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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.
Nakajima, Kaoru*; Nagano, Kengo*; Suzuki, Motofumi*; Narumi, Kazumasa; Saito, Yuichi; Hirata, Koichi*; Kimura, Kenji*
Applied Physics Letters, 104(11), p.114103_1 - 114103_4, 2014/03
Times Cited Count:6 Percentile:26.85(Physics, Applied)Hirata, Koichi*; Saito, Yuichi; Chiba, Atsuya; Yamada, Keisuke; Narumi, Kazumasa
Nuclear Instruments and Methods in Physics Research B, 314, p.39 - 42, 2013/11
Times Cited Count:4 Percentile:33.02(Instruments & Instrumentation)Tsuchida, Hidetsugu*; Majima, Takuya*; Tomita, Shigeo*; Sasa, Kimikazu*; Narumi, Kazumasa; Saito, Yuichi; Chiba, Atsuya; Yamada, Keisuke; Hirata, Koichi*; Shibata, Hiromi*; et al.
Nuclear Instruments and Methods in Physics Research B, 315, p.336 - 340, 2013/11
Times Cited Count:3 Percentile:26.71(Instruments & Instrumentation)Hirata, Koichi*; Saito, Yuichi; Chiba, Atsuya; Yamada, Keisuke; Narumi, Kazumasa; Kamiya, Tomihiro
JAEA-Review 2012-046, JAEA Takasaki Annual Report 2011, P. 165, 2013/01
Hirata, Koichi*; Saito, Yuichi; Chiba, Atsuya; Yamada, Keisuke; Takahashi, Yasuyuki*; Narumi, Kazumasa; Kamiya, Tomihiro
JAEA-Review 2011-043, JAEA Takasaki Annual Report 2010, P. 156, 2012/01
Hirata, Koichi*; Saito, Yuichi; Chiba, Atsuya; Yamada, Keisuke; Narumi, Kazumasa
Applied Physics Express, 4(11), p.116202_1 - 116202_3, 2011/11
Times Cited Count:8 Percentile:34.67(Physics, Applied)Nagame, Yuichiro; Hirata, Masaru
Radiochimica Acta, 99(7-8), p.377 - 393, 2011/08
Times Cited Count:12 Percentile:66.82(Chemistry, Inorganic & Nuclear)Hirata, Koichi*; Saito, Yuichi; Chiba, Atsuya; Yamada, Keisuke; Takahashi, Yasuyuki*; Narumi, Kazumasa
Review of Scientific Instruments, 82(3), p.033101_1 - 033101_5, 2011/03
Times Cited Count:10 Percentile:44.79(Instruments & Instrumentation)Nagame, Yuichiro; Hirata, Masaru; Nakahara, Hiromichi*
Handbook of Nuclear Chemistry, p.817 - 875, 2011/02
Hirata, Koichi*; Saito, Yuichi; Chiba, Atsuya; Yamada, Keisuke; Takahashi, Yasuyuki; Narumi, Kazumasa
Nuclear Instruments and Methods in Physics Research B, 268(19), p.2930 - 2932, 2010/10
Times Cited Count:3 Percentile:28.83(Instruments & Instrumentation)Haba, Hiromitsu*; Akiyama, Kazuhiko*; Tsukada, Kazuaki; Asai, Masato; Toyoshima, Atsushi; Yaita, Tsuyoshi; Hirata, Masaru; Sueki, Keisuke*; Nagame, Yuichiro
Bulletin of the Chemical Society of Japan, 82(6), p.698 - 703, 2009/06
Times Cited Count:10 Percentile:39.86(Chemistry, Multidisciplinary)Chloride complexation of the group-4 elements Zr and Hf in 8.0-11.9 M HCl is investigated by Extended X-ray Absorption Fine Structure (EXAFS) spectroscopy to characterize chloro complexes of the transactinide element, rutherfordium (Rf). The complexes of Zr and Hf successively vary with the concentration of HCl from a hydrated complex [M(HO) ] at 8.0 M to a hexachloro complex [MCl] at 11.9 M (M = Zr and Hf). The present structural changes of the Zr and Hf complexes well reflect the previously studied anion-exchange behavior of Zr and Hf in HCl. From both the EXAFS and anion-exchange results, we suggest that Rf forms the same complexes as those of Zr and Hf in HCl, and that the complexation strength of the hexachloro complexes of the group-4 elements, [MCl] (M = Zr, Hf, and Rf), is in the sequence of Rf Zr Hf.
