A billion years from now, oxygen levels in the Earth’s atmosphere will drop to a very large extent, making them unfit for complex aerobic life that depends for their growth on oxygen.
This finding is the summary of a study published in Nature Geoscience into the fate of the Earth’s atmosphere.
Today, oxygen makes up about 21% of the Earth’s atmosphere, and its oxygen-rich nature is ideal for large and complex organisms, such as humans, that need air to survive.
But early in Earth’s history, oxygen levels were much lower and are likely to decline again in the distant future, according to Nature.
Kazumi Ozaki of Toho University in Funabashi, Japan, and Chris Reinhard of the Georgia Institute of Technology in Atlanta have modeled the Earth’s climate, biological, and geological systems to predict how weather conditions on Earth will change.
Lack of oxygen will end life
Researchers say that the Earth’s atmosphere will maintain high levels of oxygen over the next billion years, before returning to low levels that remind us of those that existed before what is known as the Great Oxidation Event about 2.4 billion years ago.
“We found that the Earth’s atmosphere, which contains oxygen, would not be a permanent feature of it,” Ozaki tells New Scientist.
And one of the main reasons for this shift is that as the sun ages, it will get hotter and release more energy.
The researchers believe that this heat will lead to a decrease in the amount of carbon dioxide in the atmosphere, as the carbon dioxide absorbs the heat and then decomposes.
Ozaki and Reinhard estimate that within a billion years, levels of carbon dioxide will become so low that living organisms – including plants – will not be able to survive and produce oxygen.
The mass extinction of these photosynthetic organisms would be the main cause of the massive drop in oxygen levels.
“The decline in oxygen levels will be enormous,” Reinhard said. “We are talking about a million times less oxygen than there is today.”
The researchers also estimate that methane levels will simultaneously increase to 10,000 times the amount in the atmosphere today.
Once these changes in the Earth’s atmosphere begin to occur, they will advance rapidly: the team’s calculations indicate that the atmosphere may lose oxygen over just 10,000 years or so.
“The biosphere cannot adapt to such a huge shift in environmental change,” says Ozaki.
And then life on Earth will become exclusively microbial, according to Reinhard, who said that “a world in which a lot of anaerobic and primitive bacteria are now hidden in the shadows, they will return to control again.”
Terrestrial life will end, and so will aquatic life as we know it.
The ozone layer – which consists of oxygen – will also perish, exposing the earth and its oceans to high levels of ultraviolet rays and heat from the scorching sun.
This research was conducted within the framework of the NASA Nexx Habitat Planets Project, and these predictions have implications for the search for life on other planets. Biometric fingerprints that contain oxygen are usually used to identify these planets.
“Oxygen, in its many forms, is a very important biomarker because it is completely intertwined with life on Earth,” says Natalie Allen of Johns Hopkins University in Maryland.
But this new prediction shows that the presence of oxygen is variable, and it may not exist permanently on a habitable planet.
“This indicates that even in planets orbiting other stars that are very similar to Earth,” says Kevin Ortiz Ceballos of the University of Puerto Rico, “large amounts of oxygen may not be detected in their atmosphere, even if they can support or support complex life forms.”
He says that the lack of discovery of oxygen around planets does not mean that they are unfit for life.
Ozaki and Reinhard suggest that other biomarkers could be used to search for alien life in place of oxygen.
For example, layers of hydrocarbon haze in a planet’s atmosphere are a longer-lived sign of extraterrestrial life.
The importance of this study?
Imagine that we were aliens in another world, searching the sky for signs of life by searching for oxygen and ozone in the atmospheres of the outer planets.
If our apparatus passes on Earth two billion years from now, or two billion years ago, we may incorrectly explain that such planets lack a reliable “biometric”, and we proceed with our research without realizing that this planet was teeming with life, which applies to any Another planet that scientists observe or assume that there is life (that is, some kind of life) on it.
So, we need a better understanding of the history of evolution of the Earth’s atmosphere over time, and how the Earth’s surface and interior have evolved. Only then will we be in a better position to determine if there is any life living in the glow of other suns.