It happened quick, and within many thousand years or so, ice stretched over each land and ocean, from the poles to the tropics. A life lived within the oceans at the time, and the encroaching ice entombed that life, cutting it off from both the sun and the atmosphere.
“This is the one time when Earth’s natural thermostat broke,” said Noah Planavsky, a biogeochemist at yale university. “The question on everyone’s minds was: how did life make it through this?”
Glaciations will drive mass extinctions of life. Yet life, including perhaps our distant animal ancestors, somehow survived these deep freezes. In research published on Monday in Proceedings of the National Academy of Sciences, Planavsky and his colleagues report the invention of oases simply beneath the ancient ice sheets that likely helped life persevere.
Snowball Earth came to an abrupt end quite a half-billion year’s agone, however, its marks still exist in remote corners of the earth. In 2015, to succeed in one among those corners, max Lechte, and his graduate adviser at the time, Malcolm Wallace, each sedimentologist at the University of Melbourne, drove 15 hours into the South Australian outback.
They trekked over hills made from red-colored rock, and it was so hot out — about 122 degrees Fahrenheit — that the soles of Wallace’s boots melted.
“A bit of duct tape fixed that up,” said Lechte, who led the new research.
These red-hot rocks formed in the oceans during the snowball glaciations, and their color caught 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.
The rocks’ color signaled to Lechte that they are wealthy in iron, which suggests they turned red for the same reason that recent cars with iron exteriors turn red: They rusted.
Oxygen must 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 gas in those oceans. And if there was gas, then oxygen-breathing life-forms had a lifeline they could cling to.
“This is the initial direct evidence for oxygen-rich marine environments during Snowball Earth,” said Lechte, now a postdoctoral researcher at McGill University in Canada.
The ocean was a big mystery in most of the atmosphere.
But how that oxygen got into the oceans in the first place was a mystery. The atmosphere is a major source of gas for the oceans, and with the ice sheets of Snowball Earth acting as big air-blocking shields, gas in water should’ve been nonexistent.
“This could’ve led to anoxic oceans, that could’ve killed off life-forms that need gas to survive,” Lechte same. “It presents a touch of an unsolved problem.”
In labs at Yale as well as Nanjing University in China, Lechte and his team crushed the iron-rich rocks, dissolved them in acid and measured the abundances of various iron isotopes.
They found that the iron in rocks that formed far} go in the open oceans rusted much but the iron in rocks that fashioned nearer to land, right wherever ice sheets dove from continents and into the oceans.
Today, beneath ice sheets in Antarctica, glacial melt water streams flow into the Southern Ocean. That water melts from ice that can have air bubbles trapped within it, and those bubbles will seed the water streams with gas. On Snowball Earth, 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 concept for the way gas created it into the oceans is solid. “I’m interested in the idea, and I think it’s consistent with my observations,” he said.
But, Hoffman added, whether or not this gas pump was the most factor that helped several living things survive those ice ages continues to be an open question.
“We simply don’t know enough from a theoretical standpoint concerning how life would have responded to the challenge of a Snowball Earth,” he said.