunar recession to 25 Earth radii within 104–105 yr, in contrast with earlier predictions. For close-in exoplanets, we report on how their molten surfaces significantly change their spin–orbit dynamics, allowing them to evade spin–orbit resonances and accelerating their track toward tidal synchronization from a gigayear to megayear timescale. Moreover, we reevaluate the energy budgets of detected close-in exoplanets, highlighting how the surface thermodynamics of these planets are likely controlled by enhanced, fluid-driven tidal heating, rather than vigorous insolation, and how this regime change substantially alters predictions for their surface temperatures.

At a glance Rocky planets with molten surfaces experience tidal forces from their host star that dissipate energy very differently than in solid bodies. This study develops a new tidal framework for lava worlds and applies it to close-in exoplanets and the early Earth-Moon system, showing that magma oceans strongly enhance tidal heating and orbital evolution.

Abstract The prevalence of atmospheres on rocky planets is one of the major questions in exoplanet astronomy, but there are currently no published unambiguous detections of atmospheres on any rocky exoplanets. The MIRI instrument on JWST can measure thermal emission from tidally locked rocky exoplanets orbiting small, cool stars. This emission is a function of their surface and atmospheric properties, potentially allowing detections of atmospheres. One way to find atmospheres is to search for lower dayside emission than would be expected for a blackbody planet. Another technique is to measure phase curves of thermal emission to search for nightside emission due to atmospheric heat redistribution. Here, we compare strategies for detecting atmospheres on rocky exoplanets. We simulate secondary eclipse and phase curve observations in the MIRI F1500W and F1280W filters for a range of surfaces (providing our open-access albedo data) and atmospheres on 30 exoplanets selected for their F1500W signal-to-noise ratio. We show that secondary eclipse observations are more degenerate between surfaces and atmospheres than suggested in previous work, and that thick atmospheres can support emission consistent with a blackbody planet in these filters. These results make it difficult to unambiguously detect or rule out atmospheres using their photometric dayside emission alone. We suggest that an F1500W phase curve could instead be observed for a similar sample of planets. While phase curves are time-consuming and their instrumental systematics can be challenging, we suggest that they allow the only unambiguous detections of atmospheres by nightside thermal emission.

At a glance Detecting atmospheres on rocky exoplanets is a major goal of current astronomy, but no unambiguous detection exists yet. This study demonstrates that photometric phase curve observations with JWST can reliably distinguish between rocky planets with and without atmospheres by measuring how heat is redistributed from dayside to nightside.

Abstract Atmospheric energy transport is central to the cooling of primordial magma oceans. Theoretical studies of atmospheres on lava planets have assumed that convection is the only process involved in setting the atmospheric temperature structure. This significantly influences the ability for a magma ocean to cool. It has been suggested that convective stability in these atmospheres could preclude permanent magma oceans. We develop a new 1D radiative-convective model in order to investigate when the atmospheres overlying magma oceans are convectively stable. Using a coupled interior-atmosphere framework, we simulate the early evolution of two terrestrial-mass exoplanets: TRAPPIST-1 c and HD 63433 d. Our simulations suggest that the atmosphere of HD 63433 d exhibits deep isothermal layers which are convectively stable. However, it is able to maintain a permanent magma ocean and an atmosphere depleted in H₂O. It is possible to maintain permanent magma oceans underneath atmospheres without convection. Absorption features of CO₂ and SO₂ within synthetic emission spectra are associated with mantle redox state, meaning that future observations of HD 63433 d may provide constraints on the geochemical properties of a magma ocean analogous with the early Earth. Simulations of TRAPPIST-1 c indicate that it is expected to have solidified within 100 Myr, outgassing a thick atmosphere in the process. Cool isothermal stratospheres generated by low-molecular-weight atmospheres can mimic the emission of an atmosphere-less body. Future work should consider how atmospheric escape and chemistry modulates the lifetime of magma oceans, and the role of tidal heating in sustaining atmospheric convection.

At a glance Models of lava planets typically assume their thick atmospheres transport heat upward through convection, similar to boiling water. We find that some lava world atmospheres develop deep layers where convection shuts down entirely, yet the planet can still maintain a permanent magma ocean. This matters for interpreting upcoming telescope observations, because the atmospheric structure and chemistry change dramatically when convection is absent.

Abstract Interactions between magma oceans and overlying atmospheres on young rocky planets leads to an evolving feedback of outgassing, greenhouse forcing, and mantle melt fraction. Previous studies have predominantly focused on the solidification of oxidized Earth-similar planets, but the diversity in mean density and irradiation observed in the low-mass exoplanet census motivate exploration of strongly varying geochemical scenarios. We aim to explore how variable redox properties alter the duration of magma ocean solidification, the equilibrium thermodynamic state, melt fraction of the mantle, and atmospheric composition. We develop a 1D coupled interior-atmosphere model that can simulate the time-evolution of lava planets. This is applied across a grid of fixed redox states, orbital separations, hydrogen endowments, and C/H ratios around a Sun-like star. The composition of these atmospheres is highly variable before and during solidification. The evolutionary path of an Earth-like planet at 1 AU ranges between permanent magma ocean states and solidification within 1 Myr. Recently solidified planets typically host H₂O- or H₂-dominated atmospheres in the absence of escape. Orbital separation is the primary factor determining magma ocean evolution, followed by the total hydrogen endowment, mantle oxygen fugacity, and finally the planet’s C/H ratio. Collisional absorption by H₂ induces a greenhouse effect which can prevent or stall magma ocean solidification. Through this effect, as well as the outgassing of other volatiles, geochemical properties exert significant control over the fate of magma oceans on rocky planets.

At a glance The chemistry of a young planet’s magma ocean, specifically how oxidized or reduced it is, controls which gases enter the atmosphere and how quickly the surface solidifies. We systematically explored this across a wide range of chemical conditions and found that hydrogen-rich atmospheres produced under reducing conditions can trap enough heat to prevent a magma ocean from ever freezing. The planet’s oxidation state thus acts as a chemical switch between permanent magma ocean worlds and planets that solidify within a million years.

Abstract Context. The increased brightness temperature of young rocky protoplanets during their magma ocean epoch makes them potentially amenable to atmospheric characterization at distances from the Solar System far greater than thermally equilibrated terrestrial exoplanets, offering observational opportunities for unique insights into the origin of secondary atmospheres and the near surface conditions of prebiotic environments. Aims. The Large Interferometer For Exoplanets (LIFE) mission will employ a space-based midinfrared nulling interferometer to directly measure the thermal emission of terrestrial exoplanets. In this work, we seek to assess the capabilities of various instrumental design choices of the LIFE mission concept for the detection of cooling protoplanets with transient high-temperature magma ocean atmospheres at the tail end of planetary accretion. In particular, we investigate the minimum integration times necessary to detect transient magma ocean exoplanets in young stellar associations in the Solar neighborhood. Methods. Using the LIFE mission instrument simulator (LIFEsim), we assessed how specific instrumental parameters and design choices, such as wavelength coverage, aperture diameter, and photon throughput, facilitate or disadvantage the detection of protoplan-ets. We focused on the observational sensitivities of distance to the observed planetary system, protoplanet brightness temperature (using a blackbody assumption), and orbital distance of the potential protoplanets around both G- and M-dwarf stars. Results. Our simulations suggest that LIFE will be able to detect (S/N ≥ 7) hot protoplanets in young stellar associations up to distances of 100 pc from the Solar System for reasonable integration times (up to a few hours). Detection of an Earth-sized protoplanet orbiting a Solar-sized host star at 1 AU requires less than 30 minutes of integration time. M-dwarfs generally need shorter integration times. The contribution from wavelength regions smaller than 6 µm is important for decreasing the detection threshold and discriminating emission temperatures. Conclusions. The LIFE mission is capable of detecting cooling terrestrial protoplanets within minutes to hours in several local young stellar associations hosting potential targets. The anticipated compositional range of magma ocean atmospheres motivates further architectural design studies to characterize the crucial transition from primary to secondary atmospheres.

At a glance Young rocky planets glow brightly in infrared light while their surfaces are still molten, making them visible at much greater distances than cooled, habitable-zone planets. We assessed whether the proposed LIFE space telescope could detect these young, molten worlds and found it could spot Earth-sized protoplanets in nearby star-forming regions within minutes to hours of observation. Detecting planets in this early molten stage would reveal how secondary atmospheres first form on rocky worlds.

Abstract Recent research provides compelling evidence that the decay of short-lived radioisotopes (SLRs), such as ²⁶Al, provided the bulk of energy for heating and desiccation of volatile-rich planetesimals in the early Solar System. However, it remains unclear whether the early Solar System was highly enriched relative to other planetary systems with similar formation characteristics. While the Solar System possesses an elevated level of SLR enrichment compared to the interstellar medium, determining SLR enrichment of individual protoplanetary disks observationally has not been performed and is markedly more difficult. We use N-body simulations to estimate enrichment of SLRs in star-forming regions through two likely important SLR sources, stellar winds from massive stars and supernovae. We vary the number of stars and the radii of the star-forming regions and implement two models of stellar wind SLR propagation for the radioisotopes ²⁶Al and ⁶⁰Fe. We find that for ²⁶Al enrichment the Solar System is at the upper end of the expected distribution, while for the more supernovae dependent isotope ⁶⁰Fe we find that the Solar System is comparatively very highly enriched. Furthermore, combined with our previous research, these results suggest that the statistical role of ²⁶Al-driven desiccation on exoplanet bulk composition may be underestimated in typical interpretations of the low-mass exoplanet census, and that ⁶⁰Fe is even less influential as a source of heating than previously assumed.

At a glance Short-lived radioactive isotopes like aluminium-26 heated the building blocks of planets in our early Solar System, but it is unclear whether this enrichment was typical or unusual. This study develops a unified model for how these isotopes are injected into young planetary systems within star-forming regions.

Abstract Many super-Earths are on very short orbits around their host star and, therefore, more likely to be tidally locked. Because this locking can lead to a strong contrast between the dayside and nightside surface temperatures, these super-Earths could exhibit mantle convection patterns and tectonics that could differ significantly from those observed in the present-day solar system. The presence of an atmosphere, however, would allow transport of heat from the dayside towards the nightside and thereby reduce the surface temperature contrast between the two hemispheres. On rocky planets, atmospheric and geodynamic regimes are closely linked, which directly connects the question of atmospheric thickness to the potential interior dynamics of the planet. Here, we study the interior dynamics of super-Earth GJ 486b (R=1.34 R⊕, M=3.0 M⊕, T_eq≈700 K), which is one of the most suitable M-dwarf super-Earth candidates for retaining an atmosphere produced by degassing from the mantle and magma ocean. We investigate how the geodynamic regime of GJ 486b is influenced by different surface temperature contrasts by varying possible atmospheric circulation regimes. We also investigate how the strength of the lithosphere affects the convection pattern. We find that hemispheric tectonics, the surface expression of degree-1 convection with downwellings forming on one hemisphere and upwelling material rising on the opposite hemisphere, is a consequence of the strong lithosphere rather than surface temperature contrast. Anchored hemispheric tectonics, where downwellings und upwellings have a preferred (day/night) hemisphere, is favoured for strong temperature contrasts between the dayside and nightside and higher surface temperatures.

At a glance Super-Earth GJ 486b orbits so close to its star that one side permanently faces the star, creating extreme temperature contrasts. This study models how the resulting mantle convection patterns differ from Earth’s plate tectonics and could produce observable volcanic activity concentrated on specific parts of the surface.

