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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：44 Percentile：97.1(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.
Tsuchiya, Kunihiko; Kawamura, Hiroshi; Mishima, Yoshinao*; Yoshida, Naoaki*; Tanaka, Satoru*; Uchida, Munenori*; Ishida, Kiyohito*; Shibayama, Tamaki*; Munakata, Kenzo*; Sato, Yoshiyuki*; et al.
Purazuma, Kaku Yugo Gakkai-Shi, 83(3), p.207 - 214, 2007/03
no abstracts in English
Suzuki, Hiroshi; Sano, Kenji*; Tanaka, Hirotomo*; Akita, Koichi*
no journal, ,
In this study, the intergranular effect generated in a laser peened surface of a ferritic steel was evaluated using neutron diffraction. The residual stress distribution from the surface to 1 mm depth was obtained by the strain distributions measured using the 110, 200 and 211 reflections. The residual stress distributions derived from the strains of the 110 and 211 reflections were good agreement, while that of the 200 reflection, which is sensitive to the intergranular effect, indicated larger compressive stress by 100 MPa to 200 MPa in the surface layer until 0.8 mm depth from the surface. It is probably intergranular effect, so that the residual stress measurement with consideration of the intergranular effect may be required to evaluate the residual stress generated in the surface layer of the surface treated sample such as the laser peening, the shot peening and so on.
