A supercomputer simulation predicts that aerobic life on Earth’s oxygen will end in about one billion years due to the depletion of oxygen caused by the Sun’s increasing heat.
Earth’s Oxygen-Rich Atmosphere Has an Expiration Date
Earth’s surface environments are highly oxygenated, from the atmosphere to the deepest parts of the oceans.
This condition is a hallmark of an active, photosynthesis-driven biosphere.
However, the lifespan of Earth’s oxygen-rich atmosphere remains uncertain, especially when looking far into the future.
Understanding this timescale has significant implications for the future of Earth’s biosphere and for the ongoing search for life on Earth-like planets beyond our solar system.
A new study published recently in Nature Geoscience addresses this question using a sophisticated Earth system model.
The research reveals that Earth’s oxygen-rich atmosphere is likely to persist for only about one more billion years.
Modeling a Billion-Year Future
“For many years, the lifespan of Earth’s biosphere has been discussed using scientific insights into the sun’s gradual brightening and the global carbonate-silicate geochemical cycle,” says Kazumi Ozaki, Assistant Professor at Toho University.
This theoretical framework predicts a continuous decline in atmospheric CO₂ and long-term global warming. It is generally believed that the biosphere will collapse within the next 2 billion years due to overheating and a lack of CO₂ necessary for photosynthesis.
If this is true, atmospheric oxygen (O₂) levels should also decline in the distant future. However, the exact timing and process of this deoxygenation have remained uncertain.
To explore this, Ozaki and co-author Christopher Reinhard, Associate Professor at Georgia Institute of Technology, built a numerical model simulating Earth’s climate and biogeochemical processes. Because predicting the future evolution of Earth is inherently uncertain, the researchers adopted a stochastic (probability-based) modeling approach.
Ozaki ran the model more than 400,000 times with varying parameters to account for potential variability.
The result: Earth’s oxygen-rich atmosphere is likely to last for another 1.08 ± 0.14 billion years.
Life After Oxygen: A Return to Ancient Earth
According to the study, after the atmospheric deoxygenation, Earth will resemble its state before the Great Oxidation Event roughly 2.5 billion years ago.
Ozaki explains that after the great deoxygenation, the atmosphere had elevated methane, low CO₂ levels, and lacked an ozone layer.
This shift would likely support only anaerobic (non-oxygen-using) life forms.
Earth’s oxygenated atmosphere has long been viewed as a key biosignature detectable from space.
However, this research suggests that such a state is not permanent.
In fact, an oxygen-rich atmosphere may only exist for 20–30% of Earth’s total habitable lifetime. If this pattern is common among Earth-like planets, scientists may need to consider other biosignatures beyond oxygen and ozone when searching for life in the universe.
This could reshape the strategies used in the search for extraterrestrial life and exoplanet habitability.