Abstract Whilst the formation of Solar system planets is constrained by meteoritic evidence, the geophysical history of low-mass exoplanets is much less clear. The bulk composition and climate states of rocky exoplanets may vary significantly based on the composition and properties of the planetesimals they form from. An important factor influenced by planetesimal composition is water content, where the desiccation of accreting planetesimals impacts the final water content of the resultant planets. While the inner planets of the Solar system are comparatively water-poor, recent observational evidence from exoplanet bulk densities and planetary formation models suggest that rocky exoplanets engulfed by substantial layers of high-pressure ices or massive steam atmospheres could be widespread. Here we quantify variations in planetesimal desiccation due to potential fractionation of the two short-lived radioisotopes ²⁶Al and ⁶⁰Fe relevant for internal heating on planetary formation timescales. We focus on how order of magnitude variations in ⁶⁰Fe can affect the water content of planetesimals, and how this may alter the formation of extrasolar ocean worlds. We find that heating by ²⁶Al is the dominant cause of planetesimal heating in any Solar system analogue scenario, thus validating previous works focussing only on this radioisotope. However, ⁶⁰Fe can become the primary heating source in the case of high levels of supernova enrichment in massive star-forming regions. These diverging scenarios can affect the formation pathways, bulk volatile budget, and climate diversity of low-mass exoplanets.

At a glance The water and volatile content of rocky planets depends on how much heating their building blocks experienced from radioactive decay during formation. This study models how the radioactive isotopes aluminium-26 and iron-60 drive the drying of planetesimals across different planetary systems, showing that volatile delivery to planets varies widely.

Abstract Mildly irradiated mini-Neptunes have densities potentially consistent with them hosting substantial liquid-water oceans (“Hycean” planets). The presence of CO₂ and simultaneous absence of ammonia (NH₃ ) in their atmospheres has been proposed as a fingerprint of such worlds. JWST observations of K2-18b, the archetypal Hycean, have found the presence of CO₂ and the depletion of NH₃ to 4 μ m region, where CO₂ and CO features dominate: magma ocean models suggest a systematically lower CO₂ /CO ratio than estimated from free-chemistry retrieval, indicating that deeper observations of this spectral region may be able to distinguish between oceans of liquid water and magma on mini-Neptunes.

At a glance The mini-Neptune K2-18b has been proposed as a possible ocean world based on JWST atmospheric observations. This study shows that the same spectral signatures, including CO₂ and the absence of ammonia, can be explained by a magma ocean interior rather than a liquid water ocean, making it difficult to distinguish between these two very different scenarios.

Abstract Long-term magma ocean phases on rocky exoplanets orbiting closer to their star than the runaway greenhouse threshold - the inner edge of the classical habitable zone - may offer insights into the physical and chemical processes that distinguish potentially habitable worlds from others. Thermal stratification of runaway planets is expected to significantly inflate their atmospheres, potentially providing observational access to the runaway greenhouse transition in the form of a “habitable zone inner edge discontinuity” in radius-density space. Here, we use Bioverse, a statistical framework combining contextual information from the overall planet population with a survey simulator, to assess the ability of ground- and space-based telescopes to test this hypothesis. We find that the demographic imprint of the runaway greenhouse transition is likely detectable with high-precision transit photometry for sample sizes 100 planets if at least 10 % of those orbiting closer than the habitable zone inner edge harbor runaway climates. Our survey simulations suggest that in the near future, ESA’s PLATO mission will be the most promising survey to probe the habitable zone inner edge discontinuity. We determine survey strategies that maximize the diagnostic power of the obtained data and identify as key mission design drivers: 1. A follow-up campaign of planetary mass measurements and 2. The fraction of low-mass stars in the target sample. Observational constraints on the runaway greenhouse transition will provide crucial insights into the distribution of atmospheric volatiles among rocky exoplanets, which may help to identify the nearest potentially habitable worlds.

At a glance Rocky planets closer to their star than the runaway greenhouse threshold lose their oceans and become desiccated. This study predicts that this transition should create a detectable gap in the distribution of exoplanet properties, offering a way for future surveys to test our understanding of how planets lose their water.

Abstract The presence of short-lived radioisotopes (SLRs) ²⁶Al and ⁶⁰Fe in the Solar system places constraints on the initial conditions of our planetary system. Most theories posit that the origin of ²⁶Al and ⁶⁰Fe is in the interiors of massive stars, and they are either delivered directly to the protosolar disc from the winds and supernovae of the massive stars, or indirectly via a sequential star formation event. However, massive stars that produce SLRs also emit photoionising far and extreme ultraviolet radiation, which can destroy the gas component of protoplanetary discs, possibly precluding the formation of gas giant planets like Jupiter and Saturn. Here, we perfom N-body simulations of star-forming regions and determine whether discs that are enriched in SLRs can retain enough gas to form Jovian planets. We find that discs are enriched and survive the photoionising radiation only when the dust radius of the disc is fixed and not allowed to move inwards due to the photoevaporation, or outwards due to viscous spreading. Even in this optimal scenario, not enough discs survive until the supernovae of the massive stars and so have zero or very little enrichment in ⁶⁰Fe. We therefore suggest that the delivery of SLRs to the Solar system may not come from the winds and supernovae of massive stars.

At a glance The radioactive isotopes found in Solar System meteorites must have been produced by nearby massive stars, but the same stellar winds and radiation can strip material from young planetary disks. This study quantifies how photoevaporation competes with isotope enrichment in star-forming regions, helping explain the Solar System’s specific composition.

Abstract The ultra-short-period super-Earth 55 Cancri e has a measured radius of 1.8 Earth radii. Previous thermal phase curve observations suggest a strong temperature contrast between the dayside and nightside of around 1000 K with the hottest point shifted 41±12 degrees east from the substellar point, indicating some degree of heat circulation. The dayside (and potentially even the nightside) is hot enough to harbour a magma ocean. We use results from general circulation models (GCMs) of atmospheres to constrain the surface temperature contrasts. There is still a large uncertainty on the vigour and style of mantle convection in super-Earths, especially those that experience stellar irradiation large enough to harbour a magma ocean. In this work, we aim to constrain the mantle dynamics of the tidally locked lava world 55 Cancri e. Using the surface temperature contrasts as boundary condition, we model the mantle flow of 55 Cancri e using 2D mantle convection simulations and investigate how the convection regimes are affected by the different climate models. We find that large super-plumes form on the dayside if that hemisphere is covered by a magma ocean and the nightside remains solid or only partially molten. Cold material descends into the deep interior on the nightside, but no strong downwellings form. In some cases, the super-plume also moves several tens of degrees towards the terminator. A convective regime where the upwelling is preferentially on the dayside might lead to preferential outgassing on that hemisphere which could lead to the build-up of atmospheric species that could be chemically distinct from the nightside.

At a glance Super-Earth 55 Cancri e shows a puzzling temperature pattern with a hot spot shifted away from the point directly facing the star. This study uses 2D mantle convection simulations to show that extreme day-night temperature contrasts drive large super-plumes on the dayside, with preferential outgassing that could produce hemisphere-scale differences in atmospheric chemistry.

Abstract Super-Earths span a wide range of bulk densities, indicating a diversity in interior conditions beyond that seen in the solar system. In particular, an emerging population of low-density super-Earths may be explained by volatile-rich interiors. Among these, low-density lava worlds have dayside temperatures that are high enough to evaporate their surfaces, providing a unique opportunity to probe their interior compositions and test for the presence of volatiles. In this work, we investigate the atmospheric observability of low-density lava worlds. We use a radiative-convective model to explore the atmospheric structures and emission spectra of these planets, focusing on three case studies with high observability metrics and substellar temperatures spanning ∼1900–2800 K: HD 86226 c, HD 3167 b, and 55 Cnc e. Given the possibility of mixed volatile and silicate interior compositions for these planets, we consider a range of mixed volatile and rock-vapor atmospheric compositions. This includes a range of volatile fractions and three volatile compositions: water-rich (100% H₂ O), water with CO₂ (80% H₂ O+20% CO₂ ), and a desiccated O-rich scenario (67% O 2 +33% CO₂ ). We find that spectral features due to H₂ O, CO₂ , SiO, and SiO 2 are present in the infrared emission spectra as either emission or absorption features, depending on dayside temperature, volatile fraction, and volatile composition. We further simulate JWST secondary-eclipse observations for each of the three case studies, finding that H₂ O and/or CO₂ could be detected with as few as ∼five eclipses. Detecting volatiles in these atmospheres would provide crucial independent evidence that volatile-rich interiors exist among the super-Earth population.

At a glance Some super-Earths have densities low enough to suggest volatile-rich interiors, and those close to their stars may have permanent dayside lava oceans. This study assesses whether future telescope observations can distinguish between rocky planets with thin mineral vapor atmospheres and water-rich worlds, finding that mid-infrared spectroscopy offers the best diagnostic.

Abstract The abundance of the short-lived radioisotopes ²⁶Al and ⁶⁰Fe in the early Solar system is usually explained by the Sun either forming from pre-enriched material, or the Sun’s protosolar disc being polluted by a nearby supernova explosion from a massive star. Both hypotheses suffer from significant drawbacks: the former does not account for the dynamical evolution of star-forming regions, while in the latter the time for massive stars to explode as supernovae can be similar to, or even longer than, the lifetime of protoplanetary discs. In this paper, we extend the disc enrichment scenario to include the contribution of ²⁶Al from the winds of massive stars before they explode as supernovae. We use N-body simulations and a post-processing analysis to calculate the amount of enrichment in each disc, and we vary the stellar density of the star-forming regions. We find that stellar winds contribute to disc enrichment to such an extent that the Solar system’s ²⁶Al/⁶⁰Fe ratio is reproduced in up to 50 per cent of discs in dense (ρ = 1000 M⊙ pc−3) star-forming regions. When winds are a significant contributor to the SLR enrichment, we find that Solar system levels of enrichment can occur much earlier (before 2.5 Myr) than when enrichment occurs from supernovae, which start to explode at later ages (>4 Myr). We find that Solar system levels of enrichment all but disappear in low-density star-forming regions (ρ ≤ 10 M⊙ pc−3), implying that the Solar system must have formed in a dense, populous star-forming region if ²⁶Al and ⁶⁰Fe were delivered directly to the protosolar disc from massive-star winds and supernovae.

At a glance The early Solar System contained radioactive aluminium-26 and iron-60 that heated young planetesimals, but the source of these isotopes is debated. This study uses simulations of star-forming regions to show that stellar winds from massive stars can enrich protoplanetary disks with these isotopes, complementing or replacing the traditional supernova injection scenario.

Abstract Active comets have been detected in several exoplanetary systems, although so far only indirectly, when the dust or gas in the extended coma has transited in front of the stellar disk. The large optical surface and relatively high temperature of an active cometary coma also makes it suitable to study with direct imaging, but the angular separation is generally too small to be reachable with present-day facilities. However, future imaging facilities with the ability to detect terrestrial planets in the habitable zones of nearby systems will also be sensitive to exocomets in such systems. Here we examine several aspects of exocomet imaging, particularly in the context of the Large Interferometer for Exoplanets (LIFE), which is a proposed space mission for infrared imaging and spectroscopy through nulling interferometry. We study what capabilities LIFE would have for acquiring imaging and spectroscopy of exocomets, based on simulations of the LIFE performance as well as statistical properties of exocomets that have recently been deduced from transit surveys. We find that for systems with extreme cometary activities such as β Pictoris, sufficiently bright comets may be so abundant that they overcrowd the LIFE inner field of view. More nearby and moderately active systems such as є Eridani or Fomalhaut may turn out to be optimal targets. If the exocomets have strong silicate emission features, such as in comet Hale-Bopp, it may become possible to study the mineralogy of individual exocometary bodies. We also discuss the possibility of exocomets as false positives for planets, with recent deep imaging of α Centauri as one hypothetical example. Such contaminants could be common, primarily among young debris disk stars, but should be rare among the main sequence population. We discuss strategies to mitigate the risk of any such false positives.

At a glance Active comets have been detected around other stars, but only indirectly through transit events. This study shows that the planned LIFE space interferometer could directly image the thermal emission from exocometary comae, opening a new window into the volatile composition of other planetary systems.

