Earth is alive with vibrant life today, thanks to a rich atmosphere filled with oxygen. But it hasn’t always been this way. Looking ahead, scientists warn that in about a billion years, Earth’s atmosphere could shift back to one that is rich in methane and poor in oxygen.
This dramatic change won’t be a slow fade; it could happen quickly, reshaping our planet into a state reminiscent of its past, before what we call the Great Oxidation Event, which took place around 2.4 billion years ago.
Kazumi Ozaki, an environmental scientist from Toho University, shared insights about this significant shift: “Many years of research have focused on the slow brightening of the Sun and how it affects Earth’s carbon dioxide levels. This means we may face a gradual decline in oxygen and an increase in global warming over geological time.”
According to their research, atmospheric oxygen may not be a permanent feature of habitable planets. This raises questions about how we search for life beyond Earth. If oxygen levels drop significantly, it may become challenging to identify signs of life on other worlds.
Using detailed simulations, researchers modeled the future of Earth’s biosphere. They looked at how changes in solar brightness and carbon dioxide levels influence life on our planet. As carbon dioxide decreases, fewer plants can perform photosynthesis, leading to a significant drop in oxygen.
The researchers predict that a drop in oxygen levels, reaching conditions similar to ancient Earth, will likely happen before the climate becomes too hot and before significant water loss from the atmosphere occurs.
When this happens, many life forms, including humans, will face extinction. As Chris Reinhard from Georgia Tech notes, “The decline in oxygen will be extremely severe, reaching levels around a million times lower than what we experience today.”
This research is important for our search for life outside our Solar System. With advanced telescopes, scientists need to know what indicators to seek out in the vast amounts of data they collect. It may be essential to look for additional biosignatures beyond just oxygen.
The findings suggest that Earth’s habitability, marked by oxygen-rich conditions, may only last for about 20-30% of our planet’s total lifespan. While complex life may vanish, microbial life could persist long after we are gone. Ozaki explains that the atmosphere of the future could be filled with methane, low in carbon dioxide, and lacking an ozone layer. This would create a world inhabited by anaerobic organisms.
The study appears in Nature Geoscience, emphasizing how our future might look and how we should consider life in the universe.
