¹J.A. Berger et al. (>10)
Journal of Geophysical Research (Planets)(in Press) Link to Article [https://doi.org/10.1029/2025JE009350]
¹Amentum at NASA Johnson Space Center, Houston, TX, USA
Published by arrangement with John Wiley & Sons

A major mission goal for the Mars Science Laboratory’s rover, Curiosity, is to investigate the transition from clay-bearing to hydrated-Mg-sulfate-bearing sedimentary strata hypothesized to record a transition from a wet to a dry paleoclimate. Alpha Particle X-ray Spectrometer (APXS) results from this region, named the Clay-Sulfate Transition (CST), indicate an overall ∼5% increase in Ca-sulfate, but Mg-sulfate enrichment is limited to diagenetic nodules. Sulfates in the CST change sharply at the contact with the overlying Mg-sulfate unit, which has ∼5% Ca-sulfate and ∼10% Mg-sulfate in the bedrock matrix. Despite this change in sulfate assemblage, and the transition from fluvial-lacustrine to drier aeolian sedimentary deposits, the bulk chemical composition of the aeolian sandstone (sulfate-free basis) effectively has the same altered basalt chemical fingerprint as the underlying fluvial-lacustrine mudstone. That is, the composition of rocks that record the transition from a wet to a dry paleoclimate is isochemical. It is remarkable that the aeolian sandstone has the same altered bulk chemical characteristics as the fluvial-lacustrine mudstone, notwithstanding very different inferred geochemical regimes. We propose a simplified model wherein older basaltic sediment was aqueously altered in a fluvial-lacustrine regime and reworked, likely during cycles of alteration, salt formation, and reworking. This process led to an averaging of the bulk chemical composition of the Mt. Sharp group sediment, resulting in the isochemical characteristics of the paleoenvironment change.

^1,2Mu-Han Yang, ¹Qian W.L. Zhang, ³Richard W. Carlson, ^1,2Bi-Wen Wang, ¹Dongjian Ouyang^1,2Qiu-Li Li
Icarus (in Press) Open Access Link to Article [https://doi.org/10.1016/j.icarus.2025.116889]
¹State Key Laboratory of Lithospheric and Environmental Coevolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China
²College of Earth and Planetary Sciences, University of Chinese Academy of Sciences, Beijing 100049, China
³Earth and Planets Laboratory, Carnegie Institution for Science, Washington, DC, USA
Copyright Elsevier

The Moon’s formation time is a key factor for understanding the early evolution of the Earth-Moon system. The lunar magma ocean (LMO) model explains how cumulate mafic materials crystallizing from the LMO form the source of mare basalts (SMB). The SMB with an equilibrated SmNd system is considered to share an identical initial Pb isotope signature (Pb_SMB). Because Pb is volatile while U is refractory, Pb_SMB can provide constraints for the timing of volatile depletion, most likely dating the time of Moon formation by a giant impact. The Pb_SMB is a link between the initial Pb composition of lunar mare basalts and the Moon’s early evolution via a two-stage Pb evolution model that provides a simplified but informative framework. Using four mare basalts with well-constrained ages and initial Pb isotopic compositions, we estimate the Moon’s formation time at  Ma and the SMB formation time at  Ma, which we regard as the preferred solution within the statistical framework of the model. Our modelling strategy also facilitates the dating of mare basalt fragments lacking Zr-bearing minerals using the initial Pb isotopic compositions constrained by U-poor minerals.

