The Jezero Crater delta, a well-preserved ancient river delta on Mars. New research suggests sedimentary rocks made of compacted mud or clay, like those found in the Jezero Crater delta, are the most likely to contain microbial fossils.

NASA’s Perseverance Mars rover is busy at work exploring Jezero Crater.

“From orbit, this crater shows all the promising signs of a place that was likely friendly to life in the distant past,” explains a JPL website dedicated to the mission.

“The rover’s goal is to study the site in detail for its past conditions and seek the very signs of past life. Its mission is to identify and collect the most compelling rock core and soil samples, which a future mission could retrieve and bring back to Earth for more detailed study,” adds the website.

Signs of ancient life on Mars could be preserved in layered rocks like those shown in this illustration of NASA’s Perseverance rover in Jezero Crater.
Credit: NASA/JPL-Caltech

Indeed, imagery being taken by the rover is first-rate – but are we close to detecting past life on the Red Planet?

Compelling evidence

“The best case scenario for Perseverance finding compelling evidence of past life is the identification of biomediated structures that can be observed with cameras,” said Steve Ruff, a leading planetary geologist at Arizona State University in Tempe, Arizona.

NASA’s Mars Perseverance rover acquired this image on June 17, 2022 of the area in front of it using its onboard Front Left Hazard Avoidance Camera A.
Credit: NASA/JPL-Caltech

Ruff said that features like stromatolites, which occur at scales of millimeters to meters in size are candidates. 

“They form in standing water where microbial mats are mineralized, building up layers of biology and geology that can be preserved for billions of years, like found in ancient rocks on Earth,” Ruff told Inside Outer Space.

Huge win

If something like that were found by Perseverance and then sampled, this would be a huge win for the mission, Ruff said. “The sample would still need to be subjected to a battery of measurements in labs on Earth to really prove that microbes played a role.”

NASA’s Mars Perseverance rover acquired this image on June 10, 2022 using its onboard Right Navigation Camera (Navcam) located high on the rover’s mast and aids in driving.
Credit: NASA/JPL-Caltech

In terms of that material rocketed back to our planet, the risk to Earth is nil, Ruff said. “The ‘bugs’ that contributed to a stromatolite would have been dead for billions of years, since the time there was a lake in Jezero, which is when such structures could have formed. Long dead microbes from Mars, at best, are now just degraded organic matter, probably the equivalent of tar-like compounds. So zero risk of infecting Earth.”

Scientific triumph

The still-in-work Mars Sample Return mission was envisioned to go after a scenario like this, said Ruff, “finding evidence of long dead Martian microbes in samples returned to Earth,” he said.

Bottom line: “This scenario would be a scientific triumph and change our understanding about the potential for life beyond Earth,” Ruff said. “A second data point would be confirmed.”

To support the campaign to return samples from Mars, multiple robots team up to ferry to Earth select samples that are now being gathered by NASA’s Mars Perseverance rover.
Credit: NASA/ESA/JPL-Caltech

Long-sought mission

NASA is pressing ahead on the agency’s long-sought vision of rocketing back to Earth pieces of Mars. A Mars Sample Return (MSR) campaign is now being orchestrated by NASA and the European Space Agency, a multi-spacecraft enterprise.

This fast-paced, multi-billion dollar endeavor is dedicated to hauling back planetary particulars from the Red Planet to our world in the early 2030’s.

Christopher Carr, an assistant professor within Georgia Institute of Technology’s School of Earth and Atmospheric Sciences once worked on Mars Sample Return at NASA’s Jet Propulsion Laboratory in the summers of 1999 and 2000.

“My first reaction after reading a stack of slide presentations was, you’ve got to be kidding, this is so complicated,” said Carr. “It turns out the complexity was and is highly driven by the requirement to have a low probability of releasing even a very small particle of Mars material into the Earth biosphere.”

Departure of Mars Ascent Vehicle carrying Mars samples.
Credit: NASA

Carr added that even back then the technology existed to provide simultaneous protection of precious samples and protection against release of Mars particles using the right series of isolators with differential pressures. 

“This is the kind of approach used, for example, in pharmaceutical manufacturing. It is not cheap and will require a specialized facility and specific work practices,” Carr said. This planetary protection burden he views as reasonable for legal, ethical, and moral reasons until we learn more about the risks, he advises.

Ultimately, Carr suspects such extreme measures will be unnecessary, in part because the surface of Mars today is uninhabitable to life as we know it. To date, he knows of no overlap between conditions required for replication and conditions present on the surface of Mars.

Uncontrolled mass experiment

“In contrast,” Carr continues, “there is a large overlap in the temperatures and pressures in the subsurface of Mars and the range of inhabited environments on Earth,” Carr said. “Earth also continues to receive Mars meteoritic material, although most of this arrives in the form of small particles that have been in space long enough to be sterilized.”

Mars: Home for past, perhaps present-day life? Credit: NASA

Carr tags the COVID-19 pandemic and variants as “an uncontrolled mass experiment in evolution” with a virus known to be hazardous to many and deadly to some. “In that context, the back contamination [from Mars] issue can almost seem like an academic exercise, and yet we do owe it to all humans to take reasonable precautions,” he said.

Safeguard our planet

Similar in view is astrobiologist Dirk Schulze-Makuch from the Technical University Berlin and the School of the Environment at Washington State University.

In his opinion, the danger from any microbes on Mars should be extremely small, “because there are naturally meteorites landing from Mars on Earth, and this has been going on for eons,” Schulze-Makuch notes.

“On the other hand,” Schulze-Makuch says, “Earth is our only biosphere and life line, so we have to do everything we can to safeguard our planet and its biosphere from any, even very small, risk,”

To ensure this, the construction of a specially designed Sample Receiving Facility on Earth to receive samples from Mars, Schulze-Makuch concludes, “should have already begun or at least start now right away.”

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