Study pinpoints timing of oxygen’s first appearance in Earth’s atmosphere
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? MIT scientists now have an answer. In a paper appearing today in Science Advances, the team reports that the Earth’s atmosphere experienced the first significant, irreversible influx of oxygen as early as 2.33 billion years ago. This period marks the start of the Great Oxygenation Event, which was followed by further increases later in Earth’s history. The scientists have also determined that this initial rise in atmospheric oxygen, although small, took place within just 1 to 10 million years and set off a cascade of events that would ultimately lead to the advent of multicellular life. “It’s the start of...