Leonard David's INSIDE OUTER SPACE

Curiosity Chemistry & Camera image acquired on Sol 2663, February 2, 2020.
Credit: NASA/JPL-Caltech/LANL

As many of the readers of this website know…I do inspect quite a number of Curiosity Mars rover images daily.

I was intrigued by a recent new image…and I asked Pascal Lee, a planetary scientist of the Mars Institute and SETI Institute to help me identify what I’m observing. Here’s his reaction:

“The feature at the top of the image does look like a terrestrial nautiloid-form (important to keep those two words together and hyphenated)! Given that the background rock is full of spheroidal mineral concretions of the same scale, however, the nautiloid-form is most likely just a cluster of concretions that has been differentially eroded and made to stand out like a fossil might,” Lee told Inside Outer Space.

Lee added that, even if this was a fossil — which it likely isn’t” – “we should be reminded of what Carl Sagan used to say: “Extraordinary claims require extraordinary evidence.”

Credit: Pascal Lee

Tree of life…forest of life

However, Lee said, this also does bring to the fore the important point, which he has been harping about for some time, that, even if this were fossil life, no amount of fossil-finding on Mars will establish that we’ve found alien life. We would have found signs of “life off Earth,” but not necessarily established that it is life “that is not of the Earth.”

Lee said that alien life would be “establishable” as such…only if we could show that it does not fit on Earth’s Tree of Life, to which all known life forms on Earth belong (based on phylogeny, i.e., shared genetics).

“It would have to belong to a separate Tree of Life, one resulting from an independent origin. Once we’ve established that there are at least two Trees of Life in the solar system, we can speculate confidently that there must be a Forest of Life out there,” Lee advised.

Deep diving on Mars. Cavers deploy for underground exploration of the Red Planet.
Credit: Pascal Lee

Mars underground

To establish that scientists have found an alien life form on Mars, Lee added, we have to do genetics — not necessarily “DNA” sequencing, but genetic analysis in a more generic sense. To do genetics, the life form has to be alive – or dead since a very short time; biochemically still intact, he said.

“To find life that’s alive, we need to explore Mars’ underground where, deep enough, conditions at present would be warmer, wetter, and more sheltered than at the surface, sheltered especially from ionizing radiation, micrometeoritic bombardment, low atmospheric pressure, and drastic day-night temperature variations, which are likely to be bad news for any life,” Lee advised.

Loaded to the brim with samples, a robotic Mars Ascent Vehicle rockets off the planet under the watchful eye of an accompanying “go fetch” mini-rover.
Credit: NASA/JPL

Return sample

Even if we found fossils in samples returned from Mars, Lee said, “we would be hard-pressed to establish that it’s alien, as opposed to just life derived from life shared with the Earth in the past, via impacts, unless the samples actually contained extant life, which they would likely not…given that they would be from the surface of Mars or would have sat there for a long time.”

So in short, Lee said, the nautiloid-form pictured by Curiosity is indeed “weird and cool,” but ultimately, he added, “to have any chance of finding life that we’d be able to establish as alien, we must go and look for it underground.”

Interesting texture…but

“It is an interesting texture, could be anything from melted volcanic glass to weathering sedimentary concretions to slime molds from outer space sent to take over our Solar System,” adds Penelope Boston, Senior Advisor for Science Integration at NASA Ames Research Center. “I don’t know the size scale on the image nor the context of where it is from, etc.” 

“I would add that finding any fossil material on Mars would be extremely exciting but would require the building of a major framework case of the geological context, the search for any biomolecules that might have been preserved in the material ranging from organic carbon to remains of lipids,” Boston told Inside Outer Space.

Confirmation of the existence and extent of life on Mars, whether ancient or current, will benefit human exploration. Here an exobiologist examines what appears to be a porous relic of a hot spring that has fallen from the canyon wall.
Credit: NASA/Pat Rawlings

Weak evidence

Boston said there are many additional techniques to try to see whether a form is a “one-off” or is in a setting with more than one example of a form. In addition, is there a stable isotope value consistent with what we know that life on Earth does to carbon (i.e. make it lighter than the source CO2)? 

Similar in view as Pascal Lee, “we cannot tell from any of that whether it is related to Earth life or a second genesis,” Boston said. “Morphology alone is weak evidence, albeit possibly critical in drawing our attention to something to investigate, so it is super helpful but very far from definitive in any way,” she concluded.

Biological origin

As for the new Curiosity imagery showing an interesting feature, “it’s hard to say,” explains, Chris McKay, a noted Mars researcher at NASA Ames Research Center.

“There are certainly biogenic features that look like this but that’s quite a long way from saying these have to be biogenic features and could not be produced abiotically,” McKay adds.

Mars expedition probes the promise that Mars was a home address for past, possibly life today.
Credit: NASA

There are now a slew of papers that look at Curiosity images and some photos taken from the Mars Exploration Rover missions (Opportunity and Spirit) and say “these features look biotic to me,” McKay points out. “Very few people are convinced. These may or may not be biological.”

On Earth, McKay suggests, “such a claim of biological origin would be based on much better images, thin sections, etc. and backed by extensive analysis of the samples with multiple laboratory instruments. It is possible that someday a picture from Mars will be so good that its biological origin will be clear. Not yet,” he said.

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