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 宇宙機応用工学研究系 はやぶさ２プロジェクト 准教授
- 学位
- 理学博士(1989年3月 東京大学)
- 連絡先
- yoshikawa.makoto
jaxa.jp - J-GLOBAL ID
- 200901037361657011
- researchmap会員ID
- 1000304540
研究キーワード
6経歴
5-
2003年10月 - 現在
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1998年4月 - 2003年9月
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1991年4月 - 1998年3月
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1996年12月 - 1997年12月
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1989年4月 - 1991年3月
学歴
2-
1984年4月 - 1989年3月
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1980年4月 - 1984年3月
委員歴
9-
2020年10月 - 現在
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1994年4月 - 現在
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2013年1月 - 2015年3月
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2011年1月 - 2012年12月
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2009年 - 2011年
受賞
2-
2019年11月
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2018年12月
論文
274-
Science Advances 10(39) 2024年9月27日The isotopic compositions of samples returned from Cb-type asteroid Ryugu and Ivuna-type (CI) chondrites are distinct from other carbonaceous chondrites, which has led to the suggestion that Ryugu/CI chondrites formed in a different region of the accretion disk, possibly around the orbits of Uranus and Neptune. We show that, like for Fe, Ryugu and CI chondrites also have indistinguishable Ni isotope anomalies, which differ from those of other carbonaceous chondrites. We propose that this unique Fe and Ni isotopic composition reflects different accretion efficiencies of small FeNi metal grains among the carbonaceous chondrite parent bodies. The CI chondrites incorporated these grains more efficiently, possibly because they formed at the end of the disk’s lifetime, when planetesimal formation was also triggered by photoevaporation of the disk. Isotopic variations among carbonaceous chondrites may thus reflect fractionation of distinct dust components from a common reservoir, implying CI chondrites/Ryugu may have formed in the same region of the accretion disk as other carbonaceous chondrites.
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Nature Communications 15 7488 2024年8月29日 査読有りAbstract Primordial carbon delivered to the early earth by asteroids and meteorites provided a diverse source of extraterrestrial organics from pre-existing simple organic compounds, complex solar-irradiated macromolecules, and macromolecules from extended hydrothermal processing. Surface regolith collected by the Hayabusa2 spacecraft from the carbon-rich asteroid 162173 Ryugu present a unique opportunity to untangle the sources and processing history of carbonaceous matter. Here we show carbonaceous grains in Ryugu can be classified into three main populations defined by spectral shape: Highly aromatic (HA), Alkyl-Aromatic (AA), and IOM-like (IL). These carbon populations may be related to primordial chemistry, since C and N isotopic compositions vary between the three groups. Diffuse carbon is occasionally dominated by molecular carbonate preferentially associated with coarse-grained phyllosilicate minerals. Compared to related carbonaceous meteorites, the greater diversity of organic functional chemistry in Ryugu indicate the pristine condition of these asteroid samples.
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Geochimica et Cosmochimica Acta 379 172-183 2024年8月
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Meteoritics & Planetary Science 2024年7月4日
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Advances in Space Research 2024年5月
MISC
499-
ASTROPHYSICAL JOURNAL LETTERS 935(1) 2022年8月16日We have conducted a NanoSIMS-based search for presolar material in samples recently returned from C-type asteroid Ryugu as part of JAXA's Hayabusa2 mission. We report the detection of all major presolar grain types with O- and C-anomalous isotopic compositions typically identified in carbonaceous chondrite meteorites: 1 silicate, 1 oxide, 1 O-anomalous supernova grain of ambiguous phase, 38 SiC, and 16 carbonaceous grains. At least two of the carbonaceous grains are presolar graphites, whereas several grains with moderate C isotopic anomalies are probably organics. The presolar silicate was located in a clast with a less altered lithology than the typical extensively aqueously altered Ryugu matrix. The matrix-normalized presolar grain abundances in Ryugu are 4.8$^{+4.7}_{-2.6}$ ppm for O-anomalous grains, 25$^{+6}_{-5}$ ppm for SiC grains and 11$^{+5}_{-3}$ ppm for carbonaceous grains. Ryugu is isotopically and petrologically similar to carbonaceous Ivuna-type (CI) chondrites. To compare the in situ presolar grain abundances of Ryugu with CI chondrites, we also mapped Ivuna and Orgueil samples and found a total of SiC grains and 6 carbonaceous grains. No O-anomalous grains were detected. The matrix-normalized presolar grain abundances in the CI chondrites are similar to those in Ryugu: 23 $^{+7}_{-6}$ ppm SiC and 9.0$^{+5.3}_{-4.6}$ ppm carbonaceous grains. Thus, our results provide further evidence in support of the Ryugu-CI connection. They also reveal intriguing hints of small-scale heterogeneities in the Ryugu samples, such as locally distinct degrees of alteration that allowed the preservation of delicate presolar material.
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2021年1月22日The asteroid exploration project "Hayabusa2" has successfully returned samples from the asteroid (162173) Ryugu. In this study, we measured the linear polarization degrees of Ryugu using four ground-based telescopes from 2020 September 27 to December 25, covering a wide-phase angle (Sun-target-observer's angle) range from 28$^\circ$ to 104$^\circ$. We found that the polarization degree of Ryugu reached 53$\%$ around a phase angle of 100$^\circ$, the highest value among all asteroids and comets thus far reported. The high polarization degree of Ryugu can be attributed to the scattering properties of its surface layers, in particular the relatively small contribution of multiply-scattered light. Our polarimetric results indicate that Ryugu's surface is covered with large grains. On the basis of a comparison with polarimetric measurements of pulverized meteorites, we can infer the presence of submillimeter-sized grains on the surface layer of Ryugu. We also conjecture that this size boundary represents the grains that compose the aggregate. It is likely that a very brittle structure has been lost in the recovered samples, although they may hold a record of its evolution. Our data will be invaluable for future experiments aimed at reproducing the surface structure of Ryugu.
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日本惑星科学会誌遊星人 28(1) 80-86 2019年<p>リュウグウ表面の地名が国際天文学連合（IAU）のDivision F（Planetary System and Bioastronomy）のWorking Group for Planetary System Nomenclature（以降，国際天文学連合ワーキンググループ）で審議され，2018年の年末に承認された．ここでは地名の紹介と決定までの経緯について紹介する．</p>
書籍等出版物
19講演・口頭発表等
32担当経験のある科目(授業)
8-
2019年4月 - 現在太陽と太陽系の科学 (放送大学)
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2011年4月 - 現在位置天文学・天体力学 (東京大学)
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2007年4月 - 現在宇宙科学 (玉川大学)
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2006年4月 - 現在宇宙システム工学特論 III (総合研究大学院大学)
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2006年 - 現在宇宙工学概論 (総合研究大学院大学)
共同研究・競争的資金等の研究課題
15-
日本学術振興会 科学研究費助成事業 2023年4月 - 2026年3月
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日本学術振興会 科学研究費助成事業 基盤研究(B) 2018年4月 - 2021年3月
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日本学術振興会 科学研究費助成事業 基盤研究(C) 2016年4月 - 2019年3月
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日本学術振興会 科学研究費助成事業 2003年 - 2006年
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日本学術振興会 科学研究費助成事業 2003年 - 2005年
