Mars could once have hosted oceans and life, study of meteorite crater shows

When the Mars 2020 rover launches later this year, it will be heading to the red planet to look for evidence of life. Scientists don’t think it’s likely that life exists there now — but they do think that life could have existed there billions of years ago. And a new study looking at ancient meteorite sites here on Earth could give clues to how life could have developed there.

“The question that drives our interests isn’t whether there’s life on present-day Mars,” Tim Lyons, distinguished professor of biogeochemistry at the University of California Riverside, said in a statement. “We are driven instead by asking whether there was life on Mars billions of years ago, which seems significantly more likely.”

Lyons and his team wanted to know how it was possible for Mars to have had water on its surface in the past, as it is further from the sun than Earth is and at the time the sun would not have given out that much heat. “To have made the planet warm enough for liquid surface water, its atmosphere would likely have needed an immense amount of greenhouse gas, carbon dioxide specifically,” explained Chris Tino, a UCR graduate student and co-first author of the paper.

There’s no way to measure the amount of carbon dioxide that was historically in the Martian atmosphere, so the team looked for an analog here on Earth. They found the Nordlinger Ries crater in Germany, which was formed when a meteorite hit the Earth 15 million years ago. They studied this crater and found the water it had contained had a high pH level and high alkalinity, a combination that could allow microorganisms to survive.

A sample of suevite rock formed nearly 15 million years ago by the Ries Crater meteorite impact. Similarly impact-generated rocks exist on the rims of ancient crater lakes on Mars.
A sample of suevite rock formed nearly 15 million years ago by the Ries Crater meteorite impact. Similar impact-generated rocks exist on the rims of ancient crater lakes on Mars. NASA

“Ries crater rock samples have ratios of nitrogen isotopes that can best be explained by high pH,” co-author Eva Stüeken, a lecturer at the University of St. Andrews in Scotland, said. “What’s more, the minerals in the ancient sediments tell us that alkalinity was also very high.”

These findings suggest that Mars could have had similar conditions if it had extremely high levels of carbon dioxide in its atmosphere. This would have insulated the early planet and kept it warm enough to have water on its surface.

“It could be 10-20 years before samples are brought back to Earth,” Lyons said. “But I am delighted to know that we have perhaps helped to define one of the first questions to ask once these samples are distributed to labs in the U.S. and throughout the world.”

The findings are published in the journal Science Advances.

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