NASA Hunts Jezero Spots on Scotland’s Stoer Cliffs

In the summer of 2026, NASA scientists hiked tidal cliffs in Scotland to read 1.2-billion-year-old reduction spots the way Perseverance reads Jezero Crater. The Stoer formation holds lake and river rocks from a world before land plants, plus known microbial remains, a pairing that is hard to find on Earth and useful for rover data that still cannot settle life.

Those Scottish samples are now in labs. The Mars cores that raised the question are not.

They Had to Beat the Tide to Reach the Rocks

NASA’s Goddard Instrument Field Team, based at the agency’s Goddard Space Flight Center in Greenbelt, Maryland, worked the coasts and cliffs of the Clachtoll region with handheld instruments on their backs. Climbs were timed so the group could reach sites between high tides and leave while the slopes were still dry, a tight window in the wet Scottish Highlands.

At the Bay of Stoer the water level changes by 11 to 15 feet with the tides, and a tidepool sits on top of the working cliff. Field lead Mike Thorpe, a sedimentary and planetary geologist at Goddard, stood on the far edge looking for gray-green reduction spots in red sandstone while Amy McAdam and Fuen Cañadas Blasco, also of Goddard, prepared to bag rock. Adrian Broz of Purdue University worked the same face.

The spots are pale patches where iron in the red rock has been chemically reduced. On Earth they sometimes record microbes interacting with sediment, and they can form in other ways too, which is the whole problem the trip was built to probe. Deputy field lead Hemani Kalucha of Goddard later held reduction-spotted samples at Clachtoll Bay with Broz and Cañadas Blasco. The group also stopped at Split Rock.

NASA’s solar system account put the field photos out on September 29, 2026, the same day the agency posted the expedition note, stating that Perseverance had found greenish reduction spots and that spots like these can be formed by microbes.

Searching for clues about Mars’ ancient past… right here on Earth.

Our Perseverance rover found greenish "reduction spots" on Mars. On Earth, spots like these can be formed by microbes, so NASA scientists headed to Scotland to take a closer look.https://t.co/Uk88kue5yT pic.twitter.com/D1mjOwt5ku

— NASA Solar System (@NASASolarSystem) September 29, 2026

That line is cleaner than the papers. The Scottish cliffs are a calibration site, a place to watch how known life, and ordinary chemistry, both leave marks in old red rock.

Cheyava Falls Is Still on Mars

The Scotland work follows a September 10, 2025, NASA release on potential biosignatures in Sapphire Canyon, a core Perseverance drilled from a rock named Cheyava Falls in Jezero Crater. A potential biosignature, in the agency’s wording, might have a biological origin and still needs more data before anyone can say life was or was not there.

Sapphire Canyon and the Leopard Spots

Perseverance found Cheyava Falls in July 2024 in the Bright Angel formation, rocky outcrops on the edges of Neretva Vallis, an ancient river valley a quarter-mile (400 metres) wide that once fed Jezero’s lake. The arrowhead-shaped rock measures 3.2 feet by 2 feet (1 metre by 0.6 metres). PIXL and SHERLOC saw colourful spots arranged as reaction fronts the team nicknamed leopard spots, carrying the signatures of vivianite, a hydrated iron phosphate, and greigite, an iron sulfide.

Joel Hurowitz, a Perseverance scientist at Stony Brook University and lead author of the 2025 Nature paper on redox-driven mineral and organic associations, said the Bright Angel chemistry could have fed microbes. He also said seeing those signatures was not enough, on its own, to call the rock a potential biosignature.

The combination of chemical compounds we found in the Bright Angel formation could have been a rich source of energy for microbial metabolisms. But 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.

Joel Hurowitz, Perseverance scientist, Stony Brook University, NASA release

Vivianite turns up on Earth in sediments, peat, and around decaying organic matter. Some microbes can make greigite. Heat, acid, or organic binding can make the same minerals without life. Bright Angel does not show evidence of high temperatures or acidic conditions, and it is still unknown whether the organics present could have driven the reactions cold. Katie Stack Morgan, Perseverance’s project scientist at the Jet Propulsion Laboratory, said abiotic explanations look less likely given the paper and still cannot be ruled out.

