NASA’s Mars Rover Perseverance discovered a rock that contains chemical signatures and structures that might have been created by ancient Martian life forms. The rock, nicknamed Cheyava Falls, was found in Neretva Vallis during Perseverance’s journey inside Jezero Crater on Mars and was examined with the SHERLOC (Scanning Habitable Environments with Raman & Luminescence for Organics & Chemicals) instrument. The rock contains organic compounds, but it’s currently not possible to rule out that they formed through non-biological processes. The PIXL (Planetary Instrument for X-ray Lithochemistry) instrument detected iron and phosphates in black halos on the rock.
Landed on Mars on February 18, 2021, the Mars Rover Perseverance is exploring Jezero Crater, a place considered interesting also for astrobiology, as various signs indicate that it was filled with water when the red planet was young and much more similar to Earth. To search for traces of possible life forms that developed when conditions were favorable, Perseverance has instruments such as SHERLOC.
On July 21, the Mars Rover Perseverance collected a sample of the rock nicknamed Cheyava Falls found in the Neretva Vallis. That’s an ancient river valley that Perseverance has been traveling through since the beginning of 2024, about 400 meters wide, carved by the water that once poured into Jezero Crater.
The exams conducted by the SHERLOC instrument detected the presence of organic compounds. These are the building blocks of life that can also form from non-biological processes. The problem is understanding how they formed on Mars. This discovery is unprecedented but it’s only the first step in the research, as proof is needed to be able to affirm that these are compounds formed by ancient microorganisms.
The Cheyava Falls rock also shows the presence of veins of calcium sulfate. Among those veins are bands of reddish material that suggest the presence of hematite, one of the minerals that give Mars its characteristic rusty color. Small white spots surrounded by black material similar to small leopard spots are also interesting. The PIXL instrument detected the presence of iron and phosphates, a surprising finding given that on Earth that type of feature is associated with the presence of fossil microorganisms.
In a possible reconstruction of the events that led to the formation of the Cheyava Falls rock, there was originally mud that was deposited together with organic compounds that over time, got mixed up and turned into rock. Subsequently, a second episode of fluid flow led to a penetration into cracks in the rock allowing the minerals that created the calcium sulfate veins and the spots to be deposited. It must be stressed that for now, these are hypotheses that need to be verified.
Among the materials found in the Cheyava Falls rock are also very small crystals of olivine, a mineral that forms from magma. It could be olivine linked to rocks that formed in another area linked to ancient volcanic activity that crystallized and was transported to where it was found. One hypothesis is that an abiotic chemical reaction linked to olivine and sulfate generated the spots.
The team that runs the operations of the Mars Rover Perseverance did everything that could be done with the available instruments. Further exams should be conducted on samples transported to Earth but this would mean carrying out the Mars Sample Return mission. This project developed in recent years by NASA in collaboration with ESA is currently on hold due to the very high costs that were anticipated.
For now, the Cheyava Falls rock offers some clues regarding a possibility linked to ancient Martian life forms. It’s the first time that certain characteristics have been found together in a rock on Mars, and that’s very interesting but we’re still far from real proof. The journey of the Mars Rover Perseverance continues hoping to find other rocks with equally intriguing contents that might provide more useful information to understand the origin of the various compounds.
