¹S.A. Crowther et al. (>10)
Geochimica et Cosmochimica Acta (in Press) Open Access Link to Article [https://doi.org/10.1016/j.gca.2025.12.008]
Department of Earth and Environmental Sciences, The University of Manchester, UK
Copyright Elsevier

We report an I-Xe age of 7.94 ± 0.92 Myr after formation of calcium aluminium inclusions (CAI), and an iodine concentration of 67 ± 1 ppb for material returned from asteroid (162173) Ryugu by JAXA’s Hayabusa 2 mission. These were determined from multi-step laser heating xenon isotopic analysis of samples A0105-03 and A0105-12 (100 µg and 70 µg, respectively), the smaller of which had been neutron irradiated to convert 127I to 128Xe. The I-Xe age likely corresponds to the end of significant loss of volatiles from the parent body. A simple statistical model of all 24 xenon isotopic analyses of Hayabusa 2 material reported to date, including one sample that has an elevated concentration attributed to Xe-P7, suggests a bulk xenon content of 2.0–2.7 × 10−7 cm3 STP g−1 for such material. This is a factor of 12–60 times higher than suggested by analyses of CI chondrite meteorites that have been exposed to the terrestrial atmosphere.
The bulk xenon isotopic composition is enriched in the heavy isotopes (134, 136Xe) relative to Average Carbonaceous Chondrite (AVCC) xenon, consistent with loss of some planetary xenon (“Q-Xe”) during aqueous alteration allowing a greater relative contribution from presolar nanodiamonds than found in AVCC. The I-Xe age is within the range of I-Xe ages for aqueous alteration of CI material; it likely records either the closure of iodine-rich sites to xenon loss towards the end of a period of heating that was associated with aqueous alteration, or precipitation of iodine-bearing minerals driven by loss of water. We use a simple statistical model of xenon analyses of Ryugu material to investigate the concentration of xenon in CI material. The presence of the rare Xe-P7 component in one reported analysis increases the estimated gas concentration and so increases the discrepancy between xenon concentrations measured in Hayabusa2 samples and CI meteorites. This is consistent with a comparatively rare Xe-P7 carrier being susceptible to loss when exposed to the terrestrial atmosphere. We measured an iodine concentration of 67 ± 1 ppb, which is comparable to other analyses of CI chondrites by neutron-irradiation noble gas mass spectrometry (NI-NGMS). Our sample was sealed within a capillary tube during irradiation allowing us to monitor any gas lost from the sample; loss of iodine-derived 128Xe during the irradiation process cannot account for any discrepancy between our derived iodine concentration and those determined in carbonaceous chondrites by other methods.

¹Oliveira, B. H.,¹Snape, J. F.,¹Tartèse, R.,²Jeon, H.,²Whitehouse, M. J.,¹Joy, K. H.
Advances in Geochemistry and Cosmochemistry 1, 772 Open Access Link to Article [https://doi.org/10.33063/agc.v1i2.772]
¹Department of Earth and Environmental Sciences, The University of Manchester, Manchester, UK
²Department of Geosciences, The Swedish Museum of Natural History, Stockholm, Sweden

We currently do not have a copyright agreement with this publisher and cannot display the abstract here

¹Romain Tartèse et al. (>10)
Advances in Geochemistry and Cosmochemistry 1, 776 Open Access Link to Article [https://doi.org/10.33063/agc.v1i2.776]
¹Department of Earth and Environmental Sciences, The University of Manchester, Oxford Road, Manchester M13 9PL, United Kingdom

We currently do not have a copyright agreement with this publisher and cannot display the abstract here

¹Jared M. Long-Fox, ¹Humberto Campins, ¹Daniel T. Britt
Planetary and Space Science 270, 106229 Open Access Link to Article [https://doi.org/10.1016/j.pss.2025.106229]
¹University of Central Florida Department of Physics, 4111 Libra Drive Room 430, Orlando, FL, 32816, USA

We currently do not have a copyright agreement with this publisher and cannot display the abstract here

¹J.M. Comellas et al. (>10)
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2025.116902]
¹University of Hawai‘i at Mānoa, 2500 Campus Rd, Honolulu, 96822, HI, USA
²Los Alamos National Laboratory, P.O. Box 1663, Los Alamos, 87545, NM, USA
Copyright Elsevier

Manganese plays a crucial role as a paleo-environmental and geological indicator due to its sensitivity to redox potential and pH variations in the environment. On Earth, the association between the rise of atmospheric oxygen during the Great Oxidation Event and the presence of Mn in the sedimentary rock record underscores its significance. In this study, we reexamined ChemCam targets from the first 600 sols of the Mars Science Laboratory mission, focusing on identifying instances of above-average Mn within these targets. These elevated-Mn targets were categorized into distinct geologic classes, revealing a pattern linking heightened Mn levels with diagenetically altered materials, such as calcium sulfate veins and concretions, as well as clay minerals within the same targets, indicating a compelling relationship between Mn enrichment and diagenetic processes. High concentrations of Mn were observed in chemically altered targets, suggesting the occurrence of multiple fluid events: the first to alter the material and the second to deposit Mn. The observed patterns suggest multiple diagenetic events and redox cycling that facilitated the deposition and transport of Mn subsequent to the initial dissolution of basaltic materials. This research sheds light on the complexity of martian diagenetic processes and their implications for the planet’s environmental evolution.

