^1,2Jun-Feng Chen,^3,4Yu-Yan Sara Zhao,^1,4Qiao Shu,^1,5Sheng-Hua Zhou,^1,4Wei Du,⁶Jing Yang
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2024.05.008]
¹State Key Laboratory of Ore Deposit Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China
²University of Chinese Academy of Sciences, Beijing 100049, China
³Research Center for Planetary Science, College of Earth and Planetary Sciences, Chengdu University of Technology, Chengdu 610059, China
⁴CAS Center for Excellence in Comparative Planetology, Hefei 230026, China
⁵School of Earth Sciences, Zhejiang University, Hangzhou 310027, China
⁶Center for Lunar and Planetary Sciences, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China
Copyright Elsevier

Shergottite meteorites, classified as depleted, intermediate, or enriched based on incompatible trace elements and specific radiogenic isotope compositions (Sr, Nd, and Hf isotope ratios), point to multiple Martian mantle source regions. The oxygen fugacity (fO2) of these mantle regions, determined from early crystallizing minerals using the olivine-pyroxene-spinel oxybarometer, appears to correlate with incompatible trace element enrichment and isotope compositions. However, values derived from the vanadium-in-olivine oxybarometer challenge this correlation, hinting at potential biases in oxybarometry or complexities in the redox conditions of the Martian mantle. By analyzing the intermediate shergottite Northwest Africa (NWA) 11043 with various oxybarometers, this study deduced its origin from a reduced mantle source, with an average fO2 value of −0.77 ± 0.35 relative to the iron-wüstite (IW) buffer. Notably, these values coincide with those of depleted shergottites, which represent the depleted Martian mantle region. This redox similarity between intermediate and depleted shergottites contrasts with earlier notions that postulated intermediate shergottites as a mix of depleted and enriched mantle derivatives. Moreover, intermediate shergottites such as NWA 11043, Elephant Moraine (EETA) 79001A, and Allan Hills (ALH) 77005 display 176Hf/177Hf values akin to those of depleted shergottites, suggesting that intermediate mantle components can be separated from the depleted mantle source at approximately 2.2 Ga based on model age calculations. Therefore, there presents a consistent redox state between mantle magma sources of both intermediate and depleted shergottites since the Hesperian period, while enriched shergottites lean toward more oxidized conditions past source formation.

This study prompts a reassessment of conventional theories, emphasizing the nuanced redox evolution of the Martian mantle across distinct mantle source regions and underscoring the complexity of the redox evolution of the Martian mantle. The emergence of chemically diverse mantle reservoirs might predominantly arise from early magma ocean differentiation processes, albeit with inherent oxidation nuances. The differences in fO2 observed between intermediate and depleted shergottites underscore the need for more in-depth studies to decipher Martian mantle differentiation and evolution.

^1,2Dennis Harries et al. (>10)
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.14176]
¹Institute of Geoscience, Friedrich Schiller University Jena, Jena, Germany
²European Space Resources Innovation Centre, Luxembourg Institute of Science and Technology, Belvaux, Luxembourg
Published by arrangement with John Wiley & Sons

Regolith samples returned from asteroid 162173 Ryugu by the Hayabusa2 mission provide direct means to study how space weathering operates on the surfaces of hydrous asteroids. The mechanisms of space weathering, its effects on mineral surfaces, and the characteristic time scales on which alteration occurs are central to understanding the spectroscopic properties and the taxonomy of asteroids in the solar system. Here, we investigate the behavior of the iron monosulfides mineral pyrrhotite (Fe1−xS) at the earliest stages of space weathering. Using electron microscopy methods, we identified a partially exposed pyrrhotite crystal that morphologically shows evidence for mass loss due to exposure to solar wind ion irradiation. We find that crystallographic changes to the pyrrhotite can be related to sulfur loss from its space-exposed surface and the diffusive redistribution of resulting excess iron into the interior of the crystal. Diffusion profiles allow us to estimate an order of magnitude of the exposure time of a few thousand years consistent with previous estimates of space exposure. During this interval, the adjacent phyllosilicates did not acquire discernable damage, suggesting that they are less susceptible to alteration by ion irradiation than pyrrhotite.

