A recent analysis of the Sapphire Canyon mudstone core, drilled by NASA’s Perseverance rover in July 2024, adds new evidence to the ongoing search for life on Mars.
The study describes minerals and textures that – on Earth – are often linked to microbial activity. At the same time, the authors stress that nonbiological chemistry could also explain the signals.
“This finding by Perseverance is the closest we have ever come to discovering life on Mars. The identification of a potential biosignature on the Red Planet is a groundbreaking discovery, and one that will advance our understanding of Mars,” said acting NASA Administrator Sean Duffy.
“NASA’s commitment to conducting Gold Standard Science will continue as we pursue our goal of putting American boots on Mars’ rocky soil.”
The core was taken from a rock named “Chevaya Falls” in Neretva Vallis, an ancient river channel about a quarter mile wide that once fed Jezero Crater’s lake.
After drilling, Perseverance sealed the sample for possible return to Earth, where laboratory instruments can perform tests far beyond the rover’s onboard capabilities.
Inside the Martian mudstone
Lead author Joel A. Hurowitz of Stony Brook University (SBU) reports a fine-grained mudstone with circular reaction fronts informally called leopard spots, plus small nodules embedded in layered sediments.
Perseverance’s SHERLOC and PIXL instruments mapped organic carbon with phosphate, iron, and sulfur arranged in distinct, repeating patterns.
Two minerals stand out: vivianite and greigite. Vivianite is an iron phosphate, while greigite is an iron sulfide associated with iron and sulfur cycling in oxygen-poor settings.
These features show up in rocks that settled from water, not in lavas. The site on Mars lies along Bright Angel, a set of outcrops that preserve layers and veins consistent with slow changes after the mud was laid down.
Textures and chemistry point to low temperature reactions that reorganized elements already present in the mud.
That detail matters because low temperatures fit environments that life can handle, while very hot conditions tend to erase delicate signals.
Earth microbes leave similar traces
On Earth, vivianite often forms where microbes reduce iron in water-rich sediments and trap phosphorus in blue-green nodules.
Laboratory and field work document biologically mediated vivianite through extracellular electron transfer.
Greigite frequently appears where sulfate reducing bacteria drive chemistry in anoxic muds. In controlled experiments, greigite was detected only in live biotic setups after months of incubation.
The Martian rock shows rims rich in vivianite surrounding small cores enriched in greigite. That bullseye pattern matches a sequence of electron transfer reactions seen in some Earth sediments.
None of this proves metabolism happened in Bright Angel mud, but it shows the chemistry is right for it. That is a subtle point, and it is the reason scientists keep the language cautious.
Evidence of life on Mars
A potential biosignature is a feature that might have a biological origin but still needs more data to rule out nonbiological sources.
NASA points mission teams and the public to the Confidence of Life Detection, or CoLD scale, which encourages staged claims and independent checks.
The CoLD mindset is simple in practice. First detect a signal, then exclude contamination, then tackle alternatives, and only then talk about life on Mars with high confidence.
The Bright Angel work sits early on that ladder. It clears several necessary steps but leaves demanding tests for the lab.
Organic compounds can also arrive by meteorites or form without biology. The authors note those routes and describe how future analyses could tell paths apart.
Organic signals, but no certainty
The Mars rover detected organic carbon in several targets within Bright Angel. Reaction fronts rimmed with vivianite surround cores richer in greigite, a pairing consistent with iron and sulfur cycling recorded in the paper.
Mineral veins include calcium sulfate, while the mudstone remains fine-grained and low in magnesium and manganese. There is no sign of intense heating that would reset the rock or scramble tiny textures.
The outcrop sits within layered sediments deposited by water flowing through Neretva Vallis. That channel spans roughly a quarter mile across, which implies sustained flow into Jezero’s ancient lake.
Low temperature context favors life-compatible chemistry, but it does not require life. Abiotic organics and mineral reactions can sometimes copy the same shapes and signals.
Not proof, but potential life on Mars
“It’s not life itself,” said Nicky Fox, associate administrator for NASA’s Science Mission Directorate, stressing that this is a potential biosignature, not proof of life. The lead author echoed that caution.
“We cannot claim this is more than a potential biosignature,” said Hurowitz. Other officials also underscored the stakes and the limits.
“[But] this very well could be the clearest sign of life that we’ve ever found on Mars,” said Sean Duffy, acting NASA administrator.
Caution is not hedging for its own sake. It is how science avoids false alarms when the question is this important.
That would extend Mars’s habitability into a window when this part of Jezero was still wet.
If abiotic paths made the same pattern, the rock still records redox organization of iron, sulfur, and phosphorus in Martian mud. That is a window into how the planet cycles key elements without biology.
Either outcome matters for the bigger story. Mars did not just dry out, it changed its chemistry over time, and these samples let researchers track that change layer by layer.
The work also flags what to measure next. Isotopes, microtextures, and the exact structure of carbon in the core can separate metabolic signatures from chemical lookalikes.
Search for life on Mars moves forward
The authors lay out lab experiments and field analogs on Earth to test whether nonbiological reactions can reproduce these textures and mineral pairings.
They also point to analyses that require the sample in a clean Earth lab, including isotope ratios that biology tends to skew.
Sample return planning will shape how fast those tests happen. Meanwhile, the rover can keep mapping where these features cluster and how they relate to other rock units nearby.
PIXL and SHERLOC have shown enough sensitivity to guide that search. The pairing of elemental maps and Raman detections gives a consistent picture that can be applied to other outcrops.
As new targets are logged, the CoLD framework will help communicate progress without getting ahead of the data. That is how a potential biosignature becomes a result people can trust.
By Eric Ralls
Earth.com
