MIT-RapidOxygen-1_0 Published on May 18, 2016 in Study Pinpoints Timing of Oxygen’s First Appearance in Earth’s AtmosphereFull resolution (639 × 426) ← Previous Next → MIT scientists say that the Great Oxygenation Event (GOE), a period that scientists believe marked the beginning of oxygen’s permanent presence in the atmosphere, started as early as 2.33 billion years ago.