^1,2,3,7Harshit Krishna, ^1,2,4,7Asmit Gupta, ^1,2,5Sneha Bhowmick, ^1,2,6Chandan K. Sahu, ^1,2Sudipta Midha, ^1,2Liton Majumdar
The Astrophysical Journal, 1010, 23
Open Access Link to Article [DOI: 10.3847/1538-4357/ae9ba8]
¹Exoplanets and Planetary Formation Group, School of Earth and Planetary Sciences, National Institute of Science Education and Research, Jatni 752050, Odisha, India
²Homi Bhabha National Institute, Training School Complex, Anushaktinagar, Mumbai 400094, India
³Department of Physical Sciences, Indian Institute of Science Education and Research (IISER) Mohali, Knowledge City, Sector 81, Sahibzada Ajit Singh Nagar, Punjab 140306, India
⁴Indian Institute of Science Education and Research, Kolkata, Mohanpur 741246, West Bengal, India
⁵Department of Geology and Geophysics, Indian Institute of Technology, Kharagpur 721302, India
⁶Department of Geosciences, Pennsylvania State University, University Park, State College, PA 16802, USA
⁷Harshit Krishna and Asmit Gupta contributed equally to this work.

Over the past three decades, hundreds of rocky exoplanets have been discovered. Some of these show atmospheric signatures indicative of diverse chemical compositions. Interpreting these atmospheres requires a physically grounded understanding of planetary interiors, as interior composition and mineralogy govern the formation and evolution of secondary atmospheres. Rocky terrestrial exoplanets are expected to inherit the refractory composition of their host stars, providing a direct pathway to constrain their bulk composition and mineralogy. However, a large fraction of these planets orbit M-type stars, whose compositions remain poorly constrained because of limited and uncertain stellar abundance measurements. Here, we present a physically consistent framework that connects stellar abundances to the interior structure and mineralogy of rocky exoplanets by combining stellar abundance inference, devolatilization modeling to estimate bulk and mantle elemental abundances, interior structure calculations to derive pressure–temperature (P–T) profiles, and thermodynamic equilibrium modeling of mantle mineralogy. We first benchmark the framework against Earth and then apply it to the super-Earth GJ 486b using chemically consistent abundances derived from ensembles of similar M-dwarf hosts. We find that GJ 486b likely hosts an iron-rich and silica-poor mantle relative to Earth while preserving the major mantle phase transitions. Sensitivity analyses show that the overall mineralogical structure is robust to variations in bulk composition and P–T profiles, with temperature primarily modulating phase proportions near key transitions. Our results demonstrate that stellar chemical abundances, when combined with physically motivated devolatilization models, provide robust constraints on planetary interior composition and mineralogy beyond those obtainable from mass and radius measurements alone. This framework establishes a physically motivated foundation for linking rocky exoplanet interiors to atmospheric characterization in the JWST era.

¹C. D. O’Connell-Cooper et al. (>10)
Journal of Geophysical Research (Planets)(in Press) Open Access Link to Article [https://doi.org/10.1029/2025JE009001]
¹Planetary and Space Science Centre, University of New Brunswick, Fredericton, NB, Canada
Published by arrangement with John Wiley & Sons

The Mount Sharp group in Gale crater is typically interpreted to record a progressive change (with increasing elevation) from wetter fluvio-lacustrine environments to dry, eolian environments. This shift has been linked to orbital evidence for a global change in environmental and depositional conditions leading to an overall drying out of Mars. The Mars Science Laboratory Curiosity rover has documented evidence at Gale for the periodic continuation of aqueous depositional processes within the Mount Sharp group within the Clay Sulfate Transition, suggesting that, in Gale crater, it was not a simple, unidirectional drying out pattern. We present data on a series of interdune lenses at Gale crater, providing a window into locally changing environmental conditions. They represent wet (fluvial to lacustrine) deposits in the otherwise dry eolian Contigo dune field. Alpha Particle X-Ray Spectrometer geochemical data reveal compositional similarities between the interdune lenses and both the host Contigo member and unaltered basaltic sediments. Modeling indicates that the lenses may contain up to 52% basaltic sands/soils mixed with local sediment. A high degree of homogeneity in composition and sedimentary structures are identified across the lenses. This suggests a common source of influx material and a repeated process (wet episodes in a dry environment over several cycles of seasonal variations). Furthermore, differences in composition between the interdune lenses and the host Contigo member help to elucidate the timing of alteration within the Mount Sharp group.

