Oxygen on Earth has an expiration date

The Earth’s atmosphere, which today is rich in oxygen and allows life, could change within a billion years, with a predominance of methane and low levels of oxygen, which would remind us of what the planet was like in its beginnings, according to a study published this Wednesday by Nature Geoscience.

The research, conducted by the Japanese University of Toho and the US space agency NASA, suggests that atmospheric oxygen is not permanent in habitable worlds, which has implications for the search for life on other Earth-like planets.

One indicator of possible planetary life is a detectable, oxygen-rich atmosphere, like the one Earth now has, suggesting the existence of plants and photosynthesis.

Image of the crescent Moon over Earth’s atmosphere taken from the ISS.

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However, the lifespan of these biosignals based on oxygen in the Earth’s atmosphere is uncertain, especially in the distant future.

So the team modeled Earth’s systems, including climate, biological and geological processes, to examine the timescale of current atmospheric conditions on our planet.

The result was that an oxygen-rich atmosphere “will likely persist for another billion years,” before rapid deoxygenation makes it reminiscent of Earth’s before the Great Oxidation Event.

The original atmosphere of the Earth contained very little oxygen, but that began to change about 2.5 billion years ago when levels increased during the Great Oxidation, which marked a milestone in the history of the planet, allowing, with the passage of millions of years, the development of biological forms.

The authors suggest that the detection of atmospheric oxygen on Earth could be possible only during 20-30% of the planet’s life and consider that future deoxygenation will be “an inevitable consequence of the increase” of solar fluxes.

If the same happens on other planets, the study indicates, then additional biosignatures are needed in the search for extraterrestrial life.

Earth’s original atmosphere contained very little oxygen, but that began to change about 2.5 billion years ago.

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