Perseverance Maps Three Fluids Through Jezero’s Carbonate Rim

Perseverance’s SuperCam found igneous olivine on Jezero Crater’s inner rim, overprinted by three separate waters. Orbital maps had treated that carbonate as a lakeshore. An open-access SuperCam study of the Margin unit, published 21 September 2026 in Communications Earth and Environment, reconstructs carbon dioxide-rich groundwater, a later silica pulse below an old lake terrace, then hot fluorite-bearing veins in the same rocks.

Jezero sits inside one of the largest carbonate belts on Mars. What SuperCam recorded on the rim is a plumbing history, and that reading now reaches well beyond the crater.

Jezero’s Famous Carbonate Was Never a Lakeshore

NASA landed Perseverance in Jezero in February 2021 in part because orbiters saw a strong carbonate signal along the inner western rim, close to the old inlet valley. Mission planners treated the band, now called the Margin Unit, as a high-value sampling target because lake-shore carbonates on Earth can hold biosignatures. Candice Bedford, a research scientist at Purdue University and the study’s lead author, said the working idea before the rover arrived was that the carbonate seen from orbit formed from the lake that filled the crater.

Before we arrived at the Margin Unit, the main hypothesis, derived from orbital observations, was that the carbonate seen from orbit formed from interaction with the lake that existed in Jezero Crater. But now we know that this location became a sort of crossroads for aqueous systems.

Candice Bedford, research scientist, Purdue University

Purdue planetary scientist Briony Horgan, a coauthor of the new paper, had in 2020 used orbital spectra to tie deeper carbonate absorptions to the lake’s highest stand. A 2021 comparison of those deposits found the same orbital fingerprints inside and outside Jezero, which already hinted that the rim carbonates belonged to a regional olivine-bearing unit rather than a unique beach. SuperCam has now put a ground sequence on that argument. NASA’s Mars account called the result a signpost in the search for ancient life and pointed readers to a mission note on the Jezero water sequence the day the paper appeared.

Sometimes following the water can lead to surprising places💧

A new study of data from Perseverance reveals that rocks in Jezero Crater were shaped by a complex sequence of ancient lakes, groundwater systems, and hydrothermal fluids. 1/2 pic.twitter.com/HUFfQMHiYG

— NASA Mars (@NASAMars) September 21, 2026

SuperCam Shot More Than 185 Rocks Along the Rim

The instrument sits on Perseverance’s mast and can read a target’s chemical makeup from more than 20 feet, using a laser, spectrometers, and a camera built with Los Alamos National Laboratory and France’s CNES and IRAP. Bedford’s team used it on more than 185 bedrock targets across the Margin Unit, including ridges, pores, and veins. The rover entered the unit on sol 910, 11 September 2023, and the paper splits the traverse into four stretches.

THE MARGIN UNIT CAMPAIGN

1. 11 September 2023 (sol 910): Perseverance begins the Margin Unit campaign on the inner western rim.
2. Sols 911 to 1000: East Margin work at Hans Amundsen Memorial Workspace, Turquoise Bay, and Gnaraloo Bay, the lowest outcrops at about -2,423 m and -2,411 m.
3. Sol 931: SuperCam rasters the Point Cloates vein in the East Margin.
4. Sols 1021 to 1161: West Margin traverse between about -2,410 m and -2,352 m, including the Bunsen Peak workspace on sol 1069.
5. Sols 1192 to 1211: North Margin remote sensing beside Neretva Vallis and the Bright Angel formation.
6. Sols 1245 to 1280: High Margin from about -2,338 m to -2,159 m, where the olivine looks least altered.

Above about -2,350 meters, SuperCam saw slow-cooled, crystalline, olivine-rich rock with little water damage. That chemistry matches a magma body that cooled underground long enough for coarse grains to grow, then lost its cover to erosion. Farther down, toward the old lakebed, the same olivine is fractured and packed with carbonate and silica. The full elevation range in the paper, from -2,423 m in the East Margin to -2,159 m on the High Margin, is 264 meters of rock that recorded very different water histories.

