Leonard David's INSIDE OUTER SPACE

Image credit: NASA/JPL-Caltech/MSSS/Inside Outer Space screengrab

NASA’s Perseverance Mars rover is busily scouting about at its Jezero Crater site and has collected seven cores of aqueously deposited sandstones and siltstones.

These samples from the front of Jezero’s western fan are all likely older than the oldest signs of widespread life on Earth. The samples were collected by NASA’s Perseverance rover in 2022 during its exploration of the crater’s western slope.

The hydrated, sulfate-bearing mudstone has the highest potential to preserve organic matter and biosignatures. The carbonate-bearing sandstones can be used to constrain when and for how long Jezero crater contained liquid water.

Ancient Jezero Crater is depicted in this artistic view, replete with shoreline of a lake that dried up billions of years ago.
Credit: NASA/JPL-Caltech/MSSS/JHU-APL

Fan front

The findings suggest that the rocks were originally deposited by water, or may have formed in the presence of water. Jezero Crater was likely once a watery, habitable environment. This “fan front” is suspected by researchers to be an ancient delta that was created by sediment that flowed with a river and settled into what is now a dried-out lakebed.

The same minerals may preserve organic and inorganic signals of abiotic, prebiotic and biological processes. Indeed, if life existed on Mars, scientists think that it could be preserved in the layers of sediment along the fan front.

Jezero Crater – home base for Perseverance rover.
Credit: NASA/JPL-Caltech/MSSS/JHU-APL

Habitable environments

That’s the nitty-gritty of a new research paper – “Astrobiological Potential of Rocks Acquired by the Perseverance Rover at a Sedimentary Fan Front in Jezero Crater, Mars” — in the journal AGU Advances.

“These rocks confirm the presence, at least temporarily, of habitable environments on Mars,” says the study’s lead author, Tanja Bosak, professor of geobiology in MIT’s Department of Earth, Atmospheric, and Planetary Sciences.

“What we’ve found is that indeed there was a lot of water activity,” Bosak explains in an MIT statement. “For how long, we don’t know, but certainly for long enough to create these big sedimentary deposits.”

Illustration shows NASA’s Perseverance rover exploring inside Mars’ Jezero Crater, a 28-mile-wide (45-kilometer-wide) feature believed to an ancient lake-delta system in a hunt for signs of past microscopic life.
NASA/JPL-Caltech

Ideal material

Bosak and her colleagues have found evidence of certain minerals in the sediments that are known to precipitate out of water.  

“We found lots of minerals like carbonates, which are what make reefs on Earth,” Bosak states. “And it’s really an ideal material that can preserve fossils of microbial life.”

On the other hand, the researchers also identified sulfates in some samples that were collected at the base of the fan front.

Sulfates are minerals that form in very salty water — another sign that water was present in the crater at one time — though very salty water, Bosak notes, “is not necessarily the best thing for life.”

If Jezero Crater was entirely filled with very salty water, then it would be difficult for any form of life to thrive.

On the prowl at Jezero Crater, NASA’s Mars Perseverance rover is loaded with scientific equipment.
Image credit: NASA/JPL-Caltech/MSSS

Trickle-down theory

On the other hand (2), if only the bottom of the lake were briny, that could be an advantage, at least for preserving any signs of life that may have lived further up, in less salty layers, that eventually died and drifted down to the bottom, according to the MIT statement.

“However salty it was, if there were any organics present, it’s like pickling something in salt,” Bosak says. “If there was life that fell into the salty layer, it would be very well-preserved.”

All of this speculation underscores the need for the Perseverance collected samples to be intensively studied here on Earth. Bosak says laboratory instruments will have more than enough sensitivity to detect any organic matter that might lie within.

“On Earth, once we have microscopes with nanometer-scale resolution, and various types of instruments that we cannot staff on one rover, then we can actually attempt to look for life,” Bosak concludes.

Take a read of “Astrobiological Potential of Rocks Acquired by the Perseverance Rover at a Sedimentary Fan Front in Jezero Crater, Mars” at:

https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2024AV001241