研究者業績
基本情報
- 所属
- 国立研究開発法人宇宙航空研究開発機構 宇宙科学研究所 特任助教
- 研究者番号
- 60623197
- ORCID ID
https://orcid.org/0000-0002-6142-9842- J-GLOBAL ID
- 202001018349417556
- researchmap会員ID
- R000003532
研究分野
1経歴
5-
2023年8月 - 現在
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2022年7月 - 2023年7月
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2021年3月 - 2022年6月
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2019年5月 - 2021年2月
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2016年4月 - 2019年4月
学歴
4-
2012年10月 - 2016年3月
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2009年4月 - 2011年3月
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2005年4月 - 2009年3月
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2002年4月 - 2005年3月
委員歴
3-
2020年10月 - 現在
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2018年12月 - 現在
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2017年1月 - 現在
受賞
2論文
144-
The Astronomical Journal 2026年3月2日
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METEORITICS & PLANETARY SCIENCE 2026年
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Acta Astronautica 2025年12月
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The Planetary Science Journal 2025年2月1日
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ASTROPHYSICAL JOURNAL 2025年
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SPACE SCIENCE REVIEWS 2025年
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Icarus 417 116122-116122 2024年7月
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ASTRONOMY & ASTROPHYSICS 2024年6月
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MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY 2024年
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Science Advances 9(49) 2023年12月8日The carbonaceous asteroid Ryugu has been explored by the Hayabusa2 spacecraft to elucidate the actual nature of hydrous asteroids. Laboratory analyses revealed that the samples from Ryugu are comparable to unheated CI carbonaceous chondrites; however, reflectance spectra of Ryugu samples and CIs do not coincide. Here, we demonstrate that Ryugu sample spectra are reproduced by heating Orgueil CI chondrite at 300°C under reducing conditions, which caused dehydration of terrestrial weathering products and reduction of iron in phyllosilicates. Terrestrial weathering of CIs accounts for the spectral differences between Ryugu sample and CIs, which is more severe than space weathering that likely explains those between asteroid Ryugu and the collected samples. Previous assignments of CI chondrite parent bodies, i.e., chemically most primitive objects in the solar system, are based on the spectra of CI chondrites. This study indicates that actual spectra of CI parent bodies are much darker and flatter at ultraviolet to visible wavelengths than the spectra of CI chondrites.
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Communications Earth & Environment 4(1) 2023年9月27日Abstract 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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Icarus 406 115755-115755 2023年8月
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Earth, Planets and Space submitted 2023年3月9日 査読有りThe zodiacal light (ZL) is sunlight scattered by interplanetary dust (IPD) in the optical wavelengths. The spatial distribution of IPD in the Solar system may hold an important key to understanding the evolution of the Solar system and material transportation within it. The IPD number density can be expressed as n(r)∼r^{−α}, and the result of α∼1.3 was obtained by the previous observations from the interplanetary space by Helios 1/2 and Pioneer 10/11 in the 1970s and 1980s. However, no direct measurements of α based on the ZL observation from the interplanetary space outside the Earth's orbit have been conducted since then. Here we introduce the initial result of the ZL radial profile at optical wavelengths observed at 0.76-1.06 au by ONC-T with Hayabusa2# mission in 2021-2022. The obtained ZL brightness is well reproduced by the model brightness, but there is a small excess of the observed ZL brightness over the model brightness at around 0.9 au. The obtained radial power-law index is α=1.30±0.08, which is consistent with the previous results based on the ZL observations. The dominant uncertainty source in α arises from the uncertainty in the Diffuse Galactic Light estimation.
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MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY 2023年3月
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EARTH PLANETS AND SPACE 75(1) 2023年3月
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Science 379(6634) 786-+ 2023年Carbonaceous meteorites are thought to be fragments of C-type (carbonaceous) asteroids. Samples of the C-type asteroid (162173) Ryugu were retrieved by the Hayabusa2 spacecraft. We measured the mineralogy and bulk chemical and isotopic compositions of Ryugu samples. The samples are mainly composed of materials similar to those of carbonaceous chondrite meteorites, particularly the CI (Ivuna-type) group. The samples consist predominantly of minerals formed in aqueous fluid on a parent planetesimal. The primary minerals were altered by fluids at a temperature of 37 degrees +/- 10 degrees C, about 5.2(-0.7)(+0.8) million (statistical) or 5.2(-2.1)(+1.6) million (systematic) years after the formation of the first solids in the Solar System. After aqueous alteration, the Ryugu samples were likely never heated above similar to 100 degrees C. The samples have a chemical composition that more closely resembles that of the Sun's photosphere than other natural samples do.
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Journal of Evolving Space Activities 2023年
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ASTRONOMY & ASTROPHYSICS 2023年
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ASTRONOMY & ASTROPHYSICS 2023年1月
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MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY 2023年
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Earth, Planets and Space 74(1) 2022年12月
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Astronomy & Astrophysics 666 A164-A164 2022年10月Context. After landing on C-type asteroid Ryugu, MASCOT imaged brightly colored, submillimeter-sized inclusions in a small rock. Hayabusa2 successfully returned a sample of small particles from the surface of Ryugu, but none of these appear to harbor such inclusions. The samples are considered representative of Ryugu. Aims. To understand the apparent discrepancy between MASCOT observations and Ryugu samples, we assess whether the MASCOT landing site, and the rock by implication, is perhaps atypical for Ryugu. Methods. We analyzed observations of the MASCOT landing area acquired by three instruments on board Hayabusa2: a camera (ONC), a near-infrared spectrometer (NIRS3), and a thermal infrared imager. We compared the landing area properties thus retrieved with those of the average Ryugu surface. Results. We selected several areas and landforms in the landing area for analysis: a small crater, a collection of smooth rocks, and the landing site itself. The crater is relatively blue and the rocks are relatively red. The spectral and thermophysical properties of the landing site are very close to those of the average Ryugu surface. The spectral properties of the MASCOT rock are probably close to average, but its thermal inertia may be somewhat higher. Conclusions. The MASCOT rock can also be considered representative of Ryugu. Some of the submillimeter-sized particles in the returned samples stand out because of their atypical spectral properties. Such particles may be present as inclusions in the MASCOT rock.
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ASTRONOMY & ASTROPHYSICS 2022年8月
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Icarus 381 2022年7月15日 査読有り
MISC
10所属学協会
2-
2019年5月 - 現在
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2013年1月 - 現在
共同研究・競争的資金等の研究課題
8-
日本学術振興会 科学研究費助成事業 2025年4月 - 2028年3月
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会津大学宇宙情報科学研究センター 公募型共同研究事業 2024年4月 - 2025年3月
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GTC, Observatorios de Canarias Night CAT 2023年3月 - 2023年8月
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INT, Observatorios de Canarias Night CAT 2022年2月 - 2022年7月
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INT, Observatorios de Canarias Night CAT 2021年8月 - 2022年1月
