Science

Perseverance rover discovers potential biosignatures on Mars

The Perseverance rover has reached a milestone in its search for traces of ancient life on Mars by collecting the “most valuable” samples so far containing potential biosignatures to be confirmed on Earth, NASA said Thursday.

If this is not yet proof that life once existed on the red planet, these samples represent the best chance of ever detecting possible ancient microbial life with certainty.

The potential biosignature could be caused by the presence of life, as well as by some other non-life mechanism. Therefore, to consider this biosignature definitive, these samples must be analyzed with powerful laboratory tools on Earth. NASA plans to bring them back with another mission by 2033.

“I think it’s safe to say that these will be and already are the most valuable rock samples ever collected,” – David Schuster of the University of California at Berkeley.

Two pinky-sized carrots that were stored in sealed tubes aboard the rover were recovered by drilling into a rock called Wildcat Ridge. About a meter high, it is located in a delta formed about 3.5 billion years ago at the confluence of a river and an ancient lake.

This rock is especially interesting because it is a sedimentary rock that seems to have been formed when the water in the lake evaporated.

Thus, Wildcat Ridge has “high potential for biosignature preservation,” said David Schuster.

When analyzed separately with the instrument at the end of the Perseverance arm, the rock showed the most abundant presence of organic compounds found in a year and a half of the mission.

These compounds, made up of carbon in particular and which may also contain hydrogen, “are the basic elements of life,” said Ken Farley, who is in charge of the mission’s science department.

In smaller numbers, they were found by the rover during previous analyzes in Jezero crater, which contained a lake, but “as we move into the delta, the clues are getting stronger and stronger,” summed up Sunanda Sharma, a NASA scientist. Jet Propulsion Laboratory.

“Personally, I find these results very touching because it feels like we are in the right place, with the right tools, at a crucial moment,” she said.

“These stones are exactly what we came for,” said Ken Farley.

– Lava Lake –

Other rover analyzes also surprised scientists. At the bottom of the crater, they “found igneous rocks, that is, rocks that crystallized after melting,” Mr. Farley said.

The discovery points to “active volcanism” and that the crater may have been filled with a “lava lake” before water came in, he said.

Samples of these igneous rocks have been collected, and their analysis on Earth should make it possible for the first time to directly determine the age of the Martian surface. “This is something that we are only indirectly hinting at today,” explained Ken Farley.

But obtaining these samples will not be easy.

In 2028, the mission will go towards Mars. It will carry a lander with a mini-rocket on its back. The Perseverance rover will drive up to it, and a robotic arm will place the samples in a mini-rocket.

Then it will take off, and the precious cargo will be transferred to the ship, previously launched into the orbit of Mars. Once the samples are collected, this orbiter will return to Earth for a landing in the Utah Desert in 2033.

If Perseverance fails, the lander will send out two small sample-collection helicopters, which will either go to the rover itself or to a backup reserve.

Indeed, Perseverance has been collecting two specimens of each breed since the beginning of its mission. About ten of them (half the number collected) will soon be deposited on a very level area, where it will be easy to land if necessary. They are back-up samples if access to the rover is no longer possible.

Leaving this treasure on the Martian surface, Perseverance will continue its exploration in the coming weeks to fill the twenty or so tubes that are still empty.

The next goal will be to get to the shore overlooking the old lake, which will take about a year.

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