¹Ségolène Rabin, ¹Steven Goderis, ¹Lisa Krämer-Ruggiu, ¹Pim Kaskes, ²Jan Smit, ³Kasper Hobin, ³Frank Vanhaecke, ^1,4Philippe Claeys
Earth and Planetary Science Letters 674, 119721 Link to Article [https://doi.org/10.1016/j.epsl.2025.119721]
¹Archaeology, Environmental Changes, and Geo-Chemistry, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussels, Belgium
²Geology and Geochemsitry, Vrije Universiteit Amsterdam, de Boelelaan 1085, 1081HV Amsterdam, Netherlands
³Atomic & Mass Spectrometry – A&MS research unit, Ghent University, Department of Chemistry, Campus Sterre, Krijgslaan 281 – S12, 9000 Gent, Belgium
⁴Earth, Ocean and Atmospheric Sciences, University of British Columbia, Vancouver, V6T1Z4 BC, Canada
Copyright Elsevier

Stable Fe isotopic variations recorded in impact spherules provide insights in the evolution of the impact plume generated by a hypervelocity impact. This study reports the first high-precision Fe isotope ratio of both proximal and distal impact spherules, originating from the Chicxulub impact. A total of 47 impact spherules, formed as the result of melting and condensation, are investigated from different localities at different distances and directions from the source crater. The major challenge of studying 66 million years old impact spherules lies in the extensive alteration and diagenesis processes that could affect their original Fe signatures. Proximal and distal impact spherules show a comparable mean δ56Fe value of -0.036 ± 0.28 ‰ (n = 40). This Fe isotope signature, identical to the mean value for the Earth crust, shows that Fe did not significantly fractionate in the plume generated by the Chicxulub impact event. Only a few impact spherules display light isotopic composition, with δ56Fe values down to -3.01 ± 0.07 ‰, due to their high degree of alteration. The lack of Fe fractionation in the Chicxulub impact spherules likely reflects the thermal conditions within the impact generated plume. The rate of temperature change in the Chicxulub impact plume is assumed to be slower than the evaporation and condensation timescales (seconds-minutes), allowing the temperature to remain above 1300 K for a sufficient period to enable re-equilibration of the Fe isotopic system.

¹Yingnan Zhang, ¹Mi Zhou, ¹Liping Qin, ¹Bing Yang, ¹Haolan Tang, ²Thomas Smith, ²Huaiyu He
Earth and Planetary Science Letters 674, 119738 Link to Article [https://doi.org/10.1016/j.epsl.2025.119738]
¹National Key Laboratory of Deep Space Exploration/State Key Laboratory of Lithospheric and Environmental Coevolution, University of Science and Technology of China, Hefei 230026, China
²State Key Laboratory of Lithospheric and Environmental Coevolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, 19 Beitucheng Western Road, Box 9825, Beijing 100029, China
Copyright Elsevier

The fingerprints of ancient stars are preserved in the isotopic anomalies of meteorites, revealing how the Solar System’s building blocks formed and evolved. Potassium, a moderately volatile element, exhibits isotopic anomalies that can serve as tracers of volatile inventories in meteorites and terrestrial planets. We measured the K isotopic compositions in a range of meteorites. After correcting for cosmic-ray effects, all meteorites show ε40K values that are the same as or slightly higher than Earth’s. The lack of correlation with other neutron-rich isotopes, but a clear link to 30Si and 43Ca, points to stellar burning as the main source of 40K. Large 40K enrichments in CI chondrites and Tagish Lake indicate the addition of 40K-rich material, while other subgroups of carbonaceous chondrites show evidence of various degrees of mixing with this component. These patterns suggest inward migration of CI-like volatile-rich carriers in the protoplanetary disk. The uniform enrichment in meteorites implies that Earth’s slightly lower ε40K required a missing, 40K-depleted building block, likely from early-formed planetesimals that had avoided this late addition of CI-like material.

¹Axel Wittmann, ²Philippe Lambert
Earth and Planetary Science Letters 674, 119748 Link to Article [https://doi.org/10.1016/j.epsl.2025.119748]
¹Eyring Materials Center, Arizona State University, 1001 S. McAllister Ave., Tempe, AZ 85287-8301, USA
²CIRIR ‒ Centre International de Recherche et de Restitution sur les Impacts et sur Rochechouart, 2-4 Faubourg du Puy du Moulin, Rochechouart 87600, France
Copyright Elsevier

