^1,2Yexin Luo,³Aicheng Zhang,¹Qing Lin,¹Xingmei Shan,¹Zhimao Du,²Mingbao Li,⁴Qi Li,⁵Xiuhong Liao,¹Shaolin Li
Journal of Geophysical Research: Planets (in Press) Link to Article [https://doi.org/10.1029/2025JE009360]
¹Shanghai Astronomy Museum (branch of Shanghai Science & Technology Museum), Shanghai, China
²State KeyLaboratory of Lunar and Planetary Sciences, Macau University of Science and Technology, Taipa, China
³State KeyLaboratory of Critical Earth Material Cycling and Mineral Deposits, School of Earth Sciences and Engineering, NanjingUniversity, Nanjing, China
⁴Polar Sample Repository, MNR, Polar Research Institute of China, Shanghai, China
⁵State KeyLaboratory of Geological Processes and Mineral Resources, Gemmological Institute, China University of Geosciences,Wuhan, China
Published by arrangement with John Wiley & Sons

Ordinary chondrites, sourced from S-type asteroids, provide the most direct documentation of the thermal history of their parent bodies. Current research focuses predominantly on silicates, but early endogenic metamorphism overprinted by impact heating can yield ambiguous silicate records. In contrast, Fe-Ni metal, also as a major component, exhibits higher strain rates and greater temperature sensitivity than silicates. H-group ordinary chondrites possess the highest metal content, characterized by thermally informative complex microstructures. In this study, the Electron Backscatter Diffraction technique is employed on 14 H chondrites to constrain their thermal history. Martensite and duplex plessite, microstructures indicative of rapid cooling, are prevalent in the metal. Furthermore, characteristic microstructures formed by martensite tempering under distinct thermal pathways are observed, including polycrystalline martensite (low-temperature, prolonged heating), net plessite, and acicular plessite (higher-temperature tempering). Consequently, the metal records a rapid cooling event followed by widespread tempering and thermal annealing. This implies that the H parent body, similar to those of L chondrites, experienced a catastrophic impact, evidenced by their shared quenched metal structure. Subsequent tempering and annealing probably resulted from thermal effects in the re-accretion of impact debris.

¹Sergei V. Bykov et al. (>10)
Journal of Geophysical Research: Planets (in Press) Open Access Link to Article [https://doi.org/10.1029/2025JE009375]
¹Department of Chemistry, University of Pittsburgh, Pittsburgh, PA, USA,
Published by arrangement with John Wiley & Sons

We report the in situ detection of amorphous hydrated silica in the Bills Bay abrasion patch, located in the eastern portion of the Margin Unit between the rim of Jezero crater and the western delta. Here, hydrated silica co-occurs with olivine, Fe-Mg carbonates, secondary Fe-Mg silicates, and hydrated Mg-sulfate as determined by UV Raman (SHERLOC) and X-ray fluorescence (PIXL) spectrometers onboard the Perseverance rover. Almost pure hydrated silica fills the intergranular space between olivine and carbonate-bearing domains. We performed Raman analysis of terrestrial opals with various crystallinities including opal-AN, AG, CT, and C. We found that the Si−O symmetric stretching Raman band at ∼800 cm−1 is sensitive to opal crystallinity, yet insensitive to ambient temperature (at ∼77–293 K) and silica hydration. We identified the crystal structure of the Bills Bay Hydrated Silica (BBHS) as opal-A. Furthermore, we developed a Raman methodology to quantify opal-A hydration. We found that the total amount of hydration in the BBHS phases was 1.7 ± 0.2 wt. %. Most of this hydration, 1.5 ± 0.2 wt. %, reflects the presence of silanol groups. Our analysis revealed that the Raman spectrum of BBHS closely resembles that of opal-A that has lost most of its molecular water. The composition and textures of the Bills Bay abrasion indicate that BBHS is derived from olivine carbonation. Opal-A is the only silica polymorph identified in the SHERLOC data. We hypothesized that silica precipitation occurred, either during the late stages of a major carbonation event or during a brief, subsequent aqueous alteration event unrelated to carbonation.

