¹Sierra R. Ramsey,¹Piper Irvin,¹Arya Udry,²Scott A. Eckley,^3,4Amanda Ostwald,⁵Richard A. Ketcham
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1029/2025JE009220]
¹Department of Geoscience, University of Nevada, Las Vegas, NV, USA
²Amentum, NASA Johnson Space Center, Houston, TX, USA
³Department of Mineral Sciences, National Museum of Natural History, Smithsonian Institution, Washington, NW, USA
⁴Department of Earth and Environmental Sciences, Michigan State University, East Lansing, MI, USA
⁵Jackson School of Geosciences, University of Texas, Austin, TX, USA
Published by arrangement with John Wiley & Sons

Nakhlites, clinopyroxene-rich rocks, are the largest single-origin suite of samples from Mars. Despite extensive study to discern their petrogenetic histories, nakhlite emplacement mechanisms and environments are not well-constrained, and it is unknown whether they represent intrusive or extrusive igneous rocks, or a combination. Here, we use X-ray computed microtomography (XCT) and three-dimensional (3D) quantitative textural analyses (e.g., 2D–3D modal abundances, crystal size distributions [CSDs], and petrofabrics) to place additional constraints on nakhlite formation and emplacement. Modal abundances between and within the nakhlites are variable on both a 2D and 3D basis, highlighting the significance of XCT and 3D analyses when studying these samples. All nakhlites in our study have similar crystallization conditions and histories based on 3D CSDs. Cumulus phases (=olivine and pyroxene) crystallized from magma(s) with high nucleation densities, likely related to effective undercooling, and subsequently underwent a period of magma storage. The CSD profiles record evidence for magma recharge events. Pyroxene long-axis orientations in the nakhlites studied here exhibit a magmatic foliation, which likely developed during crystal settling and accumulation in low-to-no flow settings, such as magma chambers, shallow intrusions (e.g., sills and dikes), lava lake or pond infills, or thick lava flows. We also show that the pyroxenitic layer of Theo’s Flow (Canada) may not be an appropriate terrestrial analog for the nakhlites due to differences in emplacement mechanisms and conditions. Our findings suggest that lava flows may be less prevalent in the martian meteorite collection, while intrusive bodies and rocks may be more common than initially thought.

¹P. Struzynska,¹S. Alwmark,¹C. Alwmark,²M. H. Poelchau,³P. Lambert
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.70078]
¹Department of Geology, Lund University, Lund, Sweden
²Department of Geology, University of Freiburg, Freiburg, Germany
³CIRIR, Center for International Research and Restitution on Impacts and on Rochechouart, Rochechouart, France
Published by arrangement with John Wiley & Sons

Rochechouart, south-west France, is a complex impact structure. Here, we present the first report of shock barometry of quartz from what are likely parautochthonous basement units at depth, based on samples from the 2017 C.I.R.I.R drilling campaign. The crystallographic orientations of 725 sets of PDFs in 512 quartz grains in samples from four drill cores were measured. We find basal PDFs (Brazil twins) as shear indicators and rhombohedral PDFs recording moderate shock pressures of 10–15 GPa, with numbers of sets per grain ranging from 1.0 to 2.1. A staggering 59.5% of the measured parautochthonous PDF sets are basal PDFs. We find a decrease of shock-metamorphic overprint from 10–15 to 5–10 GPa at site SC16 (Montoume), ~4.5 km south of what is currently held as the apparent crater center. Based on the abundance of low-to-moderate shock pressures and a lack of more highly shocked parautochthonous units, we discuss two well-defined scenarios for this occurrence. Scenario 1 attributes Rochechouart parautochthonous basement target material to have been subjected to at most 15 GPa as per our results. In scenario 2, the drilling only sampled the flanks of the central uplift but not its more strongly shocked center. Our favored hypothesis is the latter, and thus we relate our lack of highly shocked parautochthonous units to a lack of samples from the immediate center of the structure. Finally, based on the extent of PDFs from our shock barometry study of quartz, we estimate the minimum extent for the diameter of the structure to be 24 km.

