This is not yet proof that life once existed on the Red Planet, but the best chance so far of one day being able to detect with certainty possible ancient microbial life.

A potential biosignature may have been produced by the presence of life, but also in the absence of life.

To consider this biosignature as definitive, these samples will have to be analyzed by powerful laboratory instruments on Earth.

NASA plans to bring them back, thanks to another mission, by 2033.

"I think it's safe to say that these are going to be, and are already, the most valuable rock samples ever collected," said David Shuster, who works at a press conference. on these samples.

Two cores were taken by drilling in a rock called "Wildcat ridge", about one meter high and located in a delta that formed about 3.5 billion years ago, at the meeting of a river and an old lake.

This rock is particularly interesting because it is a sedimentary rock, which seems to have formed when the water in the lake evaporated.

"Wildcat ridge" thus has "a high potential for conservation of a biosignature", declared David Shuster, of the University of California at Berkeley.

Analyzed separately by an instrument at the end of Perseverance's robotic arm, the rock revealed the presence of organic compounds -- the most abundant detected since the start of the mission a year and a half ago.

These compounds - made in particular of carbon, and which can also contain hydrogen - "are the basic elements of life", declared Ken Farley, in charge of the scientific part of the mission.

They were detected in smaller quantities by the rover during previous analyzes in the crater of Jézéro, which contained the lake, but "as we progress in the delta, the" clues become stronger and stronger, "summarized Sunanda Sharma, scientist at NASA's Jet Propulsion Laboratory.

“I personally find these results very moving, because it seems that we are in the right place, with the right instruments, at a pivotal moment,” she said.

"We don't yet know the significance of these finds, but these rocks are exactly what we came for," concluded Farley.

© 2022 AFP