¹J. Aléon et al. (>10)
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.14139]
¹Institut de Minéralogie, de Physique des Matériaux et de Cosmochimie, Sorbonne Université, Museum National d’Histoire Naturelle, CNRS UMR 7590, IRD, Paris, France
Published by arrangement with John Wiley & Sons

In order to gain insights on the conditions of aqueous alteration on asteroid Ryugu and the origin of water in the outer solar system, we developed the measurement of water content in magnetite at the micrometer scale by secondary ion mass spectrometry (NanoSIMS) and determined the H and Si content of coarse-grained euhedral magnetite grains (polyhedral magnetite) and coarse-grained fibrous (spherulitic) magnetite from the Ryugu polished section A0058-C1001. The hydrogen content in magnetite ranges between ~900 and ~3300 wt ppm equivalent water and is correlated with the Si content. Polyhedral magnetite has low and homogenous silicon and water content, whereas fibrous magnetite shows correlated Si and water excesses. These excesses can be explained by the presence of hydrous Si-rich amorphous nanoinclusions trapped during the precipitation of fibrous magnetite away from equilibrium and testify that fibrous magnetite formed from a hydrous gel with possibly more than 20 wt% water. An attempt to determine the water content in sub-μm framboids indicates that additional calibration and contamination issues must be addressed before a safe conclusion can be drawn, but hints at elevated water content as well. The high water content in fibrous magnetite, expected to be among the first minerals to crystallize at low water–rock ratio, points to the control of water content by local conditions of magnetite precipitation rather than large-scale alteration conditions. Systematic lithological variations associated with water-rich and water-poor magnetite suggest that the global context of alteration may be better understood if local water concentrations are compared with millimeter-scale distribution of the various morphologies of magnetite. Finally, the high water content in the magnetite precursor gel indicates that the initial O isotopic composition in alteration water must not have been very different from that of the earliest magnetite crystals.

¹Bennett J. K. Wilson,²Veronica E. Di Cecco,^3,4Laurence A. J. Garvie,^2,5Kimberly T. Tait,⁶Michael G. Daly
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.14140]
¹Lassonde School of Engineering, York University, Toronto, Ontario, Canada
²Department of Natural History, Center for Applied Planetary Mineralogy, Royal Ontario Museum, Toronto, Ontario, Canada
³Buseck Center for Meteorite Studies, Arizona State University, Tempe, Arizona, USA
⁴School of Earth and Space Exploration, Arizona State University, Tempe, Arizona, USA
⁵Department of Earth Science, University of Toronto, Toronto, Ontario, Canada
⁶Centre for Research in Earth and Space Science, Lassonde School of Engineering, York University, Toronto, Ontario, Canada
Published by arrangement with John Wiley & Sons

The matrix of the C2-ungrouped Tarda meteorite contains abundant smectite minerals that swell and crumble when exposed to polar liquids, causing the sample to rapidly slake. This phenomenon presents a serious challenge when polishing the meteorite, as common polishing liquids used on carbonaceous chondrites, such as water, ethanol, ethylene glycol, and isopropyl alcohol, are polar and will cause the sample to swell, making it unsuitable for some analyses. Hexane and mineral oil are nonpolar liquids that were found to not induce swelling on highly expansive montmorillonite-clay analog material and were effectively integrated into a polishing procedure for Tarda. Here, we detail a procedure for mounting, cutting, and polishing the Tarda meteorite to prepare a surface that is suitable for a variety of sensitive techniques, such as electron microprobe analysis. This work offers a practical methodology for the preparation of other clay-rich samples, which may include the recently returned Ryugu and Bennu materials.