^1,2S. R. Sutton,¹A. Lanzirotti,¹M. Newville,^3,4M. D. Dyar,⁵M. McCanta, ANGSA Team
Journal of Geophysical Research: Planets (in Press) Link to Article [https://doi.org/10.1029/2025JE009416]
¹Center for Advanced Radiation Sources, The University of Chicago, Chicago, IL, USA
²Department of the GeophysicalSciences, The University of Chicago, Chicago, IL, USA
³Planetary Science Institute, Tucson, AZ, USA
⁴Department ofAstronomy, Mount Holyoke College, South Hadley, MA, USA
⁵Department of Earth and Planetary Sciences, University ofTennessee, Knoxville, TN, USA
Published by arrangement with John Wiley & Sons

Chromium and vanadium valence measurements were obtained on 17 lunar glass beads from Apollo 15 and 17 regolith materials using microscale X-ray absorption spectroscopy methods. Interior Cr valences ranged from 1.97 ± 0.02 to 2.88 ± 0.02 (Cr2+ to Cr3+). Interior V valences ranged from 2.82 ± 0.02 to 3.76 ± 0.10 (V2+/V3+ mix to V3+/V4+ mix). The interior valences of most beads cluster near V3+ and Cr2+/Cr3+ ≅ 0.6, that is, close to valences expected at IW-1, but there is significant variability and several outliers exist. For main cluster beads, Cr valence-inferred fO2 ranged from IW-1.5 to IW+1. These beads have V valence-inferred fO2 ranges from IW-2 to IW. These ranges significantly overlap but V tends to be slightly more reduced than Cr, suggesting there could be some decoupling of the Cr and V barometers. Valences for the Apollo 15 glass beads are tightly clustered, as are the Apollo 17 bottom drive tube samples 73001. In contrast, the Apollo 17 upper-drive tube samples 73002 are variable. Cr in the bead rims tended to be oxidized relative to the interiors, whereas V tended to show no redox difference between the rims and interiors. Processes responsible for establishing the redox states of the rims must be complex. Apparent fO2 conditions inferred from Cr valence tended to be slightly more oxidized than those inferred from V. Parental magmas may have possessed variable compositions that in turn experienced varying degrees of assimilation of Cr3+-rich phase(s). Valence-altering secondary processes may also have been significant.

¹Sayantan Guha,¹Shiba Shankar Acharya,²Mruganka Kumar Panigrahi
Journal of Geophysical Research: Planets (in Press) Link to Article [https://doi.org/10.1029/2025JE009601]
¹Department of Geology, Presidency University, Kolkata, India
²Department of Geology and Geophysics, Indian Instituteof Technology, Kharagpur, India
Published by arrangement with John Wiley & Sons

The western Kutch basin, India, provides a unique window into aqueous alteration under extreme acid-sulfate conditions. While previous research focused primarily on the Matanomadh Formation, this study presents a systematic investigation of hydroxy-sulfate minerals-including jarosite, alunite, minamiite, gypsum-across several chronostratigraphic units, spanning the pre-Deccan Ghuneri Member (Late Cretaceous) through post-Deccan formations (Matanomadh, Naredi, Harudi). Using a comprehensive analytical suite (XRD, XRF, FTIR, Raman, SEM-EDS, δ34S) and laboratory-synthesized potassium jarosite dissolution experiments, this work provides a complete solution to the source, formation, and preservation of these minerals. Isotopic data identify the primary source of iron and sulfur as the oxidation of precursor pyrite by meteoric water. A significant finding is the documentation of a natural natrojarosite–natroalunite solid solution, where Al-substitution enhances structural stability, making Na-jarosite more abundant than K-jarosite. Notably, field associations and geochemical data indicate that host-rock composition exerts only a minor influence on the formation of these jarosites. Crucially, our data reveal that the formation of these hydroxy-sulfate phases cannot be attributed to a single geological event or a specific past timeframe. Instead, we demonstrate that these minerals are geologically recent and continue to form as an ongoing process under current environmental conditions. The long-term preservation of these assemblages is primarily governed by the region’s prevailing aridity and localized mineral buffering associated with their mode of occurrence along the fractures of host rock. The discovery of the natrojarosite–natroalunite solid solution provides key insights into acid-sulfate system evolution on both Earth and Mars.

¹Yaozhu Li,¹Phil J. A. McCausland,¹Roberta L. Flemming,¹Callum J. Hetherington,¹Bo. Zhao
Journal of Geophysical Research: Planets Open Access Link to Article [https://doi.org/10.1029/2026JE009662]
¹Department of Earth Sciences, Western University, London, ON, Canada, 2Department of Geosciences, Texas TechUniversity, Lubbock, TX, US
Published by arrangement with John Wiley & Sons

Ureilites are ultramafic achondrites for which the parent body is unknown. Monomict ureilites, consisting primarily of olivine and pyroxene, are thought to represent mantle residues, carrying essential information for their parent body deformation history. All monomict ureilites are found to be shocked variously, complicating the interpretation of their deformation history. In this work, four monomict ureilites, Elephant Moraine 96042, Northwest Africa 2221, Larkman Nunatak 04315, and Alan Hills A81101, are examined using electron backscatter diffraction to study shock-related and post-shock microstructural development in the strained olivine. We calculated the unit segment length (USL) to quantify the subdomain development in those olivine grains, and we further applied a modified misorientation index to study the role of shock in subdomain misorientation. A positive trend of increasing USL with increasing shock level is identified, indicating increased microstructural subdivision and decreasing subdomain size with increasing shock deformation. In LAR 04315 and ALH A81101, the development of low-angle subdomain boundaries defines an apparent foliation, consistent with a non-instantaneous, high-temperature deformation overprint following shock. Together, these results demonstrate that EBSD-derived microstructural metrics provide a robust, quantitative framework for distinguishing shock-related deformation from post-shock microstructural modification in ureilitic olivine.

