The Perseverance rover has taken a major step in its search for traces of ancient life on Mars with the collection of the “most valuable” samples to date that contain potential biosignatures, the nature of which must be confirmed once on Earth, NASA announced Thursday.
If this is not yet proof that life once existed on the Red Planet, these samples represent the best chance yet of one day being able to confidently detect possible ancient microbial life.
Analysis on Earth will be necessary
A potential biosignature may have been produced by the presence of life, but also by another mechanism that does not involve life. Therefore, to consider this biosignature definitive, these samples will need to be analyzed with powerful laboratory instruments 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 Shuster, of the University of California at Berkeley.
Two carrots the size of a little finger, and stored in sealed tubes aboard the rover, were taken by drilling into a rock called “Wildcat ridge”. About one meter high, it lies in a delta that was formed about 3.5 billion years ago, where a river and an ancient lake meet.
This rock is particularly interesting because it is a sedimentary rock that appears to have formed when the water in the lake evaporated.
“Wildcat ridge” thus has “a high potential for the preservation of a biosignature,” declared David Shuster.
“The basic elements of life” discovered by the robot
Analyzed separately by an instrument at the end of Perseverance’s robotic arm, the rock revealed the most abundant presence of organic compounds discovered in the year-and-a-half mission.
These compounds, which are mainly made of carbon and may also contain hydrogen, “are the basic building blocks of life,” declared Ken Farley, who is in charge of the science part of the mission.
They were detected in smaller amounts by the rover during earlier analyzes in the Jezero crater, which contained the lake, but “as we progress in the delta, the traces become stronger and stronger”, Sunanda summarized. Sharma, a 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 crucial time,” she said. “These rocks are exactly what we came for,” Ken Farley said.
An ancient “lava lake”
Other analyzes of the rover have also surprised scientists. At the bottom of the crater “they found igneous rocks, that is, rocks that crystallized after melting,” said Ken Farley.
This discovery indicates “active volcanism” and that the crater may have been filled “with a lava lake” before receiving water.
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. “It’s something we’re only indirectly inferring today,” Ken Farley explained.
Mission to 2028 to bring the samples back to Earth
But getting these samples won’t be easy. In 2028, a mission will take off in the direction of Mars. It will carry a lander with a mini rocket on its back. The Perseverance rover will roll up to it and the samples will be placed in the minirocket by a robotic arm.
Then it will take off and the precious cargo will be transferred to a craft previously placed in orbit around Mars. Once the samples have been collected, this orbiter will return to Earth for a landing in the Utah desert in 2033.
If Perseverance fails, the lander will send two small helicopters to collect the samples, either en route to the rover itself or to a backup reserve.
In fact, Perseverance has collected two samples of each rock since the beginning of its mission. About ten of them (half of the collected number) will soon be deposited in a very flat area where it will be easy to land if necessary. They represent the fallback samples if access to the rover became impossible.
After 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 reach the coast overlooking the old lake, which will take about a year.