The oxygen currently present in Earth’s atmosphere will be gone in a billion years, scientists say. This image of Earth’s atmosphere was taken from the International Space Station on February 26, 2021. Image via NASA.
Take a deep breath. The air that expands your chest is primarily nitrogen and oxygen, the main components of our atmosphere. Oxygen exists in our atmosphere thanks to the exhalation of plants, through photosynthesis. A study released in March 2021 shows that – a billion years from now, as the sun heats up – plants will die, carrying the oxygen into our atmosphere that humans and animals need to breathe.
Kazumi Ozaki of the University of Tokyo and Chris Reinhard of Georgia Tech have modeled the Earth’s climatic, biological and geological systems to refine scientists’ understanding of future atmospheric conditions on Earth. They conducted the study as part of a NASA program called NExSS to investigate and assess the habitability of exoplanets. Their study was published March 1, 2021 in the peer-reviewed journal Nature Geoscience
The Earth’s current atmosphere consists of 78% nitrogen, 21% oxygen, 0.9% argon, and 0.1% other gases, including carbon dioxide, methane, water vapor, and neon. The Earth has not always had such a high percentage of oxygen in the atmosphere. During Earth’s first 2 billion years, no oxygen existed 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, Earth underwent the Great Oxidation Event. At this point, oxygen began to accumulate in the atmosphere in greater amounts, whether from a slackening of volcanic outgassing or an evolutionary innovation that made cyanobacteria more successful, killing some bacteria, but the more complex life (us! ) Could evolve.
This oxygen utopia in which we currently live – where plants produce oxygen for humans and animals to breathe – is only a temporary state on Earth. As Ozaki said:
We discover that Earth’s oxygen-rich atmosphere will not be a permanent feature.
Kazumi Ozaki of the University of Tokyo, lead author of the article on the future of oxygen on Earth. Image via NASA.
As the solar system continues its life cycle, the aging sun will begin to warm up. The increased solar output will further warm the atmosphere and the carbon dioxide will respond to the rise in temperature by breaking down. Carbon dioxide levels will decline until photosynthesizing organisms – which depend on taking up carbon dioxide to live, just as we depend on oxygen to live – can no longer survive and remove the Earth’s oxygen source. (Read how scientists believe phytoplankton contributes between 50 and 85% of the oxygen in Earth’s atmosphere.) So when plants die from the lack of carbon dioxide, it’s not just a loss in the food chain, but, crucially, a loss. in the air they produce and the air we breathe.
Although the end of the oxygen is still a billion years away, when the depletion starts to take hold, it will happen quite quickly, in about 10,000 years. Reinhard explained the severity of the change:
The decrease in oxygen is very, very extreme; we are talking about a million times less oxygen than there is now.
Chris Reinhard of Georgia Tech, one of the lead authors who researched the future amount of oxygen in 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 in the atmosphere today. These shifts will occur too quickly for biosphere adaptation. The ozone layer, made of oxygen, will disappear, and ultraviolet light and heat will help extinguish both land and aquatic life. Everything but microbes will be eradicated. Reinhard said:
A world where many of the anaerobic and primitive bacteria are currently hiding in the shadows will take over again.
As in the beginning, when life on Earth was in a microbial form before it blossomed into the variety we see today, so too will the future be much like the past, as if the clock is running back and complex life forms will die out. except for small colonies of cells.
All plant and animal life on Earth needs oxygen to survive. In a billion years, Earth’s oxygen will deplete in about 10,000 years, causing everyone but microbes to die out. Image via Dikaseva / Unsplash.
Studying the Earth’s past and future is a gateway to understanding the conditions favorable to life on other planets. The presence of oxygen is an important factor in determining whether life can exist on a planet. As we see with Earth, a planet that does not have an oxygen signature can potentially support life in the future or in the past.
So while finding a planet with oxygen would be an exciting step towards finding life, not Finding oxygen should not rule out a planet ever had life.
Bottom line: In a billion years, scientists say, as the sun warms up, the warmer atmosphere will break down carbon dioxide, killing plant life, which in turn will shut off Earth’s source of oxygen.
Source: The future lifespan of Earth’s oxygen-rich atmosphere
Via New Scientist
