A groundbreaking study partially funded by NASA’s Astrobiology program reveals how Earth’s atmosphere could dramatically change over the next billion years due to increasing solar radiation. Scientists from NASA and Japan’s Toho University used advanced computer simulations to model the long-term evolution of Earth’s atmosphere, integrating climate science, biology, and geology.

Led by Kazumi Ozaki and Christopher Reinhard, the study predicts that as the Sun becomes more luminous, Earth’s atmosphere will shift from its current oxygen-rich state to one incompatible with complex life. This transformation is driven by the gradual breakdown of atmospheric carbon dioxide (CO2), which is essential for photosynthesis.

As CO2 diminishes, plants and other photosynthetic organisms will struggle to survive, leading to a sharp decline in oxygen production. Without oxygen replenishment, atmospheric oxygen levels could fall to less than 10% of today’s concentrations, creating conditions unsuitable for humans and most complex life forms.

This “great deoxygenation” would result in an atmosphere rich in methane, nearly devoid of CO2, and lacking an ozone layer—conditions similar to those on Earth billions of years ago before the Great Oxidation Event.

The study emphasizes that these changes will unfold over vast geological timescales—around one billion years—though the decline could begin within 10,000 years. This timeframe is far beyond human lifespans, offering more scientific insight than immediate concern.

The researchers also highlight how solar flares and weakening of Earth’s magnetosphere will contribute to atmospheric loss and change. These findings deepen our understanding of planetary atmospheres and have implications for the search for life on exoplanets.

By studying Earth’s past and future atmospheric evolution, scientists can better identify signs of life on other worlds and understand the temporary nature of oxygen-rich environments in the cosmos