¹Haijun Li,¹Huapei Wang
Journal of Geophysical Research (Planets)(in Press) Link to Article [https://doi.org/10.1029/2024JE008768]
¹Paleomagnetism and Planetary Magnetism Laboratory, School of Geophysics and Geomatics, China University of Geosciences, Wuhan, China
Published by arrangement with John Wiley & Sons

Meteorites preserve valuable remanent magnetization from the early solar system. However, the residence on the Earth’s surface often leads to the formation of iron oxides, which can alter or obliterate the primary remanence and complicate the paleomagnetic data interpretation. The weathering degree varies significantly depending on residence time, location, climate, and the chemical composition of the meteorite. Additionally, individual meteorites can exhibit varying oxidation degrees within a single stone due to partial burial in soil. This study examines the LL7 chondrite Northwest Africa 12780, revealing heterogeneous weathering across different parts of the meteorite. While one part shows extensive metal oxidation, another remains unoxidized. Although most oxidized subsamples contain paramagnetic iron oxides, maghemite is observed in some oxidized subsamples. Our findings highlight the presence of heterogeneous weathering in meteorites, which leads to the formation of various iron oxides, including maghemite, potentially acquiring chemical remanent magnetization and overprinting primary remanence. This also indicates that certain subsamples may retain their primary remanence even in weathered meteorites. However, systematic investigations are necessary to eliminate the influence of ferromagnetic iron oxides.

¹V. V. Kachmar, ^1,2,3,4B. L. Ehlmann
Journal of Geophysical Research: Planets, 131, e2025JE009415
Open Access Link to Article [DOI: 10.1029/2025JE009415]
¹Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA, USA
²Laboratory for Atmospheric and Space Physics, University of Colorado Boulder, Boulder, CO, USA
³Department of Geological Sciences, University of Colorado Boulder, Boulder, CO, USA
⁴Department of Astrophysical and Planetary Sciences, University of Colorado Boulder, Boulder, CO, USA

Published by arrangement with John Wiley & Sons

Water ice deposits occur on inner solar system bodies in sunlit and shadowed terrains. We develop approaches to remotely determine the mixing mode with regolith (areal vs. intimate), ice grain size, and abundance that reveal processes of ice formation, emplacement, and evolution. Given the sensitivity of existing inversion techniques to the accuracy of absolute wavelength-dependent reflectance, we evaluated and parameterized robust observables between 1.2 and 2.5 μm—band depth and band area at 1.5 and 2.0 μm, and near-infrared spectral slope—based on Hapke equations, using a data-derived regolith endmember mixed with modeled ice of varying properties. As a case study, we applied the approach to three lunar polar craters with permanent shadows—de Gerlache, Faustini, and Rozhdestvenskiy—and, in a separate companion publication, to ice on Ceres (Kachmar & Ehlmann, 2026, https://doi.org/10.1029/2025JE009421). Our inferred abundances for lunar ice (10–30 wt%, 10–100 μm) are in agreement with the ShadowCam results. The derivation of the mixing mode, grain size, and abundance is robust (<20 wt% difference) to choices or uncertainties about ice crystallinity, temperature, and regolith endmember, and is only moderately sensitive to porosity. In contrast, the model choices for surface illumination (Sun vs. shadow), ice optical constants, and phase behavior (isotropic vs. anisotropic) substantially influence the results. The approach can be applied to any planetary infrared spectroscopic data set, and its promise will be fully realized with refined ice optical constants and laboratory tests with ice-regolith mixtures at various porosities and observational geometries.

