Sample collection from asteroid (162173) Ryugu by Hayabusa2: Implications for surface evolution
Tomokatsu Morota, Seiji Sugita, Yuichiro Cho, Masanori Kanamaru, Eri Tatsumi, Naoya Sakatani, Rie Honda, N. Hirata, Hiroshi Kikuchi, Manabu Yamada, Y. Yokota, S. Kameda, M. Matsuoka, Hirotaka Sawada, C. Honda, Toru Kouyama, Kazunori Ogawa, Hidehiko Suzuki, Kazuo Yoshioka, M. Hayakawa, Naru Hirata, M. Hirabayashi, Hideaki Miyamoto, T. Michikami, T. Hiroi, Ryodo Hemmi, O. S. Barnouin, C. M. Ernst, K. Kitazato, Tomoki Nakamura, L. Riu, H. Senshu, Hiroshi Kobayashi, S. Sasaki, G. Komatsu, Naoya Tanabe, Y. Fujii, T. Irie, M. Suemitsu, Naofumi Takaki, C. Sugimoto, Koki Yumoto, M. Ishida, Hideki Kato, K. Moroi, D. Domingue, Patrick Michel, C. Pilorget, Takahiro Iwata, Masanao Abe, M. Ohtake, Yusuke Nakauchi, Kohji Tsumura, Hikaru Yabuta, Y. Ishihara, Rina Noguchi, Koji Matsumoto, Akira Miura, N. Namiki, Shogo Tachibana, Masahiko Arakawa, Hitoshi Ikeda, Koji Wada, Takahide Mizuno, Chikako Hirose, S Hosoda, Osamu Mori, T. Shimada, Stefania Soldini, Ryudo Tsukizaki, Hajime Yano, M. Ozaki, Hiroshi Takeuchi, Yukio Yamamoto, Tatsuaki Okada, Yuri Shimaki, K. Shirai, Y. Iijima, Hirotomo Noda, Shota Kikuchi, Tomohiro Yamaguchi, Naoko Ogawa, Go Ono, Yuya Mimasu, Kent Yoshikawa, T. Takahashi, Yuto Takei, Atsushi Fujii, Satoru Nakazawa, Fuyuto Terui, S. Tanaka, M. Yoshikawa, Takanao Saiki, Sei‐ichiro Watanabe, Yuichi Tsuda
Abstract
The near-Earth asteroid (162173) Ryugu is thought to be a primitive carbonaceous object that contains hydrated minerals and organic molecules. We report sample collection from Ryugu's surface by the Hayabusa2 spacecraft on 21 February 2019. Touchdown images and global observations of surface colors are used to investigate the stratigraphy of the surface around the sample location and across Ryugu. Latitudinal color variations suggest the reddening of exposed surface material by solar heating and/or space weathering. Immediately after touchdown, Hayabusa2's thrusters disturbed dark, fine grains that originate from the redder materials. The stratigraphic relationship between identified craters and the redder material indicates that surface reddening occurred over a short period of time. We suggest that Ryugu previously experienced an orbital excursion near the Sun.