A Billion Years From now There won’t be Much Oxygen in the Earth’s Atmosphere

Breathe it while you still can. A new research study forecasts the future of oxygen in the Earth’s atmosphere and finds grim news. As the sun continues to warm, carbon dioxide will bind to rocks. This will starve plants, and in as little as a billion years they won’t be able to produce enough oxygen to keep our planet habitable (for us).

Our sun, like all stars, is steadily getting warmer. Over the course of hundreds of millions of years, the fusion of hydrogen in the core leaves behind inert helium, which collects there like ash in a fire pit. With helium crowding the scene, the sun has to work harder to get the hydrogen to fuse, increasing its temperature.

As the sun continues to get larger and warmer, it’s going to make life difficult on the Earth, according to new research that charts the future history of oxygen in the atmosphere of our planet. The research is accepted for publication in Nature Geoscience.

The first problem is the upsetting of a delicate balance between the sun and our planet’s plate tectonics. Silicate rocks on the surface of the Earth can bind with carbon dioxide in the atmosphere, turning them into carbonate rocks. Due to plate tectonics, those rocks can then be buried deep in the mantle when one plate slides beneath the other. This process scrubs carbon from our atmosphere.

Much of that carbon is then later returned to the atmosphere through volcanism. But as the sun warms up, the process of carbon scrubbing (called “weathering” in geoscience circles) accelerates, outpacing the release of carbon through volcanism.

Less carbon dioxide in the atmosphere isn’t really a bad thing…unless you’re a plant. The models developed by the researchers revealed that in less than a billion years, life on Earth will be “carbon limited” – there won’t be nearly enough carbon dioxide to support the abundance of life that we experience today.

As the plants die, they won’t be able to produce oxygen. That oxygen will then leave the atmosphere through various processes, like getting mixed into our oceans. So shortly after the carbon levels drop, so do the oxygen levels.

There would still be life on Earth, but not the rich variety that we see today. This work has important implications for future exoplanet missions that depend on hunting for abundant levels of oxygen – a key biosignature – in the atmospheres of alien worlds. The lack of oxygen doesn’t always mean the lack of life – it could just be a starved world barely hanging on.