¹Anuja Sreejayan et al. (>10)
Journal of Geophysical Reseacrh: Planets (in Press) Link to Article [https://doi.org/10.1029/2025JE009544]
¹Department of Geology, University of Kerala, Thiruvananthapuram, Kerala, India
Published by arrangement with John Wiley & Sons

This study reports the first occurrence of melanterite (Fe2+SO4·7H2O), a secondary hydrous sulfate mineral, in Peninsular India and examines its formation through the oxidative weathering of marcasite associated with lignite in Neyveli, Tamil Nadu. The marcasite was exposed to normal atmospheric conditions, and melanterite was formed within 23 days via oxidative weathering. Melanterite occurs as a yellow, prismatic to fibrous, translucent crystal, either as individual fibers or clusters. Though melanterite is mineralogically characterized through different techniques like X-ray diffraction, scanning electron microscopy-energy dispersive X-ray spectroscopy, and electron probe microanalysis (EPMA), the results obtained from EPMA [(Fe0.839 Cu0.000355 Zn0.000466 Ni0.000545) SO4·7H2O] closely match the composition of standard melanterite. Fourier Transform Infrared spectroscopy identified key vibrational peaks for sulfates (450–480 cm−1) and water molecules (1,544–1,650 cm−1), while laser Raman spectroscopy provided evidence for the characteristic vibration of melanterite at 976 cm−1. Hyperspectral analysis also discerned the characteristic Fe2+ peak (0.45–0.9 μm) of melanterite. A spectrum, comparable to that of melanterite, obtained through Compact Reconnaissance Imaging Spectrometer for Mars data from the Ceti Mensa region on Mars, where it is associated with a polysulfate deposit. Since melanterite forms under acidic and oxidizing conditions in low moisture, its occurrence can provide insights into the environmental conditions under which sulfate forms. Thus, this study can provide insights into studying transient wet conditions on Mars.

^1,2Devan M. Nisson et al. (>10)
Journal of Geophysical Research: Planets (in Press) Open Access Link to Article [https://doi.org/10.1029/2025JE009395]
¹Department of Geosciences, Princeton University, Princeton, NJ, USA
²NASA Postdoctoral Program Fellow, NASA Ames Research Center, Moffett Field, CA, USA
Published by arrangement with John Wiley & Sons

Serpentinization produces hydrogen and methane through abiotic water-rock interactions, potentially supporting chemotrophic life in planetary subsurface environments. Serpentine deposits in the Martian Noachian landscapes of Nili Fossae and the Southern Highlands have been considered as potential paleo-habitable zones. However, the geochemical and physical conditions of Martian serpentinization fluids are poorly constrained because of limited data on serpentinite composition and formation environment. Furthermore, the co-occurrence of magnesite and magnesium-enriched serpentines on Mars remains enigmatic. To address such gaps, we investigated antigorite-magnesite paleo-serpentine bodies along the Highland-Vijayan suture of Sri Lanka as Martian analog sites, using thermodynamic batch reaction models to constrain alteration fluids and the production of primary (H2) and secondary (CH4) serpentinization products. Geochemist’s Workbench models combined field X-Ray Fluorescence (XRF) observations with varied protolith compositions (ultramafic or gneissic), precursor fluids (seawater or freshwater), temperatures (100–600°C), volumetric water-to-rock ratios (1–100,000), and CO2 partial pressures (0.01–1 bar). Models successfully reproduced the co-occurrence of antigorite and magnesite observed on Mars, with both minerals forming at 100°C across water-to-rock ratios. Despite their Mg-enriched composition, ultramafic protoliths produced H2 yields (up to 229 mmol/kg at W/R 1 at 100°C), supporting chemotrophic populations up to 107.5 cells/mL. Geochemical models indicate Mg enrichment from ultramafic mineralogy and Fe contribution from regional gneisses. Our thermodynamic equilibrium results show that Mg-rich serpentine systems with sufficient ferrous iron can produce biologically significant H2, establishing Sri Lankan serpentinites as valuable analogs for Noachian Mars habitability.

