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.

Mizunami Underground Research Laboratory Project; Results of the borehole investigations to understand the geological environment in and around the Main-shaft fault

Tsuruta, Tadahiko; Takeda, Masaki; Ueno, Takashi; Daimaru, Shuji; Tokuyasu, Shingo; Onoe, Hironori; Shingu, Shinya; Ishibashi, Masayuki; Takeuchi, Ryuji; Matsuoka, Toshiyuki; et al.

JAEA-Technology 2012-001, 134 Pages, 2012/03

JAEA-Technology-2012-001.pdf:41.2MB
JAEA-Technology-2012-001(errata).pdf:0.44MB
JAEA-Technology-2012-001-appendix(CD-ROM).pdf:6.37MB

Tono Geoscientific Research Unit of Japan Atomic Energy Agency (JAEA) is performing the Mizunami Underground Research Laboratory (MIU) project in order to establish comprehensive techniques for the investigation, analysis and assessment of the deep geological environment in fractured crystalline rock. The borehole investigations (two boreholes; 10MI22 borehole and 10MI23 borehole) have been carried out to obtain information on geological, hydrological and hydrochemical characteristics in and around the Main-shaft fault. These investigations provided that features of fracture and alteration on rock mass in and around the Main-shaft fault. Hydrological and hydrochemical properties based on the geological features were also obtained.

Inelastic neutron scattering on iron-based superconductors

Ishikado, Motoyuki; Nagai, Yuki; Kodama, Katsuaki; Kajimoto, Ryoichi; Nakamura, Mitsutaka; Inamura, Yasuhiro; Mizuno, Fumio; Wakimoto, Shuichi; Nakamura, Hiroki; Machida, Masahiko; et al.

no journal, , 

Three years have passed since the discovery of iron-based superconductors, its maximum superconducting transition temperature () is 55 K, resulting in second highest material system next to cuprate high- superconductors. Among various material systems in iron-based superconductors, we have systematically studied on LaFeAsOF (=28 K) of first discovered system and BaFe(As,P) which have recently attracted tremendous attention by the discovery of line nodes in its order parameter. In the session, we present recent results on "spin fluctuation and superconductivity on LaFePO", and "symmetry of order parameter on BaFe(As,P) by inelastic neutron scattering" studied by the chopper spectrometer 4SEASONS (J-PARC).

Magnetic scattering on Fe-based superconductors La1111 and BaFe(As,P)

Ishikado, Motoyuki; Nagai, Yuki; Kodama, Katsuaki; Kajimoto, Ryoichi; Nakamura, Mitsutaka; Inamura, Yasuhiro; Mizuno, Fumio; Wakimoto, Shuichi; Nakamura, Hiroki; Machida, Masahiko; et al.

no journal, , 

We report systematic studies on Fe-based superconductors LaFeAsOF ( =28 K) and BaFe(As,P) ( =31 K) by using inelastic neutron scattering measurement.