¹Yuki Masuda,²Sota Niki,²Takafumi Hirata,¹Tetsuya Yokoyama
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.14190]
¹Department of Earth and Planetary Sciences, Tokyo Institute of Technology, Meguro, Tokyo, Japan
²Geochemical Research Center, Graduate School of Science, The University of Tokyo, Bunkyo, Tokyo, Japan
Published by arrangement with John Wiley & Sons

Calcium–aluminum-rich inclusions (CAIs) in chondrites are one of the oldest materials in the solar system. Presence of refractory minerals in CAIs suggests that they formed thorough a condensation process from nebular gas of solar composition. In particular, fine-grained CAIs (FGs) have escaped melting after condensation, and thus, the elemental distribution of rare earth elements (REEs) in FG minerals provides key information for elucidating the condensation processes. Although the REE abundances of FG fragments have been investigated in previous studies, the distribution of REEs in individual FG constituent minerals remains poorly explored. Here, we demonstrate the utility of laser imaging of REE distribution in CAIs by analyzing five FGs found in the Allende CV3 chondrite using multiple-spot femtosecond laser ablation (msfsLA)-ICP-MS. The msfsLA-ICP-MS imaging system allows for a rapid acquisition of a wider range of REE distributions than previously achieved by Secondary ion mass spectrometry-based imaging techniques. Out of the five FGs examined in this study, three showed the homogeneous REE patterns, while the other two indicated variable REE patterns within each FG. These observations presumably reflect differences in the chemical processes experienced by the FGs, and indicate that multi-step chemical processes were recorded in some of the FGs. The msfsLA-ICP-MS imaging technique can characterize the elemental distribution of individual FGs under the comparable spatial resolution with high-analysis throughput, and thus, it is an effective new method for advancing the taxonomy of FGs, which will improve our understanding of the physicochemical conditions that prevailed in the early solar system.

¹Andrew F. Parisi,¹Elizabeth J. Catlos,¹Michael E. Brookfield,^2,3Axel K. Schmitt,¹Daniel F. Stöckli,⁴Daniel P. Miggins,¹Daniel S. Campos
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.14183]
¹Jackson School of Geosciences, University of Texas at Austin, Center for Planetary Systems Habitability, Austin, Texas, USA
²Institut für Geowissenschaften, Ruprecht-Karls-Universität Heidelberg, Heidelberg, Germany
³John de Laeter Centre, Curtin University, Bentley, Western Australia, Australia
⁴Oregon State University, Oregon State University Argon Geochronology Laboratory, Corvallis, Oregon, USA
Published by arrangement with John Wiley & Sons

The Slate Islands (Ontario) is one of Canada’s larger impact structures at 32 km in diameter and has been linked to the Ordovician meteorite event (OME). We report zircon U–Pb dates from two suevite and two syenite samples collected from the Slate Islands. Plagioclase 40Ar/39Ar dates were also obtained from one of the samples. The plagioclase and most zircon dates record pre-impact ages with links to known tectonic events, including those associated with the assembly of the Superior Craton at approximately 2700 Ma. However, Neoarchean zircon grains appear to be reset at 456.1 ± 6.9 Ma (±2σ) based on the lower intercept of discordia for all dated samples. The date overlaps its previously accepted age of 450 Ma and would be 2–19 million years following the parent asteroid breakup if related to the OME.

¹Peiyu Wu,¹Kyle Dayton,¹Esteban Gazel,²Teresa Porri
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.14180]
¹Department of Earth and Atmospheric Sciences, Cornell University, Ithaca, New York, USA
²Cornell Institute of Biotechnology, Cornell University, Ithaca, New York, USA
Published by arrangement with John WIley & Sons

Estimation of the composition of planetary rocks and minerals is crucial for understanding their formation processes. In this study, we present the application of X-ray nano-computed tomography (nano-XCT) for non-destructive three-dimensional (3-D) phase analysis and estimation of phase abundances in rare Martian meteorite samples, specifically chassignite Northwest Africa (NWA) 2737. We determined the most suitable laser power for minimizing artifacts and maximizing phase contrast. By utilizing nano-XCT, we successfully identified and segmented primary phases in the bulk meteorite sample. Additionally, we were able to locate and segment crystallized silicate melt inclusions within the meteorite. The phase abundances in bulk NWA 2737 and within melt inclusions calculated using nano-XCT were in good agreement with previous studies that used thin section calculations, demonstrating the reliability of nano-XCT as a non-destructive alternative for estimating bulk phase abundances in rare samples. This study develops a benchmarking protocol and demonstrates the efficacy of nano-XCT as a non-destructive technique for generating an overview of phase distribution and assemblages of melt inclusions within rare samples. Future research can benefit from combining non-destructive 3-D phase assemblage estimations with non-destructive 3-D chemical analysis techniques to achieve a fully non-destructive parental magma composition estimation of rare cumulate samples.

