Last week, the Curiosity rover stumbled upon rocks composed of pure sulfur – a material that is very important for studying Martian geology, but also in the search for traces of past life on the Red Planet. And just recently, its little brother Perseverance joined in the fun: the robot got its hands on geological formations that could well have been created by extraterrestrial organisms several billion years ago.
Right now the rover is going back up Neretva Vallisthe 400-metre-wide main artery that leads to the Jezero crater delta. This is a particularly interesting area, because it was through this channel that all the water arrived that transformed the region into a vast lake just under four billion years ago. Any discovery in this area is therefore particularly promising, knowing that this precious liquid is intimately linked to life as we know it.
Veins, spots and carbon
As the rover moved west, it came across a large rock formation that immediately caught NASA’s attention because of its unusual appearance: it is riddled with light veins that contrast with the rest of the orange matrix.
These veins are irregular, branched and intertwined. For geologists, it is the indisputable proof that they were formed in an aquatic environmentbecause this kind of structure can only appear in the presence of a moving fluid.
Preliminary analyses by the rover also showed that these veins are made up of sulfate de calcium. This is another very exciting fact, because it is a relatively stable material at the chemical level; it is capable of preserving traces of geological processes or biosignatures for billions of years, which makes it an invaluable archive in the search for life.
These discoveries would have been enough to make the rock, nicknamed Cheyava Falls, very interesting… but the NASA team was not at the end of its surprises. By analyzing the orange matrix using its SHERLOC instrument, Perseverance also detected the presence of organic compoundsthat is, carbon-based. They can be produced by a wide variety of geological processes, but they are also essential building blocks of life as we know it. While this is far from definitive proof that Mars once hosted living beings, finding organic compounds in an area that is known to have been covered in water is still very encouraging.
Looking closer, the rover also noticed a much more subtle, but equally exciting, detail. The orange part of the rock is dotted with small spots that NASA compares to those of a leopard. Using its PIXL instrument, Perseverance determined that these dark halos contain iron and phosphate.
This is a very intriguing find. We know that these spots can appear as a result of chemical reactions of hematite, the orange mineral that helps give Martian rocks their characteristic color. However, on our planet, These reactions can be exploited by microorganisms which use them as an energy source.
« On Earth, these features in rocks are often associated with the fossilized records of microbes living underground. ” , rejoices David Flannery, one of the astrobiologists of the team analyzing the data from Perseverance.
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A triple unprecedented discovery
Perseverance has already observed calcium sulfate veins, iron and phosphate halos and organic compounds several times since the beginning of its Martian adventure. However, it is the very first time he finds these three elements gathered together in precisely the same place. Cheyava Falls is therefore an exceptionally promising subject of study, and perhaps the rover’s most beautiful discovery since the start of its mission.
« We have organic compounds, colorful spots that point to chemical reactions that microorganisms can use as an energy source, and clear evidence that liquid water once circulated around the rock. ” lists Ken Farley, one of the other researchers on the team. It is the most complex, intriguing and potentially important rock discovered by Perseverance. ” he exults.
focus on Mars Sample Return
So has the rover just found the first proof of past life on Mars? It’s a real possibility… but it’s still too early to say. To validate or rule out this hypothesis with all the necessary rigor, it will be necessary to carry out extremely detailed analyses for which Perseverance is unfortunately not equipped.
“We bombarded this rock with lasers and X-rays and photographed it day and night from almost every angle imaginable “, Farley explains. Scientifically, Perseverance has nothing more to offer. To fully understand what really happened in this Martian river valley at Jezero Crater billions of years ago, the sample will have to be brought back to Earth, so that it can be studied with the powerful instruments available in laboratories. »
To do this, we will have to wait Mars Sample Returnthe highly ambitious mission through which NASA will attempt to recover the rover’s samples. Its departure is not scheduled before 2031… at the earliest. Because unfortunately, the preparations for the mission have been excessively chaotic. Several damning reports have castigated the explosion of its budget as well as the schedule, deemed totally unrealistic. NASA has therefore been forced to launch a major restructuring plan for the program.
To this day, we still don’t know exactly how Mars Sample Return will take place. So all that remains is to keep our fingers crossed while waiting for the new roadmap; it would be a shame if these planning problems deprived us of such an exceptional sample.
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