A spot-like, vein-filled rock formed by a Nasa rover on Mars contains features that suggest it may have harbored microbial life billions of years ago.
The arrowhead-shaped rock, named Cheyava Falls, was discovered by Nasa’s Perseverance rover on July 21 as it rolled along the northern edge of Neretva Vallis, an ancient river valley carved by water flowing into the red planet’s Jezero crater has.
Analysis of the 3-foot-by-2-foot rock revealed signs of organic matter, interesting surface patches similar to those associated with fossilized microbes on Earth and evidence that water once passed through the rock, the agency said.
Ken Farley, the project scientist on the mission at the California Institute of Technology, said Cheyava Falls was “the most enigmatic, complex and potentially important rock yet investigated by Perseverance”, although the team makes clear that non-biological processes are possible gave rise to to the features.
“On the one hand, we have our first compelling detection of organic matter, distinctive colorful patches indicating chemical reactions that microbial life could use as an energy source, and clear evidence that water, necessary for life, once permeated the rock went.” Farley said.
“On the other hand, we could not determine exactly how the rock formed and to what extent nearby rocks heated the Cheyava Falls and contributed to these features.”
In the ancient past, Mars was a warmer, wetter planet. If life ever evolved there, researchers believe that traces must remain within its rocks, in the form of organic matter and possibly fossilized remains.
Scans of the Cheyava Falls rock by Perseverance’s Sherlock tool indicate that it contains organic compounds. Such carbon-based molecules are considered the building blocks of life, but can also be produced by non-biological processes.
Large white veins of calcium phosphate run along the rock. Between them are bands of reddish material, probably hematite, one of the iron oxide compounds that give Mars its rusty color. Closer inspection of the tires revealed dozens of small leopard spot-like features. Each of the pure white spots is surrounded by a black ring containing iron and phosphate.
David Flannery, an astrobiologist at Queensland University of Technology in Australia and a member of the mission, called the spots “a big surprise” because on Earth similar features are “often associated with the fossilized record of microbes”.
White spots can form on rocks through chemical reactions involving hematite, which produces iron and phosphate, as well as energy that microbes can live on. Although the features are interesting, nothing yet seen appears to be an actual fossilized microbe.
Researchers are desperate to get their hands on samples for more thorough examination, but Nasa’s plans to return the Martian rocks to Earth encountered problems.
The agency’s Mars sample return mission is over budget by $11bn (£8.5bn) and badly delayed with no prospect of returning rocks before 2040. Nasa is looking for companies to return Mars samples earlier and at lower cost.
“That’s what Mars Sample Return is all about. We have never seen anything like this from Mars, not in our Martian meteorite collections, not with Mars Science Laboratory or other landings,” said Prof John Bridges, a participating scientist on Nasa’s Mars Science Laboratory mission at the University of Leicester, said.
“The reality is that we need to get these samples back to Earth to do the detailed electron microscopy and isotopic analyzes to see if they were formed by ancient microbial action or abiotically,” Bridges said.
Prof Charles Cockell, an astrobiologist at the University of Edinburgh, said: “Although these features do not provide unequivocal evidence of life, they do confirm that Mars was a very dynamic planet with all the ingredients for life, including organic carbon.
“We need to bring back samples, or in my opinion, even better, send people to see if we see the signatures of life.”
Prof Monica Grady, a planetary and space scientist at The Open University, said: “It’s an incredible rock. It makes my mouth water just to look at it. The combination of different types of minerals arranged the way they are reminds me to some of the textures found in ancient Earth rocks that preserve traces of burrowing worms.Obviously I’m not saying there were burrowing worms on Mars – but I can’t wait to see what Perseverance has in store. did not discover this part of his exploration.”