Abstract The nucleosynthetic isotope dichotomy between carbonaceous (CC) and non-carbonaceous (NC) meteorites has been interpreted as evidence for spatial separation and the coexistence of two distinct planet-forming reservoirs for several million years in the solar protoplanetary disk. The rapid formation of Jupiter’s core within one million years after the formation of calcium-aluminium-rich inclusions (CAIs) has been suggested as a potential mechanism for spatial and temporal separation. In this scenario, Jupiter’s core would open a gap in the disk and trap inward-drifting dust grains in the pressure bump at the outer edge of the gap, separating the inner and outer disk materials from each other. We performed simulations of dust particles in a protoplanetary disk with a gap opened by an early-formed Jupiter core, including dust growth and fragmentation as well as dust transport, using the dust evolution software DustPy . Our numerical experiments indicate that particles trapped in the outer edge of the gap rapidly fragment and are transported through the gap, contaminating the inner disk with outer disk material on a timescale that is inconsistent with the meteoritic record. This suggests that other processes must have initiated or at least contributed to the isotopic separation between the inner and outer Solar System.

At a glance The distinct isotopic signatures found in different classes of Solar System meteorites suggest that the early Solar System disk was split into two separate reservoirs, possibly by a forming giant planet. This study shows that dust fragmentation can allow material to leak through planetary gaps, complicating the picture of how Jupiter may have partitioned the disk.

Abstract The timing of formation for the first planetesimals determines the mode of planetary accretion and their geophysical and compositional evolution. Astronomical observations of circumstellar discs and Solar System geochronology provide evidence for planetesimal formation during molecular cloud collapse, much earlier than previously estimated. Here, we present distinct observational evidence from white dwarf planetary systems for planetesimal formation occurring during the first few hundred thousand years after cloud collapse in exoplanetary systems. A significant fraction of white dwarfs have accreted planetary material rich in iron core or mantle material. In order for the exo-asteroids accreted by white dwarfs to form iron cores, substantial heating is required. By simulating planetesimal evolution and collisional evolution we show that the most likely heat source is short-lived radioactive nuclides such as Al-2 (half life of approximately 0.7 Myr). Core-rich materials in the atmospheres of white dwarfs, therefore, provide independent evidence for rapid planetesimal formation, concurrent with star formation.

At a glance The timing of when small rocky bodies first form in a planetary system shapes how planets are built. By analyzing the compositions of asteroids accreted onto white dwarf stars, this study finds evidence that planetesimals form rapidly during the collapse of the molecular cloud, much earlier than previously thought.

Abstract Cycling of carbon dioxide between the atmosphere and interior of rocky planets can stabilize global climate and enable planetary surface temperatures above freezing over geologic time. However, variations in global carbon budget and unstable feedback cycles between planetary sub‐systems may destabilize the climate of rocky exoplanets toward regimes unknown in the Solar System. Here, we perform clear‐sky atmospheric radiative transfer and surface weathering simulations to probe the stability of climate equilibria for rocky, ocean‐bearing exoplanets at instellations relevant for planetary systems in the outer regions of the circumstellar habitable zone. Our simulations suggest that planets orbiting G‐ and F‐type stars (but not M‐type stars) may display bistability between an Earth‐like climate state with efficient carbon sequestration and an alternative stable climate equilibrium where CO₂ condenses at the surface and forms a blanket of either clathrate hydrate or liquid CO₂ . At increasing instellation and with ineffective weathering, the latter state oscillates between cool, surface CO₂ ‐condensing and hot, non‐condensing climates. CO₂ bistable climates may emerge early in planetary history and remain stable for billions of years. The carbon dioxide‐condensing climates follow an opposite trend in p CO₂ versus instellation compared to the weathering‐stabilized planet population, suggesting the possibility of observational discrimination between these distinct climate categories.

At a glance Earth-like planets can exist in two stable climate states: one with liquid water oceans and moderate CO₂, and another where CO₂ dissolves into the ocean, potentially triggering glaciation. This study maps these bistable regimes across different planetary conditions, showing that the transition depends on atmospheric CO₂ levels and stellar irradiation.

Abstract Ocean-vaporizing impacts of chemically reduced planetesimals onto the early Earth have been suggested to catalyze atmospheric production of reduced nitrogen compounds and trigger prebiotic synthesis despite an oxidized lithosphere. While geochemical evidence supports a dry, highly reduced late veneer on Earth, the composition of late-impacting debris around lower-mass stars is subject to variable volatile loss as a result of their hosts’ extended pre-main-sequence phase. We perform simulations of late-stage planet formation across the M-dwarf mass spectrum to derive upper limits on reducing bombardment epochs in Hadean-analog environments. We contrast the solar system scenario with varying initial volatile distributions due to extended primordial runaway greenhouse phases on protoplanets and the desiccation of smaller planetesimals by internal radiogenic heating. We find a decreasing rate of late-accreting reducing impacts with decreasing stellar mass. Young planets around stars ≤0.4 M ☉ experience no impacts of sufficient mass to generate prebiotically relevant concentrations of reduced atmospheric compounds once their stars have reached the main sequence. For M-dwarf planets to not exceed Earth-like concentrations of volatiles, both planetesimals, and larger protoplanets must undergo extensive devolatilization processes and can typically emerge from long-lived magma ocean phases with sufficient atmophile content to outgas secondary atmospheres. Our results suggest that transiently reducing surface conditions on young rocky exoplanets are favored around FGK stellar types relative to M dwarfs.

At a glance Impacts of chemically reduced meteorites onto the early Earth may have triggered the production of molecules relevant for the origin of life. We simulated late-stage planet formation around stars of different masses and found that planets orbiting small M-dwarf stars receive far fewer of these reducing impacts. This suggests that the chemical conditions thought to favor prebiotic chemistry are more likely around Sun-like stars than around the most common stars in the galaxy.

Abstract In the Solar system, short-lived radioisotopes, such as ²⁶Al, played a crucial role during the formation of planetary bodies by providing a significant additional source of heat. Notably, this led to early and large-scale melting and iron core formation in planetesimals and their loss of volatile elements, such as hydrogen and carbon. In the context of exoplanetary systems therefore the prevalence of short-lived radioisotopes is key to interpreting the observed bulk volatile budget and atmospheric diversity among low-mass exoplanets. White dwarfs that have accreted planetary material provide a unique means to infer the frequency of iron core formation in extrasolar planetesimals, and hence the ubiquity of planetary systems forming with high short-lived radioisotope abundances. Here, we devise a quantitative method to infer the fraction of planetary systems enriched with short-lived radionuclides upon planetesimal formation from white dwarf data. We argue that the current evidence from white dwarfs point towards a significant fraction of exoplanetesimals having formed an iron core. Although the data may be explained by the accretion of exomoon or Pluto-sized bodies that were able to differentiate due to gravitational potential energy release, our results suggest that the most likely explanation for the prevalence of differentiated material among polluted white dwarfs is that the Solar system is not unusual in being enriched in ²⁶Al. The models presented here suggest a ubiquitous pathway for the enrichment of exoplanetary systems by short-lived radioisotopes, disfavouring short-lived radioisotope enrichment scenarios relying on statistically rare chance encounters with single nearby supernovae, Wolf–Rayet, or AGB stars.

At a glance Radioactive aluminium-26 heated early Solar System planetesimals, driving melting and iron core formation. By measuring the compositions of rocky debris accreted onto white dwarf stars, this study constrains how common aluminium-26 enrichment is across exoplanetary systems, finding that the Solar System’s level of enrichment may not be unusual.

Abstract The Large Interferometer For Exoplanets (LIFE) initiative is developing the science and a technology roadmap for an ambitious space mission featuring a space-based mid-infrared (MIR) nulling interferometer in order to detect the thermal emission of hundreds of exoplanets and characterize their atmospheres. In order to quantify the science potential of such a mission, in particular in the context of technical trade-offs, an instrument simulator is required. In addition, signal extraction algorithms are needed to verify that exoplanet properties (e.g., angular separation, spectral flux) contained in simulated exoplanet datasets can be accurately retrieved. We present LIFEsim, a software tool developed for simulating observations of exoplanetary systems with an MIR space-based nulling interferometer. It includes astrophysical noise sources (i.e., stellar leakage and thermal emission from local zodiacal and exo-zodiacal dust) and offers the flexibility to include instrumental noise terms in the future. LIFEsim provides an accessible way for predicting the expected SNR of future observations as a function of various key instrument and target parameters. The SNRs of the extracted spectra are photon-noise dominated, as expected from our current simulations. From single epoch observations in our mock survey of small (R < 1.5 R_Earth) planets orbiting within the habitable zones of their stars, we find that typical uncertainties in the estimated effective temperature of the exoplanets are ≲10%, for the exoplanet radius ≲20%, and for the separation from the host star ≲2%. SNR values obtained in the signal extraction process deviate less than 10% from purely photon-counting statistics based SNRs. (abridged)

At a glance The LIFE space mission concept aims to detect thermal emission from terrestrial exoplanets using mid-infrared interferometry. This paper presents LIFEsim, an end-to-end instrument simulator, and validates its signal extraction algorithms, showing that exoplanet temperature, radius, and orbital separation can be recovered to accuracies of roughly 10%, 20%, and 2%, respectively.

Abstract Context. The Large Interferometer For Exoplanets (LIFE) initiative is developing the science and a technology road map for an ambitious space mission featuring a space-based mid-infrared (MIR) nulling interferometer in order to detect the thermal emission of hundreds of exoplanets and characterize their atmospheres. Aims. In order to quantify the science potential of such a mission, in particular in the context of technical trade-offs, an instrument simulator is required. In addition, signal extraction algorithms are needed to verify that exoplanet properties (e.g., angular separation and spectral flux) contained in simulated exoplanet data sets can be accurately retrieved. Methods. We present LIFE sim , a software tool developed for simulating observations of exoplanetary systems with an MIR space-based nulling interferometer. It includes astrophysical noise sources (i.e., stellar leakage and thermal emission from local zodiacal and exozodiacal dust) and offers the flexibility to include instrumental noise terms in the future. Here, we provide some first quantitative limits on instrumental effects that would allow the measurements to remain in the fundamental noise limited regime. We demonstrate updated signal extraction approaches to validating signal-to-noise ratio (S/N) estimates from the simulator. Monte Carlo simulations are used to generate a mock survey of nearby terrestrial exoplanets and determine to which accuracy fundamental planet properties can be retrieved. Results. LIFE sim provides an accessible way to predict the expected S/N of future observations as a function of various key instrument and target parameters. The S/Ns of the extracted spectra are photon noise dominated, as expected from our current simulations. Signals from multi-planet systems can be reliably extracted. From single-epoch observations in our mock survey of small ( R < 1.5 R Earth ) planets orbiting within the habitable zones of their stars, we find that typical uncertainties in the estimated effective temperature of the exoplanets are ≲10%, for the exoplanet radius ≲20%, and for the separation from the host star ≲2%. Signal-to-noise-ratio values obtained in the signal extraction process deviate by less than 10% from purely photon-counting statistics-based S/Ns. Conclusions. LIFE sim has been sufficiently well validated so that it can be shared with a broader community interested in quantifying various exoplanet science cases that a future space-based MIR nulling interferometer could address. Reliable signal extraction algorithms exist, and our results underline the power of the MIR wavelength range for deriving fundamental exoplanet properties from single-epoch observations.

At a glance The LIFE space mission concept aims to use mid-infrared interferometry to detect and characterize hundreds of exoplanets. This paper presents the mission architecture and key design trades for the space-based nulling interferometer, establishing the technical requirements for detecting biosignatures in exoplanet atmospheres.

Abstract We investigated the hydrogen isotopic compositions and water contents of pyroxenes in two recent ordinary chondrite falls, namely, Chelyabinsk (2013 fall) and Benenitra (2018 fall), and compared them to three ordinary chondrite Antarctic finds, namely, Graves Nunataks GRA 06179, Larkman Nunatak LAR 12241, and Dominion Range DOM 10035. The pyroxene minerals in Benenitra and Chelyabinsk are hydrated (∼0.018–0.087 wt.% H 2 O) and show D-poor isotopic signatures ( δ D SMOW from −444‰ to −49‰). On the contrary, the ordinary chondrite finds exhibit evidence of terrestrial contamination with elevated water contents (∼0.039–0.174 wt.%) and δ D SMOW values (from −199‰ to −14‰). We evaluated several small parent-body processes that are likely to alter the measured compositions in Benenitra and Chelyabinsk and inferred that water loss in S-type planetesimals is minimal during thermal metamorphism. Benenitra and Chelyabinsk hydrogen compositions reflect a mixed component of D-poor nebular hydrogen and water from the D-rich mesostases. A total of 45%–95% of water in the minerals characterized by low δ D SMOW values was contributed by nebular hydrogen. S-type asteroids dominantly composed of nominally anhydrous minerals can hold 254–518 ppm of water. Addition of a nebular water component to nominally dry inner solar system bodies during accretion suggests a reduced need of volatile delivery to the terrestrial planets during late accretion.

