Noble gases and nitrogen in samples of asteroid Ryugu record its volatile sources and recent surface evolution.

Ryuji Okazaki ,K Yoshikawa ,Toru Yada ,K Righter ,Moe Matsuoka ,Satoshi Tanaka ,Mitsuru Ebihara ,Masanobu Ozaki ,Yoshinori Takano ,Thomas Lawton ,Kentaro Hatakeda ,Akiko Miyazaki ,Y Iijima ,Naoki Shirai ,Yoshiaki Ishihara ,Hirotaka Sawada ,Michio Inagaki ,S A Crowther ,Hitoshi Ikeda ,Makoto Yoshikawa ,Ken‐Ichi Bajo ,Keita Yamada ,Rie Honda ,Tomoki Nakamura ,Hajime Yano ,Hirotomo Noda ,Shinsuke Kawagucci ,C Maden ,Fuyuto Terui ,Koji Wada ,Tatsuhiro Michikami ,Keisuke Yoshihara ,Jong Ik Lee ,O V Pravdivtseva ,Akihiro Kano ,Hiroki Senshu ,Masahiro Nishimura ,Ko Hashizume ,Naoyuki Hirata ,Daniela Krietsch ,Yukio Yamamoto ,Ayako Iwamae ,Aiko Nakato ,Ryu Uemura ,Masateru Ishiguro ,Kazunori Ogawa ,Michael W Broadley ,P L Clay ,Noriyuki Namiki ,Koji Matsumoto ,Yuto Takei ,Naoko Ogawa ,Munehiko Yamamoto ,David Byrne ,Shun Sekimoto ,Yayoi N Miura ,Shozo Nakazawa ,K Kitazato ,Takanao Saiki ,T Iwata ,Shogo Tachibana ,Daiki Yamamoto ,Saichi Hosoda ,Ryudo Tsukizaki ,Lydia Fawcett ,Saburo Sakai ,T Morota ,Chisato Okamoto ,H Busemann ,Akira Miura ,Kei Shirai ,H C Connolly ,Yuya Hitomi ,S Watanabe ,Seiji Sugita ,Ryota Fukai ,Naoyoshi Iwata ,Kanako Sakamoto ,Yasuhiro Yokota ,Д С Лауретта ,Masahiko Hayakawa ,Y Shimaki ,Shizuho Furuya ,A P Meshik ,T Hayashi ,Manabu Yamada ,Miwa Yoshitake ,Takaaki Noguchi ,Go Ono ,Reika Yokochi ,Jisun Park ,Masahiko Arakawa ,Hiroshi Naraoka ,Eri Tatsumi ,T Okada ,Hikaru Yabuta ,Naoya Sakatani ,Tetsuya Yamada ,Bernard Marty ,Shota Kikuchi ,Kazuya Kumagai ,K Nishiizumi ,Keisuke Nagao ,Hiroshi Takeuchi ,Fumio Kitajima ,Yohei Matsui ,H Yurimoto ,Kasumi Yogata ,Chikatoshi Honda ,Akizumi Ishida ,Evelyn Füri ,Yuya Mimasu ,Hiromichi Soejima ,M E I Riebe ,Rina Noguchi ,Marc W Caffee ,Naru Hirata ,J D Gilmour ,Kosuke Kawahara ,Atsushi Fujii ,Yuichi Tsuda

doi:10.1126/science.abo0431

Abstract

The near-Earth carbonaceous asteroid (162173) Ryugu is expected to contain volatile chemical species that could provide information on the origin of Earth's volatiles. Samples of Ryugu were retrieved by the Hayabusa2 spacecraft. We measured noble gas and nitrogen isotopes in Ryugu samples and found that they are dominated by presolar and primordial components, incorporated during Solar System formation. Noble gas concentrations are higher than those in Ivuna-type carbonaceous (CI) chondrite meteorites. Several host phases of isotopically distinct nitrogen have different abundances among the samples. Our measurements support a close relationship between Ryugu and CI chondrites. Noble gases produced by galactic cosmic rays, indicating a ~5 million year exposure, and from implanted solar wind record the recent irradiation history of Ryugu after it migrated to its current orbit.

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