HISAKI Project Team
Profile Information
- Affiliation
- associate professor, Institute of Space and Astronautical Science, Department of Solar System Science, Japan Aerospace Exploration AgencySchool of Physical Sciences Department of Space and Astronautical Science, The Graduate University for Advanced Studies
- Degree
- 理学博士(Feb, 1989, Nagoya University)
- Researcher number
- 20201949
- ORCID ID
https://orcid.org/0000-0002-4613-7956- J-GLOBAL ID
- 202001003492525290
- researchmap Member ID
- R000013755
（併任）
はやぶさ２プロジェクトチーム
国際宇宙探査センター火星衛星探査機プロジェクトチーム
（兼務）
関西学院大学大学院理工学研究科 客員教授
Research Areas
2Papers
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Physical Review E, 109(3), Mar 15, 2024 Peer-reviewedLast author
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Communications Earth & Environment, 4(1), Sep 27, 2023Abstract Returned samples from Cb-type asteroid (162173) Ryugu exhibit very dark spectra in visible and near-infrared ranges, generally consistent with the Hayabusa2 observations. A critical difference is that a structural water absorption of hydrous silicates is around twice as deep in the returned samples compared with those of Ryugu’s surface, suggesting Ryugu surface is more dehydrated. Here we use laboratory experiments data to indicate the spectral differences between returned samples and asteroid surface are best explained if Ryugu surface has (1) higher porosity, (2) larger particle size, and (3) more space-weathered condition, with the last being the most effective. On Ryugu, space weathering by micrometeoroid bombardments promoting dehydration seem to be more effective than that by solar-wind implantation. Extremely homogeneous spectra of the Ryugu’s global surface is in contrast with the heterogeneous S-type asteroid (25143) Itokawa’s spectra, which suggests space weathering has proceeded more rapidly on Cb-type asteroids than S-type asteroids.
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Journal of Astronomical Telescopes, Instruments, and Systems, 9(03), Sep 12, 2023 Peer-reviewed
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Earth, Planets and Space, 75(1), Aug 22, 2023 Peer-reviewedAbstract Zodiacal light (ZL) is sunlight scattered by interplanetary dust particles (IDPs) at optical wavelengths. The spatial distribution of IDPs in the Solar System may hold an important key to understanding the evolution of the Solar System and material transportation within it. The number density of IDPs can be expressed as $$n(r) \sim r^{-\alpha }$$, and the exponent $$\alpha \sim 1.3$$ was obtained by previous observations from interplanetary space by Helios 1/2 and Pioneer 10/11 in the 1970s and 1980s. However, no direct measurements of $$\alpha $$ based on ZL observations from interplanetary space outside Earth’s orbit have been performed since then. Here, we introduce initial results for the radial profile of the ZL at optical wavelengths observed over the range 0.76$$-$$1.06 au by ONC-T aboard the Hayabusa2# mission in 2021-2022. The ZL brightness we obtained is well reproduced by a model brightness, although there is a small excess of the observed ZL brightness over the model brightness at around 0.9 au. The radial power-law index we obtained is $$\alpha = 1.30 \pm 0.08$$, which is consistent with previous results based on ZL observations. The dominant source of uncertainty arises from the uncertainty in estimating the diffuse Galactic light (DGL). Graphical Abstract
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Science, 379(6634), Feb 24, 2023 Peer-reviewedSamples of the carbonaceous asteroid Ryugu were brought to Earth by the Hayabusa2 spacecraft. We analyzed 17 Ryugu samples measuring 1 to 8 millimeters. Carbon dioxide–bearing water inclusions are present within a pyrrhotite crystal, indicating that Ryugu’s parent asteroid formed in the outer Solar System. The samples contain low abundances of materials that formed at high temperatures, such as chondrules and calcium- and aluminum-rich inclusions. The samples are rich in phyllosilicates and carbonates, which formed through aqueous alteration reactions at low temperature, high pH, and water/rock ratios of <1 (by mass). Less altered fragments contain olivine, pyroxene, amorphous silicates, calcite, and phosphide. Numerical simulations, based on the mineralogical and physical properties of the samples, indicate that Ryugu’s parent body formed ~2 million years after the beginning of Solar System formation.
Misc.
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宇宙科学技術連合講演会講演集(CD-ROM), 67th, 2023
Professional Memberships
6Research Projects
5-
科学研究費助成事業, 日本学術振興会, Apr, 2023 - Mar, 2027
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科学研究費助成事業, 日本学術振興会, Apr, 2021 - Mar, 2024
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Grants-in-Aid for Scientific Research, Japan Society for the Promotion of Science, Apr, 2012 - Mar, 2015
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Grants-in-Aid for Scientific Research, Japan Society for the Promotion of Science, 2008 - 2011
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Grants-in-Aid for Scientific Research, Japan Society for the Promotion of Science, 2007 - 2009