¹M. E. Varela,²S.-L. Hwang,³P. Shen,^1,4L. N. Garcia,¹M. Saavedra,⁵T. Maruoka,⁶M. Bose
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.14120]
¹Instituto de Ciencias Astronómicas, de la Tierra y del Espacio (ICATE), Universidad Nacional de San Juan, CONICET, San Juan, Argentina
²Department of Materials Science and Engineering, National Dong Hwa University, Hualien, Taiwan, ROC
³Department of Materials and Optoelectronic Science, National Sun Yat-sen University, Kaohsiung, Taiwan, ROC
⁴Instituto de Mecánica Aplicada, Universidad Nacional de San Juan, San Juan, Argentina
⁵Faculty of Life and Environmental Sciences, University of Tsukuba, Tsukuba, Japan
⁶School of Earth and Space Exploration, Arizona State University, Tempe, Arizona, USA
Published by arrangement with John Wiley & Sons

The combined SEM and TEM studies on the metal (Fe-Ni alloy ±C) portion of the Vaca Muerta mesosiderite reveal structural and compositional evidence at micro to nanoscale, which sheds light on the solidification of taenite + graphite as a cement, and later solid-state precipitation process for the kamacite formation as grain boundary allotriomorph. Besides, it is proposed that the graphite veinlets formed through a complex partial melting process followed by a solidification toward the final eutectic transient coupled with the solid-state precipitation and later decomposition ordering of taenite. The presence of defects and taenite in graphite signal formation in a liquid environment. The δ13C values of graphite in the graphite-rich areas (e.g., ranging from −0.8 ± 1.7‰ to +15.3 ± 2.5‰) suggest a short-circuit diffusion path for C isotope fractionation.

^1,2Rhonda M. Stroud et al. (>10)
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.14128]
¹School of Earth and Space Exploration, Arizona State University, Tempe, Arizona, USA
²Materials Science and Technology Division, US Naval Research Laboratory, Washington, DC, USA
Published by arrangement with John Wiley & Sons

Transmission electron microscopy analyses of Hayabusa2 samples show that Ryugu organic matter exhibits a range of morphologies, elemental compositions, and carbon functional chemistries consistent with those of carbonaceous chondrites that have experienced low-temperature aqueous alteration. Both nanoglobules and diffuse organic matter are abundant. Non-globular organic particles are also present, and including some that contain nanodiamond clusters. Diffuse organic matter is finely distributed in and around phyllosilicates, forms coatings on other minerals, and is also preserved in vesicles in secondary minerals such as carbonate and pyrrhotite. The average elemental compositions determined by energy-dispersive spectroscopy of extracted, demineralized insoluble organic matter samples A0107 and C0106 are C100N3O9S1 and C100N3O7S1, respectively, with the difference in O/C slightly outside the difference in the standard error of the mean. The functional chemistry of the nanoglobules varies from mostly aromatic C=C to mixtures of aromatic C=C, ketone C=O, aliphatic (CHn), and carboxyl (COOH) groups. Diffuse organic matter associated with phyllosilicates has variable aromatic C, ketone and carboxyl groups, and some localized aliphatics, but is dominated by molecular carbonate (CO3) absorption, comparable to prior observations of clay-bound organic matter in CI meteorites.

^1,2T. H. Burbine,³R. C. Greenwood,⁴B. Zhang,⁵P. C. Buchanan
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.14134]
¹Department of Astronomy, Mount Holyoke College, South Hadley, Massachusetts, USA
²Planetary Science Institute, Tucson, Arizona, USA
³The Open University, Milton Keynes, UK
⁴Department of Earth, Planetary, and Space Sciences, University of California, Los Angeles, Los Angeles, California, USA
⁵Department of Geology, Kilgore College, Kilgore, Texas, USA
Published by arrangement with John Wiley & Sons

Asteroid 4 Vesta is typically thought to be the parent body of the HED (howardite, eucrite, and diogenite) meteorites due to spectral similarities. The discovery of asteroids far from Vesta with HED-like spectra like (1459) Magnya and HED-like meteorites (e.g., NWA 011) with anomalous oxygen isotopic values compared to typical HEDs is evidence that other Vesta-like bodies formed. We broadly define a Vesta-like body as a differentiated object with a crust composed primarily of low-Ca pyroxene and plagioclase feldspar. We estimate the number of Vesta-like bodies that did form by looking at the astronomical evidence; the oxygen isotopic, chemical, and petrologic evidence; and the iron meteorite evidence. Assuming that fragments of Vesta were scattered from Vesta by giant planet migration, we conservatively estimate that at least two Vesta-like bodies (Vesta and the Magnya parent bodies) existed. From the oxygen isotopic, chemical, and petrologic evidence, we also conservatively estimate that seven Vesta-like bodies formed. Analyses of iron meteorites indicate that there may be as many as 23 Vesta-like bodies (Vesta, 10 magmatic iron groups, South Byron trio, Emsland/Mbosi duo, 10 ungrouped irons). This estimate from iron meteorites is most certainly an overestimation due to the existence of a number of non-HED crustal/mantle fragments that potentially originated from bodies with magmatic iron cores. Using our three estimates as a guide, we predict that there were ~10 Vesta-like bodies (including Vesta) that formed in the early solar system. Only Vesta remains intact with the others being disrupted early in solar system history.

