Cyanobacteria scum is now considered a nuisance, but these microbes oxygenated our planet over 2 billion years ago. Credit: Washington State Dept. of HealthFrom Live Science:
The first half of Earth's history was devoid of oxygen, but it was far from lifeless. There is ongoing debate over who the main biological players were in this pre-oxygen world, but researchers are digging up clues in some of the oldest sedimentary rocks on the planet.
Most scientists believe the amount of atmospheric oxygen was insignificant up until about 2.4 billion years ago when the Great Oxidation Event (GOE) occurred. This seemingly sudden jump in oxygen levels was almost certainly due to cyanobacteria – photosynthesizing microbes that exhale oxygen.
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