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.

^1,2Timo Hopp,^1,3Nicolas Dauphas,³Maud Boyet,⁴Seth A. Jacobson,⁵Thorsten Kleine
Science 390, 819-823 Link to Article [DOI: 10.1126/science.ado062]
¹Department of the Geophysical Sciences, The University of Chicago, Chicago, IL, USA
Max-Planck-Institut für Sonnensystemforschung, Göttingen, Germany
²Department of Earth and Planetary Sciences, The University of Hong Kong, Hong Kong, China
³Laboratoire Magmas et Volcans, Université Clermont Auvergne, Centre National de la Recherche Scientifique, Institut de Recherche pour le Développement, Observatoire de Physique du Globe de Clermont-Ferrand, Clermont-Ferrand, France
⁴Department of Earth and Environmental Sciences, Michigan State University, East Lansing, MI, USA
⁵Max-Planck-Institut für Sonnensystemforschung, Göttingen, Germany
Reprinted with permission from AAAS

The Moon formed from a giant impact of a planetary body, called Theia, with proto-Earth. It is unknown whether Theia formed in the inner or outer Solar System. We measured iron isotopes in lunar samples, terrestrial rocks, and meteorites representing the isotopic reservoirs from which Theia and proto-Earth might have formed. Earth and the Moon have indistinguishable mass-independent iron isotopic compositions; both define one end of the range measured in meteorites. Combining our results with those for other elements, we performed mass balance calculations for Theia and proto-Earth. We found that all of Theia and most of Earth’s other constituent materials originated from the inner Solar System. Our calculations suggest that Theia might have formed closer to the Sun than Earth did.

^1,2Ke Zhu,³Akira Yamaguchi,⁴Paolo A. Sossi,⁵Audrey Bouvier,⁶Lu Chen,⁷Peng Ni
Proceedings of the National Academy of Sciences of the USA 122, e2519759122 Link to Article [https://doi.org/10.1073/pnas.251975912]
¹State Key Laboratory of Geological Processes and Mineral Resources, Hubei Key Laboratory of Planetary Geology and Deep-Space Exploration, School of Earth Sciences, China University of Geosciences, Wuhan 430074, China
²Bristol Isotope Group, School of Earth Sciences, University of Bristol, Bristol BS8 1RJ, United Kingdom
³National Institute of Polar Research, Tokyo 190-8518, Japan
⁴Department of Earth and Planetary Sciences, ETH Zürich, Zürich 8092, Switzerland
⁵Bayerisches Geoinstitut, University of Bayreuth, Bayreuth 95547 95440, Germany
⁶Wuhan Sample Solution Analytical Technology Co., Ltd.,Wuhan 430075, China
⁷Department of Earth, Planetary, and Space Sciences, The University of California Los Angeles, Los Angeles, CA 90095

The angrite parent body (APB) is the most volatile-depleted among known differentiated bodies in the Solar System, yet the mechanisms responsible remain poorly constrained. Here, we present high-precision nickel (Ni) isotope data from a suite of angrite samples to reconstruct the APB’s volatile depletion history. Plutonic angrites contain unusually high proportions of metallic iron and exhibit chondritic δ60/58Ni values (0.202 ± 0.028‰; per mille mass-dependent 60Ni/58Ni deviation relative to National Institute of Standards and Technology (NIST) Standard Reference Material (SRM) 986). These observations are consistent with a homogeneous Ni isotope composition of the APB after core formation and the subsequent incorporation of endogenous core material in plutonic angrites. In contrast, a dunite and megacrystic olivines from volcanic angrites, derived from the mantle, display suprachondritic δ60/58Ni values (0.4 to 0.7‰). We argue that these values are consistent with Ni loss via evaporation during a high-energy impact that follows an initial stage of volatile loss from a magma ocean generated by 26Al heating. Thermodynamic modeling confirms Ni to be more volatile than Mn, Fe, Si, and Mg during evaporation from silicate liquids, in agreement with the observed relative magnitude of isotopic fractionation. Volcanic angrite matrices show variable and often subchondritic δ60/58Ni values (down to −0.5‰), reflecting mixing with isotopically heavy megacrystic olivines and recondensation of light Ni vapor onto the crust. These findings imply that volatile elements are stratified (core–mantle–crust) in the APB and provide direct isotopic evidence for impact-driven vapor loss and recondensation on a differentiated planetary body.

