Scientists have found that the Earth’s oxygen-rich atmosphere might not be permanent, and instead, will revert back to a methane-rich environment similar to what it had around 2.4 billion years ago. The research, published in 2021, suggests that this change could happen rapidly, possibly within the next billion years.
According to the study, atmospheric oxygen levels are unlikely to be a stable feature of habitable worlds, which has implications for our search for life beyond Earth. Researchers used detailed models of the Earth’s biosphere and simulated changes in the sun’s brightness and carbon dioxide levels to reach their conclusions.
Their model projects that when atmospheric oxygen drops sharply, it will trigger a deoxygenation event before the development of moist greenhouse conditions or extensive loss of surface water from the atmosphere. This would ultimately lead to the end of life forms reliant on oxygen.
The study’s authors warn that this shift could happen more quickly than previously predicted and is likely to occur before ocean waters are lost to increased radiation from the sun, which is estimated to take around 2 billion years. They suggest that we may need to look for alternative biosignatures besides oxygen when searching for life beyond our solar system.
According to Chris Reinhard, an Earth scientist involved in the research, the drop in oxygen levels would be extremely low, potentially a million times less than what exists today. The researchers believe that microbial life could persist even after human extinction.
The study’s findings highlight the importance of understanding the Earth’s atmosphere and its potential for change, with implications for our search for life beyond Earth.
Source: https://www.sciencealert.com/extreme-drop-in-oxygen-will-eventually-suffocate-most-life-on-earth