^1,2,3C. J. Gimar et al. (>10)
Journal of Geophysical Research (Planets)(in Press) Open Access Link to Article [https://doi.org/10.1029/2025JE009304]
¹Department of Physics and Astronomy, Univeristy of Texas at San Antonio, San Antonio, TX, USA
²Center for Laboratory Astrophysics and Space Science Experiments (CLASSE), Space Science Division, Southwest Research Institute, San Antonio, TX, USA
³Space Science Division, Southwest Research Institute, San Antonio, TX, USA
Published by arrangement with John Wiley & Sons

Building on our previous studies of the far-ultraviolet (FUV) reflectance of Apollo soil 10084 and lunar soil simulants JSC-1A and LMS-1 (Gimar et al., 2022, https://doi.org/10.1029/2022je007508; Raut et al., 2018, https://doi.org/10.1029/2018je005567), we present new FUV results for Apollo soils 68501 and 71061. Heavily weathered soils (68501, 10084)–enriched in submicroscopic Fe, agglutinates, and sub-micron scale roughness as revealed by our electron microscopy investigations–are darker in the FUV and predominantly backscatter incident light. In contrast, the relatively less weathered subsurface 71061 soil is approximately twice as bright, exhibits forward scattering, and presents a steeper blue spectral slope between 130 and 160 nm compared to the weathered soils. Differences in either primary composition or mineralogy appear to have little to no effect on the FUV albedo or scattering behavior of these soils since the reflectance of high-Ti mare 10084 and low-Ti highland 68501 are nearly indistinguishable within error. Further investigation of additional Apollo-era soils across various maturity indices is needed to fully characterize the influence of space weathering on lunar soil FUV spectrophotometric response.

¹O. Beyssac et al. (>10)
Earth and Planetary Science Letters 675, 119746 Open Access Link to Article [https://doi.org/10.1016/j.epsl.2025.119746]
¹Institut de Minéralogie, de Physique des Matériaux et de Cosmochimie, CNRS UMR 7590, Muséum National d’Histoire Naturelle, Sorbonne Université, 75005 Paris, France
Copyright: Elsevier

Based on observation and data from meteorites and in situ scientific missions, experiments as well as models, the Martian mantle is assumed to share some compositional and mineralogical affinity with the terrestrial mantle. However, there might be subtle differences like the Martian mantle being more ferroan. Yet, we do not have any direct analysis of a Martian mantle rock to confirm this assumption. NASA’s Perseverance rover found olivine-rich boulder-sized float rocks on the upper Jezero fan (Mars). These boulders have an ultramafic composition and their mineralogy is dominantly composed of Fo73±3 olivine with high-Mg orthopyroxene, Cr-rich Ti-Fe oxides and minor plagioclase and high-Ca pyroxene. Microtextural and petrological analysis reveals that these minerals crystallized at equilibrium. In addition, these boulders are different from all the bedrocks analyzed by Perseverance along its traverse which are crustal igneous rocks and sediments. Comparing our data to Martian meteorites and available Mars bulk silicate models (BSM), we discuss that these boulders could represent primitive melts and/or lower crustal material, and we specifically hypothesize that they could be mantle peridotites. We propose that these putative mantle rocks could have been excavated by the succession of impacts from the shallow mantle or lower crust in the Isidis region where Jezero crater is located. These olivine-rich boulders could thereby constitute the first direct analysis of a Martian mantle rock.

^1,2Alan E. Rubin
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.70080]
¹Department of Earth, Planetary, and Space Sciences, University of California, Los Angeles, California, USA
²Maine Mineral & Gem Museum, Bethel, Maine, USA
Published by arrangement with John Wiley & Sons

The O-, N-, Mo-, Ru-, Os-, Cr-, Ti-, Ni-, Fe-, Nd-, Ca-, Zn-, Sr-, and Mg-isotopic compositions of enstatite chondrites are essentially identical to those of the Earth and Moon. These correspondences suggest enstatite chondrites formed at ≈1 AU as the only known chondrite groups that accreted in the vicinity of a major planet. Bulk Earth has a higher Mg/Si weight ratio (1.09) than enstatite chondrites (0.63–0.76) and aubrites (0.84). Earth could have accreted from a mixture of these materials along with forsterite (Mg/Si = 1.73) and niningerite [(Mg,Fe)S] from the lower mantles of aubritic parent asteroids whose crusts and upper mantles were stripped off by hit-and-run collisions. The highly reducing conditions in which enstatite chondrites formed resulted from the dehydration of the inner regions of the nebula caused by outward diffusion of water vapor; this lowered the H2O/H2 ratio of the gas. The minor fraction of oxidized material in enstatite chondrites formed earlier—when the H2O/H2 ratio was briefly enhanced by inward-migrating ice particles. Enstatite chondrites are the most shocked chondrite groups, exhibiting a large variety of shock features—for example, deformed silicate lattices; petrofabrics; brecciation; shock veins; metal globules; coesite; impact-melt textures; impact-produced phases (keilite, sinoite, graphite and F-rich minerals); and fractionated bulk REE patterns. The Ar-Ar, Rb-Sr and I-Xe ages of enstatite chondrites indicate many of these rocks were shocked early in Solar System history, 4520–4563 Ma ago. This interval stretches back to the period of giant-planet migration, when the 1 AU region became dynamically excited.

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.