What NASA says Perseverance found in Jezero’s ancient river
NASA just raised the stakes in the hunt for past life on Mars. At a September 10, 2025 briefing, the agency said its Perseverance Mars rover has identified potential biosignatures inside an ancient rock collected from the floor of Jezero Crater—an area long suspected to have hosted a lake and river delta billions of years ago.
The rock, nicknamed Cheyava Falls, was sampled in July 2024 from Neretva Vallis, a dry river channel that once funneled water into Jezero. It’s an arrowhead-shaped slab, roughly 3.2 feet by 2 feet, and crucially, it’s sedimentary—built from layers of clay and silt that settled out in calm water. On Earth, that kind of fine-grained material is a prime place to trap and preserve traces of microbes.
Perseverance threw its top tools at the target. PIXL, a micro X-ray spectrometer, mapped the elemental chemistry across the rock at the scale of a grain of sand. SHERLOC, a deep ultraviolet Raman and fluorescence instrument on the rover’s arm, scanned for organics and identified where they sit within the mineral fabric. Together, the instruments spotted colorful speckles and patterns where organic molecules, sulfur, iron oxides (think rust), and phosphorus cluster in ways that, at first pass, look a lot like energy-rich niches used by microbes on Earth.
Joel Hurowitz of Stony Brook University, the lead author on the forthcoming paper, framed the finding plainly: the mix of chemicals in this unit—nicknamed "Bright Angel" by the team—would have been an inviting buffet for simple metabolisms. Organics provide carbon; sulfur and iron offer redox gradients; phosphorus is central to energy transfer in cells. Now imagine those ingredients preserved in clay, a natural vault that shields fragile compounds from radiation and heat. That’s why this rock matters.
Nicky Fox, who leads NASA’s Science Mission Directorate, called the result a proof point for the mission’s strategy: send a rover with lab-grade tools to where the water once pooled, interrogate the rocks in fine detail, and bank the most promising samples. With this dataset now moving into peer review, NASA is opening it up to outside scientists to test every alternative explanation they can think of.
But no one at the briefing was ready to plant a flag and declare past life. Bruce Betts, chief scientist at The Planetary Society, put it in perspective: this is a step, not a finish line. The patterns look exciting, but Mars has a habit of fooling us. The infamous 1996 meteorite ALH84001 taught that lesson: features first hailed as fossil bacteria later found solid non-biological explanations.
Perseverance’s project scientist, Katie Stack Morgan, said the team pushed its toolkit to the edge: “We basically threw the entire rover science payload at this rock.” The data are rich, but there’s only so much even a sophisticated rover can do from millions of miles away with instruments the size of shoeboxes.
That’s where Mars Sample Return comes in. Perseverance has now cached 30 rock and regolith samples, and the rover is still carrying six empty tubes. The plan—subject to budget and engineering realities—is to fly some of these cores back to Earth in the 2030s for high-precision tests no rover can run: isotope geochemistry, nanoscale imaging, and contamination screening under ultra-clean conditions. If the signals in Cheyava Falls are biological, that’s where the proof will come from.
How to read a 'potential biosignature'—and what comes next
“Potential biosignature” is careful language. It means a pattern or chemical association consistent with life, but not unique to life. The Cheyava Falls sample ticks several boxes at once: organics are present, elements like sulfur and iron are spatially linked to them, and the host rock is a fine-grained sediment likely laid down in water. On Earth, microbes frequently exploit sulfur and iron chemistry for energy, especially in low-oxygen settings like lake bottoms and delta muds.
Here’s why this particular environment raises eyebrows. Jezero Crater was once a lake, fed by rivers that fanned out into a delta. In those calm waters, clay minerals formed and trapped sediments layer by layer. Fine silt and clay preserve delicate chemical gradients and microstructures far better than coarse sands. They also protect organic molecules from being scrubbed away or baked to oblivion during later geologic events. If Mars ever harbored microbes, a quiet delta mudstone is exactly where you’d expect to find their fingerprints.
PIXL’s role is to pinpoint the elements—carbon, sulfur, iron, phosphorus—and map how they are distributed within tiny patches of the rock. SHERLOC adds context by using deep ultraviolet light to make certain organic compounds fluoresce and to identify minerals through Raman scattering. When the two instruments agree—say, they both focus on a grain boundary where organics and iron oxides co-locate—you start to see a story emerge about ancient microenvironments.
But Mars is also a master of abiotic chemistry. Non-biological processes can create similar signals. Volcanic rocks altered by water can enrich sulfur and iron. Organics can arrive from meteoritic dust or form through simple atmospheric reactions driven by sunlight. Later, groundwater can shuffle elements around, overprinting the original scene. That’s why this discovery lives in the zone of “compelling, but not yet conclusive.”
