Thermally altered subsurface material of asteroid (162173) Ryugu

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

https://doi.org/10.1038/s41550-020-01271-2

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.

Examination on radioactive waste management in U.S.A. and France

Otagaki, Takao*; Higuchi, Takanao*; Ono, Takahiro*

JNC TJ8420 2001-012, 444 Pages, 2000/02

JNC-TJ8420-2001-012.pdf:14.86MB

None

None

Nemoto, K.*; Ono, Takahiro*; *; Higuchi, Takanao*; Kazama, T.*; Hashimoto, T.*

JNC TJ1420 98-019, 209 Pages, 1998/11

JNC-TJ1420-98-019.pdf:11.1MB

None

None

Nemoto, K.*; *; Higuchi, Takanao*; Endo, H.*; Ono, Takahiro*; *; *

PNC TJ1250 97-006, 165 Pages, 1997/11

PNC-TJ1250-97-006.pdf:5.17MB

None