Study pinpoints timing of oxygen's first appearance in Earth's atmosphere
Monday, May 16, 2016 - 04:30
in Physics & Chemistry
Today, 21 percent of the air we breathe is made up of molecular oxygen. But this gas was not always in such ample, life-sustaining supply, and in fact was largely absent from the atmosphere for the first 2 billion years of Earth's history. When, then, did oxygen first accumulate in the atmosphere?