An oasis in a world without oxygen

摘要

For the first half of Earth's existence, there was no oxygen to be had. The air wasn't breathable and life in the oceans was little more than primitive sludge. Even in this hostile world, though, small "oases" of oxygen-rich water persisted, fuelled by bacteria. Now it seems we have found the first hard evidence of one of these oxygen oases, preserved in ancient rocks. If a person were to step out into this ancient world, they would die of asphyxiation within minutes. It wasn't until around 2.4 billion years ago that oxygen flooded the oceans and gave rise to the air and seas we recognise.