Did ancient life forms exist on Mars?
The Perseverance rover has taken a major step to answer this question with the collection of the "most valuable" samples so far.
They contain potential biosignatures whose nature will have to be confirmed once on Earth, NASA announced on Thursday.
While this is not yet proof that life once existed on the Red Planet, these samples represent the best chance so far of being able to detect with certainty possible ancient microbial life.
A potential biosignature may have been produced by the presence of life, but also by another mechanism.
To consider this biosignature as definitive, these samples will therefore have to be analyzed by powerful laboratory instruments.
NASA plans to bring them back with another mission by 2033.
In #SamplingMars, I'm building a real science treasure chest, and my latest samples may be the most valuable yet.
Some have organic molecules – but from ancient biology, or another process?
Sending them back to Earth could help us figure it out.
More: https://t.co/sn5Wh9fRnG pic.twitter.com/GfMaXPrYnd
— NASA's Perseverance Mars Rover (@NASAPersevere) September 15, 2022
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A rock called “Wildcat ridge”
Two carrots the size of a little finger, and kept in sealed tubes on board the rover, were taken by drilling into a rock called "Wildcat ridge".
About a meter tall, it is located in a delta that 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, which seems to have formed when the water in the lake evaporated.
"Wildcat ridge" thus has "a high potential for the 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 most abundant presence of organic compounds detected in a year and a half of mission.
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.
“The clues are getting stronger and stronger”
They were detected in less quantity by the rover during previous analyzes in the crater of Jezero, which contained the lake, but "as we progress in the delta, the clues become stronger and stronger", summed up Sunanda. Sharma, a scientist at NASA's Jet Propulsion Laboratory.
Other analyzes of the rover have also surprised scientists.
At the bottom of the crater, they "found igneous rocks, that is to say rocks crystallized after melting", explained Ken Farley.
This discovery indicates “active volcanism”.
Before receiving water, the crater was possibly filled with "a lava lake".
Samples of these magmatic rocks have been collected, and their analysis on Earth should make it possible to determine for the first time directly the age of the surface of Mars.
A mission to recover them in 2033
But getting those 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 into the mini-rocket by a robotic arm.
Then it will take off, and the precious cargo will be transferred to a vessel 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.
Note that in the event of Perseverance failure, the lander will send two small helicopters to recover the samples, going either to the rover itself, or to an emergency reserve.
Indeed, the rover has been collecting two samples of each rock since the start of its mission.
A dozen of them will soon be deposited in a very flat area, where it will be easy to land if necessary.
They represent the fallback samples if it became impossible to access the rover.
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