A history of mild shocks experienced by the regolith particles on hydrated asteroid Ryugu
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Published:2023-04-20
Issue:6
Volume:7
Page:669-677
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ISSN:2397-3366
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Container-title:Nature Astronomy
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language:en
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Short-container-title:Nat Astron
Author:
Tomioka NaotakaORCID, Yamaguchi AkiraORCID, Ito MotooORCID, Uesugi MasayukiORCID, Imae Naoya, Shirai NaokiORCID, Ohigashi TakujiORCID, Kimura MakotoORCID, Liu Ming-ChangORCID, Greenwood Richard C., Uesugi KentaroORCID, Nakato AikoORCID, Yogata KasumiORCID, Yuzawa HayatoORCID, Kodama Yu, Hirahara KaoriORCID, Sakurai IkuyaORCID, Okada Ikuo, Karouji YuzuruORCID, Okazaki KeishiORCID, Kurosawa Kosuke, Noguchi TakaakiORCID, Miyake Akira, Miyahara MasaakiORCID, Seto Yusuke, Matsumoto ToruORCID, Igami YoheiORCID, Nakazawa SatoruORCID, Okada TatsuakiORCID, Saiki Takanao, Tanaka Satoshi, Terui Fuyuto, Yoshikawa Makoto, Miyazaki AkikoORCID, Nishimura Masahiro, Yada ToruORCID, Abe Masanao, Usui TomohiroORCID, Watanabe Sei-ichiroORCID, Tsuda Yuichi
Abstract
AbstractMicrometeorites, a possible major source of Earth’s water, are thought to form from explosive dispersal of hydrated chondritic materials during impact events on their parental asteroids. However, this provenance and formation mechanism have yet to be directly confirmed using asteroid returned samples. Here, we report evidence of mild shock metamorphism in the surface particles of asteroid Ryugu based on electron microscopy. All particles are dominated by phyllosilicates but lack dehydration textures, which are indicative of shock-heating temperatures below ~500 °C. Microfault-like textures associated with extensively shock-deformed framboidal magnetites and a high-pressure polymorph of Fe–Cr–sulfide have been identified. These findings indicate that the average peak pressure was ~2 GPa. The vast majority of ejecta formed during impact on Ryugu-like asteroids would be hydrated materials, larger than a millimetre, originating far from the impact point. These characteristics are inconsistent with current micrometeorite production models, and consequently, a new formation mechanism is required.
Funder
MEXT | Japan Society for the Promotion of Science National Institute of Polar Research
Publisher
Springer Science and Business Media LLC
Subject
Astronomy and Astrophysics
Reference62 articles.
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