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NASA’s Perseverance rover is exploring a long-dry river delta on Mars, and it has seen signs that indicate that the region is full of organics – molecules containing carbon that are widely considered to be the building blocks of life.

The rover has taken measurements and samples in an area called Skinner Ridge made of layered sedimentary rocks, some of which contain materials that were most likely transported from hundreds of kilometres away by running water billions of years ago.

“With the samples we’re taking now in this more sedimentary area, we’re of course right at the heart of what we wanted to do to start with,” said NASA science lead Thomas Zurbuchen during a press conference on 15 September. The goal was to look at areas similar to those on Earth that harbour signs of ancient life, he said.

These sedimentary rocks contain complex organic molecules called aromatics, as well as clays and sulphate minerals, which can be produced when water interacts with rocks. While none of these materials are definitely signs of life, known as biosignatures, they do mean we are looking in the right place.

“This is really important that this has sulphate in it and also clays, because that means that this rock has high potential for biosignature preservation, meaning that if there were biosignatures in this vicinity when that rock formed, this is precisely the type of material that will preserve that for us to study when [the samples] come back to Earth,” said at the University of California, Berkeley, during the press conference.

The prevalence of organic matter has increased over the course of Perseverance’s drive through the crater in which it landed towards the river delta. “If this is a treasure hunt for potential signs of life on another planet, organic matter is a clue,” said at NASA’s Jet Propulsion Laboratory in California during the press conference. “We’re getting stronger and stronger clues as we’re moving through our delta campaign.”

However, we most likely won’t be able to hunt for definitive signs of life in these rocks until Perseverance’s samples are brought home in a mission planned for launch in 2028.

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