Interestingly – the Earth’s surface environments are full of oxygen – from the atmosphere to the deepest places in the oceans, representing a sign of a photosynthetic active biosphere. However, the basic time frame of the oxygen-rich atmosphere on Earth remains uncertain, especially for the distant future. A great solution to this question is not only for the future of the Earth’s biosphere but for finding life on Earth-like planets outside the solar system.
New study published in Geology of nature this week tackles this problem by using a numerical model of biochemistry and climate and reveals that the longevity of the Earth’s oxygen-rich atmosphere is around a billion years.
“For many years, the life cycle of the Earth’s biosphere has been debated based on scientific knowledge of the constant glare of the sun and the global carbonate-silicate geochemical cycle. One of these forms of theoretical framework is continuous decay. in atmospheric CO2 levels and global warming on geological timeframes.In fact, the Earth’s biosphere is generally thought to end in the next 2 billion years due to the combination of preheating and CO2 shortages for photo-synthesis. If true, atmospheric O2 levels can also be expected to eventually decrease in the future. However, it is not clear when and how this will happen, “Kazumi said. Ozaki, Associate Professor at the University of Toho.
To study how the Earth’s atmosphere will change in the future, Ozaki and Christopher Reinhard, Associate Professor at the Georgia Institute of Technology, built an Earth system model similar to climate and biochemical processes. With uncertainty in modeling the future evolution of the Earth in geological and biological evolution, a stochastic approach was used, allowing the researchers to evaluate probabilistic get a lifetime of oxygen atmosphere. Ozaki ran the model more than 400 miles a time, changing the model parameter, and found that the Earth’s oxygen-rich atmosphere will last for another billion years (1.08 ± 0.14 (1σ) billion years) before rapid deoxygenation takes place. an atmosphere similar to the early Earth. before the Great Oxygen Event about 2.5 billion years ago.
“The atmosphere after the major deoxygenation is characterized by elevated methane, low levels of CO2, or ozone depletion. The Earth’s system may be a world of anaerobic life forms,” Ozaki said.
The feeling of the Earth ‘s full oxygen represents an important indicator of life that can be detected at a distance. However, this study suggests that the Earth’s oxygenated atmosphere would not be a permanent feature, and that it may only be possible to make the oxygen-rich atmosphere for 20-30% of the Earth’s total history as an inhabited planet. Oxygen (and photochemical byproduct, ozone) biosignature is accepted for finding life on the exoplanets, but if we can take this view universally on Earth-like planets, scientists need to consider biosignatures additionally relevant to the world of low oxygen and anoxic in search for a life longer than our solar system.
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The research was supported by the Japan Society for the Advancement of Science (donation number JP20K04066) and NASA ‘s Nexus for Exoplanet System Science (NExSS) (donation number 80NSSC19KO461).