^1,2Xiaofeng Lu, ³Olivier Namur, ¹Yongjiang Xu, ⁴Bernard Charlier, ¹Yanhao Lin
Earh and Planetary Science Letters 690, 120123 Open Access Link to Article [https://doi.org/10.1016/j.epsl.2026.120123]
¹Lin Earth and Planetary Laboratory, Center for High pressure Science and Technology Advanced Research, Beijing, 100193, China
²School of Earth Sciences and Resources, China University of Geosciences, Beijing, 100083, China
³Earth and Environmental Sciences, KU Leuven, 3001, Leuven, Belgium
⁴Department of Geology, University of Liège, 4000, Sart Tilman, Belgium
Copyright Elsevier

Chemical data from the MESSENGER spacecraft reveal that Mercury’s lavas are unusually sulfur-rich, suggesting highly reduced conditions during their formation. As a major volatile, sulfur profoundly affects the physical and chemical properties of silicate melts, potentially impacting key processes such as magma ocean crystallization and mantle melting. Here we conducted near-liquidus experiments (1650–2000 °C and 3–5 GPa) to quantify the effect of sulfur on phase relations in olivine- and orthopyroxene-saturated mafic compositions representative of Mercury’s mantle. Our results show that elevated sulfur contents (up to 6 wt.% S) can depress the liquidus of Mercurian mantle by up to 200 °C. The liquidus depression of silicate melt is positively correlated with sulfur concentrations, negatively correlated with pressure, and compositionally-sensitive with a larger S-effect on higher Mg/Si melt. Using a newly developed parameterization for sulfur-bearing melting, we show that the mantle potential temperatures required to produce the volcanic provinces are lower than previously estimated. Furthermore, modeling of magma ocean cooling and crystallization dynamics indicates that sulfur-induced liquidus depression can extend solidification timescales by tens to hundreds to thousands of years, especially beneath an insulating graphite crust (>100 m). Using viscosity models, we find that sulfur also reduces the critical crystal size for settling, thus promoting fractional crystallization and formation of a chemically stratified mantle. These findings provide critical constraints on Mercury’s interior structure and show that sulfur lowers the solidus and liquidus, enhances melt production, and helps to explain Mercury’s fertile mantle, extensive crustal formation, and diverse surface lavas.

¹Ioana-Bogdana Radu, ¹Cécile Deligny, ¹Henrik Skogby, ²Roland Stalder, ¹Jeremy J. Bellucci, ¹Martin J. Whitehouse
Geochimica et Cosmochimica Acta (in Press) Open Access Link to Article [10.1016/j.gca.2026.06.002]
¹Department of Geosciences, Swedish Museum of Natural History, Box 50007, SE-104 05 Stockholm, Sweden
²Institut für Mineralogie und Petrographie, Universität Innsbruck, Innsbruck 6020, Austria
Copyright Elsevier

Water on Mars has traditionally been estimated from hydrogen contents in melt inclusions and apatite, yet these may not account for magma degassing or post-crystallization dehydration. Pyroxenes offer an alternative approach, as they incorporate trace amounts of water during crystallisation via charge-balancing structural defects, that are retained after dehydration enabling experimentally reversing water loss and constraining magmatic water contents. Here we report the first hydrothermal rehydration experiments on pyroxene from both nakhlites and shergottites. The treated nakhlite augites contain 140‒185 ppm H2O, consistent with previous values for Nakhla (130 ± 26 ppm) and within the range of terrestrial basaltic pyroxene. Using clinopyroxene-melt partition coefficients, this corresponds to 1.59 ± 0.03‒1.83 ± 0.10 wt% average H2O in the nakhlite magma, slightly higher than previous estimates (0.69‒1.42 wt% H2O). The complex hydrothermal history of nakhlites, including evidence for magmatic degassing and interaction with H2O-poor, Cl-rich fluids, suggests these estimates may represent minimum values of the nakhlite magmatic water content. Assuming a low degree of partial melting, the nakhlite mantle source is expected to contain 80‒91 ppm H2O, overlapping previous estimates (59‒184 ppm), and comparable to Earth’s MORB mantle (54‒330 ppm). This is consistent with a common magmatic source for all nakhlites, and broadly consistent with water estimates for the chassignite mantle source (39‒252 ppm), suggesting that any exogenous fluid assimilation had a negligible effect on the net water budget. In contrast, shergottite pigeonites show no detectable water by Fourier Transform Infrared Spectroscopy, consistent with expected water contents of ∼ 2‒11 ppm H2O derived from published source compositions for depleted and enriched shergottites. Together, these results refine our understanding of Martian magmatic water content, consistent with a common, more water-rich mantle source for nakhlites, distinct from the more heterogeneous and generally drier shergottite mantle reservoirs

