Known as the Great Oxygenation Event, Earth froze over as oxygen accumulated in our atmosphere, nearly driving all life extinct.
We commonly think of life on Earth as an unbroken chain of biological success, beginning shortly after our planet’s formation and continuing, unchallenged, for all the time since. Part of that story is true: it really was more than 4½ billion years ago that planet Earth formed, and it truly was just a few hundred million years later, at most, that life first arose on our world. Despite an enormous number of challenges that life has faced over all the time since — from resource scarcity to ice ages to asteroid strikes and a variety of mass extinction events — its managed to persist without ever going extinct: not even once. Instead, life has thrived and evolved, enabling it to find a way to exist in practically every environmental niche that Earth possessed.
But one event came closer than any other to bringing an end to life on Earth: a catastrophe known as either the Great Oxidation Event or the Great Oxygenation Event. Oxygen, one of the hallmark characteristics of our living Earth, was a tremendous destructive force when it first arrived in any sort of meaningful abundance some ~2 billion years after…