¹Tara S. Hayden,¹Gordon R. Osinski
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.70074]
¹Department of Earth Sciences, University of Western Ontario, London, Ontario, Canada
Published by arrangement with John Wiley & Sons

Apollo sample 67015 has been classified as a fragmental breccia comprised of highlands-type clasts and is proposed to be the most complex Apollo 16 sample. 67015 is dominated by impact melt rock clasts that display a variety of textures, which have been previously interpreted to be indicative of multiple impact events. Recent modeling has indicated that the Apollo 16 regolith may contain impact basin ejecta from Nectaris, Serenitatis, Imbrium, and Orientale. Here, the textural, mineralogical, and geochemical diversity of impact melt rock clasts in several thin sections of 67015 was assessed to evaluate the provenance of these impact melts and attempt to constrain the basin ejecta emplacement at the Apollo 16 site. The petrography and mineral chemistry of the melt rock clasts is highly diverse and may indicate a variety of sources, supporting previous evidence that the Apollo 16 regolith received ejecta from numerous large impact cratering events including Imbrium and Serenitatis. The diversity of clast types observed in 67015 and textural variability of thin sections prompts discussion into the most appropriate classification of this sample as well as the nomenclature used to describe lunar melt-bearing breccia samples.

¹Karl Wimmer,²Edwin Gnos,³Beda Hofmann,⁴Sandro Boschetti,⁴Jan Walbrecker,⁴Hansruedi Maurer
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.70079]
¹Independent Researcher, Nördlingen, Germany
²Natural History Museum of Geneva and Earth and Environmental Sciences, University of Geneva, Geneva, Switzerland
³Natural History Museum Bern, Bern, Switzerland
⁴Institute of Geophysics, ETH Zürich, Zürich, Switzerland
Published by arrangement with John Wiley & Sons

With a size of 51.2 × 7.2 km, the 10.9 ± 1.7 ka old Jiddat al Harasis 091 L5 chondrite strewn field is the largest known in Oman. It consists of more than 700 meteorites with a total mass of >4.5 tons from which the largest six stones of >100 kg to 1.5 tons make up two thirds of the total mass. Small stones are underrepresented, consistent with a fracturing behavior of a meteor with low shock level. Modeling yields that a bolide with 28 ± 12 tons (115 ± 15 cm radius) entered the atmosphere at a shallow angle of 22° ± 2° with a velocity of about 16 kms−1. For ~16 s, it produced a spectacular meteor along a luminous path of ~200 km length. Mass mixing within the rather straight and narrow strewn field indicates a sequence of multiple fragmentations from below 50 km down to 7 km altitude. This can be resolved adopting a wind profile from nowadays winter season, as the weather patterns with alternating Monsoon and Passat winds in the region are rather well known and repeatable since the last ice age. The largest masses with 1447 and 842 kg, respectively, produced impact breccia consisting of limestone and meteorite fragments. According to the model, the biggest mass hit the ground at a velocity of 175 ms−1 and released an impact energy of 22 MJ, corresponding to 5.3 kg TNT. This may have produced an impact crater of ~1 m diameter which, however, is not preserved. Breccia found below a much smaller mass of 68 kg deserves an explanation beyond impact energy.