Astrobiological claims, particularly those related to the potential discovery of past extraterrestrial life, require extraordinary evidence.

Katie Stack Morgan, Perseverance project scientist, NASA Jet Propulsion Laboratory

Sapphire Canyon was one of 27 rock cores Perseverance had collected by that September 2025 release, after landing in February 2021. The core is still on Mars. In an April 2026 status update, NASA’s Science Mission Directorate told the agency’s inspector general that funding for the Mars Sample Return program was not included in fiscal 2026 appropriations.

Green Spots the Rover Could Not Touch

A separate Bright Angel member, Mount Spoonhead, shows drab green, millimetre-scale putative reduction spots next to light-toned calcium sulfate. Broz, Kalucha, and colleagues described those green reduction spots in Bright Angel at the 2025 Lunar and Planetary Science Conference. Mastcam-Z maps show the green patches are poor in ferric iron relative to the red host. One measured spot is about 2 millimetres across, with dark cores about 0.1 to 0.5 millimetres.

Engineering limits kept the rover from targeting the green spots, so their composition is still unknown. No drill core was taken at Mount Spoonhead. If those spots match terrestrial reduction spots, the dark cores could hold metals, iron sulfides, iron phosphates, organic matter, or some mix of those. The same redox story may link them to Cheyava Falls. The rover could not finish the test on Mars, which is why the same authors later stood on Scottish red beds.

FROM JEZERO TO CLACHTOLL

1. February 2021: Perseverance lands in Jezero Crater.
2. July 2024: The rover finds leopard spots on Cheyava Falls in Bright Angel and later documents green spots at Mount Spoonhead.
3. March 2025: Broz and Kalucha present the green reduction spots and compare them with terrestrial red beds.
4. September 10, 2025: NASA and a Nature paper describe Sapphire Canyon as a potential biosignature.
5. April 2026: NASA tells its inspector general that Mars Sample Return funding is not in the fiscal 2026 appropriations.
6. Summer 2026: The Goddard team samples reduction-spotted Stoer rocks at Clachtoll and the Bay of Stoer.

Perseverance was still working in September 2026 west of the Jezero rim, in an area the mission calls Lac de Charmes. The rover keeps driving. The sealed tubes do not come with it.

Why the Stoer Formation Is a Rare Match

Mars is dry now, yet both planets carry layered mudstones and siltstones rich in clay. Stoer adds something Jezero has not proven: a documented microbial record from 1.2 billion years ago, before land plants covered Earth’s surface. NASA’s field note calls that overlap hard to find and ideal for people who have to interpret rover spectra and textures from a planet they cannot yet unpack in a fume hood.

The north-west Highlands already had a life-on-land debate before anyone packed a Goddard kit. Organic-walled microfossils, microbial mats, and microbially induced sedimentary structures sit in Torridonian rocks, including Stoer. A 2010 study in the International Journal of Astrobiology reported reduction spots with vanadium-rich mica cores in these Mesoproterozoic red beds and treated them as a possible deep-biosphere signal from a time when terrestrial fossils are scarce. Later work has argued over whether some Stoer carbonates are true stromatolites or lookalikes, which is the same biogenicity fight now aimed at Jezero.

THE STOER-JEZERO MATCH

That table is the reason Clachtoll was worth the tide tables. The Scottish rock is old, wet in origin, spotted, and already known to have hosted microbes. The Martian rock is older, wet in origin, spotted, and still only a candidate. If you cannot ship Jezero home, you ship Stoer to the instruments Jezero never had.

The Jezero Spot Team Walked the Same Cliffs

The roster is not a random analog crew. Broz, first author on the Mount Spoonhead green-spot abstract, is in the Bay of Stoer photographs looking for reduction spots. Kalucha, co-lead on that same abstract, is deputy field lead and appears in the Clachtoll sample shot. Alex Jones, another Bright Angel co-author, is in the Split Rock group picture. Hurowitz, lead author of the Nature paper, is based at Stony Brook University, one of the collaborating institutions, which is also where Thorpe earned his doctorate.