¹S. A. Singerling
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.70177]
¹Schwiete Cosmochemistry Laboratory, Goethe University, Frankfurt, Germany
Published by arrangement with John Wiley & Sons

This study documents micro- to nanoscale observations of primary nebular and secondary parent body iron sulfides in the CR1 GRO 95577. Despite the extensive alteration of the bulk sample, some primary sulfides managed to avoid alteration, having originally formed in the solar nebula during chondrule formation by either fission-sulfidization or crystallization. Secondary sulfides formed by precipitation from a fluid during aqueous alteration on the parent body and show features such as lath-like or euhedral morphologies, fine-scale intergrowths with serpentine, and porosity in pyrrhotite. Microstructures in pentlandite are most consistent with formation via impact-induced shock. Experiments have the potential to better constrain the effects of shock on pentlandite. Given pentlandite’s ubiquity in both minimally and heavily altered meteorites, it has the potential to be used as a shock indicator for samples otherwise ill-suited to shock determination (i.e., heavily aqueously altered materials).

^1,2Jennifer T. Mitchell,^3,4Natasha R. Stephen,¹Zsuzsanna P. Allerton,¹Weiming Ding, Xin-Yuan Zhe
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.70181]
¹N.H. Winchell School of Earth & Environmental Sciences, University of Minnesota, 116 Church St SE, Minneapolis,Minnesota, 55455, USA
²Characterization Facility, University of Minnesota, 100 Union St, Minneapolis, Minnesota, 55455, USA
³The Geological Society of London, Burlington House, Picadilly, London, W1J 0BG, UK
⁴Department of Earth Science & Engineering, Imperial College London, Exhibition Road, London, SW7 2AZ, UK
Published by arrangement with John Wiley & Sons

This study provides an initial characterization of Stardust Mine, a fresh gabbroic enriched shergottite collected in Arizona, USA, in September 2024 and is the first Martian meteorite to be unequivocably collected on US soil. Analysis was conducted on the type specimen and finds that Stardust Mine is composed of equal proportions of pyroxene and maskelynite, with large Fe-Ti oxides and phosphates. Ti/Al ratios and two-pyroxene thermometry of the most primitive pyroxenes (Mg# >57), inferred to represent preplagioclase pyroxene crystallization, give an estimated minimum initial crystallization depth of ~40 km at ~1140°C. Sector zoning is restricted to these pyroxenes and may have developed through magmatic undercooling in response to magma ascent before storage in a staging chamber in the volcanic system. Pyroxene and plagioclase cocrystallized for almost the entirety of the crystallization sequence with evolving melt compositions, followed by phosphates and Fe-Ti oxides. Ilmenite-titanomagnetite pairs and D(Cr)pyroxene suggest the magma was relatively oxidized (fO2 ΔQFM −1.3) compared with other shergottites. Accumulation and crystal settling in a sill, dyke, or intracrustal magma chamber allowed the development of a shape-preferred orientation and decomposition of metastable pyroxenes to three-phase symplectites. Stardust Mine represents a highly fractionated lithology that extends the range of high-Al basaltic shergottites to ~8 wt% Al. Our analysis does not find a clear pairing with shergottites in literature in lieu of radiogenic isotope data, and Stardust Mine may therefore represent a previously unsampled lithology.

