D. Das¹ et al. (>10)
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.14375]
¹Los Alamos National Laboratory, Los Alamos, New Mexico, USA
Published by arrangement with John Wiley & Sons

The aim of this work is to provide a model-backed hypothesis for the formation of evaporites—sulfates, borates—in Gale crater using thermochemical modeling to determine constraints on their formation. We test the hypothesis that primary evaporites required multiple wet–dry cycles to form, akin to how evaporite assemblages form on Earth. Starting with a basalt-equilibrated Mars fluid, Mars-relevant concentrations of B and Li were added, and then equilibrated with Gale lacustrine bedrock. We simulated the cycles of evaporation followed by groundwater recharge/dilution to establish an approximate minimum number of wet–dry cycles required to form primary evaporites. We determine that a minimum of 250 wet–dry cycles may be required to start forming primary evaporites that consist of borates and Ca-sulfates. We estimate that ~14,250 annual cycles (~25.6 k Earth years) of wet and dry periods may form primary borates and Ca-sulfates in Gale crater. These primary evaporites could have been remobilized during secondary diagenesis to form the veins that the Curiosity rover observes in Gale crater. No Li salts form after 14,250 cycles modeled for the Gale-relevant scenario (approximately 10⁶ cycles would be needed) which implies Li may be leftover in a groundwater brine after the time of the lake. No major deposits of borates are observed to date in Gale crater which also implies that B may be leftover in the subsequent groundwater brine that formed after evaporites were remobilized into Ca-sulfate veins.

Kees C. WELTEN¹, Marc W. CAFFEE², Kevin RIGHTER^3,4, Ralph P. HARVEY^5,6, John SCHUTT⁵, and James M. KARNER⁷
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.14376]
¹Space Sciences Laboratory, University of California, Berkeley, California, USA
²Department of Physics and Astronomy, Purdue University, West Lafayette, Indiana, USA
³ARES, Mail Code XI2, NASA Johnson Space Center, Houston, Texas, USA
⁴Department of Earth and Environmental Sciences, University of Rochester, Rochester, New York, USA
⁵Department of Earth, Environmental and Planetary Science, Case Western Reserve University, Cleveland, Ohio, USA
⁶Antarctic Search for Meteorites (ANSMET), Case Western University, Cleveland, Ohio, USA
⁷Geology & Geophysics, University of Utah, Salt Lake City, Utah, USA
Published by arrangement with John Wiley & Sons

We reevaluated pairing relationships among 56 Antarctic howardites, eucrites, and diogenites (HED) from the Miller Range ice fields (MIL) based on new measurements of cosmogenic radionuclides and bulk composition of 28 HED samples and one HED-related dunite. These measurements were combined with petrographic examinations and find locations of the majority of the HED samples at MIL. During these studies, we reclassified 1 howardite, MIL 07665, as a brecciated diogenite and eight howardites as brecciated eucrites. We conclude that 18 of the 23 diogenites belong to a single large pairing group of brecciated diogenites. This pairing group includes at least seven samples with bulk compositions that indicate they contain 10%–25% of eucritic material, so technically the meteorites of this pairing group cross the boundary between diogenites and howardites. We also identified several smaller pairing groups (of 2–5 members each) among the eucrites and two paired samples among the howardites. The pairing relationships among the Miller Range eucrites are not fully resolved yet, as the collection contains many small specimens (<10 g) that were not included in this study. Altogether, we conclude that the 56 HED meteorites at Miller Range represent between 19 and 26 individual falls.

L. C. CHAVES^1,2*, M. S. THOMPSON², C. A. DUKES³, M. J. LOEFFLER⁴, M. F. MARTINEZ-MOTTA⁵, H. VANNIER², B. H. N. HORGAN², N. SMITH⁶, and K. ARDREY⁶
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.14371]
¹Lunar and Planetary Laboratory, The University of Arizona, Tucson, Arizona, USA
²Department of Earth, Atmospheric, and Planetary Sciences, Purdue University, West Lafayette, Indiana, USA
³Laboratory for Astrophysics and Surface Physics, University of Virginia, Charlottesville, Virginia, USA
⁴Department of Astronomy and Planetary Science, Northern Arizona University, Flagstaff, Arizona, USA
⁵Departamento de Geociencias, Facultad de Ciencias, Universidad de los Andes, Bogota, Colombia
⁶Materials Science and Engineering, University of Virginia, Charlottesville, Virginia, USA
Published by arrangement with John Wiley & Sons

