Laser-driven shock compression experiments for time-evolution analysis of impact-induced melting process

2023 Fiscal Year Final Research Report

• Project/Area Number: 20K20947
• Research Category: Grant-in-Aid for Challenging Research (Exploratory)
• Allocation Type: Multi-year Fund
• Review Section: Medium-sized Section 17:Earth and planetary science and related fields
• Research Institution: Kyoto University
• Principal Investigator: Okuchi Takuo 京都大学, 複合原子力科学研究所, 教授 (40303599)
• Co-Investigator(Kenkyū-buntansha): 梅田 悠平 京都大学, 複合原子力科学研究所, 助教 (90815705)
• Project Period (FY): 2020-07-30 – 2024-03-31
• Keywords: 衝突融解現象 / 高強度レーザー / X線自由電子レーザー

Outline of Final Research Achievements

4.6 billion years ago, in the primordial solar nebula surrounding the youngest sun, many small bodies were repeatedly colliding to merge to form planets, satellites, and asteroids. During such a process, strong compression and heating were simultaneously induced to significantly affect the state of the materials, such as inducing their melting. In this research, we attempted to understand the post-impact states of primitive meteorites by reproducing the impact-induced melting phenomenon in the laboratory by using a high-power laser and an X-ray free-electron laser as a couple to observe the diffraction as a function of time during the compression process. Specifically, we observed the time evolution of structures of anhydrous silicate, hydrous silicate, and carbonate during the compression. We found that the amorphization of hydrous silicate and carbonate more easily proceeded than that of anhydrous silicate.

Free Research Field

鉱物学

Academic Significance and Societal Importance of the Research Achievements

無水ケイ酸塩の実験によって、融解が未だ起こらない範囲の圧縮における鉱物内の原子の再配列の現象が、ナノ秒程度のごく短時間で大きく進む場合があることがわかった。これは従来の見解を覆す発見であった。短時間の圧縮は小さな天体の衝突によって起こりえるために頻度は高い。再配列の現象で生成する高密度の鉱物が多数の隕石や小惑星サンプルリターン試料に残されている可能性は高くなった。それらを丁寧に探してゆけば、地球の誕生に至る太陽系の先史の様子を具体的に描くことが可能になるだろう。