^1,2Kewei Shen, ¹Panming Xue, ¹Duojun Wang, ¹Rui Zhang, ²Guangchao Chen, ¹Kexuan Zhang, ¹Liang Wei
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2026.117132]
¹High Pressure Experiment Science Center, College of Earth and Planetary Sciences, University of Chinese Academy of Sciences, Beijing, China
²College of Materials Science and Optoelectronic Technology, University of Chinese Academy of Sciences, Beijing, China
Copyright Elsevier

The Moon shows marked differences in geophysical and geological properties between its nearside and farside, long attributed to internal thermal state. However, the present-day lunar thermal gradient remains poorly constrained. In this study, we measured the thermal conductivity and diffusivity of lunar mantle olivine under 0.5–4.0 GPa and 298–1273 K, demonstrating that lattice conduction was the dominant heat transport mechanism. Combining with regional variation parameters including crustal thickness, radiogenic heat production, and modeled surface heat flow, we constructed thermal profiles for distinct lunar regions. Our results revealed a significant nearside-farside thermal asymmetry, with temperature differences reaching ~79–180 K at depth. Elevated nearside mantle temperatures suggested that partial melting may still persist at depths greater than ~700 km. This localized partial melting likely contributes to the observed low seismic velocity and high electrical conductivity anomalies, as well as the occurrence of deep moonquakes beneath the nearside.

¹Evgeniya V. Petrova,¹Victor I. Grokhovsky,²Anna Kartashova
Icarus (inPress) Link to Article [https://doi.org/10.1016/j.icarus.2026.117147]
¹Ural Federal University, Mira Str., 19/5, 620002 Ekaterinburg, Russia
²Institute of Astronomy RAS, Pyatnitskaya Str., 48, 119017 Moscow, Russia
Copyright Elsevier

Fragmentation, ablation and significant loss of mass occur when the meteoroid passes through the Earth’s atmosphere. There a combined action of melting and shearing takes place, so a fusion crust is forming on the surface of the fragments. It combined a subsurface layer of heated matter and an outer layer consisting of remaining melted meteoroid substance.
In this publication we focused on the process of ablation from different points of view: i – registered spectra of fireballs; ii – fusion crust composition study; iii – ablation modeling ground experiments.

¹Koske Matsubara,¹Yukari Yamaguchi,¹Akiko M. Nakamura,²Sunao Hasegawa,³Takafumi Niihara,^4,5Takehiko Wada
Icarus (in Press) Open Access Link to Article [https://doi.org/10.1016/j.icarus.2026.117135]
¹Department of Planetology, Kobe University, 1-1 Rokkodai-cho, Nada-ku, Kobe 657-8501, Japan
²Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 3-1-1 Yoshinodai, Chuo-ku, Sagamihara, Kanagawa 252-5210, Japan
³Department of Applied Sciences, Okayama University of Science, 1-1 Ridai-cho, Kita-ku, Okayama-City, Okayama 700-0005, Japan
⁴National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan
⁵Astronomical Science Program, The Graduate University for Advanced Studies, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan
Copyright Elsevier

The presence of water on the Moon and on asteroids that are thought to be poor in water, either because they formed inside the snow line or because they lost much of their water during differentiation, has been suggested by multiple studies; however, its form and origin remain unclear. In this study, we conducted hypervelocity impact experiments between serpentinite projectiles and steel targets. Serpentinite contains hydroxyl and simulates hydrated impactors such as primitive asteroids. The effects of impact velocity and angle on the survival and form of water delivered to the target surface were investigated using near-infrared reflectance spectroscopy and microscopic Raman spectroscopy. Reflectance spectra of projectile materials adhered to the crater surfaces suggested that, in all head-on impact experiments with velocities of 3–7 km s−1, hydroxyl pre-existing in the projectile was almost completely lost. The spectra also showed olivine absorption features at shock pressures exceeding ~80 GPa, and the olivine Raman peaks became narrower at higher impact velocities. Based on the comparisons with results from impact experiments with anhydrous projectiles, it is suggested that molecular water can be trapped in the melt at shock pressures below ~100 GPa. In contrast, in the oblique impact experiments conducted in this study, decomposition of projectile material was suppressed, and hydroxyl was detected in crater samples. The current results, along with comparisons to impact velocities of asteroids in the main belt and on the Moon, suggest that molecular water derived from hydrated impactors can be detectable through spectroscopic observations.

