¹Shu-Zhou Wang, ¹Ai-Cheng Zhang, ¹Tian-Ran Du, ¹Jia-Ni Chen, ²Yuan-Yun Wen
Meteoritics & Planetary Science (in Press) Link to Article [DOI: 10.1111/maps.70256]
¹State Key Laboratory for Critical Earth Material Cycling and Mineral Deposits, School of Earth Sciences and Engineering, Nanjing University, Nanjing, China
²Center for Lunar and Planetary Sciences, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang, China

Published by arrangement with John Wiley & Sons

Yamato-type (CY) carbonaceous chondrites are a group of meteorites that experienced both intense aqueous alteration and subsequent dehydration. They consist of a few CY1 and CY2 samples; however, their nature and genetic relationship remains an issue of debate. Here, we report the detailed petrography and mineralogy of four sections of Dhofar 1988, a newly proposed CY chondrite. We find that Dhofar 1988 is a dimict breccia, containing a CY2-like host region (~73 area%) and numerous CY1-like dark clasts (~27 area%). Using Ti-minerals as a clue, we identified 14 calcium-aluminum-rich inclusions (CAIs) (including an Al-rich chondrule containing CAI material, with most of the CAIs present in the host region, ~1 area%) and only one CAI in dark clasts (~0.04 area%). These CAIs contain a series of Ti-minerals, including primary perovskite, Ti-rich fassaite, Ti-rich hibonite, and probably ilmenite–rutile assemblage, and secondary ilmenite, anatase, rutile, zirconolite (ideal formula CaZrTi₂O₇), and perovskite. Formation of the secondary Ti-minerals involves: (1) replacement of Ti-rich fassaite by melilite-like phase, perovskite, and minor spinel; (2) subsolidus breakdown of potential armalcolite to ilmenite and rutile and minor spinel and zirconolite; (3) alteration of perovskite to ilmenite; (4) alteration of perovskite to anatase; (5) alteration of fassaite to phyllosilicate and ilmenite; and (6) transition from ilmenite to perovskite. They probably formed during pre-alteration metamorphism (1 and 2), intense aqueous alteration (3–5), and postalteration metamorphism (6), respectively, and reflect the evolution of temperature and water/rock ratio. The similarity between the two components in Dhofar 1988 and the CY1 and CY2 samples indicates that the material from CY1 and CY2 samples was once mixed with each other through collision-induced mixing or during initial planetesimal accretion.

¹Hannah H. Kaplan, ¹Amy A. Simon, ²Victoria E. Hamilton, ³Joshua P. Emery, ¹Dennis Reuter, ¹Andy J. López-Oquendo
Meteoritics & Planetary Science (in Press)
Open Access Link to Article [DOI: 10.1111/maps.70239]
¹Solar System Exploration Division, NASA Goddard Space Flight Center, Greenbelt, Maryland, USA
²Solar System Science & Exploration Division, Southwest Research Institute, Boulder, Colorado, USA
³Department of Astronomy and Planetary Science, Northern Arizona University, Flagstaff, Arizona, USA

Published by arrangement with John Wiley & Sons

This study investigates the spatial distribution and spectral characteristics of the broad hydration feature near 3 μm across the surface of asteroid (101955) Bennu using OVIRS (OSIRIS-REx Visible and InfraRed Spectrometer) data. We analyzed multiple global OVIRS data sets obtained at different times throughout the Bennu day, revealing variations in band depth with wavelength, as well as wavelength-dependent correlations with temperature and other surface properties. Our analysis distinguishes between the behavior of the 2.74-μm and 3.0-μm features, which contribute to a broad 3-μm region absorption, suggesting they may have different origins or respond differently to surface conditions. The 2.74-μm band depth shows strong negative correlation with temperature and positive correlation with albedo and hydroxyl, whereas the 3.0-μm band depth exhibits primarily weak relationships with other spectral and surface parameters, such as temperature, albedo, and UV/visible spectral slope, indicating that these features probe different aspects of the surface materials. These findings demonstrate that space weathering likely plays a strong role within the hydration band. Specifically, temperature and time-of-day dependencies observed at 2.74-μm point to an active hydroxyl cycle on Bennu’s surface driven by solar wind hydrogen implantation, hydroxylation, and subsequent thermal desorption. Conversely, the distinct behavior of the 3.0-μm band suggests it may serve as an indicator of surface composition, including the phosphate minerals recently found in the returned sample; however, the lack of correlation with other expected diagnostic spectral features, such as a bluer UV/visible slope, currently leaves this relationship inconclusive.

