Mars may look like a frozen and barren world today, but its rocks preserve evidence of a much wetter and more active past.

NASA’s Perseverance rover has uncovered new clues suggesting that water interacted with rocks in Mars’ Jezero Crater on at least three separate occasions. The discovery provides scientists with a more complicated picture of how water moved through the ancient Martian environment — and could help researchers better understand whether Mars once offered conditions suitable for microbial life.

An unexpected discovery at Jezero Crater

Perseverance reached the inner edge of Jezero Crater in September 2023 and began investigating an area known as the “Margin Unit.”

Scientists originally expected to find sedimentary rocks there because the region lies along the shoreline of an ancient Martian lake. On Earth, sedimentary rocks can preserve important evidence of past environments, including traces associated with ancient microbial life.

Orbital observations had also revealed strong signatures of carbonate minerals in the region. Carbonates are particularly interesting because they can form when water interacts with rocks in environments such as lakes and shallow seas.

But Perseverance encountered something different.

Instead of sedimentary rocks, the rover discovered igneous rocks — rocks that formed from molten material either deep beneath the surface or through volcanic activity.

Far from being disappointing, the discovery gave scientists something extremely valuable: a detailed geological record of how water altered Mars over time.

Perseverance finds multiple episodes of water

Using its SuperCam instrument, Perseverance examined more than 185 bedrock targets across the Margin Unit.

SuperCam uses a laser to vaporize tiny portions of rocks from a distance. By analyzing the light produced by the resulting plasma, scientists can determine the chemical composition of the material.

The measurements revealed that the rocks had interacted with water at at least three different times.

Each episode appears to have left behind its own chemical signature.

First: carbon-rich groundwater

The earliest known interaction occurred when carbon-dioxide-rich groundwater came into contact with olivine-rich rocks.

Olivine is a mineral containing magnesium and iron. When water interacts with olivine under the right conditions, chemical reactions can produce carbonate minerals and silica.

At lower elevations of the Margin Unit, Perseverance found carbonate material filling fractures in the rock. Over immense periods of time, the softer surrounding rock eroded away, leaving the carbonate-filled fractures standing as ridges.

These minerals are particularly interesting to planetary scientists because similar water-rock reactions on Earth can produce hydrogen, which certain microorganisms can use as an energy source.

Second: an ancient Martian lake

A later episode of water may have been connected to the lake that once occupied Jezero Crater.

The rover found silica within some of the altered rocks, with more silica appearing in rocks that were positioned below the ancient waterline.

This suggests that the lake or associated groundwater system may have played an important role in changing the chemistry of the rocks.

Scientists cannot yet determine the exact ages of these individual water events, but they can reconstruct their sequence from the geological evidence preserved in the rocks.

Third: hot water beneath the surface

Perhaps the most intriguing evidence comes from a much later event.

In one part of the Margin Unit, Perseverance discovered mineral veins approximately 25 centimeters (10 inches) thick containing minerals including calcium sulfate and fluorite.

Fluorite is especially important because it commonly forms when hot water circulates through volcanic rocks.

That means Mars did not simply experience surface water flowing through ancient lakes. The region also appears to have experienced a later period when heated water moved through rocks underground.

Together, these discoveries suggest that Jezero Crater was influenced by several different water systems over its geological history — including groundwater, surface water and potentially hot underground fluids.

A crossroads for water on ancient Mars

The findings are significant because Jezero Crater contains one of the largest exposed regions of carbonate-bearing rocks on Mars.

Scientists had previously used orbital observations to build hypotheses about how those carbonates formed. Perseverance’s close-up investigation is now showing that the story may be considerably more complicated.

Rather than being created by a single ancient lake, the minerals may record multiple episodes of water activity occurring under different conditions.

Researchers describe the Margin Unit as a kind of “crossroads” for aqueous systems — a place where different water-driven processes left their signatures in the same geological region.

What does this mean for the search for life?

The discovery does not prove that life ever existed on Mars.

However, it provides scientists with additional evidence about environments that could have supported life in the distant past.

Water is one of the most important ingredients scientists consider when evaluating ancient habitability. But water alone is not enough. Scientists also need to understand the chemistry, energy sources and environmental conditions that existed alongside it.

The altered olivine rocks are particularly interesting because water-rock reactions can produce hydrogen, which some microbes on Earth use as an energy source.

Carbonate and silica minerals can also preserve chemical information about the environments in which they formed.

For Perseverance, understanding these environments is a major part of the mission’s astrobiology objectives. The rover is studying the geology and ancient climate of Mars while collecting and storing rock and regolith samples for potential future analysis.

Mars continues to surprise scientists

One of the most important lessons from the discovery is that Mars’ water history may be much more complicated than a simple story of rivers and lakes.

The rocks investigated by Perseverance record several different interactions with water, ranging from carbon-rich groundwater to possible lake-related activity and later hot underground fluids.

As Perseverance continues exploring Jezero Crater, scientists hope to reconstruct when these events occurred and how they were connected to the planet’s changing climate.

The ultimate goal is to understand how Mars transformed from a world that once hosted liquid water into the cold, dry planet we see today — and whether some of its ancient environments could have supported microbial life.

Every rock examined by Perseverance adds another piece to that enormous geological puzzle.

And at Jezero Crater, those pieces are revealing that Mars’ ancient water story was far more dynamic than scientists once imagined.

Source

This article is based on NASA’s September 21, 2026 report on Perseverance’s investigation of the Margin Unit in Jezero Crater. The underlying findings were published in Communications Earth & Environment.

Image Caption:
NASA’s Perseverance rover explored the Margin Unit along the edge of Jezero Crater, uncovering evidence of multiple ancient water events.