During Earth’s early geologic history, even long after the crust had cooled, the environment was torrid (despite the sun being weaker than it is now) due to very high levels of methane and carbon dioxide. However, Cyanobacteria eventually evolved, became prolific, and thru photosynthesis began consuming carbon dioxide and releasing oxygen (which had not existed as a free gas in the biosphere previously). This oxygen reacted with the methane to yield carbon dioxide which was a much less powerful greenhouse gas, while simultaneously the global exposure of silicate rocks to weathering produces calcium carbonate which removes carbon dioxide from the atmosphere — and these processes repeated themselves on and on until the greenhouse gas levels were so low that not enough thermal radiation could be trapped to keep the planet from freezing solid into Snowball Earth. Eventually, however, an ‘oxygen carbon dioxide biochemical cycle’ stabilized the greenhouse effect and an ozone layer was established, thus plant and animal life evolution became possible.
Recap: Photosynthesis releases oxygen that then reacts with methane which yields carbon dioxide that then fuels more photosynthesis which releases more oxygen that then breaks down more methane, ad infinitum...
Meanwhile, exposure of silicate rocks to weathering produces calcium carbonate which removes carbon dioxide from the atmosphere....
Thus, an atmosphere once laden with methane and carbon dioxide is almost totally replaced with oxygen (which is not a greenhouse gas).
Photosynthesis = Sunlight + 6CO2 + 6H2O → C6H12O6 + 6O2
Cyanobacteria are ‘oxygenic photosynthetic bacteria’. They harvest the sun's energy, absorb carbon dioxide, and emit oxygen. Like plants and algae, cyanobacteria contain chlorophyll and convert carbon dioxide and water into sugar through carbon fixation.
Video showing the beginnings of how and when photosynthesis first became established:
Video about resulting Snowball Earth:
Related posting:
https://samslair.blogspot.com/2020/12/agw-too-hot-too-cold-juuust-right.html?m=1
Related search parameters:
‘anaerobic aerobic bacteria early earth’
‘early earth photosynthesizing microbes’