At a glance The water content of inner Solar System bodies constrains how our planets formed. By analyzing hydrogen isotopes in the recent Chelyabinsk and Benenitra meteorite falls, this study finds evidence that inner Solar System planetesimals accreted water-bearing minerals during formation, supporting a wetter accretion history than previously assumed.

Abstract Planets smaller than Neptune and larger than Earth make up the majority of the discovered exoplanets. Those with H₂-rich atmospheres are prime targets for atmospheric characterization. The transition between the two main classes, super-Earths and sub-Neptunes, is not clearly understood as the rocky surface is likely not accessible to observations. Tracking several trace gases (specifically the loss of ammonia (NH₃) and hydrogen cyanide (HCN)) has been proposed as a proxy for the presence of a shallow surface. In this work, we revisit the proposed mechanism of nitrogen conversion in detail and find its timescale on the order of a million years. NH₃ exhibits dual paths converting to N₂ or HCN, depending on the UV radiation of the star and the stage of the system. In addition, methanol (CH₃OH) is identified as a robust and complementary proxy for a shallow surface. We follow the fiducial example of K2-18b with a 2D photochemical model (VULCAN) on an equatorial plane. We find a fairly uniform composition distribution below 0.1 mbar controlled by the dayside, as a result of slow chemical evolution. NH₃ and CH₃OH are concluded to be the most unambiguous proxies to infer surfaces on sub-Neptunes in the era of the James Webb Space Telescope (JWST).

At a glance Sub-Neptune exoplanets may be rocky worlds with thick atmospheres or mini gas planets, but distinguishing between them is difficult from mass and radius alone. This study shows that JWST spectroscopy can detect chemical signatures of atmosphere-surface interactions that would reveal a shallow rocky surface beneath the gas envelope.

Abstract We demonstrate that the deep volatile storage capacity of magma oceans has significant implications for the bulk composition, interior, and climate state inferred from exoplanet mass and radius data. Experimental petrology provides the fundamental properties of the ability of water and melt to mix. So far, these data have been largely neglected for exoplanet mass–radius modeling. Here we present an advanced interior model for water-rich rocky exoplanets. The new model allows us to test the effects of rock melting and the redistribution of water between magma ocean and atmosphere on calculated planet radii. Models with and without rock melting and water partitioning lead to deviations in planet radius of up to 16% for a fixed bulk composition and planet mass. This is within the current accuracy limits for individual systems and statistically testable on a population level. Unrecognized mantle melting and volatile redistribution in retrievals may thus underestimate the inferred planetary bulk water content by up to 1 order of magnitude.

At a glance When interpreting exoplanet observations, most models assume water exists only in the atmosphere or as surface oceans. This study shows that magma oceans can dissolve and hide large amounts of water in the planet’s interior, fundamentally changing the bulk composition and climate state inferred from mass and radius measurements alone.

Abstract Central stages in the evolution of rocky, potentially habitable planets may play out under atmospheric conditions with a large inventory of nondilute condensable components. Variations in condensate retention and accompanying changes in local lapse rate may substantially affect planetary climate and surface conditions, but there is currently no general theory to effectively describe such atmospheres. In this article, expanding on the work by Li et al., we generalize the single-component moist pseudoadiabat derivation in Pierrehumbert to allow for multiple condensing components of arbitrary diluteness and retained condensate fraction. The introduction of a freely tunable retained condensate fraction allows for a flexible, self-consistent treatment of atmospheres with nondilute condensable components. To test the pseudoadiabat’s capabilities for simulating a diverse range of climates, we apply the formula to planetary atmospheres with compositions, surface pressures, and temperatures representing important stages with condensable-rich atmospheres in the evolution of terrestrial planets: a magma ocean planet in a runaway greenhouse state; a post-impact, late-veneer-analog planet with a complex atmospheric composition; and an Archean Earth-like planet near the outer edge of the classical circumstellar habitable zone. We find that variations in the retention of multiple nondilute condensable species can significantly affect the lapse rate and in turn outgoing radiation and the spectral signatures of planetary atmospheres. The presented formulation allows for a more comprehensive treatment of the climate evolution of rocky exoplanets and early Earth analogs.

At a glance Early in their evolution, rocky planets may have atmospheres dominated by condensable gases like water vapor rather than the dilute backgrounds typical of present-day Earth. This study develops a new thermodynamic framework for simulating such steam-rich atmospheres, which is essential for modeling the climate of young terrestrial worlds and magma ocean planets.

Abstract The runaway greenhouse represents the ultimate climate catastrophe for rocky, Earth-like worlds: when the incoming stellar flux cannot be balanced by radiation to space, the oceans evaporate and exacerbate heating, turning the planet into a hot wasteland with a steam atmosphere overlying a possibly molten magma surface. The equilibrium state beyond the runaway greenhouse instellation limit depends on the radiative properties of the atmosphere and its temperature structure. Here, we use 1D radiative-convective models of steam atmospheres to explore the transition from the tropospheric radiation limit to the post-runaway climate state. To facilitate eventual simulations with 3D global circulation models, a computationally efficient band-gray model is developed, which is capable of reproducing the key features of the more comprehensive calculations. We analyze two factors that determine the equilibrated surface temperature of post-runaway planets. The infrared cooling of the planet is strongly enhanced by the penetration of the dry adiabat into the optically thin upper regions of the atmosphere. In addition, thermal emission of both shortwave and near-IR fluxes from the hot lower atmospheric layers, which can radiate through window regions of the spectrum, is quantified. Astronomical surveys of rocky exoplanets in the runaway greenhouse state may discriminate these features using multiwavelength observations.

At a glance The runaway greenhouse effect, where oceans boil away into a thick steam atmosphere, represents the worst-case climate scenario for Earth-like planets. This study investigates what happens after the runaway threshold is crossed, modeling the transition into the post-runaway state where a planet has a steam atmosphere overlying a global magma ocean.

Abstract Internal redox reactions may irreversibly alter the mantle composition and volatile inventory of terrestrial and super-Earth exoplanets and affect the prospects for atmospheric observations. The global efficacy of these mechanisms, however, hinges on the transfer of reduced iron from the molten silicate mantle to the metal core. Scaling analysis indicates that turbulent diffusion in the internal magma oceans of sub-Neptunes can kinetically entrain liquid iron droplets and quench core formation. This suggests that the chemical equilibration between core, mantle, and atmosphere may be energetically limited by convective overturn in the magma flow. Hence, molten super-Earths possibly retain a compositional memory of their accretion path. Redox control by magma ocean circulation is positively correlated with planetary heat flow, internal gravity, and planet size. The presence and speciation of remanent atmospheres, surface mineralogy, and core mass fraction of primary envelope-stripped exoplanets may thus constrain magma ocean dynamics.

At a glance When a super-Earth’s interior is fully molten, iron droplets should sink to form a metal core, setting the oxidation state of the mantle. We show that turbulent convection in deep magma oceans can keep iron droplets suspended, preventing complete core formation and preserving a chemical memory of how the planet formed. This means two super-Earths of identical mass could have very different mantle and atmospheric compositions depending on their accretion history.

Abstract Finding and characterizing extrasolar Earth analogs will rely on interpretation of the planetary system’s environmental context. The total budget and fractionation between C-H-O species sensitively affect the climatic and geodynamic state of terrestrial worlds, but their main delivery channels are poorly constrained. We connect numerical models of volatile chemistry and pebble coagulation in the circumstellar disk with the internal compositional evolution of planetesimals during the primary accretion phase. Our simulations demonstrate that disk chemistry and degassing from planetesimals operate on comparable timescales and can fractionate the relative abundances of major water and carbon carriers by orders of magnitude. As a result, individual planetary systems with significant planetesimal processing display increased correlation in the volatile budget of planetary building blocks relative to no internal heating. Planetesimal processing in a subset of systems increases the variance of volatile contents across planetary systems. Our simulations thus suggest that exoplanetary atmospheric compositions may provide constraints on when a specific planet formed.

At a glance The relative abundances of water and carbon delivered to young planets depend on both the chemistry of the surrounding gas disk and the internal heating of the rocky building blocks. We show that radioactive heating inside planetesimals can drive off volatiles on the same timescale as disk chemistry rearranges them, creating correlated carbon-to-water ratios across a planetary system. Future measurements of exoplanet atmospheres may thus reveal when and how quickly a planet’s building blocks formed.

Abstract The tectonic regime of rocky planets fundamentally influences their long-term evolution and cycling of volatiles between interior and atmosphere. Earth is the only known planet with active plate tectonics, but observations of exoplanets may deliver insights into the diversity of tectonic regimes beyond the solar system. Observations of the thermal phase curve of super-Earth LHS 3844b reveal a solid surface and lack of a substantial atmosphere, with a temperature contrast between the substellar and antistellar point of around 1000 K. Here, we use these constraints on the planet’s surface to constrain the interior dynamics and tectonic regimes of LHS 3844b using numerical models of interior flow. We investigate the style of interior convection by assessing how upwellings and downwellings are organized and how tectonic regimes manifest. We discover three viable convective regimes with a mobile surface: (1) spatially uniform distribution of upwellings and downwellings, (2) prominent downwelling on the dayside and upwellings on the nightside, and (3) prominent downwelling on the nightside and upwellings on the dayside. Hemispheric tectonics is observed for regimes (2) and (3) as a direct consequence of the day-to-night temperature contrast. Such a tectonic mode is absent in the present-day solar system and has never been inferred from astrophysical observations of exoplanets. Our models offer distinct predictions for volcanism and outgassing linked to the tectonic regime, which may explain secondary features in phase curves and allow future observations to constrain the diversity of super-Earth interiors.

At a glance Tidally locked super-Earths experience extreme temperature contrasts between their permanent dayside and nightside. This study shows that these contrasts can drive a unique tectonic regime with active convection on one hemisphere and a stagnant lid on the other, concentrating volcanic outgassing on one side of the planet.

Abstract The earliest atmospheres of rocky planets originate from extensive volatile release during magma ocean epochs that occur during assembly of the planet. These establish the initial distribution of the major volatile elements between different chemical reservoirs that subsequently evolve via geological cycles. Current theoretical techniques are limited in exploring the anticipated range of compositional and thermal scenarios of early planetary evolution, even though these are of prime importance to aid astronomical inferences on the environmental context and geological history of extrasolar planets. Here, we present a coupled numerical framework that links an evolutionary, vertically resolved model of the planetary silicate mantle with a radiative convective model of the atmosphere. Using this method, we investigate the early evolution of idealized Earth sized rocky planets with end member, clear sky atmospheres dominated by either H₂, H₂O, CO₂, CH₄, CO, O₂, or N₂. We find central metrics of early planetary evolution, such as energy gradient, sequence of mantle solidification, surface pressure, or vertical stratification of the atmosphere, to be intimately controlled by the dominant volatile and outgassing history of the planet. Thermal sequences fall into three general classes with increasing cooling timescale: CO, N₂, and O₂ with minimal effect, H₂O, CO₂, and CH₄ with intermediate influence, and H₂ with several orders of magnitude increase in solidification time and atmosphere vertical stratification. Our numerical experiments exemplify the capabilities of the presented modeling framework and link the interior and atmospheric evolution of rocky exoplanets with multiwavelength astronomical observations.

