From orbit, a carbonate-rich band of rock along the inside edge of Mars’ Jezero Crater looked like it might be the remains of an ancient lakeshore. Then NASA’s Perseverance rover drove up to it and found something more complicated.
Instead of preserving evidence from one watery environment, the rocks recorded several episodes when water moved through or interacted with them, according to a Purdue University-led study published in Communications Earth & Environment .
The research was led by Candice Bedford , a research scientist in Purdue’s Department of Earth, Atmospheric, and Planetary Sciences. Bedford and an international team used measurements and images from Perseverance, particularly its SuperCam instrument, to piece together the history of a region known as the Margin unit.
“If there is one thing I have learned after 10 years working with Mars rovers, it is that Mars constantly throws surprises at you,” Bedford said. “It is very rare that things are as we expect them to be from orbital data. They are usually far more complex and interesting, which is what makes planetary exploration so exciting.”
At higher elevations, Perseverance found coarse, crystalline rocks rich in olivine, a mineral commonly associated with igneous rocks. Their chemistry and texture suggest they originally formed from a magma that cooled slowly underground.
The story was different at lower elevations. The team found carbonate-rich ridges crossing the bedrock, evidence that groundwater once traveled through fractures and deposited minerals inside them.
“The fractures are like pipes, and the carbonate is the Mars ‘limescale’ that eventually blocked the ‘pipes’ up,” Bedford said, using an analogy from terrestrial plumbing systems.
Scientists also found widespread silica in lower-elevation rocks, along with evidence that previously formed carbonates had been altered. That points to another episode of water-rock interaction, possibly involving water from Jezero’s ancient lake or changes in the groundwater system.
Additionally, the rover found a mineral vein of fluorite and calcium sulfate. Its chemistry points to a later hydrothermal episode, when warmer fluids moved through fractures after the earlier groundwater and lake-related alteration had taken place.
Together, the findings show that the Margin Unit recorded a changing water history rather than a single ancient lake environment.
Areas like these of interaction between water and rock can create environments that intrigue scientists interested in studying the possibility of life on Mars. The Margin Unit has long been considered a promising research location since orbiting spacecraft detected strong carbonate signatures there, but Perseverance provided the close-up view needed to see the fractures, mineral veins and individual grains that revealed a much more complex history.
“Before we arrived at the Margin Unit, the main hypothesis was that these carbonates 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, which significantly altered the crystalline volcanic rocks that were originally there,” Bedford said.
The discovery was made using Perseverance’s “head” — the suite of tools called SuperCam. Since before the launch of the NASA Mars 2020 mission, Roger Wiens , professor of Earth, Atmospheric, and Planetary Sciences at Purdue, has led the SuperCam instrument team and supported the research. Briony Horgan , professor of planetary science at Purdue, contributed to the work and served as campaign science lead during Perseverance’s exploration of the Margin Unit. Former Purdue doctoral students Stephanie Connell and Brad Garczynski also contributed.
Perseverance collected rock samples from the Margin Unit during its exploration. The research plan calls for a future mission to bring those samples to Earth, where they will give scientists an even closer look at the environments recorded in the rocks and their potential to preserve signs of ancient habitability.
“I hope this work helps to reshape how scientists view the history of water in Jezero Crater and across Mars,” Bedford said. “Ultimately, I hope this study helps planetary scientists reconstruct the changing climate and habitability of early Mars and provides helpful context for future researchers when these cached Perseverance samples are returned to Earth to be analyzed for potential biosignatures.”
The paper, “Lake- and groundwater-associated alteration of the olivine-rich Margin Unit in Jezero Crater, Mars,” has been accepted for publication in Communications Earth & Environmen t . Bedford, Wiens and Connell received support from NASA for the SuperCam.
About the Department of Earth, Atmospheric, and Planetary Sciences at Purdue University
The Department of Earth, Atmospheric, and Planetary Sciences (EAPS) combines four of Purdue’s most interdisciplinary programs: geology and geophysics, environmental sciences, atmospheric sciences, and planetary sciences. EAPS conducts world-class research; educates undergraduate and graduate students; and provides our college, university, state and country with the information necessary to understand the world and universe around us. Our research is globally recognized; our students are highly valued by graduate schools and employers; and our alumni continue to make significant contributions in academia, industry, and federal and state government.
Written by: David Siple , communications specialist, Department of Earth, Atmospheric, and Planetary Sciences at Purdue University
Communications Earth & Environment
Lake- and groundwater-associated alteration of the olivine-rich Margin unit in Jezero crater, Mars
21-Sep-2026