Microscopic slickenside as a record of weak shock metamorphism in the surface layer of asteroid Ryugu

Abstract The surface morphology of regolith grains from the C‐type asteroid Ryugu was studied in search of evidence of impact events on the asteroid. Scanning electron microscopy revealed that ~8% of C0105‐042 Ryugu grains have a smooth surface on one side of the grains. One of these grains has striated linear grooves (striations) on its smooth surface. Transmission electron microscopy of the grain showed that a porous fine‐grained Mg‐Fe phyllosilicate assemblage, which is the main component of Ryugu grains, is compacted near the smooth surface. The smooth surface with striations closely resembles a slickenside, a characteristic texture found in terrestrial fault rocks formed by shear deformation. There is no evidence of melting/decomposition in the Mg‐Fe phyllosilicates near the smooth surface, indicating that the shear heating temperature is less than ~1100 K. Assuming that the average length of the striations corresponds to the minimum displacement of the micro‐fault, the shock pressure recorded in the C0105‐042 Ryugu grain is estimated to be <~4.5 GPa by a fault mechanics calculation. The shock pressures of C0105‐042, together with those of C0014 (~2 GPa) and C0055 (>~3.9 GPa) in previous studies suggest that the impact velocities recorded in these grains are < ~0.89–1.63 km s −1 . Based on the impact velocities, these grains may record an impact event that occurred when asteroid Ryugu was in the orbit in Main Belt.

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Publication Details

Journal
Meteoritics and Planetary Science
Published
2024-09-26
DOI
https://doi.org/10.1111/maps.14271
Citations
4
Primary Topic
Astro and Planetary Science
Type
article
Field-Weighted Citation Impact
1.33

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article

Microscopic slickenside as a record of weak shock metamorphism in the surface layer of asteroid Ryugu

Toru Matsumoto, Kentaro Uesugi, Megumi Matsumoto, Naotaka Tomioka et al.
4 citations
Meteoritics and Planetary Science
Astro and Planetary Science
1.33
article

Microscopic slickenside as a record of weak shock metamorphism in the surface layer of asteroid Ryugu

Toru Matsumoto, Kentaro Uesugi, Megumi Matsumoto, Naotaka Tomioka, Akira Miyake, Junya Matsuno, Hiroshi Naraoka, Ryuji Okazaki, Yuichi Tsuda, Pierre-Marie Zanetta, Masahiro Nishimura, T. J. Zega, Kanako Sakamoto, Francisco de la Peña, D. Frank, J. P. Bradley, Sei‐ichiro Watanabe, Kazuhide Nagashima, Noriyuki Kawasaki, Shogo Tachibana, Satomi Enju, Itaru Mitsukawa, R. M. Stroud, J. C. Bridges, Martin Lee, F. Langenhorst, N. M. Abreu, M. E. Zolensky, Aki Takigawa, Aiko Nakato, Sylvain Laforet, Damien Jacob, Makoto Yoshikawa, Tomoki Nakamura, Tatsuaki Okada, Masanao Abe, Satoshi Hata, Tomohiro Usui, Hisayoshi Yurimoto, H. A. Ishii, Toru Yada, Takanao Saiki, Akira Tsuchiyama, Brittany A. Cymes, Masayuki Uesugi, Fuyuto Terui, Masahiro Yasutake, Van T. H. Phan, Jennifer Gray, P. A. Bland, Mingqi Sun, Mitsutaka Haruta, Masaaki Miyahara, E. Dobrică, Tatsuhiro Michikami, Kenta K. Ohtaki, Luke Daly, L. J. Hicks, Rolando Rebois, Akihisa Takeuchi, Shota Okumura, Hugues Leroux, Dennis Harries, T. Noguchi, Yohei Igami, Akiko Miyazaki, Yusuke Seto, M. S. Thompson, Pierre Beck, Satoshi Tanaka, Yusuke Nakauchi, Corentin Le Guillou, Hikaru Saito, Bahae‐Eddine Mouloud, Naoya Sakamotoa, James Martinez, Hikaru Yabuta, S. Nakazawa, Kate Burgess, Maya Marinova
article en
4 citations

Abstract

Abstract The surface morphology of regolith grains from the C‐type asteroid Ryugu was studied in search of evidence of impact events on the asteroid. Scanning electron microscopy revealed that ~8% of C0105‐042 Ryugu grains have a smooth surface on one side of the grains. One of these grains has striated linear grooves (striations) on its smooth surface. Transmission electron microscopy of the grain showed that a porous fine‐grained Mg‐Fe phyllosilicate assemblage, which is the main component of Ryugu grains, is compacted near the smooth surface. The smooth surface with striations closely resembles a slickenside, a characteristic texture found in terrestrial fault rocks formed by shear deformation. There is no evidence of melting/decomposition in the Mg‐Fe phyllosilicates near the smooth surface, indicating that the shear heating temperature is less than ~1100 K. Assuming that the average length of the striations corresponds to the minimum displacement of the micro‐fault, the shock pressure recorded in the C0105‐042 Ryugu grain is estimated to be <~4.5 GPa by a fault mechanics calculation. The shock pressures of C0105‐042, together with those of C0014 (~2 GPa) and C0055 (>~3.9 GPa) in previous studies suggest that the impact velocities recorded in these grains are < ~0.89–1.63 km s −1 . Based on the impact velocities, these grains may record an impact event that occurred when asteroid Ryugu was in the orbit in Main Belt.

Meteoritics and Planetary ScienceVol. 59(12)
Hiroshima University (JP), University of Hawaiʻi at Mānoa (US), United States Naval Research Laboratory (US), Centre National de la Recherche Scientifique (FR), The University of Sydney (AU), Planetary Science Institute (US), Pennsylvania State University (US), Japan Agency for Marine-Earth Science and Technology (JP), Langley Research Center (US), Kyushu University (JP), Ritsumeikan University (JP), University of Arizona (US), University of Leicester (GB), Kanagawa Institute of Technology (JP), Chinese Academy of Sciences (CN), The Graduate University for Advanced Studies, SOKENDAI (JP), Tohoku University (JP), Hokkaido University (JP), Curtin University (AU), Purdue University West Lafayette (US), Kyoto University (JP), Université de Lille (FR), Japan Aerospace Exploration Agency (JP), Guangzhou Institute of Geochemistry (CN), University of Oxford (GB), Institut National de Recherche pour l'Agriculture, l'Alimentation et l'Environnement (FR), Japan Synchrotron Radiation Research Institute (JP), Luxembourg Institute of Science and Technology (LU), Institute of Space and Astronautical Science (JP), Unité Matériaux et Transformations (FR), Millennium Engineering and Integration (United States) (US), Johnson Space Center (US), Jacobs (United States) (US), University of Chinese Academy of Sciences (CN), Ehime University (JP), Osaka Metropolitan University (JP), Université d'Artois (FR), Arizona State University (US), Nagoya University (JP), Tokyo Metropolitan University (JP), École Centrale de Lille (FR), The University of Tokyo (JP), Friedrich Schiller University Jena (DE), Kōchi University (JP), University of Glasgow (GB), Université Grenoble Alpes (FR), Kindai University (JP)
Ministry of Education, Culture, Sports, Science and Technology, Japan Society for the Promotion of Science
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Astro and Planetary Science
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