At a glance The first atmosphere of a rocky planet forms when its molten surface releases trapped gases. We built a coupled model that tracks how different atmospheric gases interact with a solidifying magma ocean and control the planet’s cooling rate. Hydrogen-dominated atmospheres slow cooling by orders of magnitude compared to nitrogen or carbon monoxide, meaning the dominant outgassed species fundamentally determines a young planet’s thermal evolution.

Abstract Geochemical and astronomical evidence demonstrates that planet formation occurred in two spatially and temporally separated reservoirs. The origin of this dichotomy is unknown. We use numerical models to investigate how the evolution of the solar protoplanetary disk influenced the timing of protoplanet formation and their internal evolution. Migration of the water snow line can generate two distinct bursts of planetesimal formation that sample different source regions. These reservoirs evolve in divergent geophysical modes and develop distinct volatile contents, consistent with constraints from accretion chronology, thermochemistry, and the mass divergence of inner and outer Solar System. Our simulations suggest that the compositional fractionation and isotopic dichotomy of the Solar System was initiated by the interplay between disk dynamics, heterogeneous accretion, and internal evolution of forming protoplanets.

At a glance Meteorite evidence shows that the Solar System’s building blocks formed in two distinct chemical reservoirs, but the origin of this split was unclear. We demonstrate that the inward migration of the snow line in the young Solar System triggered two separate bursts of planetesimal formation, sampling different regions of the disk. These two populations then evolved along divergent geophysical paths, naturally explaining the compositional divide between the inner and outer Solar System.

Abstract In contrast to the water-poor planets of the inner Solar System, stochasticity during planetary formation¹,² and order-of-magnitude deviations in exoplanet volatile contents³ suggest that rocky worlds engulfed in thick volatile ice layers⁴,⁵ are the dominant family of terrestrial analogues⁶,⁷ among the extrasolar planet population. However, the distribution of compositionally Earth-like planets remains insufficiently constrained³, and it is not clear whether the Solar System is a statistical outlier or can be explained by more general planetary formation processes. Here we use numerical models of planet formation, evolution and interior structure to show that a planet’s bulk water fraction and radius are anti-correlated with initial ²⁶Al levels in the planetesimal-based accretion framework. The heat generated by this short-lived radionuclide rapidly dehydrates planetesimals⁸ before their accretion onto larger protoplanets and yields a system-wide correlation⁹,¹⁰ of planetary bulk water abundances, which, for instance, can explain the lack of a clear orbital trend in the water budgets of the TRAPPIST-1 planets¹¹. Qualitatively, our models suggest two main scenarios for the formation of planetary systems: high-²⁶Al systems, like our Solar System, form small, water-depleted planets, whereas those devoid of ²⁶Al predominantly form ocean worlds. For planets of similar mass, the mean planetary transit radii of the ocean planet population can be up to about 10% larger than for planets from the ²⁶Al-rich formation scenario.

At a glance Radioactive aluminum-26, inherited from a nearby supernova, heated the Solar System’s earliest rocky bodies and drove off their water before they could grow into planets. We show that planetary systems rich in aluminum-26, like ours, preferentially form dry, rocky worlds, while systems without it form water-rich ocean planets. This mechanism can explain why the TRAPPIST-1 planets have similar water contents despite orbiting at very different distances from their star.

Abstract Rocky planetesimals in the early solar system melted internally and evolved chemically due to radiogenic heating from ²⁶Al. Here we quantify the parametric controls on magma genesis and transport using a coupled petrological and fluid mechanical model of reactive two-phase flow. We find the mean grain size of silicate minerals to be a key control on magma ascent. For grain sizes ≳1 mm, melt segregation produces distinct radial structure and chemical stratification. This stratification is most pronounced for bodies formed at around 1 Myr after formation of Ca, Al-rich inclusions. These findings suggest a link between the time and orbital location of planetesimal formation and their subsequent structural and chemical evolution. According to our models, the evolution of partially molten planetesimal interiors falls into two categories. In the magma ocean scenario, the whole interior of a planetesimal experiences nearly complete melting, which would result in turbulent convection and core-mantle differentiation by the rainfall mechanism. In the magma sill scenario, segregating melts gradually deplete the deep interior of the radiogenic heat source. In this case, magma may form melt-rich layers beneath a cool and stable lid, while core formation would proceed by percolation. Our findings suggest that grain sizes prevalent during the internal heating stage governed magma ascent in planetesimals. Regardless of whether evolution progresses toward a magma ocean or magma sill structure, our models predict that temperature inversions due to rapid ²⁶Al redistribution are limited to bodies formed earlier than ≈1 Myr after CAIs. We find that if grain size was ≲1 mm during peak internal melting, only elevated solid-melt density contrasts (such as found for the reducing conditions in enstatite chondrite compositions) would allow substantial melt segregation to occur.

At a glance The earliest rocky bodies in the Solar System melted from the inside out due to radioactive heating, but it has been unclear how magma moved through their interiors. We find that the grain size of silicate minerals is the critical factor: coarse-grained material lets magma segregate and create chemically layered structures, while fine-grained material traps melt in place. This connects the mineral texture of meteorites to the internal evolution and differentiation of their parent bodies.

Abstract During their formation and early evolution, rocky planets undergo multiple global melting events due to accretionary collisions with other protoplanets. The detection and characterization of their post-collision afterglows (magma oceans) can yield important clues about the origin and evolution of the solar and extrasolar planet population. Here, we quantitatively assess the observational prospects to detect the radiative signature of forming planets covered by such collision-induced magma oceans in nearby young stellar associations with future direct imaging facilities. We have compared performance estimates for near- and mid-infrared instruments to be installed at ESO’s Extremely Large Telescope (ELT), and a potential space-based mission called Large Interferometer for Exoplanets (LIFE). We modelled the frequency and timing of energetic collisions using N-body models of planet formation for different stellar types, and determine the cooling of the resulting magma oceans with an insulating atmosphere. We find that the probability of detecting at least one magma ocean planet depends on the observing duration and the distribution of atmospheric properties among rocky protoplanets. However, the prospects for detection significantly increase for young and close stellar targets, which show the highest frequencies of giant impacts. For intensive reconnaissance with a K band (2.2 μm) ELT filter or a 5.6 μm LIFE filter, the β Pictoris, Columba, TW Hydrae, and Tucana-Horologium associations represent promising candidates for detecting a molten protoplanet. Our results motivate the exploration of magma ocean planets using the ELT and underline the importance of space-based direct imaging facilities to investigate and characterize planet formation and evolution in the solar vicinity. Direct imaging of magma oceans will advance our understanding of the early interior, surface and atmospheric properties of terrestrial worlds.

At a glance When rocky protoplanets collide during formation, they produce temporary magma oceans that glow in the infrared. This study calculates the brightness and duration of these post-collision afterglows and shows that next-generation telescopes could directly image them in nearby young stellar associations, providing a new way to study planet formation.

Abstract The short-lived ¹⁸²Hf-¹⁸²W decay system is a powerful chronometer for constraining the timing of metal-silicate separation and core formation in planetesimals and planets. Neutron capture effects on W isotopes, however, significantly hamper the application of this tool. In order to correct for neutron capture effects, Pt isotopes have emerged as a reliable in-situ neutron dosimeter. This study applies this method to IAB iron meteorites, in order to constrain the timing of metal segregation on the IAB parent body. The ε¹⁸²W values obtained for the IAB iron meteorites range from -3.61 ± 0.10 to -2.73 ± 0.09. Correlating εiPt with ¹⁸²W data yields a pre-neutron capture ¹⁸²W of -2.90 ± 0.06. This corresponds to a metal-silicate separation age of 6.0 ± 0.8 Ma after CAI for the IAB parent body, and is interpreted to represent a body-wide melting event. Later, between 10 and 14 Ma after CAI, an impact led to a catastrophic break-up and subsequent reassembly of the parent body. Thermal models of the interior evolution that are consistent with these estimates suggest that the IAB parent body underwent metal-silicate separation as a result of internal heating by short-lived radionuclides and accreted at around 1.4 ± 0.1 Ma after CAIs with a radius of greater than 60 km.

At a glance The IAB iron meteorites record an unusual history of partial melting and metal-silicate separation in their parent asteroid. Using tungsten and platinum isotope measurements combined with thermal modeling, this study constrains the timing and conditions of core formation in this body, shedding light on early Solar System planetesimal evolution.

Abstract Chondrules, mm-sized igneous-textured spherules, are the dominant bulk silicate constituent of chondritic meteorites and originate from highly energetic, local processes during the first million years after the birth of the Sun. So far, an astrophysically consistent chondrule formation scenario explaining major chemical, isotopic and textural features, in particular Fe,Ni metal abundances, bulk Fe/Mg ratios and intra-chondrite chemical and isotopic diversity, remains elusive. Here, we examine the prospect of forming chondrules from impact splashes among planetesimals heated by radioactive decay of short-lived radionuclides using thermomechanical models of their interior evolution. We show that intensely melted planetesimals with interior magma oceans became rapidly chemically equilibrated and physically differentiated. Therefore, collisional interactions among such bodies would have resulted in chondrule-like but basaltic spherules, which are not observed in the meteoritic record. This inconsistency with the expected dynamical interactions hints at an incomplete understanding of the planetary growth regime during the lifetime of the solar protoplanetary disk. To resolve this conundrum, we examine how the observed chemical and isotopic features of chondrules constrain the dynamical environment of accreting chondrite parent bodies by interpreting the meteoritic record as an impact-generated proxy of early solar system planetesimals that underwent repeated collision and reaccretion cycles. Using a coupled evolution-collision model we demonstrate that the vast majority of collisional debris feeding the asteroid main belt must be derived from planetesimals which were partially molten at maximum. Therefore, the precursors of chondrite parent bodies either formed primarily small, from sub-canonical aluminum-26 reservoirs, or collisional destruction mechanisms were efficient enough to shatter planetesimals before they reached the magma ocean phase. Finally, we outline the window in parameter space for which chondrule formation from planetesimal collisions can be reconciled with the meteoritic record and how our results can be used to further constrain early solar system dynamics.

At a glance Chondrules, millimeter-sized glassy beads found in most meteorites, formed in energetic events during the first million years of the Solar System, but their origin remains debated. We tested whether collisions between partially molten planetesimals could produce chondrules with the right chemistry and found that the precursor bodies must not have been fully melted. This constrains either the timing and size of early planetesimals or the efficiency of collisional destruction in the young Solar System.

Abstract The presence of an unseen ‘Planet 9’ on the outskirts of the Solar system has been invoked to explain the unexpected clustering of the orbits of several Edgeworth–Kuiper Belt Objects. We use N-body simulations to investigate the probability that Planet 9 was a free-floating planet (FFLOP) that was captured by the Sun in its birth star formation environment. We find that only 1–6 per cent of FFLOPs are ensnared by stars, even with the most optimal initial conditions for capture in star-forming regions (one FFLOP per star, and highly correlated stellar velocities to facilitate capture). Depending on the initial conditions of the star-forming regions, only 5–10 of 10 000 planets are captured on to orbits that lie within the constraints for Planet 9. When we apply an additional environmental constraint for Solar system formation – namely the injection of short-lived radioisotopes into the Sun’s protoplanetary disc from supernovae – we find the probability for the capture of Planet 9 to be almost zero.

At a glance The hypothetical Planet 9 in the outer Solar System could be a captured free-floating planet rather than one that formed in situ. This study uses simulations of the Sun’s birth environment to show that capturing a several-Earth-mass planet from another star is dynamically plausible in a dense star-forming region.