¹Haijun Cao,¹Jian Chen,¹Chengxiang Yin,^1,2Xiaohui Fu,^1,2Zongcheng Ling,³Xiaochao Che
Meteoritics & Planetary Science (in Presss) Link to Article [https://doi.org/10.1111/maps.14131]
¹Shandong Key Laboratory of Optical Astronomy and Solar-Terrestrial Environment, Institute of Space Sciences, Shandong University, Weihai, Shandong, China
²CAS Center for Excellence in Comparative Planetology, Chinese Academy of Sciences, Hefei, China
³Beijing SHRIMP Center, Institute of Geology, Chinese Academy of Geological Sciences, Beijing, China
Published by arrangement with John Wiley & Sons

Northwest Africa (NWA) 7611/10480 are lunar regolith breccia meteorites, composed of mineral fragments and various clasts including mare basalts, volcanic glasses, gabbroic lithologies, and a diverse variety of highland materials (ferroan anorthosite, Mg-suite, magnesian anorthosite, and alkali suite rocks) as well as different subvarieties of impact melt breccia. The Apollo two-component mixing model calculation reveals that the NWA 7611 source region contains 58 wt% mare materials and 42 wt% highland components, but the estimated mare components in NWA 10480 have a higher abundance (66 wt%). The predominantly very low-Ti (VLT) composition in both fine-grained basaltic and coarse-grained gabbroic lithologies indicates a provenance associated with a thick lava flow or a single magmatic system. The co-occurrence of zoning patterns and fine-scale exsolution lamellae in pyroxene debris supports a cryptomare deposit as the best candidate source. Phosphate Pb–Pb ages in matrix fragments, impact melt breccia, and basaltic clast indicate that the breccia NWA 7611 records geological events spanning approximately 4305–3769 Ma, which is consistent with the ages of ancient lunar VLT volcanism and the products of basin-forming impacts on the lunar nearside. The youngest reset age at ~3.2 Ga is potentially related to the strong shock lithification process of breccia NWA 7611. Moreover, the similar petrology, texture, geochemistry, cosmic-ray exposure data, and crystallization ages support that basaltic component in Yamato (Y)-793274, and Queen Alexandra Range (QUE) 94281, NWA 4884, and NWA 7611 clan came from the same basalt flow.

¹M. H. Leili,¹H. Chennaoui Aoudjehane,²B. Devouard,²P. Rochette,²J. Gattacceca,³L. Folco,³M. Gemelli,⁴I. Baziotis
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.14119]
¹GAIA Laboratory, Faculty of Sciences Ain Chock, Hassan II University of Casablanca, Casablanca, Morocco
²France Aix Marseille University, CNRS, Coll France, IRD, INRAE, CEREGE, Aix-en-Provence, France
³Dipartimento di Scienze della Terra, Università di Pisa, Pisa, Italy
⁴Laboratory of Mineralogy and Geology, Department of Natural Resources Management and Agricultural Engineering, Agricultural University of Athens, Athens, Greece
Published by arrangement with John Wiley & Sons