^1,2,3D. Tovar et al. (>10)
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2026.117133]
¹Planetary Sciences and Astrobiology Research Group (GCPA), Universidad Nacional de Colombia and Corporación Científica Laguna, 111321 Bogotá, Colombia
²Departamento de Geología, Geografía y Medio Ambiente, Universidad de Alcalá, 28805 Alcalá de Henares, Spain
³Departamento de Geociencias, Universidad Nacional de Colombia, 111321 Bogotá, Colombia
Copyright Elsevier

The identification of terrestrial analogs is a key strategy for advancing our understanding of the geological and geochemical evolution of Mars. This study evaluates the potential of Gorgona Island (Colombian Pacific) as a geochemical analog of Syrtis Major. Gorgona Island hosts a diversity of mafic and ultramafic lithologies, including basalts, gabbros, picrites, dunites, wehrlites, and also komatiites, which are the youngest reported on Earth. To assess the degree of compositional similarity, a meta-analysis of previously published data was conducted, comparing geochemical information from Gorgona Island with that derived from orbital instruments on Mars (TES, GRS, OMEGA, and CRISM) and from SNC meteorites. The analysis focused on classical discriminant ratios (Al₂O₃/TiO₂) and Compositional Figures of Merit (FOMc), applied both to individual datasets and to averaged values weighted by the areal proportion of lithologies on Gorgona Island. The results show that enriched and depleted basalts, along with Spinifex-Textured komatiites (containing <18% MgO), exhibit a high degree of geochemical similarity with Syrtis Major (FOMc >0.87), whereas dunites and wehrlites consistently display low values. The positive slope of the Al₂O₃/TiO₂ ratio observed in both Gorgona and Mars is characteristic of MORB-type oceanic crust, reinforcing the link between Terrestrial MORB/OIB and Martian Basalts described by previous studies. These findings highlight Gorgona Island as a robust terrestrial analog of Syrtis Major, providing a natural laboratory for investigating magmatic processes relevant to Mars. Furthermore, this work outlines future directions, including the acquisition of new high-resolution geochemical data from Gorgona Island and the integration of recent in situ data from Mars, with the aim of refining comparative models of planetary magmatism.

¹Shaofan Che, ¹Adrian J. Brearley
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2026.04.034]
¹Department of Earth and Planetary Sciences, University of New Mexico, Albuquerque, NM 87131, USA
Copyright Elsevier

Evidence of low-temperature aqueous alteration is extremely limited in CO (Ornans-type) chondrites: only a minor amount of phyllosilicates have been reported in a few members of the CO chondrite group. This observation seems to be at odds with the fact that CO chondrites of higher petrologic types (≥CO3.2) are widely affected by metasomatism. Deciphering the timing and role of fluid activities is thus a prerequisite to a comprehensive understanding of the secondary alteration history of CO chondrites. In this study, we report the widespread occurrence of submicron-sized, segmented metal assemblages in the matrix of Dominion Range (DOM) 08006, the most pristine CO chondrite known that is classified as type 3.00. The Fe,Ni metal grains are kamacite (α-Fe, body-centered cubic, bcc) that are segmented by lamellae of C-bearing material that define crystallographically controlled alteration interfaces parallel to {110} planes of the kamacite lattice. The segmented metal subgrains are rimmed by two nanometer-wide layers that are composed of an inner, Ni-enriched layer and an outer, amorphous Fe-O layer. Transmission electron microscopic data for the C-bearing regions are consistent with amorphous carbon which encloses nanoparticles of ferrihydrite.
The spatial association between metal and C-bearing regions in the segmented metal assemblages suggests that the precursor phase of the amorphous carbon in the C-bearing regions was likely mobilized during aqueous alteration of the metal on the parent body of DOM 08006. The association of ferrihydrite nanocrystals with amorphous carbon in DOM 08006 likely reflects a coprecipitation process analogous to that observed in terrestrial soils, where oxidation of Fe,Ni metal under near-neutral to slightly acidic aqueous conditions produces Fe3+-bearing hydroxides that complex with dissolved organic matter. This aqueous fluid was most likely generated by melting of water ice that accreted together with organic matter as composite particles. Therefore, the matrix metal in DOM 08006 has recorded incipient aqueous alteration on the CO3 chondrite parent body prior to the onset of thermal metamorphism. However, this aqueous alteration event only affected DOM 08006 to a subtle extent, probably due to the minor amount of fluid available for alteration. Our study of DOM 08006, combined with observations from previous studies of CO chondrites, further suggests that a small amount of low-temperature aqueous fluid could be present on the CO chondrite parent body, resulting in limited effects of aqueous alteration