Abstract Heating by short-lived radioisotopes (SLRs) such as ²⁶Al and ⁶⁰Fe fundamentally shaped the thermal history and interior structure of Solar system planetesimals during the early stages of planetary formation. The subsequent thermo-mechanical evolution, such as internal differentiation or rapid volatile degassing, yields important implications for the final structure, composition and evolution of terrestrial planets. SLR-driven heating in the Solar system is sensitive to the absolute abundance and homogeneity of SLRs within the protoplanetary disc present during the condensation of the first solids. In order to explain the diverse compositions found for extrasolar planets, it is important to understand the distribution of SLRs in active planet formation regions (star clusters) during their first few Myr of evolution. By constraining the range of possible effects, we show how the imprint of SLRs can be extrapolated to exoplanetary systems and derive statistical predictions for the distribution of ²⁶Al and ⁶⁰Fe based on N-body simulations of typical to large clusters (10³-10⁴ stars) with a range of initial conditions. We quantify the pollution of protoplanetary discs by supernova ejecta and show that the likelihood of enrichment levels similar to or higher than the Solar system can vary considerably, depending on the cluster morphology. Furthermore, many enriched systems show an excess in radiogenic heating compared to Solar system levels, which implies that the formation and evolution of planetesimals could vary significantly depending on the birth environment of their host stars.

At a glance Short-lived radioactive isotopes like aluminum-26 heated the building blocks of our Solar System and drove their internal evolution, but it is unclear how common such enrichment is elsewhere. We simulated the dispersal of supernova ejecta through young star clusters and found that the likelihood of Solar-System-level enrichment varies widely depending on the cluster’s size and structure. Many planetary systems may receive even higher doses, implying that planetesimal evolution could differ substantially across the galaxy.

Abstract The thermal history and internal structure of chondritic planetesimals, assembled before the giant impact phase of chaotic growth, potentially yield important implications for the final composition and evolution of terrestrial planets. These parameters critically depend on the internal balance of heating versus cooling, which is mostly determined by the presence of short-lived radionuclides (SLRs), such as ²⁶Al and ⁶⁰Fe, as well as the heat conductivity of the material. The heating by SLRs depends on their initial abundances, the formation time of the planetesimal and its size. It has been argued that the cooling history is determined by the porosity of the granular material, which undergoes dramatic changes via compaction processes and tends to decrease with time. In this study we assess the influence of these parameters on the thermo-mechanical evolution of young planetesimals with both 2D and 3D simulations. Using the code family I2ELVIS/I3ELVIS we have run numerous 2D and 3D numerical finite-difference fluid dynamic models with varying planetesimal radius, formation time and initial porosity. Our results indicate that powdery materials lowered the threshold for melting and convection in planetesimals, depending on the amount of SLRs present. A subset of planetesimals retained a powdery surface layer which lowered the thermal conductivity and hindered cooling. The effect of initial porosity was small, however, compared to those of planetesimal size and formation time, which dominated the thermo-mechanical evolution and were the primary factors for the onset of melting and differentiation. We comment on the implications of this work concerning the structure and evolution of these planetesimals, as well as their behavior as possible building blocks of terrestrial planets.

At a glance The porous, powdery texture of freshly formed planetesimals acts as thermal insulation, potentially trapping radioactive heat and promoting internal melting. We modeled how porosity and radioactive heating interact in 2D and 3D simulations and found that while porosity lowers the melting threshold, the size and formation time of a planetesimal are far more important in determining whether it differentiates. These results constrain which meteorite parent bodies underwent internal melting and how they contributed to terrestrial planet formation.

Abstract The astonishing diversity in the observed planetary population requires theoretical efforts and advances in planet formation theories. The use of numerical approaches provides a method to tackle the weaknesses of current models and is an important tool to close gaps in poorly constrained areas such as the rapid formation of giant planets in highly evolved systems. So far, most numerical approaches make use of Lagrangian-based smoothed-particle hydrodynamics techniques or grid-based 2D axisymmetric simulations. We present a new global disk setup to model the first stages of giant planet formation via gravitational instabilities (GI) in 3D with the block-structured adaptive mesh refinement (AMR) hydrodynamics code enzo. With this setup, we explore the potential impact of AMR techniques on the fragmentation and clumping due to large-scale instabilities using different AMR configurations. Additionally, we seek to derive general resolution criteria for global simulations of self-gravitating disks of variable extent. We run a grid of simulations with varying AMR settings, including runs with a static grid for comparison. Additionally, we study the effects of varying the disk radius. The physical settings involve disks with Rdisk = 10,100 and 300 AU, with a mass of Mdisk ≈ 0.05 M☉ and a central object of subsolar mass (M⋆ = 0.646 M☉). To validate our thermodynamical approach we include a set of simulations with a dynamically stable profile (Qinit = 3) and similar grid parameters. The development of fragmentation and the buildup of distinct clumps in the disk is strongly dependent on the chosen AMR grid settings. By combining our findings from the resolution and parameter studies we find a general lower limit criterion to be able to resolve GI induced fragmentation features and distinct clumps, which induce turbulence in the disk and seed giant planet formation. Irrespective of the physical extension of the disk, topologically disconnected clump features are only resolved if the fragmentation-active zone of the disk is resolved with at least 100 cells. The latter corresponds to a minimum requirement for all global disk setups. Our simulations illustrate the capabilities of AMR-based modeling techniques for planet formation simulations and underline the importance of balanced refinement settings to reproduce fragmenting structures. The clumps in our models are migrating inward and are eventually destroyed because of tidal disruptions, reflecting the absence of radiative feedback from the central star, which may stabilize the clumps on larger scales. We expect that the inclusion of additional physics, like a radiation transport mechanism and the formation of sink particles, will provide a detailed framework to study the formation of planets via gravitational instabilities in a global disk view.

At a glance Giant planets might form rapidly when protoplanetary disks become gravitationally unstable and fragment into clumps, but capturing this process in simulations is numerically challenging. We developed a new 3D setup using adaptive mesh refinement to resolve the fragmentation of self-gravitating disks, identifying a minimum resolution requirement for reliably resolving gravitational collapse. The resulting clumps migrate inward and are tidally destroyed, indicating that additional physics such as radiative feedback is needed to stabilize them into surviving planets.

Abstract Astronomical surveys have identified numerous exoplanets with bulk compositions that are unlike the planets of the Solar System, including rocky super-Earths and gas-enveloped sub-Neptunes. Observing the atmospheres of these objects provides information on the geological processes that influence their climates and surfaces. In this Review, we summarize the current understanding of these planets, including insights into the interaction between the atmosphere and interior based on observations made with the JWST. We describe the expected climatic and interior planetary regimes for planets with different density and stellar flux and how those regimes might be observationally distinguished. We also identify the observational, experimental, and theoretical innovations that will be required to characterize Earth-like exoplanets.

At a glance Rocky exoplanets come in a wider range of sizes and compositions than anything in our Solar System, from bare rocky surfaces to gas-enveloped sub-Neptunes. This review synthesizes what atmospheric observations, particularly from JWST, are revealing about the geological processes shaping these worlds. It identifies the observational, experimental, and theoretical advances needed to eventually characterize truly Earth-like exoplanets.

Abstract In the last few years astronomical surveys have expanded the reach of planetary science into the realm of small and dense extrasolar worlds. These share a number of characteristics with the terrestrial and icy planetary objects of the Solar System, but keep stretching previous understanding of the known limits of planetary thermodynamics, material properties, and climate regimes. Improved compositional and thermal constraints on exoplanets below 2 Earth radii suggest efficient accretion of atmosphere-forming volatile elements in a fraction of planetary systems, pointing to rapid formation, planet-scale melting, and chemical equilibration between the core, mantle, and atmosphere of rocky and volatile-rich exoplanets. Meaningful interpretation of novel observational data from these worlds necessitates cross-disciplinary expansion of known material properties under extreme thermodynamic, non-solar conditions, and accounting for dynamic feedbacks between interior and atmospheric processes. Exploration of the atmosphere and surface composition of individual, short-period super-Earths in the next few years will enable key inferences on magma ocean dynamics, the redox state of rocky planetary mantles, and mixing between volatile and refractory phases in planetary regimes that are absent from the present-day Solar System, and reminiscent of the conditions of the prebiotic Earth. The atmospheric characterization of climate diversity and the statistical search for biosignatures on terrestrial exoplanets on temperate orbits will require space-based direct imaging surveys, capable of resolving emission features of major and trace gases in both shortwave and mid-infrared wavelengths.

At a glance Astronomical surveys are now detecting rocky exoplanets small enough to be compared with Earth, but their compositions and climates challenge existing planetary science frameworks. This review covers what we know about super-Earths and Earth-like exoplanets, from their formation through magma ocean stages to their present-day atmospheres. Characterizing temperate, potentially habitable worlds will ultimately require space-based direct imaging missions capable of resolving their atmospheric composition.

Abstract Core segregation and atmosphere formation are two of the major processes that redistribute the volatile elements—hydrogen (H), carbon (C), nitrogen (N), and sulfur (S)—in and around rocky planets during their formation. The volatile elements by definition accumulate in gaseous reservoirs and form atmospheres. However, under conditions of early planet formation, these elements can also behave as siderophiles (i.e., iron-loving) and become concentrated in core-forming metals. Current models of core formation suggest that metal-silicate reactions occurred over a wide pressure, temperature, and compositional space to ultimately impose the chemistries of the cores and silicate portions of rocky planets. Additionally, the solubilities of volatile elements in magmas determine their transfer between the planetary interiors and atmospheres, which has recently come into sharper focus in the context of highly irradiated, potentially molten exoplanets. Recently, there has been a significant push to experimentally investigate the metal-silicate and magma-gas exchange coefficients for volatile elements over a wide range of conditions relevant to rocky planet formation. Qualitatively, results from the metal-silicate partitioning studies suggest that cores of rocky planets could be major reservoirs of the volatile elements though significant amounts will remain in mantles. Results from solubility studies imply that under oxidizing conditions, most H and S are sequestered in the magma ocean, while most N is outgassed to the atmosphere, and C is nearly equally distributed between the atmosphere and the interior. Under reducing conditions, nearly all N dissolves in the magma ocean, the atmosphere becomes the dominant C reservoir, while H becomes more equally distributed between the interior and the atmosphere, and S remains dominantly in the interior. These chemical trends bear numerous implications for the chemical differentiation of rocky planets and the formation and longevity of secondary atmospheres in the early Solar System and exoplanetary systems. Further experimental and modeling efforts are required to understand the potential of chemical and physical disequilibria during core formation and magma ocean crystallization and to constrain the distributions of volatile elements in the interiors and atmospheres of rocky planets through their formation and long-term geologic evolution.

At a glance During rocky planet formation, volatile elements like hydrogen, carbon, nitrogen, and sulfur are redistributed between the core, mantle, and atmosphere. This review synthesizes experimental and theoretical constraints on how these elements partition during core segregation and atmospheric outgassing, shaping the final volatile budgets of terrestrial planets.

Abstract Progressive astronomical characterization of planet-forming disks and rocky exoplanets highlight the need for increasing interdisciplinary efforts to understand the birth and life cycle of terrestrial worlds in a unified picture. Here, we review major geophysical and geochemical processes that shape the evolution of rocky planets and their precursor planetesimals during planetary formation and early evolution, and how these map onto the astrophysical timeline and varying accretion environments of planetary growth. The evolution of the coupled core-mantle-atmosphere system of growing protoplanets diverges in thermal, compositional, and structural states to first order, and ultimately shapes key planetary characteristics that can discern planets harboring clement surface conditions from those that do not. Astronomical campaigns seeking to investigate rocky exoplanets will require significant advances in laboratory characterization of planetary materials and time- and spatially-resolved theoretical models of planetary evolution, to extend planetary science beyond the Solar System and constrain the origins and frequency of habitable worlds like our own.

At a glance Understanding rocky planets requires connecting astrophysical disk processes to geophysical interior evolution, but these fields have traditionally been studied separately. This review traces how core, mantle, and atmosphere co-evolve during planetary formation, and how early divergences in thermal and chemical state determine whether a planet ends up habitable. Extending planetary science to exoplanets will demand advances in laboratory measurements and time-resolved theoretical models.

