The Great Oxidation Event

Breathable air
2.4 billion years ago

For the first half of Earth’s history, there was hardly any oxygen in the air. But then some bacteria began harnessing sunlight to make sugar from carbon dioxide and water, just like green plants today. These microbes pumped out oxygen as a waste product, creating the oxygen-rich atmosphere we have today. But the first oxygen may have caused the entire planet to freeze over into a ‘Snowball Earth’, by stripping the greenhouse gas methane from the air.

See other: History of Life

1 thought on “The Great Oxidation Event

  1. But even before this time, single-celled creatures (they hadn’t yet divided into plant and animal) added minute amounts of oxygen to the nitrogen/methane atmosphere simply by dying – the decomposition process released it into the sea, where it gradually made its way into the atmosphere as vapor – multiply these tiny amounts by billions of deaths over millions of years, and it adds up.

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