^1,2K. A. Cone et al. (>10)
Journal of Geophysical Research: Planets, 131, e2026JE009701
Open Access Link to Article [DOI: 10.1029/2026JE009701]
¹Department of Earth and Environmental Sciences, University of Rochester, Rochester, NY, USA
²Earth, Environmental and Planetary Sciences, Rice University, Houston, TX, USA

Published by arrangement with John Wiley & Sons

Hypervelocity impacts modify planetary crusts and can alter the microstructures of key minerals used to reconstruct planetary histories. We investigated the potential effects of impacts on three common accessory minerals found in terrestrial crusts by experimentally shocking zircon, apatite, and whitlockite at 5, 10, 20, and 40 GPa. The internally consistent suite of shock-metamorphosed microstructures was characterized using scanning electron microscopy, Raman spectroscopy, electron backscatter diffraction, and in situ U-Pb isotope analysis. Crystal orientation mapping reveals patchy reidite formation near zircon grain exteriors at 20 GPa and pervasive reidite domains at 40 GPa. Annealing sharpens the characteristic ∼1,006 cm⁻¹ zircon Raman peak at ≤20 GPa but does not restore this peak in the reidite formed at 40 GPa. Apatite retains crystalline domains through 40 GPa despite broadening of some Raman bands at ∼1,051 and ∼1,145 cm⁻¹, with annealing restoring spectra to pre-shock patterns. Whitlockite develops merrillite-like Raman spectra with pressure, but the data cannot resolve dehydrogenation or transformation to merrillite. Shocked zircon exhibits U-Pb discordance, whereas annealing at 950°C improves concordance, suggesting that shock-induced microstructural modification may produce matrix effects and apparent age offsets, complicating reconstruction of events such as a lunar bombardment. Collectively, these experiments also demonstrate heterogeneity in mineral responses—both among and within grains—to a single shock pressure. Thus, the absence of a diagnostic microstructure within analyzed domains does not necessarily preclude exposure to an associated shock pressure, emphasizing the importance of whole-grain micro- to nanoscale characterization and consideration of grain size in shocked planetary materials.

^1,2,3S. Andrejkovičová et al. (>10)
Journal of Geophysical Research: Planets, 131, e2025JE009610
Open Access Link to Article [DOI: 10.1029/2025JE009610]
¹NASA GSFC, Greenbelt, MD, USA
²CRESST, University of Maryland, College Park, MD, USA
³Geosciences Department, GeoBioTec, Aveiro University, Aveiro, Portugal

Published by arrangement with John Wiley & Sons

Ammonium (NH₄⁺) in the interlayer space of phyllosilicates has been proposed as a potential but underexplored nitrogen reservoir on Mars. We synthesized ammonium-exchanged smectites (montmorillonite SWy-2 and nontronite NAu-2) and analyzed them, both as pure phases and in mixtures containing five or 20 wt.% magnesium (Mg) perchlorate, under Sample Analysis at Mars (SAM)–like conditions using evolved gas analysis–mass spectrometry (EGA) and pyrolysis (GC-MS), complemented by FTIR, XRD and EA-IRMS. Ammoniated smectites released N₂ during heating even without perchlorate, whereas mixtures with Mg perchlorate yielded oxidized nitrogen species (NO and N₂O) along with N₂. The temperature ranges and release profiles of NO bear similarities to several Gale crater samples analyzed by SAM, suggesting that part of the martian NO could derive from ammonium-bearing smectites rather than exclusively from nitrate thermal decomposition. Quantitative analysis of EGA data indicates that 4.20%–29.8% of the total nitrogen in the ammoniated smectites was released as NO under SAM-like pyrolysis, depending on smectite type and oxidant abundance. XRD under dry conditions shows partial collapse of basal spacing to d(001) ≈10.8 Å (NH₄SWy-2) and 10.4 Å (NH₄NAu-2), comparable to the broad ∼10 Å peaks observed by the Chemistry and Mineralogy (CheMin) instrument in clay-bearing Gale crater materials. These results indicate that ammonium-bearing smectites are a plausible precursor phase capable of generating NO under SAM-like pyrolysis conditions and could contribute to martian nitrogen cycling in environments where smectite formation and ammonium exchange occurred, although the present martian data do not uniquely distinguish among possible nitrogen precursor phases.