¹Neil E. Bowles et al. (>10)
Journal of Geophyiscal Research: Planets (in Press) Open Access Link to Article [https://doi.org/10.1029/2025JE009333]
¹Department of Physics, University of Oxford, Oxford, UK
Published by arrangement with John Wiley & Sons

The Lunar Thermal Mapper (LTM) instrument is a UK Space Agency funded infrared radiometer designed and built for the National Aeronautics and Space Administration Lunar Trailblazer mission launched in February 2025. LTM is a pushbroom imaging filter radiometer with 15 channels that cover the wavelength range from 6.25 to 100 μm with a 40–70 m/pixel ground sampling. Lunar Trailblazer’s mission is to understand the form, abundance and distribution of water across the lunar surface. LTM provides an independent measure of temperature to investigate thermal effects on water’s mapped distribution as well as an independent measure of surface mineralogy. The LTM instrument’s 15 infrared channels include four broadband temperature sensing channels (6.25–12.5, 12.5–25, 25–50 and 50–100 μm) plus 11 additional narrow band (∼40 cm−1) filters from ∼7–10 μm to map and discriminate silicate composition. We review the LTM design and calibration campaign at the University of Oxford’s Space Instrumentation facility and show that the instrument has sensitivity from 400 K with a Noise Equivalent Temperature Difference of <0.1 K to <1 K at 110 K for typical integration times (e.g., 30 Hz readout) from a nominal 70–130 km lunar orbit design altitude.

¹Ming Ma et al. (>10)
Journal of Geophysical Research: Planets (in Press) Open Access Link to Article [https://doi.org/10.1029/2026JE009657]
¹School of Surveying and Exploration Engineering, and Key Laboratory of Architectural Cold Climate EnergyManagement, Ministry of Education, Jilin Jianzhu University, Changchun, China
Published by arrangement with John Wiley & Sons

Space weathering substantially distorts the Christiansen feature (CF) observed by LunarReconnaissance Orbiter (LRO) Diviner thermal infrared radiometer, obscuring the intrinsic compositional andthermophysical signals of lunar surface silicate minerals. In this study, we develop a two‐step correctionframework designed to remove space weathering effects from a previously topographically corrected LRODiviner CF map. The method integrates Kaguya 750 nm reflectance, optical maturity (OMAT), FeO, H‐parameter, and npFe0 parameters to model nonlinear space weathering relationships across immature,moderately mature, and mature CF pixels. The corrected CF values exhibited reduced dependence on npFe0abundances, enhanced correlation with bulk FeO abundances, and improved internal consistency withincompositionally homogeneous regions. Comparisons with correction results based on Kaguya OMAT and FeOscale factors indicate that the proposed method more effectively suppresses space weathering inducedvariability while preserving compositionally diagnostic CF signatures. Persistent low CF anomalies in highlandregions suggest additional controls beyond npFe0 accumulation, potentially related to basaltic dustcontamination, subsurface compositional heterogeneity, and silicate amorphization processes. The resulting CFproduct offers a refined thermal infrared perspective on lunar surface composition, indicating clearer basalticdistributions, particularly within the South Pole Aitken basin.

^1,2Shuya Tan et al. (>10)
Geochimica et Cosmochimica Acta (in Press) Open Access Link to Article [10.1016/j.gca.2026.06.034]
¹Earth and Space Exploration Center, Ritsumeikan University, Kusatsu, Japan
²Institute for Extra-cutting-edge Science and Technology Avantgarde Research of Life (X-star), Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Yokosuka, Japan
Copyright Elsevier

