Condensation processes of volatile elements in the primordial solar nebula revealed by multi-isotope chronology

2022 Fiscal Year Final Research Report

• Project/Area Number: 17K14423
• Research Category: Grant-in-Aid for Young Scientists (B)
• Allocation Type: Multi-year Fund
• Research Field: Geochemistry/Cosmochemistry
• Research Institution: Japan Atomic Energy Agency
• Principal Investigator: Yokoyama Tatsunori 国立研究開発法人日本原子力研究開発機構, 核燃料・バックエンド研究開発部門 東濃地科学センター, 研究職 (10750846)
• Project Period (FY): 2017-04-01 – 2023-03-31
• Keywords: 原始太陽系における元素凝縮 / マルチアイソトープ / セシウムーバリウム同位体系

Outline of Final Research Achievements

Lacks in volatile element compositions of planetary materials such as meteorites are recognized in comparison with solar compositions. In this study, we focused on "rock fragments rich in alkaline elements" in meteorites and aimed to elucidate the timing and phenomena of the lack by capturing traces of volatile elements that condensed in the primitive solar nebula through chronological studies of these fragments. In addition to the radiometric dating methods used so far, we attempted to elucidate whether the concentration of alkaline elements in rock fragments occurred in the early solar nebula by conducting dating using Cs-Ba isotope systems. As a result, we succeeded in establishing a Ba isotope measurement method and obtaining isotopic compositions of test samples such as chondrites. However we were unable to detect traces of alkaline element concentrations in the early solar nebula at this stage.

Free Research Field

宇宙地球化学

Academic Significance and Societal Importance of the Research Achievements

太陽系の形成進化を解明する惑星科学分野において、最も根本となる(小)惑星の材料物質に関する原始太陽系星雲中での元素分別過程への理解は、未だ不十分である。揮発性元素の凝縮物の痕跡を明確に捉えることは、原始太陽系星雲中での元素分別過程の全容解明へつながり、太陽系の形成進化過程に重要な制約を与えることができる。研究期間内でアルカリ元素に富む岩片から元素凝縮の証拠を得ることはできなかったが、確立した手法により引き続き実試料の分析を実施し、得られた成果は速やかに公表する。