From DamnInteresting.com by Alan Bellows.
..
The sea was host to a plethora of anaerobic microorganisms, but there were also a few members of a newly evolved variety: cyanobacteria. These adapted bacteria were the first to use water and sunlight for photosynthesis, producing oxygen as a by-product of their metabolism.The cyanobacteria were a struggling minority at first, but scientists believe that these new microbes began to dominate with the help of meltwater from a few glaciers scattered across the young continents. These glaciers spent centuries scraping across the Earth collecting minerals, ultimately depositing their rich nutrient payloads into the oceans. The cyanobacteria flourished in the presence of the increased minerals, and the rapidly growing population was soon venting increasingly large amounts of its poisonous waste oxygen into the environment.
The underwater oxygen began to chemically react with the abundant iron, eventually scrubbing the seas clean of the element through oxidation. This series of developments was nothing short of an ecological disaster– oxygen was poisonous to most of primitive Earth’s inhabitants, and many bacteria relied on the iron as a nutrient.
Once the oceans’ supply of iron was exhausted, oxygen began to seep from the sea into the air. The free oxygen they produced reacted with the air, gradually breaking down the methane which kept the Earth’s atmosphere warm and accommodating. It took at least a hundred thousand years– a short duration in geological terms– but the Earth was eventually stripped of her methane, and with it her ability to store the heat from the sun. Temperatures fell well below freezing worldwide, and a thick layer of ice began to encase the oxygen-saturated planet.
Almost every living thing on Earth died as a result of this massive bacteria-induced climate change, an event known as the oxygen catastrophe.
The survivors of the oxygen catastrophe eventually adapted to consume the abundant oxygen and produce carbon dioxide. This greenhouse gas very gradually made its way into the atmosphere, increasing in concentration and nudging temperatures back into the hospitable range over millions of years.
..
One man’s meat is another man’s poison. Just a line separates life from death.
3 Comments
Researchers find origin of ‘breathable’ atmosphere half a billion years ago. (Physorg)
Saltzman explained the chain of events this way: Tectonic activity led to increased weathering, which pulled carbon dioxide from the air and cooled the climate. Then, as the oceans cooled to more hospitable temperatures, the plankton prospered — and in turn created more oxygen through photosynthesis.
“It was a double whammy,” he said. “There’s really no way around it when we combine the carbon and sulfur isotope data — oxygen levels dramatically rose during that time.”
How did chemical constituents essential to life arise on primitive Earth? (Physorg)
Experiments show that simple molecules can combine chemically rather than biologically to form the building blocks of DNA, the key component of all life forms. These processes might have taken place on primitive earth, but how they occur is an unsolved puzzle.
Chemists at the University of Georgia have now proposed the first detailed, feasible mechanism to explain how adenine, one of the four building blocks of DNA, might be built up from the combination of five cyanide molecules. The investigation is based on extensive quantum chemical computations over several years.
A survivor in Greenland: A novel bacterial species is found trapped in 120,000-year-old ice. (EurekAlert)