The geochemical effects of freezing are becoming important in the investigation of closed aqueous environments, such as inland water on Earth and early Mars, and liquid water on planetesimals. Carbonate-bearing alkaline saline lakes in Mongolia are frozen in the cold season, with chemical species being partitioned among surface ice, lake water, and sediments. Freezing of the lakes leads to the accumulation of dissolved carbonate species, thereby decreasing the pH. The lakes are enriched not only in heavy metals, such as As, Mo, and U, but also in phosphorus. However, little is known about how metals and phosphorus are affected by chemical changes during freezing. Moreover, the mechanisms of major chemical changes are poorly understood and reproduced. Here we performed field surveys to investigate the behavior of these elements during lake freezing. Heavy metals and phosphorus accumulate in lake water during freezing, similar to major elements such as Cl−, with Mo and U concentrations reaching ∼1 mg/L. On the other hand, As and P accumulations are limited. Concentrations of heavy metals and phosphorus in ice increase with depth in the ice. We interpret the observed behavior using a geochemical model that accounts for their adsorption reactions coupled with water removal by freezing and carbonate precipitation. The model successfully reproduces the major chemical changes, including the decrease in pH, achieving quantitative accuracy by accounting for the combined effects of freezing and the revised solubility of carbonate minerals. The pH decrease promotes the adsorptions of As and P on sedimentary ferrihydrite particles, suppressing their accumulation in lake water. However, the decrease in pH is insufficient to promote adsorptions of Mo and U, resulting in their accumulations as major dissolved species. Adsorptions of heavy metals and phosphorus by iron oxides may be an important factor in their behaviors at low temperatures near the freezing point of water. Based on our model and observations, we discuss phosphate/carbonate precipitation in freezing porewater of icy planetesimals and phosphate availability in lake water on early Mars.

^1,2Juliana G. Peckenpaugh, ²Meryem Berrada, ¹Peng Jiang, ²Bin Chen
Geochimica et Cosmochimica Acta (in Press) Link to Article [10.1016/j.gca.2026.06.033]
¹Department of Earth Sciences, University of Hawaiʻi at Mānoa, Honolulu, HI 96822, USA
²Hawaiʻi Institute of Geophysics and Planetology, University of Hawaiʻi at Mānoa, Honolulu, HI 96822, USA
Copyright Elsevier

Mercury’s highly reduced formation conditions likely promoted the incorporation of silicon into its metallic core during planetary differentiation. The resulting Si-rich core composition would reduce the capacity of the metallic liquids to dissolve carbon, making carbon saturation more likely as the core cooled and crystallized. Determining the solubility of carbon in Fe-Si liquids under Mercury’s core conditions is therefore essential for evaluating whether graphite or diamond could precipitate from the core and influence Mercury’s thermal and magnetic evolution. In this study, high-pressure and high-temperature experiments were conducted on carbon-saturated Fe-Si alloys with varying silicon content from 4 to 27 wt% using a multi-anvil press at 5–20 GPa and 1673–1873  K. The analyses of the recovered samples by Scanning Electron Microscope (SEM) and Raman spectroscopy show the Fe-Si-C liquids with precipitated carbon phases in the form of graphite or diamond. Quantitative electron probe microanalysis (EPMA) results demonstrate a trend of decreasing carbon content in the Fe-Si-C alloys with increasing silicon content, described by the following equation: CFe-Si = 8.45–––0.663[Si] + 0.0134[Si]2. Higher initial silicon content within Mercury’s core due to the highly reduced conditions may result in lower solubility of carbon, suggesting a potential mechanism for the preferential exsolution of carbon-rich materials, such as graphite or diamonds. This finding suggests that carbon could precipitate within Mercury’s cooling, solidifying core under Mercurian core compositions and conditions. The segregation and accumulation of carbon could modify heat flux across the core-mantle boundary, affecting both the strength of Mercury’s early magnetic field and the longevity of dynamo action. Such compositional convection could sustain a dynamo, contributing to Mercury’s present-day magnetic field.