¹Makoto Kimura, ^2,3Michael K. Weisberg, ⁴Richard C. Greenwood, ^1,5Akira Yamaguchi
Geochemistry (Chemie der Erde) 85, 126343 Link to Article [https://doi.org/10.1016/j.chemer.2025.126343]
¹National Institute of Polar Research, 10-3 Midoricho, Tachikawa, Tokyo, 190-8513, Japan
²Kingsborough College and Graduate Center of the City University of New York, USA
³American Museum of Natural History, New York, USA
⁴Planetary and Space Sciences, The Open University, Milton Keynes, MK7 6AA, United Kingdom
⁵Department of Polar Science, the Graduate University for Advanced Studies, SOKENDAI, 10-3 Midoricho, Tachikawa, Tokyo, 190-8518, Japan
Copyright Elsevier

In this paper, we examine the diverse features of CM (Mighei-type) and related carbonaceous chondrites, including their petrologic classification, secondary heating, brecciation, and we explore anomalous CM-like chondrites. CM chondrites experienced varying degrees of aqueous alteration, resulting in a range of petrologic subtypes from 3.0 to 2.0. The most abundant subtypes are 2.3–2.0, which may reflect melting of significant amounts of ice, resulting in the formation of the heavily altered CM chondrites in the inner regions of the parent body. Additionally, some CM and related chondrites have undergone secondary heating after aqueous alteration. The source of heat for these chondrites is still uncertain, but impacts are the most likely the cause due to the evidence for a short duration of heating. CM chondrites are mainly genomict breccias and contain clasts of various petrologic grade and degree of heating, though some CMs contain xenolithic clasts. Highly recrystallized clasts are particularly important, as they might have formed in the interior, hotter regions of the CM parent body. Subsequently, these clasts may have been mixed with other typical CM lithologies due to impact events. CM chondrite fragments are commonly found in other meteorites, such as HED meteorites and ordinary chondrites. This indicates a widespread distribution of CM chondrite fragments in the main asteroid belt, with incorporation into other meteorites taking place significantly later than chondrule formation. There have been numerous descriptions of anomalous CM or related chondrites. We tentatively classify these anomalous CMs into four categories: highly 16O-rich, medium 16O-rich, an unusual mineral group, and others. However, the processes involved in the formation of these anomalous chondrites and their relationships to the more typical CMs remain unclear, as detailed documentation of most of the anomalous CMs is currently lacking. CM chondrites primarily consist of chondrules, refractory inclusions, opaque minerals, and a matrix material, similar to other C chondrites. The petrographic and bulk chemical features of CMs are most similar to CO chondrites. However, CM and CO chondrites did not originate from a single parent body. CM chondrites provide valuable information about the conditions and processes that operated in the outer region of the early solar system.

¹Justin R. Filiberto et al. (>10)
Geochemistry (Chemie der Erde)(in Press) Open Access Link to Article [https://doi.org/10.1016/j.chemer.2025.126316]
¹Astromaterials Research and Exploration Science (ARES) Division (XI), NASA Johnson Space Center, Houston, TX 77059, USA
Copyright Elsevier

One of the biggest unknowns about Venus is how volcanically active it is today. Venus has a similar size and density to Earth, suggesting it may have a comparable composition, and therefore it is expected to be volcanically active; however, exploring Venus and confirming current volcanic activity is difficult because of the thick omnipresent optically opaque clouds that hamper traditional observations of the lower atmosphere and surface. Further, surface conditions make long-lived missions challenging. Despite the difficulty, there have been tantalizing hints of currently active or very recent volcanism. Here, we review what is known about active volcanism, point out gaps in knowledge to be addressed, and highlight techniques and approaches that need to be developed before the new decade of Venus exploration. It is crucial to constrain the activity and rate of volcanism today and through time to begin to understand the geodynamic state of the planet.
We find that the combination of all evidence strongly indicates that Venus is volcanically active today. The best evidence for active volcanism comes from combining data sets and approaches – specifically at Idunn Mons, Maat Mons, and Aramaiti Corona – in contrast to those from a single study or data set alone. Considering the evidence for activity, observations do not favor so-called “catastrophic” models of resurfacing, instead they are better represented by ongoing regional scale events. To reliably detect and characterize active or recent effusive basaltic volcanism new missions must collect high-resolution imaging, repeat observations, radar polarimetry, evidence of outgassing, and high-resolution topographical data that provide insights into surface changes over time. The ability to capture and interpret these data is vital for understanding Venus’s geological activity, particularly in regions where volcanic processes are suspected to be ongoing.