Pentlandite (Fe, Ni)₉S₈ is an important accessory mineral on asteroidal surfaces. It has been identified in returned regolith samples from asteroids Itokawa, Ryugu, and Bennu. Currently, systematic studies to understand the response of this mineral phase under space weathering conditions are lacking. In this work, we performed pulsed laser irradiation to simulate micrometeoroid impacts, and ion irradiation with 1 keV H⁺ and 4 keV He⁺ to simulate solar wind exposure for pentlandite. To understand the chemical, microstructural, and spectral alterations resulting from simulated space weathering, we conducted X-ray photoelectron spectroscopy, scanning electron microscopy, transmission electron microscopy, and reflectance spectroscopy across the visible to near-infrared wavelengths. Our results reveal S depletion and a change in the Fe:Ni ratio at the sample surface with continuing ion irradiation. Ion irradiation also created compositionally distinct rims in the pentlandite samples, while laser irradiation produced a surface melt. Additionally, we identified hillocks protruding from the pentlandite rim after He⁺ irradiation. Our findings also show that laser and H⁺-irradiation cause the sample to brighten, while He⁺ ion irradiation causes darkening. The change in spectral slope for samples irradiated with the laser and He⁺ is minimal, while H⁺ causes the sample to redden slightly. This work will enable the identification of space weathering signatures on pentlandite grains present in the recently returned samples from asteroids Ryugu and Bennu.

^1,2R.H. Hewins et al. (>10)
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2025.05.037]
¹IMPMC, Sorbonne Université, MNHN, UMR CNRS7590, 75005 Paris, France
²EPS, Rutgers Univ., Piscataway, NJ 08854, USA
Copyright Elsevier

An understanding of the differences between ungrouped, or anomalous, and normal carbonaceous chondrites could provide information on the population of parent bodies required to explain a chondrite group and on first solid accretion and evolution in the outer protoplanetary disk. The CR chondrites are key in this respect, as they display a unique formation history that distinguishes them from other groups. They are known to have formed between 4.1 and 4.6 Myr after CAI, with two generations of chondrules. Northwest Africa (NWA) 14674 is a CR2 anomalous (CR2-an) chondrite with very similar oxygen isotope composition, dark inclusion (DI) content, and serpentine-magnetite matrix to Al Rais (CR2-an). Both are petrologic subtype 2.3 with fresh magnesian olivine, and partly altered ferroan olivine, pyroxene, and metal. Additionally, NWA 14674 contains residual GEMS-like material at the nanoscale within preserved moderately altered areas. DI and matrix in NWA 14674 are mineralogically similar but they have different fabrics, and matrix is more porous than both DI and fine-grained rims (FGR). Matrix has aligned framboidal magnetite aggregates swathing the chondrules, suggesting slight compaction of the chondrite. Some DI have inner chondrule fragments and concentric layers richer and poorer in magnetite, indicating formation as accretionary pellets and lapilli: they are pebbles rather than clasts. The framboidal magnetite abundance is consistent with an alkaline alteration fluid potentially due to NH3 ice mixed with the more common water ice, which implies late distal accretion. Comparison with the CR chondrites Bells (regolith-like) and NWA 801 (with high-pressure clasts) indicates that a complex history involving inward drift, disruption of the grandparent body, and reaccretion of debris along with chondrules, DI pebbles, and dust is required to explain CR chondrite formation. The diverse facies observed in CR chondrites may be explained by the formation of relatively large parent bodies, comprising distinct layers (core to regolith). Some material has been inherited from a chondritic protoplanet that formed during the oligarchic growth phase of planetary formation. Subsequently, this initial body underwent disruption and partial reaccretion into the CR parent body.

¹Wei Dai,¹Frédéric Moynier,¹Zheng-Yu,^1,2Linru Fang,³James M. D. Day,⁴Marine Paquet,¹Julien Siebert
Proceedings of the National Academy of Science of the USA (PNAS) 22, e2422726122 Link to Article [https://doi.org/10.1073/pnas.242272612]
¹Université Paris Cité, Institut de Physique du Globe de Paris, CNRS, Paris 75005, France
²Centre for Star and Planet Formation, Globe Institute, University of Copenhagen, Copenhagen K DK-1350, Denmark
³Scripps Institution of Oceanography, University of California San Diego, La Jolla, CA 92093-0244
⁴Université de Lorraine, CNRS, Centre de Recherches Pétrographiques et Géochimiques, Nancy F-54000, France

The extent of moderately volatile elements (MVE) depletion and its effects on the Moon’s evolutionary history remain contentious, partly due to unintentionally biased sampling by the Apollo missions from the Procellarum KREEP Terrane. In this study, we analyzed the Zn and K isotope compositions of a series of lunar basaltic meteorites, which vary in Th content and are likely to represent a broader sampling range than previous studies, including samples from the far side of the Moon. Our findings indicate remarkably consistent Zn and K isotope compositions across all lunar basalt types, despite significant variations in Th content. This consistency suggests a relatively homogeneous isotopic composition of volatile elements within the Moon, unaffected by subsequent impact events that formed major basins. Our results suggest that the estimates of MVE abundance and isotopic compositions from the Apollo returned samples are likely representative of the bulk Moon, supporting a globally volatile-depleted lunar interior.

