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Kitazato, Kohei*; Milliken, R. E.*; Iwata, Takahiro*; Abe, Masanao*; Otake, Makiko*; Matsuura, Shuji*; Takagi, Yasuhiko*; Nakamura, Tomoki*; Hiroi, Takahiro*; Matsuoka, Moe*; et al.
Nature Astronomy (Internet), 5(3), p.246 - 250, 2021/03
Times Cited Count：43 Percentile：96.93(Astronomy & Astrophysics)Here we report observations of Ryugu's subsurface material by the Near-Infrared Spectrometer (NIRS3) on the Hayabusa2 spacecraft. Reflectance spectra of excavated material exhibit a hydroxyl (OH) absorption feature that is slightly stronger and peak-shifted compared with that observed for the surface, indicating that space weathering and/or radiative heating have caused subtle spectral changes in the uppermost surface. However, the strength and shape of the OH feature still suggests that the subsurface material experienced heating above 300 
C, similar to the surface. In contrast, thermophysical modeling indicates that radiative heating does not increase the temperature above 200 C at the estimated excavation depth of 1 m, even if the semimajor axis is reduced to 0.344 au. This supports the hypothesis that primary thermal alteration occurred due to radiogenic and/or impact heating on Ryugu's parent body.
Kitazato, Kohei*; Milliken, R. E.*; Iwata, Takahiro*; Abe, Masanao*; Otake, Makiko*; Matsuura, Shuji*; Arai, Takehiko*; Nakauchi, Yusuke*; Nakamura, Tomoki*; Matsuoka, Moe*; et al.
Science, 364(6437), p.272 - 275, 2019/04
Times Cited Count：259 Percentile：99.73(Multidisciplinary Sciences)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.
chains of Ca
Y
Cu
O
Matsuda, Masaaki; Kakurai, Kazuhisa; Kurogi, Shogo*; Kudo, Kazutaka*; Koike, Yoji*; Yamaguchi, Hirotaka*; Ito, Toshimitsu*; Oka, Kunihiko*
Physical Review B, 71(10), p.104414_1 - 104414_8, 2005/03
Times Cited Count：13 Percentile：49.98(Materials Science, Multidisciplinary)no abstracts in English
Ishida, Shinichi; Abe, Katsunori*; Ando, Akira*; Chujo, T.*; Fujii, Tsuneyuki; Fujita, Takaaki; Goto, Seiichi*; Hanada, Kazuaki*; Hatayama, Akiyoshi*; Hino, Tomoaki*; et al.
Nuclear Fusion, 43(7), p.606 - 613, 2003/07
no abstracts in English
Ishida, Shinichi; Abe, Katsunori*; Ando, Akira*; Cho, T.*; Fujii, Tsuneyuki; Fujita, Takaaki; Goto, Seiichi*; Hanada, Kazuaki*; Hatayama, Akiyoshi*; Hino, Tomoaki*; et al.
Nuclear Fusion, 43(7), p.606 - 613, 2003/07
Times Cited Count：33 Percentile：69.14(Physics, Fluids & Plasmas)no abstracts in English
chains in CaYCu
OMatsuda, Masaaki; Nakamura, Mitsutaka; Takeda, Masayasu*; Kakurai, Kazuhisa; Yamaguchi, Hirotaka*; Ito, Toshimitsu*; Oka, Kunihiko*
Physica B; Condensed Matter, 329-333(1-4), p.711 - 712, 2003/05
Times Cited Count：0 Percentile：0(Physics, Condensed Matter)no abstracts in English
chains in CaYCuOMatsuda, Masaaki; Kakurai, Kazuhisa; Yamaguchi, Hirotaka*; Ito, Toshimitsu*; Lee, C.-H.*; Oka, Kunihiko*
Applied Physics A, 74(Suppl.1), p.S637 - S639, 2002/12
Times Cited Count：3 Percentile：16.11(Materials Science, Multidisciplinary)no abstracts in English
chains in CaYCuOMatsuda, Masaaki; Yamaguchi, Hirotaka*; Ito, Toshimitsu*; Le, C.*; Oka, Kunihiko*; Mizuno, Yoshiaki*; Toyama, T.*; Maekawa, Sadamichi*; Kakurai, Kazuhisa*
Physical Review B, 63(18), p.180403_1 - 180403_4, 2001/05
Times Cited Count：25 Percentile：75.01(Materials Science, Multidisciplinary)no abstracts in English
with short wavelength neutrons*; *; *; Morii, Yukio; Minakawa, Nobuaki; Yamaguchi, Hirotaka*
Journal of Physics and Chemistry of Solids, 60(8-9), p.1415 - 1418, 1999/00
Times Cited Count：3 Percentile：23.12(Chemistry, Multidisciplinary)no abstracts in English
Koizumi, Masumichi; *; Yamaguchi, Toshihiro; Furuya, Hirotaka
PNC TN841 75-38, 103 Pages, 1975/10
no abstracts in English
Yamaguchi, Toshihiro; *; Furuya, Hirotaka; Koizumi, Masumichi
PNC TN841 75-05, 45 Pages, 1975/03
no abstracts in English
Koizumi, Masumichi; *; Yamaguchi, Toshihiro; Furuya, Hirotaka; *; *
PNC TN841 75-02, 59 Pages, 1975/01
no abstracts in English
Koizumi, Masumichi; *; Yamaguchi, Toshihiro; *; Furuya, Hirotaka; Komatsu, Junji*
PNC TN841 74-05, 180 Pages, 1974/01
no abstracts in English
Takir, D.*; Kitazato, Kohei*; Milliken, R. E.*; Iwata, Takahiro*; Abe, Masanao*; Otake, Makiko*; Matsuura, Shuji*; Arai, Takehiko*; Nakauchi, Yusuke*; Nakamura, Tomoki*; et al.
no journal, ,
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.
