The future life span of Earth's oxygenated atmosphere

2021 Fiscal Year Final Research Report

• Project/Area Number: 20K04066
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 17020:Atmospheric and hydrospheric sciences-related
• Research Institution: Toho University
• Principal Investigator: OZAKI Kazumi 東邦大学, 理学部, 講師 (10644411)
• Project Period (FY): 2020-04-01 – 2022-03-31
• Keywords: 酸素 / 物質循環 / 数値モデリング / 生物地球化学 / 地球史 / アストロバイオロジー

Outline of Final Research Achievements

A theoretical study has been conducted to constrain the future evolution of Earth's atmospheric composition (O2,CO2,CH4) and to understand its controlling factors and biogeochemical cycles. The development of a numerical model has progressed more smoothly than expected. By incorporating the biogeochemical cycles of C, N, P, O, and S, it is enable to simulate the evolution of atmospheric chemistry and climate on geologic timescales. Using a stochastic approach, we found that the mean future lifespan of Earth's atmosphere is about 1 billion years. Earth's oxygen-rich atmosphere represents an important sign of life that can be remotely detectable. However, this study suggests that the oxygen-rich atmosphere might only be possible for 20-30% of the Earth's entire history as an inhabited planet. If we can generalize this insight to Earth-like exoplanets, then we need to consider additional biosignatures applicable to weakly-oxygenated/anoxic worlds in the search for life in the universe.

Free Research Field

地球システム科学

Academic Significance and Societal Importance of the Research Achievements

本研究によって酸素に富む地球環境が永続的に続くものではないことが初めて定量的に示されたことは、系外惑星生命探査に重要な示唆を与える研究成果である．酸素は生命存在指標（バイオシグネチャー）として注目されてきたが、地球史の大半は貧・無酸素環境であり、そのような惑星大気についてどのように生命存否を判断するのか、今後の研究の発展が期待できる．