¹Giorgio S. Senesi, ²Albert Jambon, ¹Olga De Pascale, ^3,4Lahcen Ouknine, ^3,4Hassan Nachit, ^4,5Fouad Khiri, ^3,4Abderrahmane Ibhi
Meteoritics & Planetary Science (in Press)
Open Access Link to Article [DOI: 10.1111/maps.70242]
¹CNR—Istituto per la Scienza e Tecnologia dei Plasmi (ISTP)—sede di Bari, Bari, Italy
²Université Côte d’Azur, Sorbonne Université, CNRS, OCA, IRD, Geoazur, Valbonne, France
³Earth Sciences Department, Faculty of Sciences, Ibn Zohr University, Agadir, Morocco
⁴University Meteorites Museum, Ibn Zohr University, Agadir, Morocco
⁵Faculty of Sciences, Earth Sciences Department, Laboratory of Geosciences, Environment and Geomatics (GEG), Ibn Zohr University, Agadir, Morocco

Published by arrangement with John Wiley & Sons

Despite meteorites having been recognized as the source of iron in some ancientiron artifacts, few archeological irons have been analyzed so far, as invasive methods areprecluded. In this work, four iron knives and one axe collected near Guelmime and Imilchil(Morocco) were investigated by advanced analytical techniques, including handheldlaser-induced breakdown spectroscopy (hLIBS), still not yet widely used, and portableX-ray fluorescence (pXRF). The analyzed objects are undated iron findings recoveredwithout an archeological context and represent test cases for assessing the analyticalcapabilities of hLIBS on corroded iron objects of possible meteoritic origin. Major andtrace element analyses, internal stratigraphy by depth profiling, and microscalecompositional mapping have been performed, which allowed assessment of the samplecomposition, heterogeneity, and corrosion. One of the five specimens studied appeared to bemade of meteoritic iron. The relative uncorroded state of this specimen, when compared toBronze Age irons, enabled investigation of the effect of forging on the composition,especially the mobility of Ni. In particular, the reliability of hLIBS-acquired analytical datafor the major elements Fe and Ni and the trace elements Ge and Au was shown. As well, apossible source relationship of sample #5 with NWA 859 (Taza)/Oglat Sidi Ali meteoritewas discussed and proposed, based on the chemical variations ascribed to the interplay ofprimordial heterogeneity and the introduction of carbon upon forging and corrosion.Furthermore, the analytical limitations of the hLIBS technique were suggested not to beinstrumental, but due to the heterogeneity of natural specimens, confirming that hLIBSrepresents a robust analytical tool for future field archeology and archeometric studies.

¹M. Kimura, ¹N. Imae, ²M. Komatsu, ¹A. Yamaguchi
Meteoritics & Planetary Science (in Press)
Open Access Link to Article [DOI: 10.1111/maps.70248]
¹National Institute of Polar Research, Tokyo, Japan
²Division of Liberal Arts and Sciences, Saitama Prefectural University, Saitama, Japan

Published by arrangement with John Wiley & Sons

Carbonaceous chondrites commonly contain amoeboid olivine aggregates (AOAs).Here, we investigated an AOA in the CR chondrite Y-793261. This AOA contains anunstable assemblage of forsterite and quartz. We found a rare occurrence of enstatite andquantitatively discuss its formation process. This enstatite occurs specifically betweenforsterite and quartz, indicating a solid-state reaction between them. By applying theexperimental results of Imae et al. (Proc. Japan Aca. 75: 229–234), we determined that thisAOA formed under high-temperature conditions (≳1169 K) over a period of approximately1–5 years. The reservoir where the AOA formed was enriched in 16 O. Subsequently, it cooledrapidly and was transported to the reservoir where the parent body accreted, incorporatingchondrules and matrix. The thermal history and physicochemical conditions of this AOA areapplicable to other AOAs.

^1,2,3A. Valantinas, ¹J. F. Mustard, ⁴A. Tullo, ⁵M. S. Bramble, ¹J. W. Head
Earth and Planetary Science Letters, 696, 120390
Open Access Link to Article [DOI: 10.1016/j.epsl.2026.120390]
¹Department of Earth, Environmental and Planetary Sciences, Brown University, Providence, USA
²Department of Earth and Planetary Sciences, ETH Zurich, Zurich, Switzerland
³Department of Earth Sciences, University of Cambridge, Cambridge, UK
⁴INAF, Osservatorio Astronomico di Padova, Padova, Italy
⁵Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA

