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The Perseverance rover may have found evidence of microbial life on Mars in a rock

Credit: NASA/JPL–Caltech/MSSS

The Rover Perseverance of NASA, renamed “the six-wheeled geologist“, may have found on the surface of Mars one of the best directions chemical signatures and structures created by microbial life forms that are thought to have inhabited the red planet billions of years ago. This is the conclusion, for now partial, that NASA researchers have reached by analyzing the rock renamed “Cheyava Falls” which lies at the bottom of the Jezero Crateran ancient river valley 400 meters wide, carved out by liquid water more than 3 billion years ago.
The analyses were mainly conducted with the instrument SHERLOCK (Scanning Habitable Environments with Raman & Luminescence for Organics & Chemicals) which showed the presence of organic compounds inside the rock, the fundamental building blocks of life. All the analyses that are possible on the surface of the planet have been conducted by Perseverance, consequently in order to be able to rule out origins other than life it will be necessary collect these samples and bring them back to Earth, a goal that unfortunately is still far away, but which NASA and ESA are working towards with the mission program Mars Sample Return (MSR).

Perseverance’s discovery of the rock

The rock “Cheyava Falls“, about a meter longwas discovered by NASA’s Perseverance rover on July 21stwhile the little geologist robot explored the Jezero Crateron the edge of the ancient river valley Neretva Valleyroughly astride the equator of Mars.

This valley was dug by theliquid water that flowed on Mars more than three billion yearsconsequently this makes it a ideal place where to look for chemical signatures and structures attributable to ancient microbial life forms.

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360-degree panorama of Mars taken by the Perseverance rover. The “Cheyava Falls” rock was found in the center-right area of ​​the image, about 100 meters from the rover. Credits: NASA/JPL–Caltech/ASU/MSSS

During the photographic exploration of the area, the Perseverance team noticed a arrowhead shaped rock full of whitish veins that immediately caught their attention.

After directing the rover to that area, Perseverance began photographing and analyzing this rock using its onboard instruments, including the SHERLOCKone spectrograph able to determine the chemical composition of rocks, and the instrument PIXL (Planetary Instrument for X-ray Lithochemistry), an imager to X-ray for the chemical analysis of rocks.

What the rock discovered by Perseverance looks like

Cheyava Falls“, named after a waterfall in the Grand Canyon, has large white veins of calcium sulphateinterspersed with bands of reddish material suggesting the presence of hematiteone of the minerals that gives Mars its characteristic color that led to it being nicknamed “the red planet”.

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Image of the “Cheyava Falls” rock found on Mars by the Perseverance rover. Credits: NASA/JPL–Caltech/MSSS

Inside the whitish veins were found olivine crystals millimeter-sized, a mineral that forms from magma, while inside the reddish bands Perseverance found dozens of whitish spots of irregular shape, also millimetric, each surrounded by black materialwhich make these spots similar to those of a leopard.

By analyzing the spots with the PIXL and SHERLOC instruments, Perseverance determined that the black ring of leopard spots contains iron, phosphatebut above all organic compoundsthe fundamental building blocks of life.

The possible consequences of the discovery

The spots shown by the rock “Cheyava Falls“they were a huge surprise for scientists. On Earth, in fact, this type of characteristics are tangible evidence of chemical reactions associated with microbial life, as they are used by the latter as energy source. Not to mention that the very presence of organic molecules is another strong indicator of life, constituting the essential building blocks.

The other big novelty in this discovery is that it is the first time they have been detected in a Martian sample in contemporary way both the compounds that provide an energy source for the microbes and the presence of organic substances associated with the microbes themselves.

Possible non-biological explanations

A biological origin It is of course not the only plausible explanation to the characteristics shown by “Cheyava Falls“. For example, one hypothesis is that the rock was initially deposited as mud mixed with organic compounds that eventually cemented into rock, only to later be traversed by mineral-rich fluids that created the white veins of calcium sulfate.

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Schematic representation of the CoLD scale, the 7-step review process NASA uses to confirm or deny the biological origin of Martian findings. Credits: NASA/Aaron Gronstal

Carl Sagan stated that “extraordinary claims require extraordinary evidence.” For this reason, NASA, before taking for granted the biological origin of the characteristics of “Cheyava Falls“, will submit the tests to a seven-step processknown as scale CoLD (Confidence of Life Detection), capable of confirming or categorically excluding that it was in fact extraterrestrial microbes on Mars that were responsible for the characteristics displayed by the Martian rock.