The Great Oxidation Event

Earth history has many tipping points, some that are regional and others that are global and epoch defining. None was as all encompassing as the Great Oxidation Event (GOE), a geological episode occurring around 2.35 billion years ago. With the GOE, the atmosphere switched from being oxygen free to having a small percentage of oxygen that would hold for 1.5 billion years, at which point a second leap in oxygen occurred, around 700 million years ago. The GOE's net effect is widespread oxygenic photosynthesis and, subsequently, oxygen-breathing organisms from which descended diverse multicelled and complex life. Sophisticated new isotopic analyses, as well as cross-disciplinary work by geochemists, biochemists, geologists, and others, are fueling a fresh examination of the GOE. By better understanding the early oxygenation of the planet, researchers say, scientists can find answers to the origins of complex life. In 2013, the National Science Foundation (NSF) launched the Early Oxygen initiative (www.earlyo2.org), a 5-year effort by 21 US researchers to unravel “one of the major mysteries” in Earth science, focusing particularly on the role the Earth's interior played in the GOE. “The GOE is probably the most fundamental transformation in the history of the planet, aside from the origin of life itself,” says Arizona State geochemist Ariel Anbar, who leads the initiative. “But we still don't really understand fully how it happened.”