^1,3Noah Jäggi, ¹Adam K. Woodson, ²Paul S. Szabo, ³Johannes Brötzner, ³Friedrich Aumayr, ¹Catherine A. Dukes
Icarus (in Press) Open Access Link to Article [https://doi.org/10.1016/j.icarus.2026.117231]
¹Laboratory for Astrophysics and Surface Physics, University of Virginia, 395 McCormick Road, Charlottesville, 22904, VA, USA
²Space Sciences Laboratory, University of California, 7 Gauss Way, Berkeley, 94720, CA, USA
³Institute of Applied Physics, TU Wien, Wiedner Hauptstraße 8-10/E134, Vienna, 1040, Austria
Copyright Elsevier

Binary collision approximation (BCA) codes are potentially powerful tools to simulate ion irradiation ejecta properties, such as the composition and the angular and energy distributions of the sputter yield. However, recent advances in the sputtering of minerals have highlighted the low predictive fidelity of BCA codes such as SDTrimSP when compared to experimental measurements. We demonstrate how a sputtering model that underestimates the forward sputtering on a flat surface at large ion incidence angles from surface normal will lead to an erroneous result for rough and porous surfaces, where most ejected particles are directed along the surface normal. We demonstrate how this is the case for an existing model, which reliably predicts sputtering mass yields from a flat enstatite surface but fails to accurately reproduce the angular distribution of sputtered particles. We then compare this to a BCA model incorporating higher surface-binding energies—based on a molecular dynamics description of plagioclase—which underestimates mass yields but significantly reduces back-sputtering and better reproduces laboratory sputter angle distributions measured at large ion incidence angles. We conclude that the BCA model cannot simultaneously reproduce both the sputter yield and the sputter angle distribution arising from He irradiation of mineral targets, either due to the inherent geometric simplicity of the BCA or because the model neglects yield-enhancing processes such as molecule and cluster sputtering. This demonstrates a structural limitation of current BCA-based models when realistic surface morphologies are considered, rather than a problem that can be resolved by parameter tuning alone.

¹Xing Wu, ²Beatrice Baschetti, ^1,3Yang Liu, ²Cristian Carli, ^1,3Xiang Zhou, ¹Yazhou Yang, ¹Yongliao Zou
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2026.117235]
¹State Key Laboratory of Space Weather, National Space Science Center, Chinese Academy of Sciences, Beijing, 100190, China
²Italian National Institute for Astrophysics (INAF) – Institute for Space Astrophysics and Planetology (IAPS), Via del Fosso del Cavaliere, 100, Rome 00133, Italy
³College of Earth and Planetary Sciences, University of Chinese Academy of Sciences, Beijing 100049, China
Copyright Elsevier

Quantitative spectral unmixing is essential for identifying and characterizing mineral assemblages on planetary surfaces. The Hapke and Shkuratov models are the most widely used radiative transfer models (RTMs) for interpreting reflectance spectra, yet their quantitative accuracy remains largely untested due to limited laboratory validation. In this study, both models are applied to binary and ternary laboratory powder mixtures composed of phyllosilicates, including nontronite and saponite, sulfates represented by hexahydrite, and basaltic analogs relevant to Martian surface materials. The effects of endmember variability, spectral noise, and spectral sampling interval on unmixing performance are systematically evaluated. The results show both models reproduce measured spectra and compositional trends accurately when correct endmembers are used, achieving abundance retrievals within ~10 wt% for binary mixtures and ~ 15 wt% for ternary mixtures, except in systems with strong reflectance contrasts. The Shkuratov model provides lower errors and greater stability overall, whereas the Hapke model shows slightly better tolerance to compositional mismatch between Al-rich and Al-poor nontronite. Incorporating multiple compositional variants as an endmember bundle effectively mitigates mismatch effects. Estimated grain sizes fall within realistic physical ranges but show large uncertainties for bright or spectrally neutral materials, reflecting reduced model sensitivity to grain size variations. Additionally, we also find the unmixing performance remains robust under spectral noise levels of at least 25 dB and spectral sampling intervals up to 50, consistent with the capabilities of Mars orbital instruments. These results demonstrate that radiative transfer based unmixing, particularly using the Shkuratov model, provides a reliable and physically grounded framework for quantitative mineralogical analysis of Martian hyperspectral data.

