Blurs

Around 2.4 billion years ago, something happened that permanently changed Earth. For most of the planet's early history, free oxygen was scarce in the atmosphere. Then oxygen began accumulating. The consequences were enormous. Atmospheric chemistry changed. Oceans changed. Minerals that had never encountered abundant oxygen began reacting with it. Some organisms were poisoned by the new environment, while others eventually evolved ways to exploit oxygen's extraordinary chemical potential. Much later, oxygen-dependent complex life would become possible. This transformation is known as the Great Oxidation Event. It is one of the fundamental chapters in Earth's history. But there is an intriguing problem. Much of what we think we know about the environmental changes surrounding this transformation comes from something remarkably fragile: the chemical signatures preserved in ancient rocks. And new research is demonstrating just how easily those signatures can be misread. The im...