The air we breathe may seem like a permanent feature of our planet, but new research suggests it’s far from eternal. A study published in Nature Geoscience by scientists from NASA and Japan’s Toho University paints a stark picture: Earth’s oxygen-rich atmosphere, which supports complex life, will likely collapse within the next billion years. Even more striking, the initial decline could begin as soon as 10,000 years from now—a blink of an eye in geological time.
The sun’s warming could trigger a chain reaction
Researchers led by Kazumi Ozaki of Toho University modeled the long-term evolution of Earth’s atmosphere, focusing on the relationship between the planet’s oxygen levels and the Sun’s gradual warming. Over time, the Sun is expected to increase in luminosity, pushing Earth into a hotter climate. That warming will accelerate the breakdown of carbon dioxide (CO2) in the atmosphere. Plants, which rely on CO2 for photosynthesis, will struggle to survive, cutting off the planet’s main source of oxygen.
Without oxygen-generating plants, Earth will lose its ozone layer, exposing the surface to dangerous levels of ultraviolet radiation. At the same time, methane—a greenhouse gas that oxygen currently keeps in check—will build up in the air. “After the great deoxygenation, the atmosphere will be characterized by a high concentration of methane, low levels of CO2, and the absence of an ozone layer,” Ozaki said in a statement.
Complex life won’t survive the shift
The consequences for life on Earth would be devastating. Humans and other oxygen-dependent species could not survive in an atmosphere with such low oxygen levels. The study suggests that oxygen levels could eventually drop to a million times lower than they are today, effectively suffocating most forms of life. Only anaerobic microorganisms—tiny organisms that thrive without oxygen—might endure in the new, toxic environment.
This shift would mirror the conditions of the early Earth billions of years ago, before the Great Oxidation Event flooded the atmosphere with oxygen. If the researchers’ predictions hold, our planet could return to that ancient state, becoming a microbial world once again.
A timeline that starts sooner than you think
While the final collapse is still about a billion years away, the process leading to it could begin much earlier. The researchers estimate the first measurable drop in oxygen levels could happen in roughly 10,000 years. That’s a vanishingly short period when viewed on a planetary timescale. Once the decline starts, it will be irreversible.
Importantly, the study emphasizes that this is part of Earth’s natural evolution, not a consequence of human-driven climate change. But the findings underscore a broader point: habitable conditions on planets are temporary. As Christopher Reinhard, a co-author from the Georgia Institute of Technology, noted in a related discussion, “The lifespan of oxygen-rich atmospheres may be shorter than we previously thought.”
Why this matters beyond Earth
The research has implications far beyond our planet. Astronomers searching for life on exoplanets often look for oxygen as a key biosignature. But as this study shows, a planet can have oxygen for billions of years before losing it again. That means finding oxygen in an exoplanet’s atmosphere doesn’t necessarily mean it’s permanently habitable.
Earth’s eventual loss of oxygen won’t directly affect our species, which is unlikely to be around in a billion years. But it offers a sobering reminder that even the most stable-seeming planetary systems are temporary. Understanding how and why Earth will change could help scientists refine their search for life elsewhere—and better appreciate the delicate balance that keeps our own world alive.