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Oxygen accumulated in Earth's primordial oceans 250 million years before the atmosphere

"This helps us theorize not only about early life on Earth but also about the signatures of life that we might find on other planets," said grad student Mojtaba Fakhraee.

By Brooks Hays
Oxygen accumulated in Earth's primordial oceans 250 million years before the atmosphere
Oxygen began accumulating in the oceans of early Earth some 250 million years earlier than previously thought. Photo by ESA

Jan. 25 (UPI) -- Oxygen began accumulating in early Earth's oceans some 250 million years before it first showed up in the atmosphere some 2.45 billion years ago.

Scientists arrived at the revelation after creating a model of early ecosystems in Earth's primordial oceans.

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Scientists used observations of ancient sedimentary rocks and the preserved chemical signatures of primordial seawater to build a model of early ocean biochemistry. The model looked closely at the sulfur cycle to better understand how different isotopic sulfur patterns became preserved in ancient ocean sediment.

"We're trying to reconstruct the functioning of early life and early environments," Sergei Katsev, a professor at the University of Minnesota Duluth, said in a news release. "No one was really looking at how the isotopic signals that were being generated in the atmosphere and the ocean were being transformed in the sediment."

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The new analysis -- published this week in the journal Science Advances -- suggests bacteria began eating enough sulfur to allow oxygen to accumulate in early Earth's oceans some 2.7 billion years ago.

"When tiny bacteria in the ocean began producing oxygen, it was a major turning point and changed the chemistry of the earth," said Katsev. "Our work pinpoints the time when the ocean began accumulating oxygen at levels that would substantially change the ocean's chemistry and it's about 250 million years earlier than what we knew for the atmosphere. That is about the length of time from the first appearance of dinosaurs till today."

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Scientists say their work is helping to resolve some of the contradictions present in the records provided by ancient rock samples. It's also helping researchers better understand the biochemical patterns of the earliest communities of single-cell microbes.

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"This helps us theorize not only about early life on Earth but also about the signatures of life that we might find on other planets," said grad student Mojtaba Fakhraee.

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