The 205 Ma Rochechouart impact structure in southern France exhibits variable levels of erosion that mask its original diameter for which estimates vary between 10 and 35 km. Exclusively at Chassenon, the size-sorted, “ash-like” impactoclastite deposit occurs as the last preserved material directly produced by the impact. To test whether impactoclastite is indeed a fallback deposit from the impact plume, we studied 18 Rochechouart impactite samples, of which 15 are dike-like intercalations of impactoclastite in suevite from Chassenon. We found 63 impact spherules in 13 samples from Chassenon, down to a drill core depth of 27.65 m. These spherules are impact melt droplets that record suspended flight. Of these spherules, 30 % crystallized Ni-bearing spinel, 11 % contain small NiO particles, and one includes a ∼140 nm Pt-Os-Ru-Ir-Rh-Pd nugget; these are impactor components, confirming formation in close proximity to the point of impact. The exclusive occurrence of impact spherule-bearing impactoclastite associated with suevite at the Chassenon location suggests special formation conditions that we link to the collapse of the Rochechouart central peak, which induced the down-thrusting of the ∼3 km2 “Chassenon slab”. Resulting fissures in suevite were filled with debris that fell back from the ejecta plume one hour to ca. 1 day after the impact. This interpretation negates the deposition of the Chassenon suevite from marine resurgence immediately following the impact. Instead, we invoke a “debris-inhalation” process that injected impactoclastite dikes due to brief vacuum conditions generated in the sub-crater floor during collapse of the Chassenon slab.

¹Cuiping Wang, ²Haolan Tang, ³ Miao, ² Yu, ¹ He, ^1,4 Liu, ²Fang Huang, ⁵Frederic Moynier, Jingao Liu
Earth and Planetary Science Letters 674, 119747 Link to Article [https://doi.org/10.1016/j.epsl.2025.119747]
¹State Key Laboratory of Geological Processes and Mineral Resources, and Frontiers Science Center for Deep-time Digital Earth, China University of Geosciences, Beijing 100083, China
²National Key Laboratory of Deep Space Exploration/State Key Laboratory of Lithospheric and Environmental Coevolution, University of Science and Technology of China, Hefei 230026, China
³Institution of Meteorites and Planetary Materials Research, Key Laboratory of Planetary Geological Evolution, Guilin University of Technology, Guilin 541006, China
⁴Key Laboratory of Earth and Planetary Physics, Chinese Academy of Sciences, CNRS, Beijing, China
⁵Université Paris cité, Institut de Physique du Globe de Paris, Paris 75005, France
Copyright Elsevier

Primitive differentiated meteorites serve as key messengers to reveal the formation and evolution of planetesimals in the early solar system. Ureilites, a group of achondritic meteorites, are interpreted as remnants of a disrupted asteroid’s residual mantle, yet the accretion location of their parent body remains uncertain. Here we report that ureilites exhibit distinct Mg and Si isotopic compositions, characterized by heavy Mg isotope (δ26Mg = -0.22 ‰ ± 0.01) and light Si isotope (δ30Si =-0.50 ‰ ± 0.02) compositions relative to ordinary and carbonaceous chondrites (δ26MgOC&CC:0.27 ‰ ± 0.01, δ30SiOC&CC:0.44 ‰ ± 0.01). Following an assessment of pressure and redox conditions on Si isotopic fractionation between silicate and metal, we propose that the subchondritic δ30Si signature of ureilites reflects the accretion of the ureilite parent body (UPB) occurred in an extremely reduced environment. The suprachondritic δ²⁶Mg signatures are attributed to evaporation processes from the UPB precursors during early accretionary stages. To constrain the precursors of the UPB, we conducted numerical simulations of Si-Mg isotopic variations in chondritic planetesimals under early nebular conditions, incorporating vapor loss. Results indicate that the UPB precursors possessed a Si isotope composition similar to enstatite chondrites. Collectively, we conclude that the UPB accreted proximal to the reservoirs of enstatite chondrites in the inner solar system under reduced conditions, and the UPB’s precursors had experienced silicon and magnesium loss via magma ocean evaporation.