¹V. E. Hamilton et al. (>10)
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.70176]
¹Southwest Research Institute, Boulder, Colorado, USA
Published by arrangement with John Wiley & Sons

Remote spectroscopy is used to characterize the mineralogy and infer the history of planetary bodies. Carbonaceous asteroids, such as B-type (101955) Bennu, represent the earliest stages of planet formation. B types have a blue (negative) spectral slope and comprise <5% of asteroids. Samples from Bennu returned by the OSIRIS-REx spacecraft complement remote observations of this rare population. We show here, using laboratory spectra that are directly comparable to spacecraft data, that OSIRIS-REx accurately determined Bennu’s dust content and most of its surface composition. However, spectra of the asteroid exhibit stronger water absorptions than those of bulk samples, possibly due to hydrous, Mg-rich phosphate or solar wind implantation at Bennu’s uppermost surface. Bennu samples spectrally resemble the most aqueously altered carbonaceous meteorites and samples of (162173) Ryugu, indicating similarly pervasive aqueous alteration. However, one carbon-enriched Bennu stone does not appear to have a spectral analog among Ryugu samples or meteorites. Our findings demonstrate the leverage obtained using a wide range of wavelengths and that sample analysis anchors the interpretations of remote sensing, leading to more robust characterization of planetary surface composition and evolution.

¹Raiza R. Quintero,²Aaron J. Cavosie,³Noreen J. Evans,³Bradley J. McDonald,⁴Sanna Alwmark,²Nicholas E. Timms,⁵Malcolm P. Roberts,⁶Jayson Meyers
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.70154]
¹Department of Geology, University of Puerto Rico at Mayaguez, Mayaguez, Puerto Rico
²Space Science and Technology Centre, School of Earth and Planetary Science, Curtin University, Perth, Western Australia,Australia
³John de Laeter Centre, Curtin University, Perth, Western Australia, Australia
⁴Department of Geology, Lund University, Lund, Sweden
⁵Centre for Microscopy, Characterisation and Analysis, The University of Western Australia, Crawley, Western Australia,Australia
⁶Resource Potentials LTD PTY, Osborne Park, Western Australia, Australia
Published by arrangement with John Wiley & Sons

The Ora Banda structure in Western Australia is situated within an Archean greenstone terrane known for orogenic gold deposits. It is defined by concentric gravity anomalies up to 4 km in diameter, and gravity and passive seismic data indicate the presence of a central uplift and annular trough. Shatter cones were found in surface samples and drill core during gold exploration. Breccia samples from drill core in the annular trough contain shocked quartz and glass with a projectile component. Planar deformation features (PDFs) were found in 17 quartz grains from suevite, and are oriented along crystallographic orientations typical for shock metamorphism, including $$ and $$, recording shock pressures from 15 to 20 GPa. Analysis of glass in suevite by EMPA and LA-ICP-MS shows the composition is basaltic andesite (avg = 54 wt% SiO₂), with major oxide compositions reflecting mixing of local Archean greenstone target rocks. Average abundances of Ni (2640 ppm), Co (205 ppm), Ir (290 ppb), and other PGEs (Rh, Pd, Pt) in the glass are significantly higher than mafic and ultramafic target rock lithologies and are interpreted to be meteoritic in origin, with Cr-Ir abundances indicating an iron projectile. Previous palynological analysis of crater fill sediments overlying the breccias indicates the impact event was likely Early Cretaceous or older. The Ora Banda structure offers insights into the cratering process near the simple-to-complex size transition, including the first documented occurrence of well-preserved “Ries-type” suevite described from Australia. In addition, Ora Banda represents one of the oldest known sites with strong geochemical evidence for an iron meteorite projectile and is one of few confirmed impact structures formed in an Archean greenstone terrane.

¹Lucas R. Smith,^1,2Pierre Haenecour,¹Jessica J. Barnes,¹Kenneth Domanik,²Mason Neuman,^2,3Kun Wang,²Piers Koefoed,¹Elias Bloch,⁴Ryan Ogliore
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.70166]
¹Lunar and Planetary Laboratory, The University of Arizona, Tucson, Arizona, USA
²Department of Earth and Planetary Sciences, Washington University in St. Louis, St. Louis, Missouri, USA
³McDonnell Center for the Space Sciences, Department of Physics, Washington University in St. Louis, St. Louis, Missouri,USA4 Department of Physics, University of Central Florida, Orlando, Florida, USA
Published by arrangement with John Wiley & Sons

