The oxygen currently in the Earth’s atmosphere will disappear in a billion years, scientists say. This image of the Earth’s atmosphere was taken from the International Space Station on February 26, 2021. Image by NASA.
Breathe deeply. The air that expands your chest is largely nitrogen and oxygen, the main components of our atmosphere. Oxygen exists in our atmosphere due to the expiration of plants, through the process of photosynthesis. A study launched in March 2021 shows that – over a billion years, with the warming of the sun – plants will disappear, taking with them the oxygen from our atmosphere that humans and animals must breathe.
Kazumi Ozaki of the University of Tokyo and Chris Reinhard of Georgia Tech modeled the Earth’s climate, biological and geological systems to regulate scientists’ understanding of future atmospheric conditions on Earth. They undertook the research as part of a NASA program called NExSS to explore and evaluate the habitability of exoplanets. Their study was published on March 1, 2021 in the peer-reviewed journal Geoscience of nature.
The Earth’s current atmosphere is made up of 78% nitrogen, 21% oxygen, 0.9% argon and 0.1% other gases, including carbon dioxide, methane, water vapor and neon. The earth did not always have such a high percentage of oxygen in its atmosphere. In the first 2 billion years of the Earth, there was no oxygen in the atmosphere. Low oxygen levels first appeared when cyanobacteria, also called blue-green algae, began to release oxygen as a byproduct of photosynthesis. Then, about 2.4 billion years ago, the Earth suffered the Great Event of Oxidation. At this time, either through a weakening of volcanic eruptions or through an evolutionary innovation that made cyanobacteria more successful, oxygen began to accumulate in larger amounts in the atmosphere, destroying some bacteria but allowing a lifetime. more complex (us!) to evolve.
This oxygen utopia we live in today – where plants produce oxygen for humans and animals to breathe – is only a temporary condition on Earth. As Ozaki said:
We discover that the oxygenated atmosphere of the Earth will not be a permanent feature.
Kazumi Ozaki from the University of Tokyo, lead author of the study of the future of oxygen on Earth. Image via NASA.
As the solar system continues its life cycle, the aging sun will begin to heat up. Increased solar production will heat the atmosphere even more, and carbon dioxide will react to rising temperatures through decomposition. Carbon dioxide levels will drop until photosynthesizing organisms – which rely on carbon dioxide to live, just as we rely on oxygen to live – can no longer survive, removing the source of oxygen from Earth. (Read about how scientists believe that phytoplankton contribute between 50 and 85% of the oxygen in the Earth’s atmosphere.) So when plants die from a lack of carbon dioxide, it’s not just a loss in the food chain, but in crucially, a loss in the air we produce and the air we breathe.
While the end of oxygen is still a billion years away, when depletion begins to catch on, it will take place fairly quickly, in about 10,000 years. Reinhard explained the seriousness of the change:
The decrease in oxygen is very, very extreme; we are talking about a million times less oxygen than we have today.
Chris Reinhard of Georgia Tech, one of the lead authors who researched the future amount of oxygen in the Earth’s atmosphere. Image via NExSS.
The future deoxygenation event will coincide with an increase in methane, until methane levels are about 10,000 times higher than they are in the atmosphere today. These changes will take place too soon to adapt to the biosphere. The ozone layer, made up of oxygen, will disappear, and ultraviolet light and heat will help extinguish terrestrial and aquatic life. All but microbes will face extermination. Reinhard said:
A world where many of the anaerobic and primitive bacteria currently hiding in the shadows will take over again.
Just as in the beginning, when life on Earth was in a microbial form before it flourished in the variety we see today, so the future will be much like the past, as if the clock were going backwards and complex life forms they will disappear except for small cell colonies.
All plant and animal life on Earth needs oxygen to survive. In a billion years, the Earth’s oxygen will be depleted in about 10,000 years, causing global extinction for all but microbes. Image by Dikaseva / Unsplash.
Studying the past and future of the Earth is a gateway to understanding the favorable conditions for life on other planets. The presence of oxygen is an important factor in determining whether life could exist on a planet. As we see with Earth, however, a planet that does not have an oxygen signature may be able to sustain life in the future or in the past.
Thus, while finding a planet with oxygen would be an interesting step towards finding life, not finding oxygen should not rule out the possibility that a planet ever he had life.
Bottom line: A billion years from now, scientists say, as the sun warms, the warmer atmosphere will decompose carbon dioxide, destroying plant life, which in turn will shut down the Earth’s oxygen source.
Source: Future life of the Earth’s oxygenated atmosphere
Through New Scientist
