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Image credit: Barbara David












Last month, I wrote a story for Space.com that focused on the issue of finding evidence of life on Mars…but would we recognize it?

Go to: https://www.space.com/perseverance-rover-search-for-life-on-mars-is-difficult

Indeed, NASA’s Perseverance rover is on-duty, scurrying around on the Red Planet, wheeling and dealing with Jezero Crater.

Jezero Crater definitely has a story to tell. And that’s why the rover landed there in the first place.

Ancient Jezero Crater is depicted in this artistic view, replete with shoreline of a lake that dried up billions of years ago.

Microbial life could have lived in that area during a wetter period of time in its past. If so, signs of their remains might be found in the ancient lakebed or shoreline sediments that formed billions of years ago.

Eye-catching features

That said, the robot recently came across some eye-catching circular rock structures. They are attention-grabbers because they resemble ones formed by microbial communities in some lakes on Earth.

Those rover observations became the focus of an informative “Mars Guy” episode that called attention to Perseverance finding features resembling reef-like structures.

Image credit: Mars Guy



“In the very place it might be reasonable to expect, Perseverance discovered circular rock structures resembling ones formed by microbial communities in some lakes on Earth. This exciting possibility called for a closer look,” Mars Guy explained at:


Mother Nature on Mars

The finding also underscores, perhaps, how Mother Nature on the Red Planet can make it difficult to conclude what might or might not constitute evidence for life on that world.

What’s up with that rover finding? I asked Ken Farley, a professor of geochemistry in the Division of Geological and Planetary Sciences at the California Institute of Technology. He is the project scientist for Mars 2020, the Perseverance sleuthing of Jezero Crater.

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

“We investigated that rock with our remote sensing instruments, and we acquired two abrasion patches and two sample cores from similar rocks in close proximity,” Farley told Inside Outer Space. “We also recognized the very peculiar and suggestive concentric-domelike morphology.”

Currently favored hypothesis

Farley said as an alternative to a biological origin – for example, a stromatolite – Mars scientists on the rover mission also considered the hypothesis that these features are simply spheroidal weathering.

That’s a very common phenomenon on Earth, Farley pointed out, and one seen elsewhere in Jezero, in both igneous and sedimentary rocks.

“Although we are still interpreting the data, the latter hypothesis is far less extraordinary, and at least partly for this reason, currently favored,” Farley said.

NASA Mars 2020 rover is collecting samples, storing the specimens in tubes, then depositing the tubes on the surface for later pick-up.
Credit: NASA/ESA

Plausible manifestations

As to the general question, Farley added, if ancient life were present, would Perseverance recognize it?

“My answer is ‘maybe.’ Based on ancient terrestrial analogs there are plausible manifestations we could detect with our instrument suite, but many plausible manifestations too subtle for us to confidently identify,” Farley explained.

“This is of course a key motivation for sample return,” Farley added. “As an example, compared to the organic molecule detection capabilities on Perseverance, those in terrestrial laboratories are at least a factor of 10,000 more sensitive.”

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