2023 Fiscal Year Final Research Report

Experimental Studies on Roles of Solar Energetic Particles in the Generation of Life on the Primitive Earth

Research Project

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Project/Area Number	20H02014
Research Category	Grant-in-Aid for Scientific Research (B)
Allocation Type	Single-year Grants
Section	一般
Review Section	Basic Section 17050:Biogeosciences-related
Research Institution	Yokohama National University
Principal Investigator	Kobayashi Kensei 横浜国立大学, 大学院工学研究院, 名誉教授 (20183808)
Co-Investigator(Kenkyū-buntansha)	三田肇福岡工業大学, 工学部, 教授 (00282301) 癸生川陽子横浜国立大学, 大学院工学研究院, 准教授 (70725374)
Project Period (FY)	2020-04-01 – 2023-03-31
Keywords	太陽エネルギー粒子 / 銀河宇宙線 / 生命の起源 / 一酸化炭素 / 有機炭素 / アミノ酸 / 陽子線照射 / 紫外線照射
Outline of Final Research Achievements	Roles of solar energetic particles (SEPs) in prebiotic chemistry in early Earth was examined experimentally. It was shown that SEPs could yield a large amount of amino acids from the early Earth atmosphere even if it was such weakly reducing one as a mixture of carbon dioxide, carbon monoxide / methane, nitrogen and water. The amino acid formation pathway driven by SEPs suggested was not the conventional equilibrium reaction like the Strecker synthesis. Nitrous oxide, which has large greenhouse effect, was formed, and it might have prevent the early Earth from freezing under the faint young Sun. SEPs would generate spin-polarized muons after the interaction with atmospheric molecules. It was suggested that such asymmetric muons may have produce the seeds of amino acid homochirality by irradiation of DL-alanine with muons.
Free Research Field	アストロバイオロジー
Academic Significance and Societal Importance of the Research Achievements	生命の誕生に必要なアミノ酸などの有機物の生成の場としては地球大気と地球外環境が考えられているが，近年では初期地球大気は弱還元的で有機物生成に不利とされてきた。本研究では太陽フレアに由来する太陽高エネルギー粒子のエネルギーを考慮すれば，弱還元的な初期地球大気からも大量のアミノ酸生成が可能であったことを模擬実験により示した。この時の反応機構は従来広く考えられてきたストレッカー合成のような平衡反応ではないことも示され，新たな化学進化の道筋の探索の重要性が示唆された。