¹S. S. Russell et al. (>10)
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.70151]
¹Planetary Materials Group, Natural History Museum, London, UK
Published by arrangement with John Wiley & Sons

Aqueously altered carbonaceous astromaterials are dominated by secondary minerals, but a minor fraction of primary, anhydrous silicates and oxides escape alteration, offering insight into the original composition of asteroid parent bodies. We report the mineralogy, petrology, mineral chemistry, and oxygen isotopes of anhydrous minerals—50 olivine grains, 12 pyroxene grains, two spinel grains, and one hibonite grain—in aqueously altered particles returned from asteroid Bennu by the OSIRIS-REx mission. These primordial grains are heterogeneously distributed, being more abundant (up to a few area percent for olivine) in less aqueously altered clasts. Olivine is typically forsteritic (Fo100–Fo93), but we found three fayalitic examples (Fo80–Fo75). Of the pyroxenes, seven grains are enstatite (En100–En94); two are enstatite with more Fe (En83 and En87); one is Fe-rich, low-Ca clinopyroxene; one is Mg-rich, aluminous low-Ca pyroxene; and one is high-Al, Ca-rich clinopyroxene. Chromium is present in olivine grains at high abundances (up to 1.3 wt% Cr2O3), indicating that the grains have not experienced significant thermal metamorphism. The olivines fall into two clusters: one with 16O-rich compositions (δ18O = −43 to −51‰) typical of refractory inclusions in carbonaceous chondrites and one with comparatively 16O-poor compositions (δ18O = −11 to +7.5‰) more typical of chondrules. Pyroxenes all fall in the 16O-poor cluster (δ18O = −2.6 to +13.5‰). For both olivine and pyroxene, the more Fe-rich examples are associated with heavier oxygen isotope compositions. One isolated spinel grain has an oxygen isotope composition typical of Ca-Al–rich inclusions, whereas a spinel–hibonite object has an unusual oxygen isotope composition consistent with fractionated unknown nuclear (FUN) compositions. Together, our data suggest that Bennu’s parent body accreted a population of finer grained (≤10 μm) silicate and oxide grains that as a population are distinct from the anhydrous minerals in most chondrite groups but comparable to those in CI chondrites. The Bennu samples, as well as those from asteroid Ryugu and CI chondrites, appear to have accreted from a distinct reservoir that may have been in the outer protoplanetary disk.

^1,2Cheng-Yu Du, ^1,2Shao-Bing Zhang, ³Hejiu Hui, ¹Ting Liang, ¹Wan-Cai Li, ¹Yong-Fei Zheng
Geochimica et Cosmochimica Acta (in Press) Link to Article [10.1016/j.gca.2026.05.006]
¹State Key Laboratory of Lithospheric and Environmental Coevolution, School of Earth and Space Sciences, University of Science and Technology of China, Hefei 230026, China
²Deep Space Exploration Laboratory/School of Earth and Space Sciences, University of Science and Technology of China, Hefei 230026, China
³State Key Laboratory for Mineral Deposits Research & Lunar and Planetary Science Institute, School of the Earth Sciences and Engineering, Nanjing University, Nanjing, China
Copyright Elsevier

China’s Chang’E-5 (CE-5) lunar mission retrieved the youngest known mare basalt with low magnesium number (Mg#) and high incompatible element contents. However, the nature of its mantle source remains debated. Here we carried out in-situ analyses of major and trace element contents in olivine and pyroxene for CE-5 basalt clasts to constrain the petrogenetic process and mantle source of CE-5 basalt. The results indicate that the pyroxene Ti# (molar Ti/(Ti + Cr)) rose sharply at an early stage into the high-Ti basalt field and subsequently remained constant, implying extensive fractional crystallization of the CE-5 basalt. The near constant Ti content in olivine records an early crystallization of ilmenite at an olivine Mg# of approximately 60. Calculated TiO2 and Cr2O3 contents of the melt equilibrated with the most forsteritic olivine yielded TiO2 content of 6.06 ± 0.77 wt% and Cr2O3 content of 0.516 ± 0.089 wt%. Pyroxene exhibits concurrent decreases in LREE/HREE ratios, Zr/Y ratio and Al content as its Mg# decreases, whereas the early decrease of olivine Zr/Y ratio indicates a primitive melt with high Zr/Y ratio. Integrating these findings with previously reported isotopic data, theoretical modelling supports a hybrid mantle source dominated by orthopyroxene cumulate, with a small proportion of ilmenite-bearing cumulate (IBC, 0.40–0.55%) and KREEP (0.11–0.15%). Such a source region supports a geodynamic mechanism for the young mare magmatism that the IBC-rich hot plume rises from the core-mantle boundary heating the upper mantle that contains small amounts of IBC and KREEP to melt.

¹Hisayoshi Yurimoto et al. (>10)
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.70158]
¹Department of Natural History Sciences/IIL, Hokkaido University, Sapporo, Japan
Published by arrangement with John Wiley & Sons

NASA’s OSIRIS-REx mission delivered pristine regolith samples from the near-Earth carbonaceous asteroid (101955) Bennu, enabling direct assessment of primitive asteroid material free from terrestrial alteration. We report comprehensive analyses of H, C, O, S, Cl, and Hg in Bennu samples using X-ray fluorescence (XRF), thermogravimetric analysis coupled with mass spectrometry (TG-MS), combination analyses of pyrolysis and combustion (EMIA-Step), and direct Hg measurements. Quantification of O, Si, S, Cl, and Ge by XRF is reported for Bennu samples for the first time. TG-MS reveals ~15 mass% total mass loss, with H2O and CO2 release patterns attributed to phyllosilicates, carbonates, and organic matter. Bennu samples contain substantially higher interlayer H2O than those from asteroid Ryugu, consistent with subsurface deeper sampling by OSIRIS-REx. Total carbon abundance is ~4.1 mass%, dominated by organic carbon (~2.9 mass%), comparable to Ryugu samples. Mercury abundances (82–141 ng g−1) are far lower than those reported for CI chondrites, indicating pervasive terrestrial contamination in meteorite samples. We recommend a Hg abundance of 98 ± 2 ng g−1 for Bennu samples and pristine CI-like material, demonstrating that returned asteroid samples provide the most reliable record of primitive carbonaceous matter.

¹Sohei Wada,¹Ken-ichi Bajo,¹Hisayoshi Yurimoto
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.70161]
¹Department of Earth and Planetary Sciences, Hokkaido University, Sapporo, Japan
Published by arrangement with John Wiley & Sons

The surfaces of small celestial bodies are continuously modified by spaceweathering and surface gardening, yet their interaction remains poorly understood due toobservational gaps between micrometer and centimeter scales. Here we analyzed thetwo-dimensional distribution of helium in the carbonaceous chondrite NWA 801 (CR2)using the LIMAS secondary neutral mass spectrometer with micrometer resolution. Theresults show that 4He is concentrated mainly in the fine-grained matrix, forming a distinctHe-rich network surrounding He-poor fine-grained regions. This structure suggests thatspace-weathered particles were transported into the subsurface. The process may involve agranular convection driven by impact-induced vibrations. It likely occurred during the earlysolar system on time scales of 10,000 years and at depths ranging from tens of centimetersto meters. Such mixing repeatedly exposed fresh material to solar wind irradiation,producing three-dimensional 3He-enriched deposits rather than purely surface-limitedaccumulations. These findings provide direct microstructural evidence for the dynamiccoupling between space weathering and surface gardening and highlight a potentialmechanism for forming solar wind–derived helium and hydrogen resources on small celestialbodies.

^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.