Take a deep breath—breathe in, then breathe out. The gases you took into your lungs just now have sustained complex life on this Earth for billions of years. Thanks to some unicellular bacteria some 2 to 2.4 billion years ago, a gradual spectacle called the Great Oxidation Event (or GOE, which may have been kickstarted by volcanoes, according to some new studies) caused oxygen levels in our dear planet to rise, which marked the beginning of the development of multicellular organisms on the planet.
And mind you, we breathe in or out at about 22,000 times a day—that’s quite an amount of oxygen just for yourself. However, a recent study published in the journal Nature Geoscience argues that we should probably count our blessings; according to the study, changes in the atmosphere brought about by the GOE are bound to be reversed—and they will revert fast.
The research duo behind the paper, formed by Toho University researcher Kazumi Ozaki and Georgia Institute of Technology Earth scientist Chris Reinhard, argues that oxygen isn’t really a permanent presence in planets with habitable atmospheres.
Ozaki and Reinhard ran simulations of our biosphere to get the data they needed to reach this astounding conclusion. They factored in both the Sun’s fluctuating brightness and the “corresponding drop” in carbon dioxide (CO2) levels following such a change.
You see, the Sun will only get hotter as it continues to age and consume its stellar fuel. Once temperatures around our place reach higher levels than even today, CO2 gets broken down by the heat from the Sun, which then inhibits the growth of plants and other photosynthesizing organisms—leading to the oxygen drop mentioned before.
As Ozaki mentioned to news outlet New Scientist: “We find that the Earth’s oxygenated atmosphere will not be a permanent feature.” Reinhard followed: “The drop in oxygen is very, very extreme. We’re talking around a million times less oxygen than there is today.”
The sudden drop in oxygen levels is expected to happen in a very short time in geologic terms—within about 10,000 years or so after it starts. The duo also expects an upwards of 10,000 times increase in methane levels in the atmosphere.
In the words of Ozaki himself: “the biosphere cannot adapt to such a dramatic shift in environmental change.” The drop in oxygen levels would spell doom for any complex life still around by the time it is predicted to occur; only anaerobic organisms are expected to be left behind, as lifeforms in both land and sea will feel the gradual suffocation by the loss of oxygen in their environment.
Interestingly, Ozaki’s and Reinhard’ s research is part of NASA’s Nexus for Exoplanet System Science (NxESS) project, which investigates the habitability of other exoplanets. To Ozaki and Reinhard, their findings are also set to impact just how we look beyond our skies for worlds like our own.
To them, it might be necessary to look for other biosignatures—markers in a planet’s composition that may indicate the presence of life on its surface—instead of simply seeking oxygen, as our life-giving gas may be doomed not to last forever in any atmosphere.
No need to panic, though—the atmospheric oxygen level reversal isn’t expected to happen for at least a couple of a billion years, according to the duo.
References
- Breathing. (2014, August 20). The Lung Association. https://www.lung.ca/lung-health/lung-info/breathing
- Nield, D. (2021, October 9). Enjoy it while you can: Dropping oxygen will eventually suffocate most life on earth. ScienceAlert. https://www.sciencealert.com/enjoy-it-while-you-can-dropping-oxygen-will-eventually-suffocate-most-life-on-earth
- Ozaki, K., & Reinhard, C. T. (2021). The future lifespan of Earth’s oxygenated atmosphere. Nature Geoscience, 14(3), 138–142. https://doi.org/10.1038/s41561-021-00693-5
- Shah, K. (2021, March 1). Most life on Earth will be killed by lack of oxygen in a billion years. New Scientist. https://www.newscientist.com/article/2269567-most-life-on-earth-will-be-killed-by-lack-of-oxygen-in-a-billion-years/
