Is This Discovery the Closest We’ve Come to Finding Life On Another Planet?

Micah Hanks·
Perseverance life on other worlds
Credit: NASA/JPL-Caltech

Welcome to this edition of The Intelligence Brief… This week, NASA’s Perseverance rover has uncovered compelling chemical signatures in Jezero Crater’s Bright Angel formation that scientists say could represent potential biosignatures of ancient Martian life. In our analysis, we’ll be looking at 1) how fine-grained mudstones rich in organic carbon, sulfur, and oxidized iron may have provided energy sources for microbes, 2) the detection of unusual mineral features such as “poppy seeds” and “leopard spots” tied to microbial metabolisms on Earth, 3) the debate among researchers over whether the evidence points to biological or purely geological processes, and 4) why bringing core samples back to Earth is key to determining whether Mars once hosted life.

Quote of the Week

“We have to seriously consider the possibility that they were made by creatures like bacteria living in the mud in a Martian lake more than three billion years ago.”

  – Michael tice, Ph.d., Texas A&M geobiologist/astrobiologist 

RECENT NEWS from The Debrief

Discovery at Jezero Crater Raises Questions About Ancient Life on Mars

Last week, NASA announced that the last year, the Perseverance rover had uncovered compelling chemical signatures in a region of Jezero Crater known as the Bright Angel formation, which raises the possibility that ancient Martian rocks preserve evidence of microbial activity.

The findings, which were featured in a study that appeared in Nature, point to organic carbon and mineral structures that resemble processes often driven by life on Earth.

Writing about the discovery last week for The Debrief, our prolific reporter Ryan Whalen wrote that the Bright Angel formation, which is found along the Neretva Vallis channel, yielded samples which, following analysis of the local rocks, “revealed the presence of clay and silt, excellent materials for preserving ancient microbial life, along with high amounts of organic carbon, sulfur, oxidized iron, and phosphorus.”

“The combination of chemical compounds we found in the Bright Angel formation could have been a rich source of energy for microbial metabolisms,” according to Joel Hurowitz, lead author of the Nature study, who cautioned that “just because we saw all these compelling chemical signatures in the data didn’t mean we had a potential biosignature. We needed to analyze what that data could mean.”

So what exactly do the findings by Hurowitz and his team indicate, and could this be the best evidence we’ve found to date of the existence of life on another planet, albeit at some point in its ancient past?

The Case for Microbial Life on the Red Planet

At the heart of the discovery are the fine-grained mudstones from which the samples were collected by Perseverance, which are rich in oxidized iron, phosphorus, sulfur, and most notably organic carbon. Organic carbon can form in several ways—one method is abiotic formation through sources like meteorites. However, the position of the sample and its proximity to redox-sensitive minerals suggest a potential energy source for early microorganisms.

Researchers emphasize that the evidence is not proof of past life, but it meets NASA’s criteria for “potential biosignatures” worthy of further investigation.

Micahel Tice, Ph.D., a geobiologist and astrobiologist in the Department of Geology and Geophysics at Texas A&M University and a co-author of the recent study, said that the samples the team examined “showed evidence of chemical cycling that organisms on Earth can take advantage of to produce energy.” This prompted a closer look, which, according to Tice, revealed “things that are easy to explain with early Martian life but very difficult to explain with only geological processes.”

Promising Signs of Biology

Perseverance’s SHERLOC and PIXL spectrometers were able to detect nodules and reaction fronts, nicknamed “poppy seeds” and “leopard spots”, enriched in ferrous iron phosphate (likely vivianite) and iron sulfide (likely greigite). Because these minerals normally form in low-temperature, water-rich environments, they are often tied to microbial metabolisms on Earth. In the case of the Martian stone in question, the arrangement of these features suggests they may have formed through redox cycling of iron and sulfur—a process that microbes exploit to generate energy.

Even more intriguing to the research team, at a site dubbed “Apollo Temple,” Perseverance succeeded in detecting an even stronger signal of organic carbon alongside the iron- and sulfur-bearing minerals. “This co-location of organic matter and redox-sensitive minerals is very compelling,” Tice noted. Still, he cautioned that “organic” in this context does not necessarily mean biological, only that carbon-carbon bonds are present.

According to Tice, Hurowitz, and their colleagues, one of two possible scenarios can likely explain the team’s findings: either the chemical reactions were driven by purely geological processes, or microbial life had to have been present to influence the unique mineral formations.

And, since many sulfur-related features usually require high temperatures (which the rocks do not appear to have experienced in this case), the biological explanation remains plausible.

Microbes on Mars, or Something Else?

Since the news broke last week, several experts have pushed back on the notion that biology could explain the recent discoveries at Jezero crater.

“Maybe the organic molecules we’ve been seeing on Mars are not produced by biological processes at all,” wrote Dirk Schulze-Makuch, a professor for planetary habitability and astrobiology at the Technical University of Berlin, Germany, in a recent commentary at Big Think. Noting that small organics can often appear as a result of both nonbiological and biological chemistry, Schulze-Makuch asked whether “the compounds we’re detecting are the breakdown products of larger organic molecules (which could be signs of past life), or simply the durable products of nonbiological chemistry?”

“Fifty years after Viking, it’s time to launch another life-detection mission,” Schulze-Makuch added, “so we don’t have to keep guessing about the evidence we’ve gathered so far.”

Much to Schulze-Makuch’s point, Tice and the team behind the recent study have also advocated for the sample’s return to Earth, where it can be properly studied.

“Bringing this sample back to Earth would allow us to analyze it with instruments far more sensitive than anything we can send to Mars,” Tice said in a statement last week. “We’d also be able to perform more tests to determine the highest temperatures experienced by these rocks, and whether high-temperature geochemical processes might still be the best way to explain the potential biosignatures.”

Beyond just geochemistry, if the sample is returned to Earth in the future, scientists could study isotopic signatures, fine-scale mineralogy, and even search for the presence of any potential microfossils.

For now though, while the Bright Angel discoveries provide one of the clearest windows yet into Mars’ watery past, and highlight the tantalizing possibility that microbial life at least may once have thrived in the planet’s ancient lakes, we are still a good way from finding irrefutable evidence of life on other worlds.

That concludes this week’s installment of The Intelligence Brief. You can read past editions of our newsletter at our website, or if you found this installment online, don’t forget to subscribe and get future email editions from us here. Also, if you have a tip or other information you’d like to send along directly to me, you can email me at micah [@] thedebrief [dot] org, or reach me on X: @MicahHanks.

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