Three Fluids Rewrote the Same Olivine

The team cannot yet date each pulse, but the order is clear from how the minerals cut one another. First came neutral-to-alkaline, carbon dioxide-rich fluids that turned olivine into Fe/Mg carbonate inside fractures. Softer rock later wore away and left the harder carbonate standing as ridges. Cluster analysis of the SuperCam points puts a carbonate-rich group at 17 percent of the dataset, with low silica and high magnesium, and those ridge shots are more than half carbonate.

THREE FLUIDS IN THE MARGIN UNIT

A high-silica cluster, 7 percent of the points and about 69.3 wt percent SiO2, appears only in the East and West Margin, below the second terrace mapped from orbit as a later lake level after a rim breach. Eleni Ravanis, a planetary scientist at the University of Hawaii at Manoa and a coauthor, said some Margin Unit rocks contain silica, that turning olivine into carbonate can leave silica behind, and that SuperCam sees more of that silica in rocks that sat below the water line. On Earth, the same olivine-water reaction can release hydrogen that some microbes use, and the carbonate and silica it leaves can hold traces of that chemistry.

The lake is still in the story. It is episode two, not the rock’s origin, and not the only fluid that made carbonate. Séítah, an olivine-rich unit on the crater floor that also sat below lake level, shows much less of this alteration and lacks the Margin Unit’s ridges, which the authors read as lower fracture permeability when groundwater was moving. Parts of the East Margin show possible cross-beds and rounding, and the North Margin at Pearce Canyon includes a clast-rich debris-flow layer, so the igneous body was locally reworked near Neretva Vallis and the western fan.

A 25-Centimeter Vein Carries the Heat

The last pulse is the one orbital maps could not see. At Point Cloates in the East Margin, SuperCam found a light-toned vein about 25 centimeters (10 inches) thick that runs several meters east and northeast. The laser points show calcium sulfate plus CaF2, fluorite, and the surrounding bedrock is too poor in calcium, sulfur, and fluorine for the vein fluid to have been a local leftover of the earlier carbonate event.

Fluorite can form as a minor phase in cold Martian groundwater below 13 C, but a vein this large matches hydrothermal fluorite on Earth. A 2024 SuperCam team abstract on the same target modeled 5 to 17 percent fluorite by weight at three of five laser points, with gypsum-to-anhydrite sulfates as the main fill. Jezero has a candidate volcanic edifice on its rim, igneous rocks on the crater floor, and the Syrtis Major volcanic plateau next door, so later volcanism-driven circulation is the authors’ preferred heat source.

That heat pulse is also the detail most often flattened into a life claim. The paper does not report organisms. It reports a late fluid that was hotter, chemically different, and younger than the lake. Hydrothermal systems can feed microbes on Earth, which is why the vein raises the astrobiology stakes of the cached cores, but the mineral sequence is the result, and the dates of each episode remain open.

Which Margin Unit Samples Sit in the Cache?

Perseverance did not only shoot the rocks. It abraded patches and sealed cores from the same interval, which is why the authors call the Margin Unit a primary target if those tubes ever reach Earth laboratories. The East Margin supplied the two cores tied directly to the SuperCam campaign in this paper, and the West Margin added a third at Bunsen Peak.

CORES AND ABRASION PATCHES

• Pelican Point: Core taken at Hans Amundsen Memorial Workspace in the East Margin, listed as the mission’s 22nd sample during sols 911 to 926.
• Lefroy Bay: Core taken at Turquoise Bay, where the orbital carbonate signal is especially strong.
• Comet Geyser: Core collected at the Bunsen Peak workspace on sol 1069 in the West Margin, after the Castle Geyser abrasion.
• Amherst Point and Bills Bay: Abrasion patches at HAMW and Turquoise Bay used for close-up PIXL and SHERLOC work on fresh rock.
• Old Faithful Geyser and Emerita Mesa: Later abrasions on the descent to Neretva Vallis and on the High Margin, the latter with no core.

