(CN) – To help scientists determine whether Mars was ever home to vast oceans or some forms of life, researchers in California are searching for clues in rocks and other sediment tucked within a meteorite crater in Germany, according to a study released Wednesday.
The fourth planet from the sun is too frigid to hold liquid water on its surface, making it uninhabitable for life as we know it.
Tim Lyons, biochemistry researcher at the University of California at Riverside, said in a statement he and his colleagues set out to determine what life-sustaining conditions may have looked like on ancient Mars.
"The question that drives our interests isn't whether there's life on present-day Mars," said Lyons. "We are driven instead by asking whether there was life on Mars billions of years ago, which seems significantly more likely."
Lyons said evidence exists that Mars had oceans on its surface roughly 4 billion years ago – when the sun generated less heat than it does today – and that the task for scientists was to understand how that was possible.
In southern Germany's Nordlinger Ries crater, researchers found conditions that resembled ancient Mars’ surface, according to the study published Wednesday in the journal Science Advances.
The crater’s well-preserved layers of rocks and minerals first developed over 15 million years ago when a meteorite struck Earth.
Chris Tino, a UCR graduate student, said in the statement the site’s biological and chemical makeup – particularly its carbon dioxide content – bears a resemblance to the Martian surface and could hold clues to its water-sustaining properties.
"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," said Tino, who co-wrote the study with University of St. Andrews lecturer Eva Stüeken.
Specifically, researchers hope to understand more about the alkalinity, pH and nitrogen content of ancient waters on Mars.
While Tino said Mars likely had insufficient oxygen to have hosted complex life forms like humans or animals, the study found that some microorganisms could have survived if water on Mars had neutral pH levels and was highly alkaline.
Those conditions could mean carbon dioxide levels in ancient Mars’ atmosphere were thousands of times more than what surrounds Earth today, potentially warming the red planet enough to make liquid water possible, the study said.
"Ries crater rock samples have ratios of nitrogen isotopes that can best be explained by high pH," Stüeken said in the statement. "What's more, the minerals in the ancient sediments tell us that alkalinity was also very high."
While that atmosphere’s planet-warming ability partially answers the Martian water question, researchers said questions remain about how suck carbon dioxide levels could have been maintained over time.
"Before this study, it wasn't clear that something as straightforward as nitrogen isotopes could be used to estimate the pH of ancient waters on Mars; pH is a key parameter in calculating the carbon dioxide in the atmosphere," Tino said.
NASA’s Mars 2020 rover is set to land in a similarly structured, well-preserved ancient crater on the red planet which, like Ries, featured liquid water in its past.
Lyons said he hopes the rover’s nitrogen isotope samples will hold clues about ancient Mars’ atmosphere and whether even microbial life could have formed millions of years ago.
"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."
Researchers did not immediately respond to requests for further comment on the study.
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