Mineralogy and petrology of carbonaceous chondrites and cometary particles: Insights to the evolution of water-bearing asteroids.

2019 Fiscal Year Final Research Report

• Project/Area Number: 16K05603
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Research Field: Petrology/Mineralogy/Economic geology
• Research Institution: The Graduate University for Advanced Studies
• Principal Investigator: Komatsu Mutsumi 総合研究大学院大学, 教育開発センター, 助教 (50609732)
• Project Period (FY): 2016-10-21 – 2020-03-31
• Keywords: 原始太陽系 / 炭素質コンドライト / 水質変成 / 難揮発性包有物

Outline of Final Research Achievements

In order to understand the evolution of primitive C-type asteroids, the detailed formation history of primitive meteorites was examined. We focused on the mineralogy of Renazzo-type carbonaceous (CR) chondrites. CR chondrites are understood as one of the most primitive meteorites; however, because of the rarity of CR chondrites, their parent body is not well understood. Our results show CR chondrites escaped from thermal metamorphism, but the degree of aqueous alteration is highly variable. We also found one amoeboid olivine aggregate (AOA) in one of our samples. It contains minerals with 16O-rich compositions consistent with the nebular setting. The AOA provides direct evidence that silica condensed from gas in a CAI/AOA-forming region in our solar system indicates that gas became Si-rich as Mg condensed and may explain the origin of silica detected from infrared spectroscopy of T Tauri and asymptotic giant branch stars.

Free Research Field

隕石学

Academic Significance and Societal Importance of the Research Achievements

本研究では、原始太陽系での凝縮過程から始原的小惑星の進化を理解するため、始原的隕石の水質変成・加熱履歴を詳細な条件を明らかにすることを目的とした。始原的小惑星は、原始太陽系星雲内の固体物質の形成過程から、始原的小惑星の集積過程と初期の母天体活動を保存する重要な物質である。また、始原的小惑星には水や有機物が多く含まれており、その進化を明らかにすることは、原始地球の海や生命の起源を理解するという意味でも大きな社会的意義を持つ。また本研究は「はやぶさ２」探査とも連携しており、今後「はやぶさ２」探査の帰還試料分析と本研究を発展させることで、原始太陽系での物質進化の詳細が解明されることが期待される。