¹Chen, Ying Wang,²Shiyong Liao,²Le Zhang,¹Pengli He,³Lei Jin,¹Yuri Amelin,^1,2Yi-Gang Xu
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.70075]
¹State Key Laboratory of Deep Earth Processes and Resources, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou, China
²Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing, China
³State Key Laboratory of Lunar and Planetary Sciences, Macau University of Science and Technology, Macau, China
Published by arrangement with John Wiley & Sons

Mesosiderites are widely believed to have originated from a metal-silicate mixing event triggered by planetesimal collisions in the early solar system. However, a key unresolved issue in this model is the physical state (liquid vs solid) of the metallic materials involved, which complicates our understanding of mesosiderite formation. Melt pockets and comb plessites in the Dong Ujimqin Qi mesosiderite provide critical insights into this issue. The melt pockets exhibit quenched textures of dendritic troilite-metal intergrowths, typically cooled at a rate of >9500°C s−1 above 950°C. In contrast, the Ni profile in kamacite, pentlandite, taenite, and cordierite inside melt pockets points to a subsequent burial-induced slow cooling process, which starts below 780°C with a maximal estimated rate of ~2°C Myr−1. The two-stage cooling pathway of melt pockets aligns well with thermal fingerprints expected from the catastrophic disruption and reassembly of the mesosiderite parent body. More importantly, the impact has led to shock deformation of metal nodules to varying degrees, as reflected by the extension of kamacite polygonization associated with melt pockets into some comb plessite domains. This provides vital evidence that the metal nodules remained partially solid during the mixing process. Accordingly, we propose a revised mesosiderite formation model that involves an impact mixing with a partially solidified metal planetesimal. The revised model better accounts for several issues regarding the formation of mesosiderites, such as three-orders-of-magnitude variations of bulk Ir concentrations, slow metallographic cooling rates, bimodal size distribution of the metallic nodule and matrix, and deficient olivine materials.

¹Ryota Fukai et al. (>10)
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.70077]
¹Japan Aerospace Exploration Agency, Sagamihara, Japan
Published by arrangement with John Wiley & Sons

Analyzing primitive extraterrestrial samples from asteroids is key to understanding the evolution of the early solar system. The OSIRIS-REx mission returned samples from the B-type asteroid Bennu, providing a valuable opportunity to compare them with the Ryugu samples collected by the Hayabusa2 mission. This study examines the representativeness of a fraction of the Bennu samples, which was allocated from NASA to JAXA, by nondestructive characterization of their physical and spectral properties without atmospheric exposure. The reflectance and observed spectral features in the visible-to-infrared range of the Bennu sample resemble those from the spectroscopic analysis of different fractions. Additionally, we found differences in the slope of the visible range and band-center of ~2.7 μm band between the samples and the asteroid surface, which could be explained by the degree of space weathering. A comparative analysis of the Bennu and Ryugu samples revealed spectral similarities, including absorption features indicative of Mg-rich phyllosilicates, organics, and carbonates, without any evidence of sampling bias or terrestrial alteration. This finding can be used as a benchmark for subsequent Ryugu–Bennu comparative studies.

¹Baptiste Le Bellego, ¹Célia Dalou, ¹Béatrice Luais, ²Pierre Condamine, ³Vincent Motto-Ros, ¹Laurent Tissandier
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2025.11.038]
¹Université de Lorraine, CNRS, CRPG, F-54000 Nancy, France
²Laboratoire Magmas et Volcans, Université Clermont Auvergne, CNRS UMR 6524, OPGC-IRD, F-63000 Clermont-Ferrand, France
³Institut Lumière Matière UMR 5306, Université Lyon 1 – CNRS, Université de Lyon, Villeurbanne, France
Copyright Elsevier