¹Tom Boonants,¹Steven Goderis,¹Bastien Soens,¹Flore Van Maldeghem,^2,3Stepan M. Chernonozhkin,²Frank Vanhaecke,⁴Matthias van Ginneken,¹Christophe Snoeck,¹Philippe Claeys
Meteoritics & Planetary Science (in Press)  Link to Article [https://doi.org/10.1111/maps.14188]
¹Archaeology, Environmental Changes and Geo-Chemistry, Vrije Universiteit Brussel, Brussels, Belgium
²Department of Chemistry, Atomic & Mass Spectrometry A&MS Research Unit, Ghent University, Ghent, Belgium
³Chair of General and Analytical Chemistry, Montanuniversität Leoben, Leoben, Austria
⁴Centre for Astrophysics and Planetary Science, School of Physical Sciences, University of Kent, Canterbury, UK
Published by arrangement with John Wiley & Sons

Upon passage through Earth’s atmosphere, micrometeorites undergo variable degrees of melting and evaporation. Among the various textural and chemical groups recognized among cosmic spherules, that is, melted micrometeorites, a subset of particles may indicate anomalously high degrees of vaporization based on their chemical and isotopic properties. Here, a selection of such refractory element-enriched cosmic spherules from Widerøefjellet (Sør Rondane Mountains, East Antarctica) is characterized for their petrographic features, major and trace element concentrations (N = 35), and oxygen isotopic compositions (N = 23). Following chemical classification, the highly vaporized particles can be assigned to either the “CAT-like” or the “High Ca-Al” cosmic spherule groups. However, through the combination of major and trace element concentrations and oxygen isotopic data, a larger diversity of processes and precursor materials are identified that lead to the final compositions of refractory element-enriched particles. These include fragmentation, disproportional sampling of specific mineral constituents, differential melting, metal bead extraction, redox shifts, and evaporation. Based on specific element concentrations (e.g., Sc, Zr, Eu, Tm) and ratios (e.g., Fe/Mg, CaO + Al2O3/Sc + Y + Zr + Hf), and variations of O isotope compositions, “CAT-like” and “High Ca-Al” cosmic spherules likely represent a continuum between mineral endmembers from both primitive and differentiated parent bodies that experienced variable degrees of evaporation.

¹Benjamin H. Gruber,^1,2Robert W. Nicklas,¹James M. D. Day,¹Emily J. Chin,³Minghua Ren,⁴Rachel E. Bernard
Meteortics & Planetary Science (in Press) Open Access Link to Artivcle [https://doi.org/10.1111/maps.14179]
¹Scripps Institution of Oceanography, University of California San Diego, La Jolla, California, USA
²Department of Earth and Environmental Sciences, Boston College, Chestnut Hill, Massachusetts, USA
³Department of Geoscience, University of Nevada, Las Vegas, Las Vegas, Nevada, USA
⁴Department of Geology, Amherst College, Amherst, Massachusetts, USA
Published by arrangement with John Wiley & Sons

Brachinites and brachinite-like achondrites are olivine-rich meteorites that represent materials after partial metal–silicate differentiation on multiple early Solar System bodies. Both meteorite types show macroscopic textures of olivine crystals, which make up >70 modal percent of their mineralogy. We investigated the orientations of olivine using electron backscatter diffraction (EBSD) and elemental compositions from paired brachinite-like achondrites and one brachinite. The olivine orientations are characterized by a strong concentration of [010] axes with maxima perpendicular to the foliation/layering and a concentration of [001] axes distributed in a girdle or, in a few samples, as point maxima. Trace element abundances of the olivine in these meteorites determined using laser ablation inductively coupled plasma–mass spectrometry have uniformly low concentrations of sodium (<300 μg g−1), aluminum (<70 μg g−1), and titanium (<40 μg g−1) that are distinct from olivine in chondrites or within terrestrial lavas. Instead, brachinite and brachinite-like olivine compositions broadly overlap those of olivine from melt-depleted mantle lithologies on Earth. Evidence from olivine trace element geochemistry, in conjunction with mineral fabrics, supports that these meteorites formed as melt residues on their host planetary body(ies).

