A study published in January 2026 resolves a long-standing Martian geological debate by concluding that a pale band along the western inner rim of Jezero Crater features ancient lakeshore beach deposits alongside altered igneous rock, expanding the known window of potentially habitable surface-water conditions on Mars.
Crater Rim Exploration Shatters Previous Sampling Paces
NASA’s Perseverance rover has been scaling the rough terrain of Jezero Crater, operating at its fastest science-collection tempo since touching down on the Red Planet more than four years ago. After climbing the western wall of the crater for 3.5 months, the rover reached the rim on December 12, 2024, and began exploring a roughly 445-foot-tall slope named phys.org
The rocky bounty found along the heights has exceeded expectations. During previous science campaigns in Jezero, it could take several months to find a rock that was significantly different from the last rock we sampled and scientifically unique enough for sampling,
said Katie Stack Morgan, Perseverance’s project scientist at NASA’s Jet Propulsion Laboratory in Southern California.
“But up here on the crater rim, there are new and intriguing rocks everywhere the rover turns. It has been all we had hoped for and more.”
Katie Stack Morgan, NASA’s Jet Propulsion Laboratory
This high-altitude diversity stems from ancient meteor impacts—including possibly the one that produced Jezero Crater—which hurled fragmented, once-molten subterranean rocks billions of years ago. These buried boulders now sit side-by-side with well-preserved layered rocks native to the rim.
Unlocking Ancient Noachian Rocks and Serpentinization
Among the historic acquisitions, Perseverance cored its first crater-rim rock sample, named Silver Mountain,
on January 28. Extracted from a source rock called “Shallow Bay,” the sample likely formed at least 3.9 billion years ago during the Noachian period, Mars’ earliest geologic period.
The journey across the high ground brought engineering hurdles alongside scientific triumphs. After crumbly rock forced the team to abandon coring an igneous outcrop rich in deep-crust minerals, the rover drove about 520 feet northwest to an outcrop dubbed “Tablelands.” Instruments indicated the rock consists almost entirely of serpentine minerals, created when large amounts of water react with iron- and magnesium-bearing minerals.
While drilling the Tablelands rock went smoothly, sealing the resulting “Green Gardens” sample tube on March 2, 2025, presented mechanical challenges.
Resolving the Mystery of the Pale Margin Unit
From orbit, planetary geologists long debated the origin of the pale band tracing Jezero Crater’s western inner rim. Some researchers argued the Margin unit represented sediment left behind by an ancient lake, while others maintained it was igneous rock that water later altered.
A study published in January 2026 by an Imperial College London-led team concluded that both sides were partly right. By dividing the geological belt into eastern and western sub-units using Mastcam-Z mosaics and 3D outcrop models, supported by SuperCam observations and detailed close-up images, researchers mapped distinct histories for each section.
The Western Margin Unit consists primarily of structureless to parallel-layered rock draped against the crater rim, which the study says may be most consistent with a variably carbonated olivine cumulate. Study author Sanjeev Gupta noted that the transformation indicates that water circulated below the surface of the Margin unit, altering the rock over vast timescales.
Ancient Waves and the Discovery of a Martian Beach
The eastern stretch of the margin tells a distinctly sedimentary story. Lower outcrops investigated by the team revealed well-stratified, medium-grained sandstone featuring rounded, sand-sized grains of olivine and carbonate, cross-stratification, and erosion surfaces.
Alex Jones, PhD researcher and lead author of the January 2026 study published in the Journal of Geophysical Research: Planets, summarized the findings bluntly: We are looking at what was once a beach.
“These findings show that the history of water in Jezero crater was far more complex in both time and space than we imagined.”
Alex Jones, Imperial College London
Reconstructed geological models suggest that the waves of the ancient Jezero lake eroded and reworked local igneous bedrock, rounding the grains and depositing them as a sandy layer along the shore. Because this shoreline deposit sits underneath the Jezero river delta, researchers suggest that lake conditions existed before deposition of the overlying delta, extending the window of potentially habitable surface-water conditions at Jezero.
Deep Crust Views in the Wild West Beyond the Rim
Continuing its push westward, Perseverance captured a 61-image self-portrait on March 11, the 1,797th Martian day, or sol, of the mission, at a locale named Lac de Charmes.
Snapped using the WATSON camera mounted on its robotic arm, the composite shows the vehicle targeting the “Arathusa” outcrop.
Analysis of the abraded outcrop confirmed that it contains igneous minerals that likely predate the formation of Jezero Crater, offering direct windows into Mars’ deep early crust. What I see in this image is excellent exposure of likely the oldest rocks we are going to investigate during this mission,
said Ken Farley, Perseverance’s deputy project scientist at Caltech.
As the rover maps out subsequent drives toward the olivine-bearing rocks at “Gardevarriand eventually southeast toward
Singing Canyon,” these ancient rim materials continue to redefine scientists’ understanding of early Martian volcanism, water dynamics, and planetary habitability.
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