^1,2Tian Zhang, ^1,2,3Hong Tang, ^1,2,3Xiongyao Li, ^1,3Bing Mo, ¹Yuanyun Wen, ⁴Sheng Zhang, ^1,3Wen Yu, ^1,2Chuanjiao Zhou, ^1,2Haiyan Long, ^1,2,3Jianzhong Liu
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2025.11.047]
¹Center for Lunar and Planetary Sciences, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China
²College of Earth and Planetary Sciences, University of Chinese Academy of Sciences, Beijing 100049, China
³CAS Center for Excellence in Comparative Planetology, Hefei 230026, China
⁴College of Resources and Environment Engineering, Guizhou University, Guiyang 550025, China
Copyright Elsevier

The degassing of solar wind-related volatiles is thought to contribute to volatile cycling on the Moon. However, it remains uncertain which lunar minerals preferentially release them. Here, we report an unusual foamy texture found only on the surface of ilmenite crystals within a Chang’e-6 (CE-6) basalt clast. The distribution and chemical composition of this texture indicates that it results from in-situ melting of the ilmenite surface rather than from an impact-induced splash melt. Considering the evidence—including the long exposure time, presence of deep-seated planar defects, open vesicles, large spherical np-Fe⁰ particles, and a rutile-like mineral—the foamy texture is interpreted to result from the intense release of abundant solar wind-related volatiles (e.g., H/H2, He, and OH/H2O) by an impact-induced conductive heating event. Restriction of the foamy texture to the surface of ilmenite within the CE-6 basalt clast indicates that solar wind composition, especially for H-related volatiles, are released more intensely from ilmenite than from silicate minerals such as pyroxene and plagioclase. Our findings suggest that solar wind-related volatiles released from high-Ti mature regolith likely made a greater contribution to the lunar exosphere and the lunar surface volatiles, including polar deposits, relative to those from low-Ti immature regions. This has important implications for understanding volatile cycles and future in-situ resource utilization on the Moon.

^1,2Michael T. Thorpe,²Elizabeth B. Rampe,^3,4Juergen Thieme,³Eric Dooryhee,^2,5Seungyeol Lee,⁶Roy Christoffersen
American Mineralogist 110,1689-1701 Open Access Link to Article [https://doi.org/10.2138/am-2023-9290]
¹University of Maryland, NASA Goddard Space Flight Center, and CRESST II, Greenbelt, Maryland 20771, U.S.A.
²NASA Johnson Space Center, Houston, Texas 77058, U.S.A.
³Brookhaven National Lab, NSLS-II, Upton, New York 11973, U.S.A.
⁴Institute for X-Ray Physics, Georg-August University Goettingen, Goettingen University, Göttingen 37073, Germany
⁵Department of Earth and Environmental Sciences, Chungbuk National University, Seowon-Gu, Cheongju, Chungbuk 28644, Korea
⁶Amentum JETS-II contract, NASA Johnson Space Center, Houston, Texas 77058, U.S.A.
Copyright: The Mineralogical Society of America

Mudrocks and mud-sized sediments (i.e., silt to clay) dominate the surface of Earth and Mars. These fine-grained sediments preserve a rich history of sedimentary processes from source to sink and shed light on ancient climates. However, both the physical and chemical nature of these materials make them difficult to fully characterize with traditional laboratory techniques. Here, we explore a cross-disciplinary and high-resolution approach using synchrotron radiation for X-ray diffraction, pair distribution function analysis, and submicrometer-scale X-ray fluorescence, combined with transmission electron microscopy, to better understand the nanostructure and composition of mud-sized sediments from a glacio-fluvial watershed in southwest Iceland. Our results demonstrate that sediments in the cold and wet climate of Iceland are more altered than previously thought, as evidenced by the identification of kaolinite and mixed-layer kaolinite-smectite. Additionally, sediments are enriched in amorphous materials and nanocrystalline phases, as determined from grain morphologies and compositions consistent with allophane, hisingerite, ferrihydrite, and halloysite. These alteration products are present as intimate mixtures that vary across depositional sites, demonstrating the dynamic nature of the secondary assemblage from source to sink. This work has implications for Mars, where, for example, basalt-sourced sedimentary rocks from Gale crater are abundant in clay minerals and amorphous materials. Finally, this work underpins the importance of using high-resolution techniques, a coordinated methodology, and developing innovative approaches for future planetary sample return missions (e.g., Mars sample return).

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.