日本地球惑星科学連合2023年大会

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[J] 口頭発表

セッション記号 M (領域外・複数領域) » M-IS ジョイント

[M-IS20] 水惑星学

2023年5月25日(木) 15:30 〜 16:45 304 (幕張メッセ国際会議場)

コンビーナ:関根 康人(東京工業大学地球生命研究所)、玄田 英典(東京工業大学 地球生命研究所)、福士 圭介(金沢大学環日本海域環境研究センター)、渋谷 岳造(海洋研究開発機構)、座長:玄田 英典(東京工業大学 地球生命研究所)、福士 圭介(金沢大学環日本海域環境研究センター)、臼井 寛裕(東京工業大学地球生命研究所)、渋谷 岳造(海洋研究開発機構)

16:30 〜 16:45

[MIS20-10] Liquid and supercritical CO2 as an organic solvent in Hadean seafloor hydrothermal systems

*渋谷 岳造1高井 研1 (1.海洋研究開発機構)

Prebiotic chemical evolution and the emergence of life in the seafloor hydrothermal systems of Hadean Earth is one of the most plausible and popular hypotheses for the origin of life on Earth. In contrast, many studies indicated that this hypothesis intrinsically harbors a critical unsolved problem called the “water paradox”: abundant water limits synthetic dehydration and facilitates hydrolysis of organic molecules during the early stage of chemical evolution. Nevertheless, many of these criticisms have not referred to the presence of abundant liquid/supercritical CO2 (L/SC-CO2) fluids and pools in modern hydrothermal systems. Indeed, the L/SC-CO2 fluids and pools create dry environments and behave as hydrophobic solvents at and beneath the seafloor. In this work, we theorize the generation and preservation mechanisms of a L/SC-CO2 pool in modern seafloor hydrothermal systems then reinterpret the fossil hydrothermal systems preserved in early Archean seafloor basalts. The theoretical consideration of subseafloor phase separation and phase segregation of CO2-rich hydrothermal fluids points to the presence of L/SC-CO2 fluids and pools also in Hadean seafloor hydrothermal systems. Because they behave as hydrophobic organic solvents, L/SC-CO2 has the great potential to drive the dehydration synthesis of organic molecules in seafloor hydrothermal systems. Furthermore, at the interface between L/SC-CO2 and H2O-rich fluid (seawater or hydrothermal fluid), amphiphilic molecules might be generated and triggered into self-assembled growth. Based on the abundant occurrence and physico-chemical properties of L/SC-CO2 fluids, we propose a new stepwise concept for the origin of life, whereby prebiotic chemical evolution was co-hosted and facilitated by L/SC-CO2 in Hadean water-rich seafloor hydrothermal systems. This “liquid/supercritical CO2 hypothesis” probably overcomes the water paradox and strengthens the idea that earthly life was hatched in deep-sea hydrothermal systems.