Humans were not good for the health of the planet, but even if we pollute ourselves to extinction, the earth will continue. After all, it survived enormous asteroid impact and mega-volcanoes. A few primates are not going to fare worse in the long run. The ultimate fate of life on earth lies a billion years in the future. A new study backed by NASA’s feasibility study on the exoplanet shows how the sun will eventually bake the planet, transforming the earth from a lush, oxygen – rich world into a dried-up shell with no complex life.
NASA is interested in the future of the earth, because it is the only habitable planet we can study up close. As such, scientists have attempted to extrapolate the properties of Earth-like planets that we could potentially detect from great distances. Kazumi Ozaki at Toho University in Japan and Chris Reinhard at the Georgia Institute of Technology created a model of the Earth’s climate, biology and geology to see how it would change.
According to Ozaki and Reinhard, the earth’s oxygen – rich atmosphere is not a permanent feature. There was very little of it in the atmosphere until 2.4 billion years ago when cyanobacteria evolved to take up carbon dioxide and expel oxygen – this is known as the Great Oxidation Event. This has given rise to all forms of multicellular life we see on Earth today. There is only one problem: the sun. As stars age, they become warmer and the sun is about a billion years off the grid of the earth.
The study predicts that the sun will become so hot in a billion years that it breaks down carbon dioxide. The levels of CO2 will become so low that plants with photosynthesis cannot survive, and that means no more oxygen for the rest of us. If this happens, the changes will be sudden. Ozaki and Reinhard say in the study, published in Natural Sciences, that it can take about 10,000 years before oxygen levels drop to a millionth of what it is now. This is a blink of an eye in geological terms. Meta levels will also start to rise, reaching 10,000 times the level seen today.
Cyanobacteria like these gave the atmosphere oxygen, but the era of oxygen can be volatile.
This harsh, suffocating atmosphere will be incompatible with any multicellular life as it exists today. The globe will be handed over to bacteria and archaea, the most hearty living organisms to see the planet through the rest of its existence until it is swallowed up by the sun. Even if a more complex life did survive, it would be irradiated by the increasingly lighter 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 it may not be a permanent feature of planets with life. It can change how we categorize exoplanets in future – even without oxygen there can be many unicellular lives.
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