Privileged Planet: snowball Earth had a source of oxygen: (Introduction)

by David Turell @, Wednesday, December 04, 2019, 05:38 (211 days ago) @ David Turell

Snowball Earths have appeared in the past, the Earth entirely covered by ice. How did life survive and get oxygen. The answer is iron, rusted:

"...from about 720 to 635 million years ago, temperatures swerved the other way as the planet became encased in ice during the two ice ages known as Snowball Earth.

"It happened fast, and within just a few thousand years or so, ice stretched over both land and sea, from the poles to the tropics. Life lived in the oceans at the time, and the encroaching ice entombed that life, cutting it off from both the sun and the atmosphere.


" In 2015, to reach one of those corners, Max Lechte and his graduate adviser at the time, Malcolm Wallace, both sedimentologists at the University of Melbourne, drove 15 hours into the South Australian outback.

"They trekked over hills made of red-colored rock, and it was so hot out — about 122 degrees Fahrenheit — that the soles of Dr. Wallace’s boots melted.

"These red-hot rocks formed in the oceans during the snowball glaciations, and their color caught Dr. Lechte’s eye, so he took a few samples. Then, in 2015 and 2016, he traveled to Namibia and Death Valley in California and found more rocks — also red — that formed at the same time.


"Oxygen needs to be present for iron to rust. It also needs to be present for animals and many other organisms to survive. If the iron rocks below the ancient oceans rusted, then there was also oxygen in those oceans. And if there was oxygen, then oxygen-breathing life-forms had a lifeline they could cling to.

“'This is the first direct evidence for oxygen-rich marine environments during Snowball Earth,” said Dr. Lechte, now a postdoctoral researcher at McGill University in Canada.

"But how that oxygen got into the oceans in the first place was a mystery. The atmosphere is a major source of oxygen for the oceans, and with the ice sheets of Snowball Earth acting as giant air-blocking shields, oxygen in seawater should’ve been nonexistent.


"Dr. Lechte and his team crushed the iron-rich rocks, dissolved them in acid and measured the abundances of different iron isotopes. They found that the iron in rocks that formed far out in the open oceans rusted much less than the iron in rocks that formed closer to land, right where ice sheets dove from continents and into the oceans.

"Today, beneath ice sheets in Antarctica, glacial meltwater streams flow into the Southern Ocean. That water melts from ice that can have air bubbles trapped inside it, and those bubbles can seed the meltwater streams with oxygen. On Snowball Earth, Dr. Planavsky explained, such oxygen-laden streams flowed into the oceans around the edges of continents and sustained life.

"Paul Hoffman, a geologist at Harvard University who pioneered the Snowball Earth hypothesis, thinks this idea for how oxygen made it into the oceans is solid. “I’m attracted to the idea, and I think it’s consistent with my own observations,” he said."

Comment: the Earth was constructed to solve all problems, as this shows. Special by design? After bacteria life had to be able to survive all challenges. Not all just by adaptation but by the resources of the Earth itself.

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