^1,2Haiyang Xian,^1,2Jianxi Zhu,¹Yiping Yang,^1,2Shan Li,^1,2Jiaxin Xi,¹Xiaoju Lin,^1,2Jieqi Xing,¹Xiao Wu,^1,2Hongmei Yang,^1,2Hongping He,^2,3Yi-Gang Xu
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.14174]
¹CAS Key Laboratory of Mineralogy and Metallogeny/Guangdong Provincial Key Laboratory of Mineral Physics and Materials, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou, China
²University of Chinese Academy of Sciences, Beijing, China
³State Key Laboratory of Isotope Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou, China
Published by arrangement with John Wiley & Sons

Charge disproportionation of ferrous iron has been considered as one of the mechanisms for the formation of metallic iron on the lunar surface. However, the detailed mechanism of the disproportionation reaction on the Moon is yet to be elucidated. We provide direct evidence for the ferrous disproportionation reaction that produces nano phase metallic iron (npFe0) during a rapid cooling process after splash melting from a lunar sample returned by China’s Chang’e-5 mission. Space weathering processes have resulted in the formation of three distinct zones at the rim of a pyroxene fragment, as observed through transmission electron microscopy. These zones, made up of splashed melts, newly formed melts from the substrate, and the mineral, are distinguished as I, II, and III. Quantitative analyses of the iron valence state by electron energy loss spectroscopy show that disproportionation reactions occurred in zone II at a low temperature of <570°C during a rapid cooling process. The reaction led to the production of α-structure npFe0 and Fe3+ reserve in the glass phase. The npFe0 produced by the disproportionation reaction has a larger grain size than those formed from solar wind irradiation, implying that micrometeoroid impacts mainly contribute to the darkening of visible and near-infrared reflectance. These findings reveal a novel rim structure by repeated space weathering and a universal formation mechanism of npFe0 during micrometeoroid impacts, suggesting that the disproportionation reaction could be widespread on airless bodies with impact-induced splash processes.

^1,2,3Phillip Gopon,^3,4James O. Douglas,^3,5Hazel Gardner,³Michael P. Moody,²Bernard Wood,^2,6Alexander N. Halliday,²Jon Wade
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.14184]
¹Department of Applied Geosciences and Geophysics, University of Leoben, Leoben, Austria
²Department of Earth Science, University of Oxford, Oxford, UK
³Department of Materials, University of Oxford, Oxford, UK
⁴Department of Materials, Imperial College London, London, UK
⁵Culham Science Centre, UK Atomic Energy Authority, Abingdon, UK
⁶Earth Institute, Columbia University, New York, New York, USA
Published by arrangement with John Wiley & Sons

Millimeter-to-nanometer-sized iron- and nickel-rich metals are ubiquitous on the lunar surface. The proposed origin of these metals falls into two broad classes which should have distinct geochemical signatures—(1) the reduction of iron-bearing minerals or (2) the addition of metals from meteoritic sources. The metals measured here from the Apollo 16 regolith possess low Ni (2–6 wt%) and elevated Ge (80–350 ppm) suggesting a meteoritic origin. However, the measured Ni is lower, and the Ge higher than currently known iron meteorites. In comparison to the low Ni iron meteorites, the even lower Ni and higher Ge contents exhibited by these lunar metals are best explained by impact-driven volatilization and condensation of Ni-poor meteoritic metal during their impact and addition to the lunar surface. The presence of similar, low Ni-bearing metals in Apollo return samples from geographically distant sites suggests that this geochemical signature might not be restricted to just the Apollo 16 locality and that volatility-driven modification of meteoritic metals are a common feature of lunar regolith formation. The possibility of a significant low Ni/high Ge meteoritic component in the lunar regolith, and the observation of chemical fractionation during emplacement, has implications for the interpretation of both lunar remote-sensing data and bulk geochemical data derived from sample return material. Additionally, our observation of predominantly meteoritic sourced metals has implications for the prevalence of meteoritic addition on airless planetary bodies.

^1,2Naoya Imae et al. (>10)
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.14178]
¹National Institute of Polar Research (NIPR), Tachikawa, Tokyo, Japan
²The Graduate University for Advanced Studies (SOKENDAI), Tachikawa, Japan
Published by arrangement with John Wiley & Sons

Although CI chondrites are susceptible to terrestrial weathering on Earth, the specific processes are unknown. To elucidate the weathering mechanism, we conduct a laboratory experiment using pristine particles from asteroid Ryugu. Air-exposed particles predominantly develop small-sized euhedral Ca-S-rich grains (0.5–1 μm) on the particle surface and along open cracks. Both transmission electron microscopy and synchrotron-based computed tomography combined with XRD reveal that the grains are hydrous Ca-sulfate. Notably, this phase does not form in vacuum- or nitrogen-stored particles, suggesting this result is due to laboratory weathering. We also compare the Orgueil CI chondrite with the altered Ryugu particles. Due to the weathering of pyrrhotite and dolomite, Orgueil contains a significant amount of gypsum and ferrihydrite. We suggest that mineralogical changes due to terrestrial weathering of particles returned directly from asteroid occur even after a short-time air exposure. Consequently, conducting prompt analyses and ensuring proper storage conditions are crucial, especially to preserve the primordial features of organics and volatiles.