Copyright Elsevier

The origin of the >100,000 km² regional olivine unit in the Nili Fossae-Jezero region has been variously attributed by orbital studies to airfall, effusive lavas, impact melt, or intrusive emplacement. In situ characterization of olivine-bearing igneous rocks in Jezero crater by the Mars 2020 Perseverance rover has revealed olivine cumulate textures indicative of effusive or intrusive magmatism, but conduits in the shallow-crustal feeder system that transported olivine-saturated magma have not been identified. Here we combine sub-meter pansharpened imagery from the Colour and Stereo Surface Imaging System (CaSSIS) and the High Resolution Imaging Science Experiment (HiRISE) with near-infrared spectral analysis from the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) to characterize a population of olivine-rich ridges and elongated features that crosscut the Fe/Mg-smectite basement at the “Horseshoe” site in Nili Fossae, ∼200 km north of Jezero. The features display a continuum of morphologies, from planar dike-like ridges through sinuous and braided lineaments that locally crosscut topography. Analysis of the 1 µm olivine near-infrared absorption places the features along the same compositional trend as the regional olivine–carbonate assemblage, and CRISM spectra resolve weak 1.9 and 2.32 µm absorptions diagnostic of hydrated/hydroxylated phases, indicating partial alteration of the intrusive olivine. We interpret these features as exhumed magmatic intrusions in a hydrated smectite basement, possibly exploiting pre-existing fault networks, and propose that they form part of a broader Jezero-Nili Fossae magmatic province. Magma-clay contact zones of this kind may provide a unique class of habitable environments in the shallow Noachian crust of Mars.

^1,2Xiaojia Zeng, ^1,2Xiongyao Li
Geochimica et Cosmochimica Acta (in Press) Link to Article [DOI: 10.1016/j.gca.2026.10.025]
¹State Key Laboratory of Critical Mineral Research and Exploration, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang, China
²Center for Lunar and Planetary Sciences, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang, China

Copyright Elsevier

Electrostatic discharge in Martian dust storms may significantly drive the chemical alteration and cycling of surface materials. Troilite is expected on Mars from magmatic and meteoritic sources but remains undetected by rovers, raising the question of possible electrostatic discharge-driven alteration. However, this hypothesis lacks direct experimental support. In this study, we experimentally simulate electrical discharge under Martian conditions by exposing troilite to such discharge in a CO₂ atmosphere at low pressure. We found that electrical discharge rapidly oxidizes troilite to magnetite (Fe₃O₄), forming a ∼ 100 nm thick, polycrystalline, defect-rich alteration layer on the troilite surface. This oxidation is driven by reactive oxygen species attack Fe-S bonds, displace sulfur, and convert the residual iron framework into magnetite. Such an electrical discharge-driven pathway offers a new water-free mechanism for magnetite formation on Mars, specifically active during the hyper-arid Amazonian epoch. This work also provides an additional explanation for the missing troilite in Martian soils and the widespread occurrence of magnetite in Martian dust. More broadly, this study expands our understanding of Martian surface evolution beyond water-dominated scenarios and highlights oxidative role of ongoing dust activities on present-day Mars.

^1,2,3Laura E. Jenkins, ^1,2Roberta L. Flemming, ^1,2Sam Nicholson, ⁴Mark Burchell, ⁴Kathryn Harriss, ^5,6Anne H. Peslier, ⁵Roy G. Christoffersen, ^7,8Jörg Fritz, ⁹Cornelia Meyer
Journal of Geophysical Research: Planets, 131, e2026JE010049
Open Access Link to Article [DOI: 10.1029/2026JE010049]
¹Department of Earth Sciences, Western University, London, ON, Canada
²Institute for Earth & Space Exploration, Western University, London, ON, Canada
³Now at: Diamond Light Source, Didcot, UK
⁴Centre for Astrophysics and Planetary Science, School of Engineering, Mathematics and Physics, University of Kent, Canterbury, UK
⁵Jacobs, NASA Johnson Space Center (JSC), Houston, TX, USA
⁶Department of Geological Sciences, New Mexico State University, Las Cruces, NM, USA
⁷Saalbau Weltraum Projekt, Heppenheim, Germany
⁸Zentrum für Rieskrater und Impaktforschung Nördlingen (ZERIN), Nördlingen, Germany
⁹Horizontereignis gUG, Berlin, Germany

Published by arrangement with John Wiley & Sons

Shock metamorphism is a ubiquitous process in our solar system. Shock pressure can be related to the lattice strain (ε) of individual minerals within a shocked sample. The lattice strain can be quantified within intact samples by in situ micro-X-ray diffraction (μXRD) using the Williamson-Hall method. The Williamson-Hall lattice strain (W-H ε) method has so far only been calibrated for olivine. This work extends the W-H ε method to high-Ca clinopyroxene. We obtained three sets of experimentally shocked clinopyroxene samples and calculated ε for each sample using μXRD. We created a calibration curve that relates ε to peak shock pressure experienced. Its trend line has the equation P = 222.85ε−8.60 GPa, with an error of ±9 GPa. The calibration curve was applied to the Martian meteorites Nakhla, Zagami, and Allan Hills A77005 (ALHA 77005) to compare these results with the meteorites’ optically determined shock stages. The peak shock pressures returned by the calibration curve are: 15 ± 9 GPa for Nakhla, 35 ± 9 GPa for Zagami, and 68 ± 9 GPa for ALHA 77005. These results agree with the meteorites’ previously determined shock stages. The development of a W-H ε calibration curve for high-Ca clinopyroxene is preliminary; however, it expands this method for evaluating shock metamorphism of shocked clinopyroxene-bearing samples, such as Martian shergottites.