Hirata, Koichi*; Saito, Yuichi; Chiba, Atsuya; Adachi, Masahiro*; Yamada, Keisuke; Narumi, Kazumasa
Nuclear Instruments and Methods in Physics Research B, 266(10), p.2450 - 2452, 2008/05
Times Cited Count:13 Percentile:64.63(Instruments & Instrumentation)Hirata, Koichi*; Saito, Yuichi; Chiba, Atsuya; Narumi, Kazumasa
Applied Physics Express, 1(4), p.047002_1 - 047002_3, 2008/04
Times Cited Count:4 Percentile:18.78(Physics, Applied)Nagame, Yuichiro; Tsukada, Kazuaki; Asai, Masato; Toyoshima, Atsushi; Akiyama, Kazuhiko; Ishii, Yasuo; Sato, Tetsuya; Hirata, Masaru; Nishinaka, Ichiro; Ichikawa, Shinichi; et al.
Radiochimica Acta, 93(9-10), p.519 - 526, 2005/00
Times Cited Count:30 Percentile:87.1(Chemistry, Inorganic & Nuclear)no abstracts in English
Haba, Hiromitsu*; Tsukada, Kazuaki; Asai, Masato; Toyoshima, Atsushi; Akiyama, Kazuhiko; Nishinaka, Ichiro; Hirata, Masaru; Yaita, Tsuyoshi; Ichikawa, Shinichi; Nagame, Yuichiro; et al.
Journal of the American Chemical Society, 126(16), p.5219 - 5224, 2004/04
Times Cited Count:43 Percentile:72.51(Chemistry, Multidisciplinary)Fluoride complexation of element 104, rutherfordium (Rf), produced in the Cm(O,5n)Rf reaction has been studied by anion-exchange chromatography on an atom-at-a-time scale. The anion-exchangechromatographic behavior of Rf was investigated in 1.9-13.9 M hydrofluoric acid together with those of the group-4 elements Zr and Hf produced in the O-induced reactions on Ge and Gd targets, respectively. It was found that the adsorption behavior of Rf on anion-exchange resin is quite different from those of Zr and Hf, suggesting the influence of relativistic effect on the fluoride complexation of Rf.
Nagame, Yuichiro; Haba, Hiromitsu*; Tsukada, Kazuaki; Asai, Masato; Toyoshima, Atsushi; Goto, Shinichi*; Akiyama, Kazuhiko; Kaneko, Tetsuya; Sakama, Minoru*; Hirata, Masaru; et al.
Nuclear Physics A, 734, p.124 - 135, 2004/04
Times Cited Count:11 Percentile:56.88(Physics, Nuclear)no abstracts in English
Nagame, Yuichiro; Haba, Hiromitsu; Tsukada, Kazuaki; Asai, Masato; Akiyama, Kazuhiko; Hirata, Masaru; Nishinaka, Ichiro; Ichikawa, Shinichi; Nakahara, Hiromichi; Goto, Shinichi*; et al.
Czechoslovak Journal of Physics, 53, p.A299 - A304, 2003/00
Times Cited Count:7 Percentile:46.52(Physics, Multidisciplinary)no abstracts in English
Nagame, Yuichiro; Hirata, Masaru; Nakahara, Hiromichi
Handbook of Nuclear Chemistry, Vol.2, p.219 - 282, 2003/00
no abstracts in English