^1,3Haoan Yin, ^1,2Hong Tang, ^1,2Xiongyao Li, ^1,2Wen Yu, ¹Chuanjiao Zhou, ¹Tian Zhang, ¹Erbin Shi
Icarus (in Press) Link to Article [DOI: 10.1016/j.icarus.2026.117367]
¹Center for Lunar and Planetary Sciences, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China
²CAS Center for Excellence in Comparative Planetology, Hefei 230026, China
³University of Chinese Academy of Sciences, Beijing 100049, China

Copyright Elsevier

Phyllosilicates and hydrated sulfates record aqueous activity on ancient Mars and may participate in present–day atmosphere–regolith water vapor exchange. However, their temperature–dependent spectral behavior has rarely been compared under consistent conditions, limiting discrimination between intrinsic thermal effects and adsorbed water loss. We measured diffuse reflectance infrared spectra of kaolinite, montmorillonite, gypsum, and jarosite from −90 to 30 °C and analyzed H₂O/OH band positions, full widths at half maximum, and areas. Band positions remained generally stable in kaolinite, montmorillonite, and jarosite, whereas gypsum hydration bands shifted toward shorter wavelengths during warming. The ~2.75 μm feature of montmorillonite and ~ 3 μm feature of kaolinite narrowed and decreased in area, indicating adsorbed water loss. In contrast, the ~2.9–3 μm features of gypsum and jarosite broadened and increased in area, reflecting changes in molecular vibrations and hydrogen bonding. These mineral–specific responses distinguish adsorbed water exchange from intrinsic thermal effects, improve interpretation of orbital and in situ spectra, and clarify temperature–driven water vapor exchange mechanisms relevant to present-day Martian habitability.

¹Merel E. Onderwater, ¹Elishevah M. M. E. van Kooten, ²Glenn J. MacPherson, ³Alexander N. Krot, ^1,4Martin Bizzarro
Geochimica et Cosmochimica Acta (in Press)
Open Access Link to Article [DOI: 10.1016/j.gca.2026.10.033]
¹Centre for Star and Planet Formation, Globe Institute, University of Copenhagen, Copenhagen, Denmark
²Department of Mineral Sciences, National Museum of Natural History, Smithsonian Institution, Washington DC, USA
³Hawai‘i Institute of Geophysics and Planetology, University of Hawai‘i at Mānoa, Honolulu, HI, USA
⁴Institut de Physique du Globe de Paris, Université de Paris, Paris, France

Copyright Elsevier

Calcium-aluminium-rich inclusions (CAIs) in chondritic meteorites are the first solids that formed in the Solar System, as established by U-Pb chronology. After initial condensation, coarse-grained CAIs (Compact Type A, Type B, Type C) experienced melting, resulting in igneous partitioning and spatial redistribution of trace elements among constituent minerals. Understanding these distributions is essential for identifying trace-element host phases and interpreting U-Pb ages. Rare earth elements (REEs) and the actinides Th and U are particularly informative tracers, yet actinide behavior in coarse-grained CAIs remains poorly constrained. Further, the decay of short-lived ²⁴⁷Cm to ²³⁵U (t_1/2 = 15.6 Myr) complicates U-Pb age determination of bulk CAIs, but its impact at the mineral scale remains elusive.

Here, we present major- and trace-element distribution maps of six coarse-grained CAIs mainly composed of melilite, Al,Ti-pyroxene, anorthite and spinel (±forsterite) from CV3 (Vigarano-type) chondrites acquired by femtosecond laser ablation ICP-MS. In CAIs lacking perovskite or hibonite, our results show that Al,Ti-pyroxene is the dominant host of U, Th, and most REEs, with strong enrichments observed toward pyroxene grain edges, whereas light REEs reside in melilite. Trace-element zonation reflects igneous fractional crystallization and is overprinted by melt evaporation, which caused depletion of the most volatile REEs (Yb, Eu, Ce) and U in CAI outer regions and rims. Using Nd and Th distribution maps as proxies for Cm, we model the effects of ²⁴⁷Cm-²³⁵U decay on mineral-scale U isotopic compositions. Variable Cm-U partitioning among coexisting minerals is predicted to generate resolvable inter-mineral ²³⁵U/²³⁸U variations, with the largest excesses in melilite. These variations can produce apparent U-Pb age offsets of ∼0.1–1.0 Myr when U isotopic compositions and radiogenic Pb are derived from isotopically distinct mineral reservoirs, but generally remain small (< 0.15 Myr) when using bulk U isotopic compositions. Our results demonstrate that fractional crystallization and melt evaporation exert a primary control on U distribution and isotope systematics in igneous CAIs and provide new constraints on the interpretation and robustness of high-precision U-Pb chronology of the earliest Solar System solids.