Thorpe joined Goddard in July 2022 after a postdoctoral fellowship at NASA’s Johnson Space Center in Houston, where he was later contracted as a Mars Sample Return scientist at Johnson. His work follows sediment from mountains to lakes, source to sink, on Earth and on Mars. McAdam, the Goddard geochemist he has called his mentor, was on the Scottish cliff with him. The field lead who used to plan for returned Mars cores was bagging the Earth rocks that have to stand in for them.

Johnson Space Center, the University of Glasgow, the University of Maryland, Purdue University, Stony Brook University, and the University of Cambridge collaborated. Dina Bower, Jessie Wilde, S. J. Ralston, William McMahon, David Davis, Zachary Dickeson, and photographer Pedro Cota round out the named Split Rock line-up. Glasgow’s presence puts local Torridonian expertise on a trip that could otherwise have read as a NASA fly-in.

Reduction Spots Can Form With or Without Life

Terrestrial red beds are full of bleached spheroids with dark, metal-rich centres. John Parnell and colleagues have argued that metalliferous cores in reduction spheroids record iron-reducing microbes at depth, because the round shape implies growth after the sediment was already compacted, and because vanadium, uranium, copper, and selenium all precipitate when those bacteria switch electron acceptors. They also flagged the colour contrast as a more realistic Mars target than fossil cells.

Broz’s Jezero abstract is careful in the other direction. On Earth, microbes often take part in the iron reduction that turns a patch of red bed green. Decaying organic matter can create a local reducing pocket without live cells doing the work at that moment. Sulfur and iron can also reduce ferric iron with no biology in the loop. Mount Spoonhead’s red matrix had no detectable organics in the rover data, unlike Cheyava Falls, so later oxidation may have stripped organics there and left them in the leopard-spot rock.

HOW REDUCTION SPOTS CAN FORM

• Iron-reducing microbes: Bacteria use ferric iron as an electron acceptor and bleach a rounded patch, sometimes concentrating vanadium or other metals in a dark core.
• Dead organic matter: Local decay soaks a pocket of sediment and reduces iron without a living colony still sitting in the spot.
• Sulfur-iron chemistry: Abiotic reactions between sulfur and iron can drain ferric colour from red beds on their own.
• Wet-dry soils: Broz notes filamentous and oblong green patches that may match redoximorphic features in wetland soils rather than deep-burial spheroids.

In 2026, Sean McMahon and colleagues at the University of Edinburgh ran a direct lab test. Mixed microbial communities from reducing Winogradsky columns bleached millimetre-to-centimetre spots in anaerobic sand-ferrihydrite slurries within weeks. Sterile controls did not. DNA from the bleached zones was rich in iron-reducing genera. That result backs a microbial pathway. It does not close an abiotic pathway on Mars, and it does not turn Sapphire Canyon into a fossil.

NASA’s public sentence, that spots like these can be formed by microbes, is true and incomplete. Scotland is where the team can hold both a spotted rock and a confirmed microbial record in the same hand, then ask which measurements actually separate the two.

The Cores That Can Be Carried Sit in Earth Labs

With the Stoer samples home, the work moves to instruments that will not fit in a backpack and will not fly on a rover turret. NASA says follow-on analysis is meant to sharpen the reading of Mars data, help mission teams plan new rover investigations, and prepare the community for possible Martian sample work later. The same campaign is also aimed at gaps in Earth’s own geologic record, where 1.2-billion-year-old terrestrial life is still thinly sampled and sometimes disputed.

GIFT’s job is planetary analog research: take an extreme place on Earth, treat it as a stand-in, and learn how to read a similar place on another world. The team has used Iceland’s lakes and vents as stand-ins for Jezero and Gale. Clachtoll is a tighter match to the specific texture now in dispute, a red bed with reduction spots and a known biota, not a general wet-basalt analogue.

Handheld X-ray and mineral tools told the group what to bag. The decisive chemistry, the isotope work, the high-resolution maps of vanadium or sulfur in a two-millimetre green patch, happen after the tide has come back in. Those are the measurements Perseverance could not make on Mount Spoonhead and cannot make at the sensitivity of a university lab on Sapphire Canyon while that core stays in Jezero.

Cheyava Falls remains on Mars. The Stoer cliffs can be walked again on the next low tide. For now, the rocks that can actually go on a bench are the 1.2-billion-year-old Scottish ones, and they are already off the beach.