¹M. C. Deahn et al. (>10)
Journal of Geophysical Research: Planets, 131, e2025JE009471
Open Access Link to Article [DOI: 10.1029/2025JE009471]
¹Purdue University, West Lafayette, IN, USA

Published by arrangement with John Wiley & Sons

The Mars 2020 rover is currently traversing the western rim of Jezero, a Middle to Late Noachian‐aged crater formed by an impactor that struck the northwest edge of Isidis Planitia (hereafter referred to as theIsidis basin) on Mars. Previous studies suggest that pre‐Isidis basin and Noachian outcrops are preservedthroughout this region; however, the nature of these exposures in the Jezero crater rim is unclear. It has beenhypothesized that crater‐forming processes should expose these ancient crustal rocks in the Jezero craterrim—presenting a unique opportunity to explore ancient Mars outcrops that are otherwise typically buried byyounger units. Jezero’s rim has undergone extensive erosion and modification since its formation ∼3.9 billionyears ago. To investigate these ancient lithologies, the Mars 2020 Science Team produced a 1:2500 scalegeologic map and interpreted a bedrock map of the ∼14.5 × 3.5 km area around the western Jezero crater rim.We identified, mapped, and defined nine bedrock units on Jezero crater’s rim to make connections to regionalgeologic units and identify deposits or features unique to Jezero crater. We found that the rim likely preserves arecord of pre‐Isidis bedrock, the Isidis and Jezero impacts, and post‐impact geologic processes. We alsoobserved candidate megabreccia, hydrothermal ridges, and regional volcanics that may be targets for futurerover‐based investigations. Our results show that in situ investigation of pre‐Isidis and Noachian‐agedlithologies preserved on the rim will provide insight into the nature of Mars’ early crustal formation andcratering processes.

¹M. M. Morris, ¹J. A. Hurowitz, ¹L. Ehm
Journal of Geophysical Research: Planets, 131, e2026JE010007
Link to Article [DOI: 10.1029/2026JE010007]
¹Department of Geosciences, Stony Brook University, Stony Brook, NY, USA

Published by arrangement with John Wiley & Sons

Fe-Mg carbonates on Mars preserve key evidence of past aqueous chemistry and climate, yet their formation conditions remain poorly constrained. We conducted low-temperature (∼25°C) anoxic precipitation experiments under Mars-like conditions, systematically varying pH, Fe:Mg ratio, Ca²⁺ content, and carbonate saturation state. Results show initial pH and saturation state as primary controls: near-neutral pH favored siderite (FeCO₃) and chukanovite (Fe₂(CO₃)(OH)₂) precipitation, while alkaline conditions promoted the precipitation of hydrated Mg-carbonate and Fe-substituted Mg-hydroxide and layered double hydroxides. Ca²⁺ suppressed amorphous Fe-carbonate precursor precipitation, enhancing the growth of rhombohedral carbonate and enabling partial Ca²⁺ substitution. A limited number of elevated temperature experiments (50°C) did not enhance Mg²⁺ substitution in siderite, but instead resulted in the precipitation of very high-magnesium calcite (MgCa(CO₃)₂) overgrowths. Mg²⁺ incorporation into siderite (at the level of ∼10 mol%) occurred only under low Fe:Mg ratios and high magnesite (MgCO₃) saturation, highlighting kinetic barriers to Mg²⁺ substitution.

¹Emmanuel Jacquet
Meteoritics & Planetary Science (in Press)
Open Access Link to Article [DOI: 10.1111/maps.70247]
¹Institut de Minéralogie, de Physique des Matériaux et de Cosmochimie, UMR 7590, Muséum National d’Histoire Naturelle, CNRS, Paris, France

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Chondrule sizes are an important discriminant of chondrite groups and chondrule formation theories. Yet most studies report 2-D sizes without attempting the somewhat tedious corrections to 3-D proposed in the past literature. I show here that 3-D size averages can be simply calculated directly from 2-D averages of appropriate powers of sizes (and vice-versa), without having to reconstruct 3-D distributions, although explicit formulas to that end are also provided. This illuminates the comparison between 3-D and 2-D arithmetic size averages, which are confirmed to be little different for the published data sets. Yet I suggest another type of average, the “sphere-weighted average” (i.e., weighted by the chondrule equal-volume sphere area), a measure of the surface/volume ratio of the whole chondrule population, which is more robust against omission of small chondrules. While larger than the arithmetic averages, it is best in line with previous literature estimates based on less exhaustive surveys of chondrules.