Martian microbes?: A study reinforces the theory of possible past life on Mars.

Just a year ago, NASA revealed the discovery of an " intriguing rock " with the most promising signs yet discovered of possible ancient life on Mars. These weren't, of course, dinosaur footprints or fossils of giant animals like those we find on Earth; they were subtle traces of what could have been the colonization of that rock by microbes that lived there billions of years ago, when the Red Planet wasn't the frozen desert we know today, but a world where water flowed freely over its surface.

That discovery made by the Perseverance rover in Jezero Crater opened the door to confirming what many experts believe is almost certain: that life, at least in the form of microorganisms, once existed on our neighbor. Now, a study published in Nature bolsters that theory, pointing out that subsequent studies are compatible with ancient biological processes.

Discovered in July 2024, the first in-situ analyses conducted by Perseverance's instruments found tiny blue and greenish nodules embedded in rocks billions of years old. These markings, dubbed "poppy seeds" and "leopard spots," contain phosphorus and sulfur minerals bound to iron, specifically vivianite and greigite, substances that on our planet typically form in low-temperature aquatic environments. And, in many cases, with the help of microbes.

“It’s the most puzzling, complex, and potentially important rock Perseverance has investigated so far,” Ken Farley, Perseverance project scientist at Caltech in Pasadena, noted a year ago. “On the one hand, we have our first convincing detection of organic material, distinctive colored flecks that indicate chemical reactions that microbial life could use as an energy source, and clear evidence that water, necessary for life, once passed through the rock. On the other hand, we haven’t been able to determine exactly how the rock formed and to what extent nearby rocks may have heated the rock and contributed to these features,” he admits.

The discovery was made in the Bright Angel Formation in the Neretva Valley, on the western rim of Jezero Crater. There, Perseverance drilled and analyzed shales—fine-grained sedimentary rocks—that revealed a surprising combination: organic compounds and reduced minerals occurred together, while the most oxidized areas were virtually devoid of organic matter.

"It's a very clear inverse relationship: where there is more vivianite and greigite, there are more organic compounds and less oxidation of the rock," the researchers explain in the journal 'Nature'.

The team proposes two hypotheses: on the one hand, that these transformations occurred purely chemically, with organic molecules acting as reducing agents in an aqueous environment (i.e., without the intervention of any living being, as occurs on Earth); or that microorganisms capable of "breathing" iron or sulfate existed, as occurs in lakes and sediments on our planet, leaving behind minerals that are now considered potential biosignatures (signs of life).

For now, this study doesn't settle the question of whether life existed on Mars. What it does demonstrate is that a complex and varied chemistry developed on the red planet billions of years ago, with water, minerals, and organic compounds interacting over long periods.

The scientific community points out that not much more can be learned about this intriguing rock with the tools Perseverance has: everything that could be analyzed has already been done. However, this rover was also designed to take samples of the Martian terrain, something it also did in this case.

The idea, at least initially, was that all the tubes collected by Perseverance would be recovered and brought back to Earth for analysis in our laboratories thanks to the Mars Sample Return mission, a NASA-ESA collaboration scheduled to launch later this year. However, the project was already in doubt under the previous administration, which explained that its budget had ballooned to $11 billion (about €10.14 billion) and that it needed to be completely rethought to cut costs and, at the same time, ensure the launch date wouldn't be pushed back into the next decade.

The current administration, headed by Donald Trump, has already expressed support for scrapping the mission and focusing on the goal of landing humans directly on the Martian surface. However, the mission is still up in the air. And so are the promising Martian samples.