Abstract Astronomers are debating whether the plentiful “sub-Neptune” exoplanets, worlds a bit larger than Earth but smaller than Neptune, are predominantly rocky planets, water-rich “ocean worlds,” or gas-enshrouded mini-Neptunes. This question is crucial because such sub-Neptune-sized planets are among the most common in our galaxy, yet we have no analog in our own solar system, making them a key to understanding planet formation and diversity. It also directly impacts the search for habitable worlds: larger-than-Earth planets with solid surfaces or oceans could support life, whereas gas-rich mini-Neptunes likely cannot. However, distinguishing these types using only a planet’s mass and radius is very challenging, because different compositions can produce similar densities, leaving a world’s nature ambiguous with current data. The proposed Habitable Worlds Observatory (HWO), a future NASA flagship telescope, offers a solution. HWO could directly image and spectroscopically analyze starlight reflected from 50 100 sub-Neptunes around nearby stars, aiming to reveal their atmospheric compositions and potential surfaces. Using visible and near-infrared spectroscopy along with sensitive polarimetry, HWO would detect atmospheric gases (such as water vapor, methane, and carbon dioxide) and search for telltale surface signatures, including rock absorption features and the characteristic reflectivity patterns of oceans. By analyzing these signals, we could determine whether sub-Neptunes are large rocky planets or water worlds rather than gas-dominated mini-Neptunes. Crucially, expanding the search beyond Earth-sized planets to include these abundant sub-Neptunes may uncover entirely new classes of potentially habitable worlds, directly advancing HWO’s mission to identify and characterize planets that could support life.

At a glance Sub-Neptune-sized exoplanets could be rocky, water-rich, or gas-enshrouded, but current telescopes cannot easily distinguish between these possibilities. This study evaluates how the planned Habitable Worlds Observatory could use reflected-light spectroscopy to tell rocky planets from water worlds among this common class of exoplanets.

Abstract PLATO (PLAnetary Transits and Oscillations of stars) is ESA’s M3 mission designed to detect and characterise extrasolar planets and perform asteroseismic monitoring of a large number of stars. PLATO will detect small planets (down to <2R Earth Earth ) around bright stars (<11 mag), including terrestrial planets in the habitable zone of solar-like stars. With the complement of radial velocity observations from the ground, planets will be characterised for their radius, mass, and age with high accuracy (5%, 10%, 10% for an Earth-Sun combination respectively). PLATO will provide us with a large-scale catalogue of well-characterised small planets up to intermediate orbital periods, relevant for a meaningful comparison to planet formation theories and to better understand planet evolution. It will make possible comparative exoplanetology to place our Solar System planets in a broader context. In parallel, PLATO will study (host) stars using asteroseismology, allowing us to determine the stellar properties with high accuracy, substantially enhancing our knowledge of stellar structure and evolution. The payload instrument consists of 26 cameras with 12cm aperture each. For at least four years, the mission will perform high-precision photometric measurements. Here we review the science objectives, present PLATO‘s target samples and fields, provide an overview of expected core science performance as well as a description of the instrument and the mission profile towards the end of the serial production of the flight cameras. PLATO is scheduled for a launch date end 2026. This overview therefore provides a summary of the mission to the community in preparation of the upcoming operational phases.

At a glance PLATO is an ESA space mission designed to discover and characterize Earth-like planets in the habitable zones of Sun-like stars. By combining ultra-precise transit photometry with asteroseismology, PLATO will determine planetary radii, masses, and ages with unprecedented accuracy for hundreds of rocky worlds.

Abstract We present the database of potential targets for the Large Interferometer For Exoplanets (LIFE), a space-based mid-infrared nulling interferometer mission proposed for the Voyage 2050 science program of the European Space Agency. The database features stars, their planets and disks, main astrophysical parameters, and ancillary observations. It allows users to create target lists based on various criteria to predict, for instance, exoplanet detection yields for the LIFE mission. As such, it enables mission design trade-offs, provides context for the analysis of data obtained by LIFE, and flags critical missing data. Work on the database is in progress, but given its relevance to LIFE and other space missions, including the Habitable Worlds Observatory, we present its main features here. A preliminary version of the LIFE database is publicly available on the German Astrophysical Virtual Observatory.

At a glance The LIFE space mission aims to study the atmospheres of nearby exoplanets in the mid-infrared. This paper presents a curated database of candidate target stars, their known planets, and circumstellar disks, providing the observational foundation for mission planning and target selection.

Abstract Ultra-cool dwarf stars are abundant, long-lived, and uniquely suited to enable the atmospheric study of transiting terrestrial companions with JWST. The most prominent target is the M8.5V star TRAPPIST-1 and its seven rocky planets. While JWST Cycle 1 observations have started to yield preliminary insights, the overall interpretation of the data remains inconclusive. This paper presents a community roadmap for the atmospheric characterization of the TRAPPIST-1 planets with JWST, identifying optimal observing strategies for each planet and outlining the sequence of observations needed to first detect atmospheres and then characterize their compositions. A coordinated multi-cycle JWST program can determine whether the TRAPPIST-1 planets retain substantial atmospheres and constrain their molecular inventories, providing the first empirical census of terrestrial exoplanet atmospheres.

At a glance The TRAPPIST-1 system, with seven rocky planets orbiting an ultra-cool dwarf star, is a prime target for atmospheric characterization with JWST. This community paper lays out a systematic observing strategy for studying these planets’ atmospheres, from initial detection to detailed composition measurements.

Abstract The search for life beyond the Earth is the overarching goal of the NASA Astrobiology Program, and it underpins the science of missions that explore the environments of Solar System planets and exoplanets. However, the detection of extraterrestrial life, in our Solar System and beyond, is sufficiently challenging that it is likely that multiple measurements and approaches, spanning disciplines and missions, will be needed to make a convincing claim. Life detection will therefore not be an instantaneous process, and it is unlikely to be unambiguous-yet it is a high-stakes scientific achievement that will garner an enormous amount of public interest. Current and upcoming research efforts and missions aimed at detecting past and extant life could be supported by a consensus framework to plan for, assess and discuss life detection claims (c.f. Green et al., 2021). Such a framework could help increase the robustness of biosignature detection and interpretation, and improve communication with the scientific community and the public. In response to this need, and the call to the community to develop a confidence scale for standards of evidence for biosignature detection (Green et al., 2021), a community-organized workshop was held on July 19-22, 2021. The meeting was designed in a fully virtual (flipped) format. Preparatory materials including readings, instructional videos and activities were made available prior to the workshop, allowing the workshop schedule to be fully dedicated to active community discussion and prompted writing sessions. To maximize global interaction, the discussion components of the workshop were held during business hours in three different time zones, Asia/Pacific, European and US, with daily information hand-off between group organizers.

At a glance Detecting life beyond Earth requires rigorous standards for what counts as evidence. This community report from NASA’s Biosignatures Standards of Evidence Workshop establishes a framework for evaluating potential biosignature detections, emphasizing the need to rule out false positives before claiming a detection of extraterrestrial life.

Abstract The recently adopted Ariel ESA mission will measure the atmospheric composition of a large number of exoplanets. This information will then be used to better constrain planetary bulk compositions. While the connection between the composition of a planetary atmosphere and the bulk interior is still being investigated, the combination of the atmospheric composition with the measured mass and radius of exoplanets will push the field of exoplanet characterisation to the next level, and provide new insights of the nature of planets in our galaxy. In this white paper, we outline the ongoing activities of the interior working group of the Ariel mission, and list the desirable theoretical developments as well as the challenges in linking planetary atmospheres, bulk composition and interior structure.

At a glance ESA’s Ariel mission will survey the atmospheres of hundreds of exoplanets, providing composition data that constrains their interiors. This white paper outlines how Ariel’s atmospheric measurements can be used to infer planetary interior structures, compositions, and formation histories, connecting atmospheric chemistry to bulk properties.

Abstract Ariel, the Atmospheric Remote-sensing Infrared Exoplanet Large-survey, was adopted as the fourth medium-class mission in ESA’s Cosmic Vision programme to be launched in 2029. During its 4-year mission, Ariel will study what exoplanets are made of, how they formed and how they evolve, by surveying a diverse sample of about 1000 extrasolar planets, simultaneously in visible and infrared wavelengths. It is the first mission dedicated to measuring the chemical composition and thermal structures of hundreds of transiting exoplanets, enabling planetary science far beyond the boundaries of the Solar System. The payload consists of an off-axis Cassegrain telescope (primary mirror 1100 mm x 730 mm ellipse) and two separate instruments (FGS and AIRS) covering simultaneously 0.5-7.8 micron spectral range. The satellite is best placed into an L2 orbit to maximise the thermal stability and the field of regard. The payload module is passively cooled via a series of V-Groove radiators; the detectors for the AIRS are the only items that require active cooling via an active Ne JT cooler. The Ariel payload is developed by a consortium of more than 50 institutes from 16 ESA countries, which include the UK, France, Italy, Belgium, Poland, Spain, Austria, Denmark, Ireland, Portugal, Czech Republic, Hungary, the Netherlands, Sweden, Norway, Estonia, and a NASA contribution. This presentation provides an overall summary of the science and instrument design for Ariel and presents the many activities that the Ariel team have planned to engage the science community at large and the public prior to launch. These include the Ariel Dry-Run program and citizen-science programs such as ExoClock and the Ariel Data Challenges.

At a glance Ariel is an ESA medium-class space mission launching in 2029 to survey the atmospheres of roughly 1000 exoplanets from gas giants to rocky worlds. By measuring atmospheric compositions across a diverse sample, Ariel will reveal how exoplanets form, evolve, and whether their chemistries relate to their host star environments.

Abstract Exoplanet science is one of the most thriving fields of modern astrophysics. A major goal is the atmospheric characterization of dozens of small, terrestrial exoplanets in order to search for signatures in their atmospheres that indicate biological activity, assess their ability to provide conditions for life as we know it, and investigate their expected atmospheric diversity. None of the currently adopted projects or missions, from ground or in space, can address these goals. In this White Paper, submitted to ESA in response to the Voyage 2050 Call, we argue that a large space-based mission designed to detect and investigate thermal emission spectra of terrestrial exoplanets in the mid-infrared wavelength range provides unique scientific potential to address these goals and surpasses the capabilities of other approaches. While NASA might be focusing on large missions that aim to detect terrestrial planets in reflected light, ESA has the opportunity to take leadership and spearhead the development of a large mid-infrared exoplanet mission within the scope of the “Voyage 2050” long-term plan establishing Europe at the forefront of exoplanet science for decades to come. Given the ambitious science goals of such a mission, additional international partners might be interested in participating and contributing to a roadmap that, in the long run, leads to a successful implementation. A new, dedicated development program funded by ESA to help reduce development and implementation cost and further push some of the required key technologies would be a first important step in this direction. Ultimately, a large mid-infrared exoplanet imaging mission will be needed to help answer one of humankind’s most fundamental questions: “How unique is our Earth?”

At a glance Characterizing the atmospheres of rocky, potentially habitable exoplanets is a central goal of exoplanet science. This white paper makes the case for a large mid-infrared space interferometer to detect biosignatures, assess habitability, and survey the diversity of terrestrial exoplanet atmospheres, laying the scientific foundation for what became the LIFE mission concept.

Abstract The primary objective of this white paper is to illustrate the importance of the thermal infrared in characterizing terrestrial planets, leveraging our experience in characterizing extra-solar jovian worlds. Thermal emission measurements provide access to the atmospheric temperature structure, molecular abundances, and cloud properties of exoplanets. For terrestrial planets specifically, the mid-infrared contains key molecular features of water, ozone, methane, and carbon dioxide that are essential for assessing habitability and potential biosignatures. We argue that a future space mission capable of mid-infrared spectroscopy of terrestrial exoplanets should be a high priority for the coming decades.

At a glance Thermal infrared spectroscopy provides unique access to molecular features in exoplanet atmospheres that complement shorter-wavelength observations. This white paper argues that mid-infrared emission measurements are essential for understanding terrestrial exoplanet atmospheres and should be a priority for future space missions.

