When could Earth have developed a biosphere?

2018 Fiscal Year Final Research Report

• Project/Area Number: 17KK0089
• Research Category: Fund for the Promotion of Joint International Research (Fostering Joint International Research)
• Allocation Type: Multi-year Fund
• Research Field: Astronomy
• Research Institution: Tokyo Institute of Technology
• Principal Investigator: Brasser Ramon 東京工業大学, 地球生命研究所, 特任准教授 (30747142)
• Research Collaborator: Mojzsis Stephen University of Colorado Boulder, Geological Sciences, Professor
• Project Period (FY): 2018
• Keywords: origin of life / large impact / crater chronology / rna chemistry

Outline of Final Research Achievements

We have established when life could have begun on the Earth. Our best estimate is between 4.4 and 4.3 billion years ago (Ga). We have determined the following: Approximately 4.5 Ga the Moon formed, which melted the Earth and thus would destroy any life that was present. This catastrophic event was followed by the late veneer event at 4.48 Ga, wherein the Earth was struck by a moon-sized object. This impact melted a large portion of Earth's crust again and reset some of the U-Pb ages in the crust. The metallic core of this object was torn apart in the impact and subsequently rained onto Earth as a metallic hail. This hail reacted with water to form a temporary hydrogen atmosphere. This atmosphere created a reducing environment to form the chemical building blocks for RNA-based life, or another form of life. The temporary hydrogen atmosphere was gone by about 4.2 Ga, so that life must have begun around 4.3 Ga. Oxygen isotopes on Earth shod there was a hydrosphere at 4.3 Ga.

Free Research Field

Planetary science

Academic Significance and Societal Importance of the Research Achievements

全ての生命活動は水を必要とする。約43億年前、地球には安定的な海があった。それ以前は、表面が溶けており、生命が存在するには暑すぎる環境だった。43億年前、今日のように地球が温暖になり、生命が誕生した可能性がある。44.8億年前に地球へ大きな衝突があったことにより、水素大気が形成され、海洋の化学物質と反応することでRNAベースの生命が誕生した。