2 Billion-Year-Old Salt Rock Reveals How Life Began On Ancient Earth

Posted: Mar 24 2018, 6:26am CDT | by , Updated: Mar 24 2018, 10:38am CDT, in Latest Science News

 

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2 Billion-Year-Old Salt Rock Reveals How Life Began on Ancient Earth
A sample of 2 billion year old pink salt rock extracted from Russia Credit: Aivo Lepland, Geological Survey of Norway; courtesy of Science/AAAS

Researchers have found that rise in oxygen levels that occurred about 2.3 billion years ago was much more substantial than previously indicated

Oxygen is a key ingredient of life. We and all other animals wouldn’t exist on Earth today if our planet didn't have a lot of oxygen in its atmosphere and oceans.

Researchers have found evidence that oxygen levels significantly increased about 2.3 billion years ago and transformed the Earth from an inhabitable place to a planet capable of supporting life. And the transformation, known as the Great Oxidation Event, was much more substantial than previously thought.

“Instead of a trickle, it was more like a firehose," said lead author Clara Blättler from Princeton University. "It was a major change in the production of oxygen."

The evidence for the dramatic rise in oxygen levels comes from crystallized salt rocks recovered from Karelia region in northwest Russia. These rocks are estimated to be 2 billion years old and left behind when ancient seawater evaporated. Researchers have found that the rocks contained a surprisingly large amount of a seawater component called sulfate, which was created as a result of interaction between sulfur and oxygen.

“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," said co-author Aivo Lepland, a geology specialist at Tallinn University of Technology. "This is much higher than previously thought and will require considerable rethinking of the magnitude of oxygenation of Earth's 2-billion-year-old atmosphere-ocean system."

Today, oxygen makes up 20 percent of the air. Tracking the concentration of oxygen Earth’s atmosphere over billions of years ago, however, isn't easy because there is no way to directly measure the composition of ancient Earth's atmosphere. Therefore, geologists were uncertain whether the buildup in oxygen was a slow event that took millions of years or it occurred rapidly.

"It has been hard to test these ideas because we didn't have evidence from that era to tell us about the composition of the atmosphere,” Blättler said.

The recently discovered salt rocks in Russia are important evidence and they are about a billion years older than any previously discovered salt deposits. Normally these minerals dissolve easily and disappear over time, but in this case, they were exceptionally well preserved deep within the Earth and their unique qualities make the value in piecing together the history of ancient Earth.

"This is a pretty special class of geologic deposits," said John Higgins from Princeton University. "There has been a lot of debate as to whether the Great Oxidation Event, which is tied to increase and decrease in various chemical signals, represents a big change in oxygen production, or just a threshold that was crossed. 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."

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<a href="/latest_stories/all/all/47" rel="author">Hira Bashir</a>
The latest discoveries in science are the passion of Hira Bashir (). With years of experience, she is able to spot the most interesting new achievements of scientists around the world and cover them in easy to understand reporting.

 

 

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