2 Billion-Year-Old Pink Sea Salt Rocks Reveal How Life Began on Ancient Earth

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A sample of 2 billion-year-old salt was discovered 1.2 miles underground in Russia. Credit: Aivo Lepland, Geological Survey of Norway; courtesy of Science/AAAS

Recently discovered pieces of pink sea salt rocks dating back 2 billion years may shed light on when oxygen started to rise in Earth's atmosphere.

The crystallized rocks, which were collected from a 1.2.-mile deep hole drilled in northwest Russia, were analyzed by scientists. Those scientists think the rocks show that the Great Oxidation Event—the first large buildup of atmospheric oxygen—happened at a much different pace than previously thought.

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"Instead of a trickle, it was more like a firehose," Clara Blättler, a postdoctoral research fellow at Princeton University who co-authored a study about the rocks, said in a statement. "It was a major change in the production of oxygen."

Upon analyzing the mineral deposits, Blättler and her colleagues discovered that they contained an unusually large amount of sulfate, which is what you get when sulfur and oxygen react.

"This is the strongest ever evidence that the ancient seawater from which those minerals precipitated had high sulfate concentrations reaching at least 30 percent of present-day oceanic sulfate as our estimations indicate," Aivo Lepland, senior author and researcher at the Geological Survey of Norway, said in a statement.

Typically, the types of minerals discovered wouldn't last very long and would eventually dissolve away; however, the samples found are very well intact, as seen in the photo above. They're also the oldest-ever salt deposits collected by geologists. The closest samples in age are a billion years younger, according to the statement.

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The Great Oxidation event has long-posed a mystery to scientists, but discoveries such as this help them better understand when Earth became a capable place to live. There are, however, many questions that remained.

"The bottom line is that this paper provides evidence that the oxygenation of the Earth across this time period involved a lot of oxygen production," John Higgins, study author and assistant professor of geosciences at Princeton University, said about the findings which are published in the journal Science.