NASA rover finds three separate ancient water events in Mars crater

NASA's Perseverance rover has found that a stretch of rock along the rim of Mars' Jezero Crater was shaped by water on at least three separate occasions billions of years ago, revealing a far more complex history than scientists anticipated when the rover first rolled into the area.

The findings, published Monday in the journal Communications Earth & Environment, are based on data gathered at a geologic formation called the Margin Unit, which hugs the inner edge of Jezero Crater's rim along the shoreline of what was once an ancient lake. NASA published details of the discovery on September 21.jpl.nasa+1

A Surprise in the Rocks

When Perseverance reached the Margin Unit in September 2023, scientists expected to find sedimentary rock — the kind that forms from layers of sand and silt and is good at preserving signs of past microbial life on Earth. Mars orbiters had detected strong carbonate mineral signals from the area, reinforcing expectations of lake-deposited sediment.phys+1

Instead, the rover found igneous rock, formed from cooled magma either deep underground or through volcanic activity. Using its SuperCam instrument, which fires a laser at rocks to reveal their chemistry, Perseverance analyzed more than 185 bedrock targets across the unit.NASA+1

"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," said Candice Bedford, a research scientist at Purdue University and the study's lead author. "But now we know that this location became a sort of crossroads for aqueous systems."NASA

Three Distinct Water Episodes

The research team reconstructed the sequence of the water events, though not their precise timing. The first involved carbon-dioxide-rich groundwater reacting with olivine minerals, creating carbonate ridges that now stand exposed as softer surrounding rock erodes away.phys+1

The second episode appears linked to the ancient lake itself. Researchers found silica deposits concentrated in rocks that once sat below the waterline. "Turning olivine into carbonate can leave silica behind, and we see more of that silica in rocks that sat below the water line," said Eleni Ravanis, a planetary scientist at the University of Hawaii at Manoa and a coauthor of the study.NASA

The third and final event left thick mineral veins — about 10 inches (25 centimeters) across — containing calcium sulfate and fluorite, a mineral that typically forms when hot water circulates through volcanic rocks.skyatnightmagazine+1

Why It Matters

The interaction between water and olivine on Earth can release hydrogen, a potential food source for microbes, leaving behind carbonate and silica that can preserve traces of past life. The discovery that this process occurred at the Margin Unit strengthens the case that conditions there were once favorable for biology.dailygalaxy+1

"It is very rare that things are as we expect them to be from orbital data," Bedford said. "I hope this work helps reshape how scientists view the history of water in Jezero Crater and across Mars."NASA