^1,2Takuma Sumitani, ^1,3Kohei Fukuda, ^4,5Takayuki Ushikubo, ⁶Rei Kanemaru, ⁷Noriko T. Kita, ⁸Koki Tsutsui, ⁹Changkun Park, ⁹Hwayoung Kim, ⁹Pilmo Kang, ¹Kentaro Terada
Geochimica et Cosmochimica Acta (in Press) Open Access Link to Article [10.1016/j.gca.2026.04.046]
¹Department of Earth and Space Science, Graduate School of Science, The University of Osaka, Toyonaka, Osaka, Japan
²Department of Earth and Planetary Science, Graduate School of Science, The University of Tokyo, Bunkyo, Tokyo, Japan
³Forefront Research Center, Graduate School of Science, The University of Osaka, Toyonaka, Osaka, Japan
⁴Kochi Institute for Core Sample Research, Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Nankoku, Kochi, Japan
⁵Marine Core Research Institute, Kochi University, Nankoku, Kochi, Japan
⁶Institute of Space and Astronautical Science (ISAS), Japan Aerospace Exploration Agency (JAXA), Sagamihara, Kanagawa, Japan
⁷WiscSIMS, Department of Geoscience, University of Wisconsin-Madison, Madison, Wisconsin, USA
⁸Department of Earth Sciences, Tohoku University, Sendai 980-8578, Japan
⁹Division of Glacier & Earth Sciences, Korea Polar Research Institute (KOPRI), Incheon 21990, the Republic of Korea
Copyright Elsevier

The isotopic dichotomy in the bulk meteorites suggests limited mixing between the non-carbonaceous (NC) and carbonaceous (CC) reservoirs. However, recent multi-isotope analyses of chondrules revealed mixing across this separation. Understanding the efficiency of the mixing process between the two reservoirs is crucial for revealing the diversity and evolution of solar system bodies. In this study, we analyzed the oxygen (O) isotopic compositions of fifteen chemically and petrographically rare chondrules, including FeO-rich chondrules (Mg# < 98) relative to the majority of FeO-poor chondrules (Mg# ≥ 98) in CV chondrites, dusty olivine chondrules, an enveloping compound chondrule, layered chondrules, and barred olivine (BO) chondrules, from the NWA 6991 (CV3) carbonaceous chondrite. The FeO-rich chondrules and dusty olivine chondrules constitute ∼5% of the NWA 6991 chondrule population. Among them, the O-isotopic compositions of four FeO-rich and two dusty olivine chondrules were analyzed, and all of them exhibit NC-like O-isotopic signatures with the host Δ17O values (=δ17O − 0.52 × δ18O) ranging from −0.5 ± 1.1‰ to +0.4 ± 0.7‰ (2σ), suggesting formation in the NC reservoir and subsequent transport outward into the CC reservoir. The other dusty olivine chondrule, Ch63, shows O-isotopic variations among constituent minerals, including NC-like dusty relict olivines in the interior (Δ17O = 0.5 ± 2.4‰; 2SD), CC-like olivine rims (Δ17O = −6.1 ± 2.0‰; 2SD), and NC-CC intermediate high-Ca pyroxene (Δ17O = −0.8 ± 2.2‰; 2SD). This O-isotopic characteristic suggests that the precursors of this chondrule formed in the NC reservoir and were then transported outward, where they experienced O-isotopic exchange with 16O-richer ambient gas than the NC-like precursor dust during partial melting in the CC reservoir. The enveloping compound, layered, and BO chondrules exhibit CC-like host Δ17O values (−5.8 ± 0.7‰ ≤Δ17O ≤ −2.3 ± 0.8‰; 2σ), despite previous evidence of NC-like Cr and Si isotopic compositions. The uniformly CC-like O-isotopic compositions of layered and BO chondrules studied here also suggest that these objects experienced O-isotopic exchange between NC-like precursor dust and 16O-rich ambient gas that was generated from refractory inclusions and/or earlier generations of CC chondrules. Importantly, the O-isotopic compositions of layered chondrules and olivine rims of the dusty olivine chondrule Ch63 are consistent with the majority of FeO-poor CV chondrules, indicating that the majority of CV chondrules formed from isotopically diverse precursors, but in a common O-isotopic reservoir that is characterized by Δ17O ∼ −5‰. The presence of ≥5% chondrules that are probably related to NC-like materials in the CV chondrite NWA 6991 infers that the CV chondrite parent body incorporated a larger fraction of chondrules that were transported outward from the NC reservoir than the other CC chondrite parent bodies. The higher abundance of NC-like materials compared to other CC chondrites suggests that the CV chondrite parent body accreted in a region closer to the NC reservoir, possibly near the H2O snowline.

