If we think about it objectively, the ability to send a vehicle to another planet, capable of traveling dozens of kilometers a day, analyzing the terrain, the weather, storing samples and sending data to Earth, is something incredible. That is precisely what the rovers we send to Mars do. And now one of them, Perseverance, has found a treasure.
If there is a Holy Grail on Mars, it is probably a specific type of rock: a rock so important that contains compelling clues to the ancient habitability of Mars. In fact, if you ask scientists what the sample would be like, the answer is easy: one that showed evidence of ancient water and was not of the type that preserves ancient organic material.
And Perseverance may have found it while exploring a geological region on the inner rim of Jezero Crater. The region lies in a narrow band along the western rim of the crater. Orbital observations showed that it is one of the richest regions in carbonates on the planet.
“Its presence, together with the adjacent river delta, turned the Jezero crater into the most attractive landing site for the mission Perseverance Mars 2020,” scientists noted at the 2024 Lunar and Planetary Science Conference.
The Perseverance team decided to take samples and store the sample along with the rest of its cores for eventual return to Earth. But first they scanned the rock surface with the rover's spectrometers. Then, they scraped the surface of the rock and scanned it again. The results show that the sample It is made up of 75% cemented carbonate grains each other using almost pure silica.
“Simply put, this is the type of rock we expected to find when we decided to investigate Jezero Crater,” says Ken Farley, Perseverance project scientist at Caltech in Pasadena, California. “Almost all of the minerals in the rock we just sampled were formed in water. On Earth, minerals deposited in water are usually good for trapping and preserving ancient organic material and biosignatures. “The rock can even tell us about the climatic conditions on Mars that were present when it formed.”
Here on our planet, carbonate minerals can form directly around microbial cells. Once encapsulated, cells can quickly become fossils and are preserved for a long time. This is what happened to some of the first evidence of life on our planet.
But there is something that makes this exhibition even more intriguing. They are microcrystalline rocks, meaning they are made of crystals so small that only microscopes can see them. On Earth, microcrystalline rocks such as Precambrian chert contain fossilized cyanobacteria. Could the same happen with this one?
“The silica and parts of the carbonate appear microcrystalline, which makes them extremely good at trapping and preserving signs of microbial life that may have once lived in this environment – concludes Sandra Siljeström, Perseverance scientist at the Swedish Research Institutes (RISE). in Stockholm – that makes this show excellent. for biosignature studies if returned to Earth. Additionally, the sample could be one of the oldest cores collected so far by Perseverance, and that's important because Mars was at its most habitable early in its history.”