Earth will lose oxygen in a billion years, killing most living things

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Humans have not been good for the health of the planet, but even if we pollute ourselves to extinction, the Earth will continue. He survived huge asteroid impacts and megavolcanoes, after all. A few primates aren’t going to do any worse in the long run. The ultimate fate of life on Earth is a billion years in the future. A new study backed by NASA’s exoplanet habitability research explains how the sun will eventually bake the planet, transforming Earth from a lush, oxygen-rich world into a complex lifeless dried up shell.

NASA is interested in the future of Earth because it is the only habitable planet that we can study closely. As such, scientists have attempted to extrapolate the properties of Earth-like planets that we might be able to detect at great distances. Kazumi Ozaki from Toho University in Japan and Chris Reinhard from Georgia Institute of Technology have created a model of the Earth’s climate, biology and geology to see how that will change.

According to Ozaki and Reinhard, the oxygenated atmosphere of the Earth is not a permanent feature. There was very little of it in the atmosphere until 2.4 billion years ago, when cyanobacteria evolved to absorb carbon dioxide and expel oxygen – this is called the great oxidation event. This gave birth to all of the multicellular life forms we see on Earth today. There is only one problem: the sun. As the stars age, they get hotter, and the Sun is about a billion years from Earth’s roasting.

The study predicts that in a billion years, the Sun will get so hot that it breaks down carbon dioxide. The CO2 levels will get so low that photosynthetic plants will be unable to survive, which means there will be no oxygen left for the rest of us. When this happens, the changes will be abrupt. Ozaki and Reinhard say in the study, published in Geoscience of nature, that it may take a little less than 10,000 years for oxygen levels to drop to a millionth of what they are today. It’s a blink of an eye in geological terms. Methane levels will also begin to rise, reaching 10,000 times the level seen today.

This harsh and stifling atmosphere will be incompatible with all multicellular life as it exists today. The globe will be delivered to bacteria and archaea, the warmest living organisms to see the planet through the rest of its existence until swallowed by the Sun. Even if a more complex life survived, it would be irradiated by the increasingly bright Sun. Without oxygen, the ozone layer will evaporate and expose the surface to more intense UV radiation.

Ozaki and Reinhard conclude that oxygen is an important biomarker, but that it may not be a permanent feature of living planets. It could change the way we classify exoplanets in the future – even without oxygen, there could be a lot of single-celled life.

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