^1,2,3D. P. Moriarty III,¹N. E. Petro,¹B. A. Cohen
Journal of Geophysical Research: Planets Open Access Link to Article [https://doi.org/10.1029/2025JE009429]
¹NASA GSFC, Greenbelt, MD, USA
²University of Maryland, College Park, MD, USA
³Center for Research andExploration in Space Science and Technology, Greenbelt, MD, USA
Published by arrangement with John Wiley & Sons

Several national space agencies and commercial entities are currently targeting the Moon’s south polar region for human and robotic exploration. Of particular interest are materials excavated and ejected from the Moon’s largest and oldest impact structure, the South Pole-Aitken Basin (SPA), as these ancient materials are a window into the early history of the Moon. SPA ejecta and impact melt are associated with the presence of Fe, Th, and pyroxene minerals. Mons Kocher, within the NASA Artemis exploration zone, exhibits elevated Fe, Th, and pyroxene abundance and presents a viable opportunity for Artemis astronauts to sample SPA material. Using orbital hyperspectral data from the Moon Mineralogy Mapper, we investigated the distribution of mafic minerals across the Mons Kocher region. We identified two types of mafic-bearing units: small (∼300 m) craters and sun-facing slopes. Spectral properties of the small craters (as well as the nearby ∼21 km Kocher crater) are consistent with low-Ca pyroxene, whereas the illuminated slopes exhibit similar pyroxenes with possible signatures of hematite-driven space weathering. Using least cost path models, we generate optimized traverse paths to the mafic craters through integration of topographic slope, average Earth visibility, and average solar illumination data.

^1,2Sean Czarnecki,¹Craig Hardgrove,³Liz Rampe,²Patrick Gasda
Journal of Geophysical Research: Planets Open Access Link to Article [https://doi.org/10.1029/2025JE009199]
¹Arizona State University, Tempe, AZ, USA
²Los Alamos National Laboratory, Los Alamos, NM, USA
³NASA JohnsonSpace Center, Houston, TX, USA
Published by arrangement with John Wiley & Sons

Both water and organic matter are required for the development and persistence of life.Phyllosilicates (clay minerals) have high surface areas that easily sorb water and organic matter. The Curiosityrover has investigated several hundred meters of stratigraphy in Gale crater, including where clays weredetected from orbit. Previous results have suggested that subsurface hydration is greatest in units with the mostabundant clays, suggesting that these minerals may be hydrated. Organics have also been found throughout Galecrater. Smectites are the most common and abundant phyllosilicates in Gale crater samples and can expand andsorb water and organics in interlayer sites. The most common organic sorption processes on Earth typicallyinvolve water or hydroxyl, so hydrated phyllosilicates are good candidates for organic preservation. Usingnewly derived subsurface hydration results with previously published mineralogy and geochemistry, we derivedmodeled constraints on the abundances of hydrated amorphous phases, “excess” water, and “excess” cations.These “excess” phases are not accounted for by published crystalline phase abundances or by amorphous phasesconstrained here. We found correlations between smectites and both “excess” water and “excess” cationabundances, indicating that smectites in Gale crater are hydrated and that cation bridging could be a mechanismfor sorption of organics. Our results also show the persistence of amorphous sulfates, opal‐A, and volcanic orimpact glass, which indicate low water‐rock interactions. Increased abundances of sulfates and glass instratigraphically higher samples may indicate lower water availability and environmental aridification duringthe time these units were being deposited.

^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/10.1029/2025JE009329]
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

Iron-nickel metals, primarily taenite and kamacite, are major components in most meteorites. Taenite exhibiting the M-shaped Ni profile has traditionally been interpreted as a product of slow cooling and is widely used to estimate the thermal histories of planetary bodies. However, our Electron Backscatter Diffraction analyses of H chondrites reveal that metal grains with M-shaped Ni profiles consist of a low-Ni martensite core surrounded by a high-Ni tetrataenite rim. The presence of martensite, which forms via rapid quenching of taenite, is difficult to reconcile with its formation by slow cooling. Integrating these microstructural observations with the thermal history of H chondrites, we propose that these metal assemblages most likely formed during impact-related reheating events. In this scenario, impact-induced heating facilitates the nucleation and growth of high-nickel tetrataenite along the margins of pre-existing kamacite monocrystals, followed by the formation of lower-nickel taenite in the core. This process results in a metallic assemblage characterized by the M-shaped nickel profile. During subsequent rapid cooling, the taenite core transforms either martensitically into martensite or via spinodal decomposition into duplex plessite. When martensite forms, it inherits the Ni composition of the precursor taenite core, preserving the M-shaped profile. These results suggest that, at least for the samples investigated here, M-shaped Ni profiles may record impact-related thermal processes. The formation of these assemblages requires shock metamorphism of at least stage S3.

^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.