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.

¹KATHERINE DE KLEER,^1,2ERY C. HUGHES,³FRANCIS NIMMO,¹JOHN EILER,⁴AMY E. HOFMANN,^5,6,7STATIA LUSZCZ-COOK,⁸KATHY MANDT
Science 384, 682-687 Link to Article [DOI: 10.1126/science.adj0625]
¹Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125, USA.
²Earth Structure and Processes, Te Pū Ao | GNS Science, Avalon 5011, Aotearoa New Zealand.
³Department of Earth and Planetary Sciences, University of California Santa Cruz, Santa Cruz, CA 95064, USA.
⁴Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA.
⁵Liberal Studies, New York University, New York, NY 10023, USA.
⁶Columbia Astrophysics Laboratory, Columbia University, New York, NY 10027, USA.
⁷Department of Astrophysics, American Museum of Natural History, New York, NY 10024, USA.
⁸NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA.
Reprinted with permission from AAAS

Jupiter’s moon Io hosts extensive volcanism, driven by tidal heating. The isotopic composition of Io’s inventory of volatile chemical elements, including sulfur and chlorine, reflects its outgassing and mass-loss history and thus records information about its evolution. We used submillimeter observations of Io’s atmosphere to measure sulfur isotopes in gaseous sulfur dioxide and sulfur monoxide, and chlorine isotopes in gaseous sodium chloride and potassium chloride. We find 34S/32S = 0.0595 ± 0.0038 (equivalent to δ34S = +347 ± 86‰), which is highly enriched compared to average Solar System values and indicates that Io has lost 94 to 99% of its available sulfur. Our measurement of 37Cl/35Cl = 0.403 ± 0.028 (δ37Cl = +263 ± 88‰) shows that chlorine is similarly enriched. These results indicate that Io has been volcanically active for most (or all) of its history, with potentially higher outgassing and mass-loss rates at earlier times.

¹Justin Filiberto,²Molly C. McCanta
American Mineralogist 109, 805-813 Link to Article [https://doi.org/10.2138/am-2023-9015]
¹Astromaterials Research and Exploration Science (ARES) Division, NASA Johnson Space Center, Houston, Texas 77058, U.S.A.
²Department of Earth and Planetary Sciences, University of Tennessee at Knoxville, Knoxville, Tennessee 37996, U.S.A.
Copyright: The Mineralogical Society of America

The surface of Venus is in contact with a hot (~470 °C), high pressure (92 bars), and caustic (CO2 with S, but little H2O) atmosphere, which should cause progressive alteration of the crust in the form of sulfate and iron-oxide coatings; however, the exact rate of alteration and mineral species are not well constrained. Different experimental approaches, each with its own limitations, are currently being used to constrain mineralogy and alteration rates. One note is that no experimental approach has been able to fully replicate the necessary conditions and sustain them for a significant length of time. Furthermore, geochemical modeling studies can also constrain surface alteration mineralogy, again with different assumptions and limitations. Here, we review recent geochemical modeling and experimental studies to constrain the state of the art for alteration mineralogy, rate of alteration, open questions about the surface mineralogy of Venus, and what can be constrained before the fleet of missions arrives later this decade.

Combining the new results confirms that basalt on the surface of Venus should react quickly and form coatings of sulfates and iron-oxides; however, the mineralogy and rate of alteration are dependent on physical properties of the protolith (including bulk composition, mineralogy, and crystallinity), as well as atmospheric composition, and surface temperature. Importantly, the geochemical modeling results show that the mineralogy is largely controlled by atmospheric oxygen fugacity, which is not well constrained for the near-surface environment on Venus. Therefore, alteration experiments run over a range of oxygen and sulfur fugacities are needed across a wide range of Venus analog materials with varying mineralogy and crystallinity.