¹M. V. Goryunov,²G. Varga,²Z. Dankházi,¹A. V. Chukin,³I. Felner,⁴E. Kuzmann,⁴Z. Homonnay,¹R. F. Muftakhetdinova,¹V. I. Grokhovsky,¹M. I. Oshtrakh
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.14363]
¹Institute of Physics and Technology, Ural Federal University, Ekaterinburg, Russian Federation
²Department of Materials Physics, Eötvös Loránd University, Budapest, Hungary
³Racah Institute of Physics, The Hebrew University, Jerusalem, Israel
⁴Laboratory of Nuclear Chemistry, Institute of Chemistry, Eötvös Loránd University, Budapest, Hungary
Published by arrangement with John Wiley & Sons

A fragment of the Kayakent IIIAB iron meteorite was analyzed using optical microscopy, scanning electron microscopy (SEM) with energy-dispersive spectroscopy (EDS) and electron backscatter diffraction (EBSD), X-ray diffraction (XRD), magnetization measurements, and Mössbauer spectroscopy. Optical microscopy and SEM show the presence of (i) the pure α2-Fe(Ni, Co) grains, (ii) the γ-Fe(Ni, Co) phase grains, (iii) the γ-Fe(Ni, Co) rims around the α2-Fe(Ni, Co) phase areas, (iv) the cloudy zone (a mixture of the γ-FeNi(Co) and α2-Fe(Ni, Co) phases), (v) plessite structures, and (vi) schreibersite inclusions in the α-Fe(Ni, Co) phase. The α-Fe(Ni, Co) phase demonstrates the ε-structure αε-Fe(Ni, Co) with the presence of at least three different orientations of the αε-Fe(Ni, Co) microcrystals, as shown by EBSD. EDS indicates variations in the Ni concentrations in the following ranges: (i) ~5.4–7.2 atom% in the α-Fe(Ni, Co) phase, (ii) ~15–18 atom% in the α2-Fe(Ni, Co) phase, and (iii) ~29–47 atom% in the γ-Fe(Ni, Co) phase grains. Schreibersite inclusions contain ~23.5–23.6 atom% of P, ~45.1–46.5 atom% of Fe, and ~28.8–31.4 atom% of Ni. The presence of ~98.1 wt% of the α-Fe(Ni, Co) phase and ~1.9 wt% of the γ-Fe(Ni, Co) phase is found by XRD in the powdered sample, while schreibersite is detected by XRD in the surface of the section only. Magnetization measurements show ferromagnetic multiphase material and a magnetic saturation moment of 175 emu g−1. The room temperature Mössbauer spectrum of the powdered Kayakent IIIAB sample demonstrates six magnetic sextets related to the ferromagnetic α2-Fe(Ni, Co), α-Fe(Ni, Co), and γ-Fe(Ni, Co) phases and one singlet assigned to the paramagnetic γ-Fe(Ni, Co) phase. In addition, the Mössbauer spectrum shows six minor magnetic sextets associated with 57Fe in the M1, M2, and M3 sites in schreibersite and one minor doublet shape assigned to the superparamagnetic rhabdite microcrystals. The iron fractions in the detected phases can be roughly estimated as follows: (i) ~11.9% in the α2-Fe(Ni, Co) phase, (ii) ~75.6% in the α-Fe(Ni, Co) phase, (iii) ~5.7% in the disordered γ-Fe(Ni, Co) phase with Ni content of ~34–40 atom%, (iv) ~1.5% in the more ordered γ-Fe(Ni, Co) phase with a higher Ni content (~46–47 atom%), (v) ~0.5% in the paramagnetic γ-Fe(Ni, Co) phase (~29–33 atom% of Ni), (vi) ~3% in schreibersite, and (vii) ~2% in rhabdite.