In this work, we investigate macroscopic characteristics, magnetic susceptibility, mineralogy, and mineral composition of Al Haggounia 001. The samples were collected during eight field missions in the period between 2015 and 2019. In the strewn field of about 65 km in length, the specimens are found either on the surface or shallowly buried in loose sediments, which rules out the previous suggestions that this meteorite is a fossil meteorite. Macroscopically, the samples exhibit three major lithologies with various colors, porosities, and distributions of oxidized veins. The data obtained using transmitted and reflected light microscopy, scanning electron microscopy, and electron microprobe analysis confirm the macroscopic observations and show a heterogenous distribution of silicates and metal sulfides. Al Haggounia 001 is composed of enstatite, plagioclase, kamacite, taenite, schreibersite, daubreelite, troilite, graphite, sinoite, and silica polymorphs. We identified a new type of chondrules that are flattened and composed of rods of albite and enstatite, as well as elongated nodules of metal and sulfides, in addition to compression fractures in the form of subparallel veinlets. These features presumably reflect the deformation caused by shock. The magnetic susceptibility of Al Haggounia 001 (4.39 ± 0.20) is much lower than that of usual EH (5.48 ± 0.16) and EL (5.46 ± 0.04) chondrites but is in the range of E finds (5.05 ± 0.43). The thermomagnetic and hysteresis measurements are controlled by type, size, distribution of metal-sulfide nodules, arrangement of oxyhydroxide veins, and weathering. Al Haggounia 001 is an anomalous meteorite with a polymict nature. It records multiple events revealing its unique origin which expends the groups of enstatite chondrites and provides insights into the complex formation and evolution history of their parent body.

¹Matthieu Clog,²Paula Lindgren,³Sevasti Modestou,¹Alex McDonald,¹Andrew Tait,¹Terry Donnelly,¹Darren Mark,⁴Martin Lee
Geochimica et Cosmochimica Acta (in Press) Open Access Link to Article [https://doi.org/10.1016/j.gca.2024.01.023]
¹Scottish Universities Environmental Research Centre, Glasgow, United Kingdom
²Geological Survey of Sweden, Lund, Sweden
³University of Northumbria, Newcastle upon Tyne, United Kingdom
⁴School of Geographical and Earth Sciences, University of Glasgow, Glasgow, United Kingdom
Copyright Elsevier

The CM carbonaceous chondrites are key archives for understanding the earliest history of the solar system. Their C-complex asteroid parent body(ies) underwent aqueous alteration, among the products of which are carbonate minerals that can faithfully record the conditions of their formation. In this study we report carbon, triple oxygen and clumped isotope compositions of carbonates in six CM chondrites which span a range in degrees of aqueous alteration (Allan Hills 83100, Cold Bokkeveld, LaPaz Icefield 031166, Lonewolf Nunataks 94101, Murchison, Scott Glacier 06043). Δ¹⁷O values range from -1 to -2.6‰ (±0.1), and where calcite and dolomite co-exist their Δ¹⁷O differ by 0.6 permil, suggesting precipitation from distinct fluids. Calculated crystallization temperatures range from 5 to 51⁰C for calcite (typically ±10⁰C) and 75 to 101(±15)⁰C for dolomite. The δ¹⁸O_VSMOW of the aqueous fluids from which they formed ranges from -6.6 to 2.3‰, with no relationship to the δ¹³C of carbonates. As the population of carbonates in any one CM chondrite can include multiple generations of grains that formed at different conditions, these values represent the mode of the temperature of carbonate formation for each meteorite. We observe that in the more altered meteorites carbonate Δ¹⁷O values are lower and formation temperatures are higher. These correlations are consistent with aqueous alteration of the CM chondrites being a prograde reaction whereby the hotter fluids had undergone greater isotope exchange with the anhydrous matrix. Our data are broadly consistent with the closed system model for water/rock interaction, but carbonate mineral formation in the latter stages of aqueous alteration may be linked to fluid movement via fractures.

¹T. Le Pivert-Jolivet et al. (>10)
Nature Astronomy 7, 1445-1453 Link to Article [DOI https://doi.org/10.1038/s41550-023-02092-9]
¹Institut d’Astrophysique Spatiale, Université Paris-Saclay, CNRS, Orsay, France

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^1,2Tara S. Hayden,^1,3Thomas J. Barrett,¹Mahesh Anand,⁴Martin J. Whitehouse,
⁴Heejin Jeon,¹Xuchao Zhao,¹Ian A. Franchi
Nature Astronomy (in Press) Open Access Link to Article [DOI https://doi.org/10.1038/s41550-023-02185-5]
¹School of Physical Sciences, The Open University, Milton Keynes, UK
²Department of Earth Sciences, University of Western Ontario, London, Ontario, Canada
³Center for Lunar Science and Exploration, Lunar and Planetary Institute, Houston, TX, USA
⁴Department of Geosciences, Swedish Museum of Natural History, Stockholm, Sweden

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