¹J. Michael Brown, ²Olivier Bollengier, ¹Ula Jones, ³Steven D. Vance, ¹Baptiste Journaux
Geochimica et Cosmochimica Acta (in Press)
Open Access Link to Article [DOI: 10.1016/j.gca.2026.10.019]
¹Earth and Space Sciences, University of Washington, Seattle, 98195, WA, USA
²Chemistry Department, University of Nantes, Nantes, France
³Astrobiology Group 322A, MS183-301, Jet Propulsion Laboratory, California Institute of Technology, Pasadena, 91109, CA, USA

Copyright Elsevier

We present a new Gibbs energy representation for aqueous NaCl, based on new sound speed and phase equilibrium measurements, using local basis functions. Throughout, NaCl(aq) denotes the bulk aqueous component—the sum of ${\text{NaCl}}^{\text{0}}$, Na${}^{+}$ and Cl${}^{-}$—rather than the neutral complex, with the degree of dissociation implicit in the measurements rather than imposed. This comprehensive equation of state, valid for pressures to $10000MPa$, temperatures from $230K\text{to}2000K$, and molality to $7mol{kg}^{-1}$, allows us to address chemical processes within Earth and interior structure and evolution of large icy moons with possible oceans. The region below $500MPa$ at temperatures above $500K$, which contains water’s saturation curve and critical point, is excluded for want of constraining measurements; within the domain represented the fluid is a single phase. In regimes unconstrained by data, it assumes near-gas behavior at high temperatures and volume mixing of water and salt at extreme pressures. Differentiation of the representation yields all equilibrium properties, including volumes, specific heat capacities, and chemical potentials. The model is validated by its accurate prediction of ice Ih and VI melting and brucite dehydration in saline solutions, and by its reproduction of antigorite dehydration in pure water through two changes in reaction product to beyond $6000MPa$. We describe three applications of the Gibbs energy representation. (1) The depth during subduction of the antigorite dehydration reaction in the presence of saline geofluids is estimated to be reduced by $2km\text{to}4km$ per mole of NaCl in solution, substantially less than the up to $10km$ per mole implied by previously inferred pressure-dependent water activities. (2) A ${\text{H}}_{\text{2}}\text{O}-\text{NaCl}$ phase diagram to $1000MPa$ and $230K\text{to}400K$ identifies the pressure-variant eutectics for hydrohalite and disodium chloride decaheptahydrate, and places the cenotectic—the absolute limit of liquid stability—at $205MPa$, $235K$ and $3.90mol{kg}^{-1}$, where the liquid coexists with ice Ih, ice II and disodium chloride decaheptahydrate rather than with hydrohalite. (3) Icy moons: structural models of Ganymede, Callisto, and two Titan cases with $1.90mol{kg}^{-1}$ aqueous NaCl show that melting point suppression stabilizes ices II, III, V, and VI, and that ices II and III can be buoyant in the coexisting fluid, with the sense of the ice II contrast reversing between 50 and $100g{kg}^{-1}$. The resulting co-occurrence of ices II and III, not previously reported, admits multiphase overturning and implies that salinity governs the geodynamics of these $>100km$ lithospheres. Finally, we set out how a bulk Gibbs energy surface interfaces with species-based frameworks such as HKF and the Deep Earth Water model, and propose that the pressure derivative of the surface can be used to constrain the degree of association at high pressure.