Consider a few rival explanations scientists will now test:
- Abiotic organics: Carbon-bearing molecules can come from meteorites or be cooked up by ultraviolet light in Mars’ thin atmosphere, then trapped in clays without life ever being involved.
- Water-rock reactions: Interactions between basaltic rock and water can generate iron oxides and concentrate sulfur, building redox gradients that look biologically useful but formed on their own.
- Diagenesis: After the sediments were laid down, later fluids could have migrated through, moving elements and organics and creating patterns that mimic biology.
- Radiation and oxidation: Mars’ surface is bombarded by radiation and oxidants that can alter organic molecules, changing their signatures in ways that complicate interpretation.
The way to sort this out is through context and scale. On Earth, the gold standard for ancient life is a convergence of evidence: chemistry that makes sense, structures that fit biology, and isotopic ratios that are hard to get without metabolism. Perseverance can handle the first two in a limited way; isotopes and ultrastructures at the nanometer scale require Earth labs.
There’s also the strategic question of where Cheyava Falls sits in the bigger Jezero story. The team’s naming scheme—Cheyava Falls, Bright Angel, and other Grand Canyon nods—marks out units and outcrops across the river channel and delta. If multiple rocks in this unit show the same chemical fingerprints, the case strengthens. If the signatures appear only in one place, that might point to a localized process unrelated to life. That’s why the rover’s abrasion patches, mosaics, and repeated instrument passes matter: breadth plus depth beats a one-off hit.
We’ve seen this arc before. The ALH84001 meteorite made headlines in 1996 for worm-like features and unusual chemistry that looked biological. Over years of work, researchers showed how simple heating and mineral growth could mimic those shapes. The takeaway wasn’t that Mars couldn’t host life; it was that you need multiple independent lines of evidence to cross the bar.
Perseverance’s mission was built around that idea. Its driving orders are to read the story of water in Jezero, assess habitability, and collect a suite of samples diverse enough to answer big questions later. That’s why its cores include igneous rocks to date the crater’s history, mudstones from quiet waters, and sulfate-rich layers that record drying episodes. Cheyava Falls adds a candidate signal of past energy sources—the kind microbes could have tapped if they were there.
There’s also a time dimension. Jezero’s lake likely filled during the Noachian to early Hesperian period, more than 3 billion years ago, when Mars was warmer and wetter. Rivers carved Neretva Vallis and carried fine sediments into the crater. The clays that formed then are known on Earth to adsorb organic molecules and keep them intact for eons. If Perseverance has indeed found organics nestled in those clays alongside sulfur and iron, that’s a snapshot of a potentially habitable setting from very deep time.
So what now? First, outside teams will comb the data. NASA’s release means laboratories worldwide can compare the rover’s spectra to their own standards and analog samples. Expect papers that test whether the organics match meteoritic signatures, whether the mineral associations track known abiotic pathways, and whether the observed textures line up with microbial mats or with purely chemical precipitates.
Second, the mission will keep triaging targets. With six sample tubes left, every drill becomes a strategic choice. Do you double down on the Bright Angel unit to see if the patterns repeat? Or do you push to new exposures where different minerals could lock in complementary clues? Perseverance’s abrasion tool—used to grind fresh surfaces for clean measurements—will continue to be the scouting step before committing a precious tube.
Third, the community will thread this result into the broader Mars exploration plan. Europe’s Rosalind Franklin rover aims to drill below the radiation-processed surface to look for preserved organics underground. Orbiters will keep mapping mineral hotspots from above. The synergy is obvious: rovers find the context, orbiters guide the path, and sample return settles the arguments.
None of this downplays the moment. A Martian rock, lifted from an ancient riverbed, now holds chemical patterns that look like the scaffolding of simple life. That doesn’t mean life was there. It does mean Mars keeps meeting the tests we set for habitability: water, energy gradients, and carbon chemistry in the right rock types. Every time that trifecta shows up, the case for a once-livable world gets a little stronger.
NASA’s caution is not hedging; it’s the discipline that turns clues into knowledge. If Cheyava Falls’ signals are biological, the proof will be extraordinarily difficult, which is why bringing samples home is non-negotiable. If they’re not, we’ll learn just as much about how Mars cooks up life-like chemistry without biology. Either way, the science moves forward.
For now, the rover keeps rolling. Thirty samples down, six to go, and a delta’s worth of questions still sitting out there in the rocks.
