Privileged Planet: great oxidation event came earlier (Introduction)

by David Turell , Sunday, February 12, 2023, 16:34 (651 days ago) @ David Turell

A totally different discovery about oxygen:

https://www.discovermagazine.com/planet-earth/earths-first-stable-dose-of-oxygen-nearly...

"The world was an unrecognizable place more than 2.45 billion years ago. But for most of the tiny organisms that lived on the planet at the time, things were just fine; at least, until the cyanobacteria started to proliferate.

"As a result, these photosynthetic bacteria began to produce oxygen — so much of it that the tiny microbes sparked the "Great Oxidation Event" that infused the gas into our atmosphere.

“'You could argue that that’s the biggest poisoning event of Earth’s history,” says Simon Poulton, a biogeochemist at the University of Leeds in the U.K.

"The event proved fatal for the planet's countless species of anaerobic bacteria, capable of metabolizing their food without oxygen, resulting in a mass extinction. But the infusion of oxygen was essential for humans and a great numbers of animals alive today.

“'We’re talking about probably the most significant environmental event in the history of our planet,” adds Poulton.

***

"The Great Oxidation Event began around 2.45 billion years ago during the Paleoproterozoic era. Previously, researchers had believed that this period lasted only about 113 million years, ending 2.32 billion years ago.

"This period was chaotic, characterized by several glaciations where the whole planet was frozen over in what is sometimes referred to as “Snowball Earth,” says Poulton. “If you went back in a time machine and landed in one of those glaciations, you would be unbearably cold.”

"The strong glaciation periods likely came about due to rising oxygen levels, Poulton says. But once the oceans were covered in ice, the productivity of the cyanobacteria in the oceans would have dropped again, meaning less oxygen. Eventually, the buildup of greenhouse gases in the atmosphere from volcanic activity melted much of the ice. These intermittent periods after glaciations were likely even warmer than our world is today.

"Poulton and his colleagues began working on ancient rocks in the Transvaal Supergroup in South Africa. These rocks date back to the period when researchers believed that the Great Oxidation Event stopped and beyond. They measured multiple types of sulfur isotopes from cores drilled into the rocks.

“'What we got was really cool and a little bit surprising,” he says. The sulfur isotopes showed several fluctuations that suggested the atmosphere was far from stable until roughly 2.22 billion years ago. This meant the Great Oxidation Event may have lasted for 100 million years more than previously believed.

***

"Once said and done, the amount of oxygen became relatively stable afterwards, though it still took a long time for more complex lifeforms to evolve. It wasn’t until the end of the Precambrian period — around 541 million years ago — that the Earth experienced a second major rise in oxygen levels, after a long era Poulton and other geologists call “the boring billion,” when life evolved at a much slower pace." (my bold)

Comment: The Cambrian Explosion gap coincides with increasing oxygen (in my bold), an event noted here long ago. Extremophile survival managed to maintain life through this glacial period until more advanced life could begin, using oxygen as a dangerous fuel, requiring the development of special protective anti-oxygen mechanisms.