We performed an in-depth study of the mineralogy, petrology, chemical composition, and presolar grain abundance of the C3.00-ungrouped chondrite Chwichiya 002 using a combination of in situ and bulk analytical methods. Chwichiya 002’s bulk composition is significantly enriched compared to CI chondrites (over 20 × CI for Sr, Ba, U) in rare earth and trace elements like Li, Sr, Ba, U, and Pb, indicating effects of terrestrial weathering. Concentrations of Ti and Al are similar to CI chondrites, but notably depleted relative to other carbonaceous chondrite groupings, suggesting that the parent body of Chwichiya 002 accreted from a source with a near CI composition of refractory elements, and with a low quantity of calcium–aluminum-rich inclusions. A slight reduction in Fe is linked to the predominance of FeO-poor chondrules and olivine, likely a remnant of Chwichiya 002’s formation history. Our findings uncovered phyllosilicates in the matrix and combinations of tochilinite–cronstedtite, confirming that Chwichiya 002 underwent more extensive alteration on its parent body than previously believed. We identified 12 O-anomalous presolar grains (8 Group 1, 4 Group 4) and nine presolar SiC grains, with abundances of 12.1 + 4.6/−3.5 ppm for O-rich grains and 7.8 + 3.6/−2.6 ppm for SiC grains. The relatively low occurrence of O-rich presolar grains is similar to what is seen in CM2 chondrites and samples from asteroid 162173 Ryugu, despite Chwichiya 002 being classified as type 3.00 petrologically. We conclude that Chwichiya 002 formed from a refractory-poor source similar to CM and CO chondrites, primarily consisting of FeO-poor chondrules and olivine, and underwent a moderate level of aqueous alteration on its parent body. Furthermore, the mineralogy, petrology, and compositional data reported in this study, combined with previous data on the O-isotopes of Chwichiya 002, suggest that the sample may better be classified as a CM2.8 or CM 2.9 chondrite.

¹L. Perez,¹M. Roskosz,²F. Danoix,¹L. Kern,¹V. Megevand,¹C. Brillatz,³B. Devouard,³J. Gattacceca,¹M. Gounelle
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.70172]
¹IMPMC, Museum National d’Histoire Naturelle, Sorbonne Universite, Paris, France
²Groupe de Physique des Materiaux, CNRS UMR 6634, Universite de Rouen, Saint Etienne du Rouvray, France
³Aix-Marseille Universit´e, CNRS, INRA, IRD, Coll France, CEREGE UM34, Aix en Provence, France
Published by arrangement with John Wiley & Sons

This study provides the first petrographic, crystallographic, and chemical comparison between El Médano 300 (EM 300) and Northwest Africa 8155 (NWA 8155), two particular IAB-ungrouped iron meteorites. Both contain exceptionally large graphite nodules and “flowers”, providing unique insights into carbon behavior in metallic melts and cooling conditions. Despite these similarities, they differ in their petrography, crystallography, and chemical composition. Whereas EM 300 exhibits a homogeneous metallic phase with rounded kamacite grains, originating from at least two taenite crystals, NWA 8155 displays a heterogeneous composition with elongated kamacite crystals, from a unique taenite crystal, along with martensite and residual taenite. Variations in nickel and highly siderophile elements contents point to different degrees of partial melting, indicating in turn formations within two different metallic pools, most probably on separate parent bodies. Troilite textures in EM 300 (spidery), compared to NWA 8155 (bulky), suggest an impact-related origin. Abundant small schreibersite grains in EM 300 indicate faster post-impact cooling. Finally, the absence of silicates in both meteorites suggests efficient metal-silicate segregation or formation within metallic parent bodies. These results provide new insights into the diversity of thermal and collisional histories among IAB-ungrouped iron meteorites, supporting the idea that each one may represent a single parent body and therefore reflecting the diversity of early planetesimal natures and evolutions.