^1,2Zhi Li,^1,3Ying-Kui Xu,^4,5Shui-Jiong Wang,⁴Si-Zhang Sheng,^1,3Shi-Jie Li,^1,3Xiong-Yao Li,^1,3Jian-Zhong Liu,⁶Dan Zhu
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.14369]
¹Center for Lunar and Planetary Sciences, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang, China
²College of Earth and Planetary Sciences, University of Chinese Academy of Sciences, Beijing, China
³CAS Center for Excellence in Comparative Planetology, Hefei, China
⁴State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences (Beijing), Beijing, China
⁵Frontiers Science Center for Deep-Time Digital Earth, China University of Geosciences (Beijing), Beijing, China
⁶State Key Laboratory of Ore Deposit Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang, China
Published by arrangement with John Wiley & Sons

High-energy impact events prevalent during planetary accretion in the solar system’s evolution significantly shaped planetary bodies, though the effects of shock metamorphism on nickel (Ni) isotope fractionation remain unclear. To investigate the effect of the shock process on Ni isotopes, we selected three shocked ordinary chondrites (OCs) and obtained three sample pairs, each consisting of a melted region and its corresponding unmelted region. We also prepared two whole rock samples and four pairs of magnetic and coupled nonmagnetic samples. The shock melt pockets (SMPs) from three shocked OCs (Chelyabinsk LL5, Viñales L6, Tassédet 004 H5) show δ⁶⁰Ni values of 0.15 ± 0.05‰, 0.14 ± 0.02‰, and 0.20 ± 0.04‰, while adjacent unmelted parts show δ⁶⁰Ni values of 0.21 ± 0.03‰, 0.19 ± 0.01‰, and 0.19 ± 0.03‰. These data are slightly higher than the BSE value (0.11 ± 0.01‰) but generally overlap with the Ni isotopic variation of OCs (0.15–0.51‰) reported in previous studies. The SMPs do not show discernible isotopic variations relative to coupled unmelted parts, suggesting that shock-induced evaporation could not cause Ni isotope fractionation. The value of bulk OCs is calculated by compiling data from previous and this study, yielding a value of ‰0.21−0.11+0.28‰. Moreover, no consistent Ni isotopic variations from four pairs of magnetic and nonmagnetic counterparts are observed. Several possible processes resulting in Ni isotopic variations are discussed. A slight negative correlation between S content and Ni isotopic composition, along with a positive correlation between Ni elemental and isotopic composition in shocked OCs, suggests that the Ni isotopic characteristics may be predominantly influenced by the relative proportions of metal and sulfide phases.

¹Masaaki Miyahara,²Takaaki Noguchi,³Akira Yamaguchi,¹Toru Nakahashi,¹Yuto Takaki,^2,4Toru Matsumoto,⁵Naotaka Tomioka,²Akira Miyake,²Yohei Igami,⁶Yusuke Seto
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.14370]
¹Graduate School of Advanced Science and Engineering, Hiroshima University, Higashi-Hiroshima, Japan
²Division of Earth and Planetary Sciences, Kyoto University, Kyoto, Japan
³National Institute of Polar Research, Tokyo, Japan
⁴The Hakubi Center for Advanced Research, Kyoto University, Kyoto, Japan
⁵Kochi Institute for Core Sample Research, X-star, JAMSTEC, Nankoku, Japan
⁶Department of Geosciences, Osaka Metropolitan University, Osaka, Japan
Published by arrangement with John Wiley & Sons

Djerfisherite, a K-bearing Fe-Ni sulfide, was identified in grain C0105-042 collected from the subsurface of asteroid Ryugu through SEM and TEM analyses. The mineral occurs as an isolated crystal embedded within a matrix of Mg-Fe phyllosilicates. Although djerfisherite is known to form as a condensate phase in enstatite chondrites and aubrites, its mode of occurrence in Ryugu grain C0105-042 is markedly different. Two possible origin scenarios are considered: (i) an extrinsic origin, in which a djerfisherite fragment derived from enstatite chondrites or aubrites was deposited onto asteroid Ryugu, and (ii) an intrinsic origin, where djerfisherite formed in situ through a localized reaction between K-bearing hot fluid or vapor and Fe-Ni sulfide under reducing alkaline conditions within asteroid Ryugu’s body. Isotopic data, which could directly constrain its origin, are currently unavailable; thus, the origin of djerfisherite remains unresolved. Nonetheless, this finding suggests the presence of exotic material or localized chemical heterogeneities within Ryugu’s body, offering new insights into the complex evolutionary processes that shaped primitive bodies in the early Solar System.

