¹Zelia Dionnet et al. (>10)
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.14068]
¹CNRS, Institut d’Astrophysique Spatiale, Université Paris-Saclay, Orsay, France
Published by arrangement with John Wiley & Sons

We report μm-scale nondestructive infrared (IR) hyperspectral results (IR computed tomography, IR-CT) in 3-D and IR surface imaging, IR-S) in 2-D, at SOLEIL) combined with X-ray nano-computed tomography analyses (at SPring-8) performed on eight small Ryugu fragments extracted from mm-sized grains coming both from touchdown first and second sites. We describe the multiscale assembly of phyllosilicates, carbonates, sulfides, oxides, and organics. Two types of silicates, as well as diverse kinds of organic matter, were detected inside Ryugu material. Their spatial correlations are described to discuss the role of the mineralogical microenvironments in the formation/evolution of organic matter. In particular, we have shown that there is a redistribution of the organic matter diffuse component during aqueous alteration on the parent body, with a preferential circulation among fine-grained phyllosilicates.

^1,2Iori Kajitani,³Mizuho Koike,⁴Ryoichi Nakada,⁵Gaku Tanabe,^2,6Tomohiro Usui,⁷Fumihiro Matsu’ura,⁸Keisuke Fukushi,⁵Tetsuya Yokoyama
Earth and Planetary Science Letters 620, 118345 Link to Article [https://doi.org/10.1016/j.epsl.2023.118345]
¹Department of Earth and Planetary Science, Graduate School of Science, The University of Tokyo. 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
²Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency. 3-1-1 Yoshinodai, Sagamihara, Kanagawa 252-5210, Japan
³Earth and Planetary Systems Science Program, Department of Advanced Science and Engineering, Hiroshima University. 1-3-1 Kagamiyama, Higashihiroshima, Hiroshim 739-8526, Japan
⁴Kochi Institute for Core Sample Research, Institute for Extra-cutting-edge Science and Technology Avant-garde Research (X-star), Japan Agency for Marine-Earth Science and Technology (JAMSTEC). 200 Monobe, Nankoku, Kochi 783-8502, Japan
⁵Department of Earth and Planetary Sciences, School of Science, Tokyo Institute of Technology. 2-12-1 Ookayama, Meguro, Tokyo 152-8550, Japan
⁶Earth-Life Science Institute, Tokyo Institute of Technology. 2-12-1 Ookayama, Meguro, Tokyo 152-8550, Japan
⁷International Center for Isotope Effects Research, Nanjing University, Nanjing, Jiangsu Province 210023, China
⁸Institute of Nature and Environmental Technology, Kanazawa University, Kanazawa, Ishikawa, Japan
Copyright Elsevier

The aqueous environment and possible habitability of early Mars have been widely studied based on orbital and in situ explorations, as well as analyses of Martian meteorites. Using microscale X-ray absorption near edge structure (μ-XANES) analysis, we report the first sulfur (S) speciation of the carbonates in a Martian meteorite, Allan Hills 84001, precipitated in the 4-billion-year-old aqueous alteration on Mars. The XANES data show diagnostic signatures of oxidized sulfur in the carbonates, indicating that carbonate-associated sulfate (CAS) formed from coexisting sulfate ions (SO
) in the aqueous fluid. A thermodynamic calculation suggests that the CAS deposited from a fluid with a moderately oxidizing to reducing and neutral to slightly alkaline pH condition. The possible sources of SO
ions are the minor SOx species in the Noachian atmosphere and/or the supply from volcanic gas. It is concluded that considerable amounts of the atmospheric volatiles including CO2 and SOx may have been stored as alteration products (e.g., carbonates) in the Martian underground system.

^1,2Andrea Patzer,¹Emma S. Bullock,¹Conel M. O’D. Alexander
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2023.08.021]
¹Earth and Planets Laboratory, Carnegie Institution for Science, 5241 Broad Branch Rd. NW, Washington D.C. 20015, USA
²Geosciences Center, University of Göttingen, Goldschmidtstr. 1, 37077 Göttingen, Germany
Copyright Elsevier

In continuation of our comprehensive study of the carbonaceous chondrites, we here present data for the CM chondrites. Our study’s aim is to determine the abundances and the average elemental compositions of the major and minor chondritic components. The overarching goal has been to explore the fundamental question of whether chondrules and matrix are complementary, i.e., genetically related, or if these major chondritic components evolved separately before accretion as in the four-component model.

Using point-counting and electron microprobe analyses, we investigated the most primitive CMs known to date: Asuka (A) 12169 (CM3.0), A 12236 (CM2.9) and Paris (CM2.7-2.9). Despite their primitiveness, however, none of the samples is completely devoid of signs of terrestrial and/or parent body alteration. For instance, we found evidence for the mobilization and heterogenous redistribution of Ca, as well as for the leaching of Al from chondrules and redeposition into matrix. There is also a trend of the Ca and Al abundances in both, chondrules and matrix, to become increasingly heterogeneous with increasing parent body alteration. We were, therefore, unable to test chondrule-matrix complementarity and the four-component model using Al and Ca. Assuming that Mg and Si are insignificantly affected by alteration and that the Mg/Si ratios of the components in A 12169 are unaltered, our data indicate the pre-accretionary loss from matrix of ∼12 wt.% forsterite (matching our results for the primitive COs and CRs) and the addition of a roughly similar amount of forsterite to the chondrules (contrary to our results for the COs and CRs). These results are inconsistent with the four-component model but, based on the matrix/chondrule abundance ratio, complementarity predicts that the addition of forsterite to chondrules should have been significantly higher. This and the possibility that A 12169 component compositions have been modified to some degree means that our results do not unambiguously favor either model.