The Surface composition of asteroid 162173 Ryugu from Hayabusa2 near-infrared spectroscopy

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.*; Takir, D.*; Domingue, D.*; 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*

The near-Earth asteroid 162173 Ryugu, the target of Hayabusa2 sample return mission, is believed to be a primitive carbonaceous object. The Near Infrared Spectrometer (NIRS3) on Hayabusa2 acquired reflectance spectra of Ryugu's surface to provide direct measurements of the surface composition and geological context for the returned samples. A weak, narrow absorption feature centered at 2.72 micron was detected across the entire observed surface, indicating that hydroxyl (OH)-bearing minerals are ubiquitous there. The intensity of the OH feature and low albedo are similar to thermally- and/or shock-metamorphosed carbonaceous chondrite meteorites. There are few variations in the OH-band position, consistent with Ryugu being a compositionally homogeneous rubble-pile object generated from impact fragments of an undifferentiated aqueously altered parent body.