Spectral characteristics of asteroid (162173) Ryugu with Hayabusa2 NIRS3

Takir, D.*; Kitazato, Kohei*; Milliken, R. E.*; Iwata, Takahiro*; Abe, Masanao*; Otake, Makiko*; Matsuura, Shuji*; Arai, Takehiko*; Nakauchi, Yusuke*; Nakamura, Tomoki*; Matsuoka, Moe*; Senshu, Hiroki*; Hirata, Naru*; Hiroi, Takahiro*; Pilorget, C.*; Brunetto, R.*; Poulet, F.*; Riu, L.*; Bibring, J.-P.*; Domingue, D. L.*; Vilas, F.*; Barucci, M. A.*; Perna, D.*; Palomba, E.*; Galiano, A.*; Tsumura, Koji*; Osawa, Takahito  ; Komatsu, Mutsumi*; Nakato, Aiko*; Arai, Tomoko*; Takato, Naruhisa*; Matsunaga, Tsuneo*; Takagi, Yasuhiko*; Matsumoto, Koji*; Koyama, Toru*; Yokota, Yasuhiro*; Tatsumi, Eri*; Sakatani, Naoya*; Yamamoto, Yukio*; Okada, Tatsuaki*; Sugita, Seiji*; Honda, Rie*; Morota, Tomokatsu*; Kameda, Shingo*; Sawada, Hirotaka*; Honda, Chikatoshi*; Yamada, Manabu*; Suzuki, Hidehiko*; Yoshioka, Kazuo*; Hayakawa, Masahiko*; Ogawa, Kazunori*; Cho, Yuichiro*; Shirai, Kei*; Shimaki, Yuri*; Hirata, Naoyuki*; Yamaguchi, Akira*; Ogawa, Naoko*; Terui, Fuyuto*; Yamaguchi, Tomohiro*; Takei, Yuto*; Saiki, Takanao*; Nakazawa, Satoru*; Tanaka, Satoshi*; Yoshikawa, Makoto*; Watanabe, Seiichiro*; Tsuda, Yuichi*

JAXA spacecraft and sample return mission Hayabusa2 has arrived at the near-Earth asteroid 162173 Ryugu, which is classified a primitive carbonaceous object. Here we report recent results of near-infrared spectrometer (NIRS3) on the Hayabusa2 spacecraft. The observations provide direct measurements of the surface composition of Ryugu and context for the returned samples. NIRS3 has detected a weak and narrow absorption feature centered at 2.72 micrometer across entire observed surface. This absorption feature is attributed to the presence of OH-bearing minerals. The NIRS3 observations also revealed that Ryugu is the darkest object to be observed up-close by a visiting spacecraft. The intensity of the OH feature and low albedo are consistent with thermally-and/or shock-metamorphosed, and/or carbon-rich space-weathered primitive and hydrated carbonaceous chondrites.