¹Brynna G. Downey, ¹Robin M. Canup
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2026.117208]
¹Solar System Science and Exploration Division, Southwest Research Institute, 1301 Walnut Street, Boulder, 80302, CO, USA
Copyright Elsevier

In the giant impact theory for the origin of the Moon, a protoplanet collided with the Earth, producing a disk of melt-vapor debris from which the Moon accreted. Simulations of canonical impacts in which the impactor is  Mars-sized produce disks with mass 1 to  (lunar masses). However, most prior models of lunar accretion require that the initial disk have mass  because of the assumed disk state, modelled processes, and initial conditions. This inconsistency has been a challenge for the canonical impact model. To bridge this gap, we (i) update a model of the disk interior to the Roche limit to treat melt and vapor as separate, vertically stratified layers, and (ii) adopt as initial conditions for the accretion model more realistic radial mass distributions for the disk based on impact simulations. We find that treating the inner melt and vapor as vertically stratified layers lowers the final Moon mass by 20% on average compared to prior work that assumed they remained well-mixed, a relatively small effect. In contrast, the initial radial mass distribution has a substantial effect. We show that for outer disk mass , which is often 60% of the total disk mass, an  Moon accretes in as little as  days and at most  months. For almost all successful cases, only 5% of the final Moon is from the inner melt and vapor layers that might have isotopically equilibrated with the Earth’s vapor atmosphere. The Moon’s rapid accretion from material originally emplaced in an outer canonical disk requires that the isotopic similarities between the Earth and Moon be inherited from similarities between Earth and the impactor Theia, rather than through disk-planet equilibration.

¹Dylan M. Seal, ¹Melody Z. Chen, ²Robert W. Nicklas, ¹Ethan F. Baxter, ³James M.D. Day, ⁴Ben G. Rider-Stokes, ⁵Anthony B. Love, ⁴James Malley
Geochimica et Cosmochimica Acta (in Press) Link to Article [10.1016/j.gca.2026.06.035]
¹Department of Environmental Sciences, Boston College, Chestnut Hill, MA 02467, USA
²Lunar and Planetary Institute, USRA, Houston, TX 77058, USA
³Scripps Institution of Oceanography, University of California, San Diego, La Jolla, CA 92093-0244, USA
⁴School of Physical Sciences, The Open University, Milton Keynes MK7 6AA, UK
⁵Department of Geological and Environmental Sciences, Appalachian State University, Boone, NC 28608, USA
Copyright Elsevier

Here we report on the petrology, mineralogy, geochemistry, and O and Sm-Nd isotope compositions for Northwest Africa (NWA) 13441, an olivine-phyric shergottite rich in melt glass that was recovered from Algeria in 2019. The meteorite is a basalt containing abundant olivine megacrysts set in a groundmass of pigeonite, olivine, and maskelynite with accessory chromite and merrillite. The Fe/Mn ratios of olivine (56.1 ± 7.2; 2σ, n = 15) and pyroxene (30.1 ± 2.1; 2σ, n = 10), and bulk rock O isotope ratios of Δ17O = 0.270 ± 0.014 ‰, confirm its martian origin. Pyroxene Ti/Al barometry indicates that crystallization began near the crust-mantle boundary of Mars. The meteorite contains ∼7 vol% pyroxene-dominated melt glass that together with undulatory extinction and mosaicism in olivine, mechanical twinning in pyroxene, and amorphized plagioclase, suggests a relatively high level of shock metamorphism at estimated peak conditions of ∼28–34 GPa and ∼200–250 °C. The bulk rock rare earth element pattern ((La/Yb)CI = 0.64) suggests an affinity to intermediate shergottites. Hand-picked mineral separates and leachates define a 147Sm-143Nd errorchron corresponding to an age of 1273 ± 21 Ma (MSWD = 19; n = 9) and a chondritic εNdi composition of + 0.93 ± 1.04 that is distinct from other shergottites, which are typically younger (<600 Ma). Comparison with the 147Sm-143Nd evolution of different martian sources indicates that the chondritic composition of NWA 13441 could represent a previously unsampled undifferentiated reservoir or mixing between known enriched and depleted shergottite sources. Regardless, NWA 13441 expands the temporal and isotopic range of shergottite magmatism and demonstrates that the martian meteorite record incompletely samples the diversity of compositions produced from the melting of Mars’ mantle.