Scientists supported by NASA modeling suggest Earth’s breathable air has an expiration date, though it is billions of years away. New research indicates the planet will lose most of its oxygen-rich atmosphere around one billion years from now, making it uninhabitable for complex life.
The study, from Toho University in Japan, used planetary and atmospheric simulations to forecast Earth’s climate and chemical makeup far into the future. It predicts that as the Sun ages and becomes hotter, it will disrupt the Earth’s delicate balance of gases necessary for life as we know it.
Rising temperatures will cause the carbon cycle to break down, reducing the carbon dioxide available for plants. This impacts photosynthesis, the process plants use to produce oxygen. Less plant life means less oxygen generation.
Eventually, the Earth Atmosphere will revert to a state resembling its ancient past before the Great Oxidation Event that occurred billions of years ago. It will become low in Oxygen and rich in methane and other greenhouse gases.
While the oxygen depletion is approximately one billion years in the future, the process may accelerate rapidly once triggered. Some models suggest oxygen levels could plummet dramatically over a period of only about 10,000 years after the initial decline begins. This shift would render the planet unsuitable for aerobic organisms, which require oxygen to survive. Only certain anaerobic microbes might endure under the changed conditions.
This long-term forecast differs from more immediate concerns such as climate change, meteorite impacts, or potential global conflicts or pandemics, which scientists say would not eliminate all microbial life or deplete the planet's oxygen on such a grand scale.
The findings also carry implications for the search for extraterrestrial life. The assumption that oxygen is always a strong indicator of life on other planets may need reconsideration, as Earth's own oxygen-rich period appears to be temporary within the planet's full lifespan.
Although the event is not an immediate threat, the research offers perspective on cosmic time and the transient nature of the conditions that support complex life on Earth.
"It’s a reminder that even a planet like Earth won’t stay habitable forever,” said Christopher Reinhard, a co-author of the study.