A pristine record of outer Solar System materials from asteroid Ryugu's returned sample

Volatile and organic-rich C-type asteroids may have been one of the main sources of Earth's water. Our best insight into their chemistry is currently provided by carbonaceous chondritic meteorites, but the meteorite record is biased: only the strongest types survive atmospheric entry and are then modified by interaction with the terrestrial environment. Here we present the results of a detailed bulk and microanalytical study of pristine Ryugu particles, brought to Earth by the Hayabusa2 spacecraft. Ryugu particles display a close compositional match with the chemically unfractionated, but aqueously altered, CI (Ivuna-type) chondrites, which are widely used as a proxy for the bulk Solar System composition. The sample shows an intricate spatial relationship between aliphatic-rich organics and phyllosilicates and indicates maximum temperatures of -30 °C during aqueous alteration. We find that heavy hydrogen and nitrogen abundances are consistent with an outer Solar System origin. Ryugu particles are the most uncontaminated and unfractionated extraterrestrial materials studied so far, and provide the best available match to the bulk Solar System composition.

Motoo Ito, Naotaka Tomioka, Masayuki Uesugi, Akira Yamaguchi, Naoki Shirai, Takuji Ohigashi, Ming-Chang Liu, Richard C. Greenwood, Makoto Kimura, Naoya Imae, Kentaro Uesugi, Aiko Nakato, Kasumi Yogata, Hayato Yuzawa, Yu Kodama, Akira Tsuchiyama, Masahiro Yasutake, Ross Findlay, Ian A. Franchi, James A. Malley, Kaitlyn A. McCain, Nozomi Matsuda, Kevin D. McKeegan, Kaori Hirahara, Akihisa Takeuchi, Shun Sekimoto, Ikuya Sakurai, Ikuo Okada, Yuzuru Karouji, Masahiko Arakawa, Atsushi Fujii, Masaki Fujimoto, Masahiko Hayakawa, Naoyuki Hirata, Naru Hirata, Rie Honda, Chikatoshi Honda, Satoshi Hosoda, Yu-ichi Iijima, Hitoshi Ikeda, Masateru Ishiguro, Yoshiaki Ishihara, Takahiro Iwata, Kosuke Kawahara, Shota Kikuchi, Kohei Kitazato, Koji Matsumoto, Moe Matsuoka, Tatsuhiro Michikami, Yuya Mimasu, Akira Miura, Osamu Mori, Tomokatsu Morota, Satoru Nakazawa, Noriyuki Namiki, Hirotomo Noda, Rina Noguchi, Naoko Ogawa, Kazunori Ogawa, Tatsuaki Okada, Chisato Okamoto, Go Ono, Masanobu Ozaki, Takanao Saiki, Naoya Sakatani, Hirotaka Sawada, Hiroki Senshu, Yuri Shimaki, Kei Shirai, Seiji Sugita, Yuto Takei, Hiroshi Takeuchi, Satoshi Tanaka, Eri Tatsumi, Fuyuto Terui, Ryudo Tsukizaki, Koji Wada, Manabu Yamada, Tetsuya Yamada, Yukio Yamamoto, Hajime Yano, Yasuhiro Yokota, Keisuke Yoshihara, Makoto Yoshikawa, Kent Yoshikawa, Ryota Fukai, Shizuho Furuya, Kentaro Hatakeda, Tasuku Hayashi, Yuya Hitomi, Kazuya Kumagai, Akiko Miyazaki, Masahiro Nishimura, Hiromichi Soejima, Ayako Iwamae, Daiki Yamamoto, Miwa Yoshitake, Toru Yada, Masanao Abe, Tomohiro Usui, Sei-ichiro Watanabe, Yuichi Tsuda