The segregation of metallic cores from silicate mantles during early planetary differentiation is a key process shaping the chemical evolution of terrestrial bodies. A critical factor controlling metal-silicate equilibration during this stage is the diffusive behavior of moderately siderophile elements, which governs chemical exchange timescales. As a moderately siderophile and moderately volatile element, Ge is particularly sensitive to redox conditions, pressure, temperature, and the presence of light elements in the metal phase, making it an ideal tracer of core formation processes. However, experimental constraints on Ge diffusion under relevant high-pressure, high-temperature, and low oxygen fugacity conditions are lacking.
Here, we present new experimental measurements of Ge diffusion coefficients in Fe-Ni metal and silicate (CMAS) melt, analogous to planetary cores and mantles, under high-pressure (0.5 – 1 GPa), high-temperature (1350 °C) conditions and low oxygen fugacities (IW − 5.4 to IW − 1.5). Ge diffusion in liquid silicate and liquid metal was found to be significantly faster (∼10−11 m2/s) than in solid metal (∼10−13 m2/s), with transport further influenced by oxygen fugacity and Si content. Under highly reducing conditions, high Si concentrations inhibit Ge diffusion in solid metal by reducing vacancy availability and inducing partial melting, forming immiscible metal droplets that act as localized Ge sinks. Diffusion timescale calculations indicate that, for Earth-like planets, even at high temperatures (1800 °C), estimated equilibration times are too long for large metal fragments (> 10 m) to fully equilibrate before descending to the core. Thus, additional processes such as turbulent convection or percolation are required for efficient metal–silicate exchange. In contrast, on Mars-like bodies with long-lived magma oceans, solely diffusion, even at low temperature (1350 °C), could be sufficient to equilibrate large metal fragments.

¹Addi Bischoff,¹Maximilian P. Reitze,²Julia Roszjar,¹Markus Patzek,^3,4Jean-Alix Barrat,⁵Jasper Berndt,⁶Tommaso Di Rocco,⁶Andreas Pack, Iris Weber
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.70072]
¹Institut für Planetologie, University of Münster, Münster, Germany
²Department of Mineralogy and Petrography, Natural History Museum Vienna, Vienna, Austria
³Univ Brest, CNRS, Ifremer, IRD, LEMAR, Institut Universitaire Européen de la Mer (IUEM), Place Nicolas Copernic, Plouzané, France
⁴Institut Universitaire de France, Paris, France
⁵Institut für Mineralogie, University of Münster, Münster, Germany
⁶Universität Göttingen, Geowissenschaftliches Zentrum, Göttingen, Germany
Pubslished by arrangement with John Wiley & Sons

A bright fireball was seen at 4:46 a.m. CET on November 19, 2020, over Austria, and also eye witnessed in Italy and Germany. The resulting Kindberg meteorite was the fifth well-approved meteorite fall in Austria, and all rocks represent ordinary chondrites. One specimen of Kindberg, measuring 233.08 g, was recovered on July 4, 2021, largely covered by a dark brownish fusion crust. The meteorite is an L6 ordinary chondrite (OC) breccia; Kindberg’s highly equilibrated type 6 character is also supported by the large-sized plagioclase grains (An9-12; with grains >100 μm) and the homogeneous compositions of olivine (Fa24.4±0.4) and low-Ca pyroxene (Fs20.6±0.3). The meteorite shows remarkable shock effects in the form of easily visible dark shock veins cross-cutting the bulk rock. The olivine in Kindberg is dominated by grains with undulous extinction or planar fractures, indicating a weakly shocked (S3 [C-S3]) chondritic rock. Close to the shock veins, olivine can also show mosaicism. In addition, wadsleyite, a high-pressure polymorph of olivine, was identified by Raman and IR spectroscopy. Wadsleyite, sometimes in paragenesis with maskelynite and locally part of an intergrowth with majorite and perhaps ringwoodite, was found within and close to the veins. The occurrence of high-pressure phases of olivine and maskelynite in a weakly shocked bulk rock clearly indicates their formation at relatively low equilibrium shock pressures of <20 GPa (S3/S4 transition). Equilibrium shock pressures consistent with those experienced by bulk rocks shocked to S5 (>30–35 GPa) and S6 (>45 GPa; S5/S6 transition) are not required to form high-pressure polymorphs of olivine. The L-chondrite classification is confirmed by O isotope data. The bulk chemical composition also supports L-group membership.