Earth labs could separate lake water from groundwater in the silica, test whether the Point Cloates chemistry matches a volcanic heat pulse, and read carbon isotopes in the carbonate that SuperCam can only fingerprint from a few meters away. No return date is set, and no returned-sample result exists. Until those tubes are opened, the three-fluid order is a relative sequence, not a calendar.

The Nili Fossae Belt Now Looks Like Plumbing

Jezero is 45 km across and sits on the northwest side of the 1,200 km Isidis impact basin, northeast of Syrtis Major, in the Nili Fossae olivine-carbonate province. Bedford said the Margin Unit findings matter because Jezero sits inside one of the largest carbonate exposures on Mars, so the lesson reaches well beyond this crater. High-standing olivine on the High Margin shows almost no water alteration, which means the orbital carbonate that made this rim famous is concentrated where fluids could actually move, not spread evenly across a beach.

After 10 years working with Mars rovers, Bedford said, Mars constantly throws surprises, and it is very rare that things are as expected from orbital data. She hopes the work helps reshape how scientists view water in Jezero and across Mars, and that it helps reconstruct the changing climate and habitability of early Mars. The paper’s last line is drier and sharper: multiple groundwaters and lake exposure make the Margin Unit, and the samples Perseverance already took there, primary astrobiology targets.

Orbital carbonate maps will still mark Nili Fossae as a water province. They should no longer be read as a paleoshoreline by default. The rim NASA chose for a lake-shore core is a slow-cooled magma body that groundwater carbonated, a lake or later fluid silicified, and a hot vein cut last, and that stacked record is what the tubes in the cache actually hold.

Frequently Asked Questions

What Is the Margin Unit in Jezero Crater?

It is a narrow olivine- and carbonate-rich band along Jezero’s inner western rim, near the Neretva Vallis inlet, mapped from orbit as a strong carbonate strip and split by the rover team into East, West, North, and High Margin localities. The High Margin is an informal uphill extension of those orbital contacts, reaching about -2,159 m, and the paper excludes a separate olivine occurrence at Mist Park on the inner rim because that patch sits outside the continuous deposit and may include impactites.

Why Does Olivine Matter for Habitability Studies?

Olivine crystals lock in the temperature and chemistry of the magma that grew them, so they are clocks for the original rock, and when water later attacks those grains the reaction can yield hydrogen, carbonate, and silica. On Earth that hydrogen can feed microbes, and the carbonate and silica can preserve chemical traces of the fluid; SuperCam’s high-silica points, clustered around 69.3 wt percent SiO2, sit in the matrix around fractured olivine in the East and West Margin, which is why those cores are being treated as energy-and-preservation targets together.

How Does SuperCam Identify Rock Chemistry From a Distance?

A mast-mounted laser vaporizes a spot as small as a pencil point, and spectrometers in the rover body read the plasma, while a separate infrared spectrometer and a remote micro-imager record minerals and context; the mast head masses 12 pounds (5.6 kg), the body unit 10.6 pounds (4.8 kg), and the suite draws 17.9 watts. Spain’s University of Valladolid supplied a deck calibration target with 36 individual standards, which is how the team can turn those plasma lines into oxide weight percents for olivine, carbonate, and silica clusters.

When Did Perseverance Explore the Margin Unit?

The rover reached the unit on sol 910, 11 September 2023, ran the East Margin through sol 1000, the West Margin on sols 1021 to 1161, the North Margin on sols 1192 to 1211, and the High Margin on sols 1245 to 1280. Sol 931 is the Point Cloates raster, and sol 1069 is the Bunsen Peak workspace where the Comet Geyser core was taken, so the mineral sequence in the paper is tied to a documented stretch of the traverse rather than a single stop.

Could the Fluorite Vein Have Formed Without Hot Water?

Yes as a minor mineral: models allow fluorite to drop from cold Martian brines below 13 C, and SuperCam has seen CaF bands in other Jezero rocks and soils since early in the mission. The authors still favor a hydrothermal vein at Point Cloates because the fill is tens of centimeters thick, chemically unlike the host, and paired with Ca-sulfate in a geometry that on Earth tracks hot fluids through volcanic rock, a reading that will stay a hypothesis until a returned sample is dated and heated in a lab.