Earth lost almost all of its oxygen 2.3 billion years ago

Earth’s transition to permanently an oxygen-rich atmosphere was a quitting process that took 100 million years longer than previously believed, according to a new study.

When the Earth was first formed 4.5 billion years ago, the atmosphere was almost nonexistent oxygenBut 2.43 billion years ago, something happened: Oxygen levels started to rise and then fall, accompanied by massive climate changes, including several ice ages that may have covered the entire world in ice.