Abstract Modern astronomy has finally been able to observe protoplanetary disks in reasonable resolution and detail, unveiling the processes happening during planet formation. These observed processes are understood under the framework of disk-planet interaction, a process studied analytically and modeled numerically for over 40 years. Long a theoreticians’ game, the wealth of observational data has been allowing for increasingly stringent tests of the theoretical models. Modeling efforts are crucial to support the interpretation of direct imaging analyses, not just for potential detections but also to put meaningful upper limits on mass accretion rates and other physical quantities in current and future large-scale surveys. This white paper addresses the questions of what efforts on the computational side are required in the next decade to advance our theoretical understanding, explain the observational data, and guide new observations. We identified the nature of accretion, ab initio planet formation, early evolution, and circumplanetary disks as major fields of interest in computational planet formation. We recommend that modelers relax the approximations of alpha-viscosity and isothermal equations of state, on the grounds that these models use flawed assumptions, even if they give good visual qualitative agreement with observations. We similarly recommend that population synthesis move away from 1D hydrodynamics. The computational resources to reach these goals should be developed during the next decade, through improvements in algorithms and the hardware for hybrid CPU/GPU clusters. Coupled with high angular resolution and great line sensitivity in ground based interferometers, ELTs and JWST, these advances in computational efforts should allow for large strides in the field in the next decade.

At a glance Modern telescope observations are revealing the detailed structure of protoplanetary disks where planets form. This white paper argues that large-scale computational efforts, including high-resolution simulations of disk-planet interactions, are essential for interpreting these observations and advancing our understanding of planet formation.

Abstract As recent advancements in physics and astronomy rewrite textbooks in a very rapid pace, there is a growing need in keeping abreast of the latest knowledge in these fields. Reading preprints is one of the effective ways to do this. However, by having journal clubs where people can read and discuss journals together, the benefits of reading journals become more prevalent. We present an investigative study of understanding the factors that affect the success of preprint journal clubs in astronomy, more commonly known as Astro-ph/Astro-Coffee (hereafter called AC). A survey was disseminated to understand how universities and institutions from different countries implement AC. We interviewed 9 survey respondents and from their responses, and we identified four important factors that make AC successful: commitment (how the organizer and attendees participate in AC), environment (how conducive and comfortable AC is conducted), content (the discussed topics in AC and how they are presented), and objective [the main goal (s) of conducting AC]. These four factors are shown to correlate with each other. We also present the format of our AC, an elective class which was evaluated during the Spring semester 2020 (March 2020-June 2020). Our evaluation with the attendees showed that enrollees (those who are enrolled and are required to present papers regularly) tend to be more committed in attending compared to audiences (those who are not enrolled and are not required to present papers regularly). In addition, participants tend to find papers outside their research field harder to read, which makes introducing and explaining basic knowledge without the assumption of the audience already knowing the topic very important. Finally, we showed an improvement in the weekly number of papers read after attending AC of those who present papers regularly, and a high satisfaction rating of our AC. We summarize the areas of improvement in our AC implementation, and we encourage other institutions to evaluate their own AC in accordance with the four aforementioned factors to assess the effectiveness of their AC in reaching their goals.

At a glance Astrobites is a graduate-student-run platform that publishes daily summaries of astrophysics research papers in accessible language. This paper describes how Astrobites serves as a model for community-led science communication and education, supporting early-career astronomers and broadening access to the scientific literature.

Abstract It is important that we are able to accurately model the atmospheres of (exo)planets. This is because atmospheres play a central role in setting a planet’s thermochemical environment at a given point in time, and also in regulating how it evolves over geological timescales. Additionally, it is primarily by observation of their atmospheres that we are able to characterise exoplanets. There is particular demand for accurate models in the context of so-called lava worlds: planets with molten interiors (or `magma oceans’). AGNI is a Julia program designed to solve for the temperature and radiation environment within the atmospheres of rocky (exo)planets. It leverages a well established FORTRAN code to calculate radiative fluxes from a given atmospheric temperature structure and composition, which, alongside representations of convection and other processes, enables an energy-conserving numerical solution for the atmospheric conditions. In contrast to most other numerical atmosphere models, AGNI uses a Newton-Raphson optimisation method to obtain its solution, which enables improved performance and scalability. Our model was specifically developed for use alongside planetary interior models within a coupled simulation framework. However, it can also be applied to scientific problems standalone when used as an executable program; it reads TOML configuration files and outputs figures and NetCDF datasets. AGNI can also function as a software library; it is used in this sense within the Jupyter notebook tutorials of our GitHub repository (https://nichollsh.github.io/AGNI/dev/)

At a glance Modeling the atmospheres of rocky exoplanets requires accurate calculations of how radiation and convection transport energy, especially for planets with molten surfaces. AGNI is an open-source atmospheric model purpose-built for lava worlds that uses an efficient numerical solver to calculate temperature profiles and radiation environments. It is designed to couple with interior evolution models within the PROTEUS simulation framework, enabling self-consistent simulations of how rocky planets evolve over time.

Abstract The Large Interferometer For Exoplanets (LIFE) is a proposed space mission to directly detect and characterize the thermal emission of temperate terrestrial exoplanets in the mid-infrared (6 to 17 microns) using a formation-flying nulling interferometer. This paper presents the current optical and instrument design of LIFE, including the beam combination scheme, spectral resolution requirements, detector technology, and the integration of single-mode fibers for spatial filtering. We demonstrate the technical feasibility of achieving the sensitivity and angular resolution needed to study rocky exoplanets in the habitable zones of nearby stars, and discuss the key technology development milestones required to advance LIFE toward a future ESA mission.

At a glance The LIFE mission concept proposes a formation-flying mid-infrared nulling interferometer in space to directly detect and characterize exoplanet atmospheres. This paper presents the optical and instrument design, demonstrating the technical feasibility of studying rocky exoplanets in the thermal infrared.

At a glance This DPhil thesis used coupled atmosphere-interior numerical models to investigate the evolution and observable properties of rocky exoplanets. It examined how interactions between magma oceans and overlying atmospheres shape the thermal evolution, volatile cycling, and spectral signatures of terrestrial worlds across different evolutionary stages.

At a glance This MSc thesis modelled the chemical equilibrium between atmospheres, mantles, and metal cores of magma ocean exoplanets. It found that SiO and H₂O enrichment in equilibrated atmospheres could help distinguish magma ocean planets from those with hydrogen-dominated envelopes, while CO and CO₂ abundances traced the interior temperature.

At a glance This MSc thesis investigated the performance of single-mode optical fibers for spatial filtering in the planned LIFE space interferometer. Simulations showed that a single fiber cannot cover the full 4.5 to 18 micron wavelength range efficiently, requiring at least two fibers with a bandpass split near 9.1 microns and wavefront errors below 0.2 microns for acceptable coupling.

At a glance This BSc thesis used the AGNI radiative-convective model to characterize four M-star rocky exoplanets (GJ 486b, GJ 367b, TRAPPIST-1b, TRAPPIST-1c) from JWST mid-infrared observations. Bayesian model selection was applied to distinguish bare-rock surfaces from atmosphere scenarios, finding that heat redistribution and observational degeneracies complicate definitive atmosphere detection.

At a glance This BSc thesis developed and extended Zalmoxis, an open-source interior structure code for rocky exoplanets, and integrated it into the PROTEUS coupled atmosphere-interior framework. Simulations of fully molten rocky planets across the 1 to 7 Earth-mass range revealed a mass dependence in crystallization timescales and volatile outgassing efficiency.

At a glance This BSc thesis investigated whether tidal heating from the early Moon could have prolonged Earth’s magma ocean phase and sustained quasi-steady thermal states conducive to prebiotic chemistry. Using coupled interior-atmosphere simulations with PROTEUS, it found that tidal heating can extend magma ocean lifetimes from 30 to 500 million years, with implications for the production of life’s building blocks.

At a glance This BSc thesis modelled the timescale and conditions for surface ocean formation on Earth-like exoplanets after magma ocean solidification. It investigated how planetary properties and atmospheric conditions influenced when liquid water could first accumulate on the surface and what composition those early oceans would have had.

At a glance This BSc thesis modelled volatile-depleted rock-vapour species in lava exoplanet atmospheres using the VapoRock code across a range of compositions, iron contents, and oxidation states. It identified SiO and SiO₂ as tracers of the mantle redox state, Cr, Fe, and Na as indicators of reducing conditions, and highlighted CrO₂ and CrO₃ as markers of highly oxidized environments.

At a glance This BSc thesis examined how the oxidation state of a rocky planet’s mantle and atmosphere influences the threshold for the runaway greenhouse effect. It used radiative-convective models to test whether more oxidized or reduced atmospheric compositions shift the critical radiation limit at which oceans are lost.

At a glance This BSc thesis investigated the population of exoplanets between super-Earths and sub-Neptunes that have lower densities than expected for purely rocky compositions. It explored what internal structures, volatile inventories, and atmospheric envelopes could explain these under-dense planets.

At a glance This MSc thesis simulated the long-term geodynamical evolution of ultra-short-period exoplanet GJ 367b, one of the densest known rocky planets. It found that the planet develops a 20 to 100 km deep dayside magma ocean and a 300 km thick nightside lithosphere, with the evolution depending strongly on whether the planet started hot or cold.

At a glance This BSc thesis modelled the atmospheric spectra of volcanically active terrestrial exoplanets to determine whether different geological states can be distinguished remotely. It found that CO₂, SO₂, H₂O, and NH₃ absorption features in the 5 to 30 micron range are the primary discriminants, and that planets orbiting Sun-like stars produce more distinct spectral signatures than those around M-dwarfs.

At a glance This BSc thesis assessed the feasibility of distinguishing surface compositions on rocky exoplanets using the planned LIFE space interferometer. Using LIFEsim simulations, it found that surface spectra may be distinguishable out to 4 to 5 parsecs, with integration time and distance being the dominant limiting factors.

At a glance This BSc thesis modelled the thermal emission from recently formed, still-cooling protoplanets to estimate their detectability with next-generation astronomical surveys. It assessed which combinations of planet mass, age, and distance could yield detections with upcoming infrared instruments.

At a glance This BSc thesis investigated how water vapor abundance affects the atmospheric structure, composition, and emission spectra of hot rocky exoplanets during their magma ocean phase. It found that steam content significantly impacts vertical temperature profiles, molar compositions, and emission spectra, providing insights into the conditions for habitable atmosphere formation.

At a glance This MSc thesis modelled the transport and distribution of liquid water within planetesimals heated by radioactive decay during early Solar System formation. It investigated how water percolated through porous rock under the influence of radiogenic heating, self-gravity, and capillary forces, shaping the volatile budgets delivered to growing planets.

At a glance This BSc thesis modelled percolative core formation in planetesimals and protoplanets, where molten iron migrates through a solid silicate matrix driven by buoyancy and capillary forces. Using two-phase flow simulations, it investigated the efficiency and timescale of this mechanism for metal-silicate separation during early Solar System evolution, complementing the more commonly studied large-scale overturn and diapir sinking scenarios.

At a glance This PhD thesis investigated the thermal evolution of rocky planets during their formation, tracing how the decay of short-lived radioactive isotopes like aluminium-26 drives internal melting, iron core segregation, and the loss of water and other volatiles from planetesimals. It established a quantitative link between the birth environment of a planetary system and the long-term volatile budget and habitability potential of its rocky planets.

At a glance This MSc thesis predicted the observability of magma oceans created by giant collisions between protoplanets during terrestrial planet formation. Using 1D magma ocean cooling models, N-body collision statistics, and the performance specifications of future instruments (E-ELT/METIS, Darwin-like space telescope), it computed detection probabilities for ten nearby young stellar associations, identifying the Beta Pictoris and TW Hydrae groups as the most promising targets.

At a glance This MSc thesis simulated gravitational instabilities in compact, massive protoplanetary disks using 3D adaptive mesh refinement hydrodynamics. It investigated the conditions, including disk mass, temperature, and cooling rates, under which self-gravitating disks fragment into bound clumps that could become gas giant planets or brown dwarfs.

At a glance This BSc thesis investigated how stellar oscillation measurements (asteroseismology) can improve the characterization of exoplanet host stars. By constraining fundamental stellar parameters such as mass, radius, and age more precisely, it showed how asteroseismology propagates into tighter constraints on the physical properties of transiting exoplanets.