2022 Fiscal Year Final Research Report

The chemical composition of the asteroid Ryugu is determined by X-ray fluorescence analyses

Research Project

PDF

Project/Area Number	20H02773
Research Category	Grant-in-Aid for Scientific Research (B)
Allocation Type	Single-year Grants
Section	一般
Review Section	Basic Section 34020:Analytical chemistry-related
Research Institution	Tokyo University of Science
Principal Investigator	NAKAI Izumi 東京理科大学, 理学部第一部応用化学科, 教授 (90155648)
Co-Investigator(Kenkyū-buntansha)	由井宏治東京理科大学, 理学部第一部化学科, 教授 (20313017) 圦本尚義北海道大学, 理学研究院, 教授 (80191485) 寺田靖子公益財団法人高輝度光科学研究センター, 分光推進室, 主幹研究員 (90307695) 阿部善也東京電機大学, 工学研究科, 助教 (90635864)
Project Period (FY)	2020-04-01 – 2023-03-31
Keywords	蛍光X線分析 / 放射光X線分析 / はやぶさ2 / 小惑星試料 / XAFS / リュウグウ / ラマン分光分析 / X線顕微鏡
Outline of Final Research Achievements	We developed a technique to analyze whole rocks by wavelength dispersive-X-ray fluorescence (WD-XRF) without pressurizing and molding a trace powder sample of the asteroid Ryugu, which was successfully brought back to Earth by the aster-oid probe “Hayabusa 2.” The composition of Ryugu is similar to that of Ivuna-type carbonaceous meteorites (CI chondrite). The sample is characterized with a high water content, which could be directly quantified by determining its total oxygen (O) content. The fundamental parameter method using ferroalloy as a standard enabled the quantitative analysis of carbon (C). Energy dispersive XRF enabled the analysis of C by introducing an SDD detector that uses graphene as a detector window material. The proposed method allows the nondestructive analysis of light elements (C, O, and chlorine) and expands the applications of XRF analysis to a wide range of geological samples.
Free Research Field	X-ray analysis
Academic Significance and Societal Importance of the Research Achievements	はやぶさ2が、リュウグウから持ち帰ることに成功した貴重な実試料を分析することができるので、起原の不明な隕石試料と比べて格段に高精度のデータがえられる。はやぶさ2により、小惑星の試料を地球に持ち帰ることに成功した夢とロマンのある試料の研究で多くの人の注目を集めた。このプロジェクトの成功により日本の宇宙科学技術の高さを世界に示すことが出来た。今回の化学分析は，人類初のC型小惑星物質の分析であり分析の学術的意義は大きい。