¹Naotaka Tomioka,^2,3Kosuke Kurosawa,⁴Akira Miyake,⁴Yohei Igami,⁵Takayoshi Nagaya,⁴Takaaki Noguchi,⁴Toru Matsumoto,⁶Masaaki Miyahara,⁷Yusuke Seto
American Mineralogist 110, 945-955 Link to Article [https://doi.org/10.2138/am-2024-9540]
¹Kochi Institute for Core Sample Research, X-star, Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Nankoku, Kochi 783-8502, Japan
²Department of Human Environmental Science, Graduate School of Human Development and Environment, Kobe University, 3-11, Tsurukabuto, Nada-ku, Kobe, Hyogo 657-8501, Japan
³Planetary Exploration Research Center, Chiba Institute of Technology, Narashino, Chiba 275-0016,Japan
⁴Division of Earth and Planetary Sciences, Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan
⁵Department of Environmental Sciences, Tokyo Gakugei University, Koganei, Tokyo 184-8501, Japan
⁶Earth and Planetary Systems Science Program, Graduate School of Advanced Science and Engineering, Hiroshima University, Higashihiroshima, Hiroshima 739-8526, Japan
⁷Department of Geosciences, Graduate School of Science & School of Science, Osaka Metropolitan University, Sumiyoshi-ku, Osaka 558-8585, Japan
Copyright: The Mineralogical Society of America

Shock recovery experiments were performed using a two-stage light gas gun to clarify the progressive deformation microstructures of calcite at the submicrometer scale concerning pressure. Decaying compression pulses were produced using a projectile that was smaller than the natural marble target. In two experiments, natural marble samples were shocked to 13 and 18 GPa at the epicenters of the targets. Calcite grains shocked in the pressure range of 1.1–18 GPa were examined using polarized light microscopy and (scanning) transmission electron microscopy. The density of free dislocations in the grains shocked at 1.1–2.2 GPa [108–9 (cm−2)] is comparable to that of unshocked Carrara calcite grains. Subparallel bands of entangled dislocations <1 μm are formed at 4.2 GPa, and strongly entangled dislocations spread throughout the focused ion beam (FIB) sections at 7.3–18 GPa. Dislocations selectively nucleate and entangle near the slip planes at pressures above ∼3 GPa, corresponding to the transition from sharp extinction to undulatory extinction, according to the microstructural evolution with shock pressure. Above ∼6 GPa, the dislocations nucleated homogeneously throughout the calcite crystals. The dislocation microstructure in a calcite grain collected from the asteroid Ryugu particle is similar to that of the experimentally shocked calcite at 4.2 GPa. The estimated pressure of 2–3 GPa, determined through fault mechanics analyses and the presence of dense sulfide minerals in the Ryugu particles, is in line with this pressure.

¹Sylvain Laforet,¹Hugues Leroux,¹Corentin Le Guillou,²Maya Marinova,¹Adrien Néri,¹Adrien Teurtrie,¹Francisco de la Peña,¹Damien Jacob,²Alexandre Fadel,³David Troadec
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.14366]
¹Université de Lille, CNRS, INRAE, Centrale Lille, UMR 8207-UMET-Unité Matériaux et Transformations, Lille, France
²Université de Lille, CNRS, INRAE, Centrale Lille, Université Artois, FR 2638-IMEC-Institut Michel-Eugène Chevreul, Lille, France
³Université de Lille, CNRS, Centrale Lille, Junia, Univ. Polytechnique Hauts-de-France, UMR 8520 – IEMN – Institut d’Electronique de Microélectronique et de Nanotechnologie, Lille, France
Published by arrangement with John Wiley & Sons

The first few microns of the surface of airless bodies are subject to severe changes due to the harsh environment of space, known as space weathering. The Hayabusa2 sample return mission from the asteroid Ryugu provides the first opportunity to study these effects on a carbonaceous and hydrated body. Understanding the structural and chemical changes that occur in the space weathered layers of Ryugu is crucial to correctly interpreting the mechanisms involved in such processes. This study employs transmission electron microscopy to achieve the spatial resolution necessary to analyze the nanoscale heterogeneities in these modified layers. The chemical analyses indicate that features present are likely to represent the spattering of a Ryugu-like material, possibly from a different lithology of the asteroid. However, such material appears to be completely dehydroxylated and depleted in sulfur by approximately 20%. Furthermore, the nanoscale dispersion of vesicles and rounded nanosulfides found in these melt layers helps to estimate the temperatures (>1300°C) and the time scales (<10−8 s) involved in their formation. In addition, this study describes and discusses a unique spherical feature not previously observed in Ryugu samples. The 3 μm-sized object shows strong similarities to microchondrules observed in some carbonaceous (CM2) and ordinary chondrites, suggesting a divergent thermal history from that of the melt layers.