¹Hina Dohi,¹Minako Hashiguchi,¹Koichi Mimura
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.70173]
¹Department of Earth and Environmental Sciences, Graduate School of Environmental Studies, Nagoya University, Nagoya, Japan
Published by arrangement with John Wiley & Sons

A substantial fraction of organic carbon in carbonaceous chondrites has long been described as “missing,” reflecting incomplete recovery and limited resolution of operationally defined organic components. Here, we present a quantitative reassessment of the carbon budget in the Murchison meteorite using an integrated extraction–recovery mass-balance approach that constrains the distribution of carbon among operational fractions. Insoluble organic matter accounts for 69% ± 1.4% of total carbon, while acid-hydrolyzable organic matter (AOM) constitutes 15% ± 2.9%, representing a carbon pool comparable to soluble organic matter (SOM, 14% ± 2.7%). Carbonate-derived carbon accounts for 2% ± 2.0% of the total carbon inventory. The total recovered organic carbon reaches 88% ± 1.4% of bulk carbon. Carbon previously regarded as “missing” can be quantitatively reassigned to specific organic fractions, including uncollected AOM (7%) and SOM (2%), substantially reducing the previously unconstrained carbon fraction. Replicate analyses of three independently processed subsamples yield consistent residue-based carbon partitioning, supporting the robustness of the mass-balance framework. These results indicate that much of the missing carbon reflects incomplete recovery in analytical workflows rather than an unidentified reservoir, refining the organic carbon inventory of Murchison and providing a framework for reassessing carbon partitioning in primitive planetary materials.

^1,2,3Yan Fan,^1,4Deze Liu,^1,5Shijie Li,⁶Xiangdong Li,³Shen Liu,¹Dehan Shen,⁷Qing-Zhu Yin
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.70175]
¹Center for Lunar and Planetary Sciences, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang, China
²Xi’an Center, China Geological Survey, Xi’an, China
³State Key Laboratory of Continental Dynamics and Department of Geology, Northwest University, Xi’an, China
⁴Department of Earth Sciences, University of Oxford, Oxford, UK
⁵Chinese Academy of Sciences, Center for Excellence in Comparative Planetology, Hefei, China
⁶Environmental Engineering Unit, Department of Civil and Structural Engineering, The Hong Kong Polytechnic University,Kowloon, Hong Kong
⁷Department of Earth and Planetary Sciences, University of California at Davis, Davis, California, USA
Published by arrangement with John Wiley & Sons

This study assesses mercury (Hg) concentrations and their isotopic compositions in Antarctic chondrites, desert chondrites, and drilled samples from the Jilin chondrite (H5). Desert chondrites show mercury concentrations between 2.2 ng g−1 and 156.8 ng g−1, with δ202Hg ranging from −3.69‰ to 1.19‰. Δ199Hg and Δ201Hg vary from −0.23‰ to −0.02‰ and −0.2‰ to 0.02‰, respectively, showing a weak positive correlation among these parameters (slope 0.74 ± 0.24, R2 = 0.46). These Hg concentrations and isotopic composition data of desert chondrites indicate that Hg in desert chondrites has been altered due to terrestrial processes in addition to evaporation loss during its terrestrial residence period. Antarctic chondrites exhibit mercury concentrations from 8.0 ng g−1 to 3940.8 ng g−1, with δ202Hg from −2.51‰ to 1.16‰. Δ199Hg and Δ201Hg range from −0.83‰ to −0.05‰ and −0.71‰ to 0.10‰, with a significant correlation (slope 0.93 ± 0.15, R2 = 0.76), likely influenced by Antarctic snow that has experienced significant photochemical processes during atmospheric mercury depletion events (AMDEs) and has elevated mercury content (such as drifted snow). Jilin meteorite’s δ202Hg, Δ199Hg, and Δ201Hg vary between −3.74‰ to −1.79‰, −0.12‰ to 0.09‰, and −0.12‰ to −0.01‰, respectively. A weak positive correlation between Δ199Hg and Δ201Hg (slope 1.45 ± 0.28, R2 = 0.67) suggests localized Hg evaporation due to shock processes on the parent body; however, Hg isotopic heterogeneity from nebular or parent body processes cannot be excluded. Terrestrial weathering and shock events could alter Hg content and isotopic compositions in chondrites, challenging their use as accurate indicators of Hg’s cosmochemical behavior.