Perseverance Finds Three Water Episodes in Jezero Rocks

NASA's Perseverance rover found Jezero Crater's Margin Unit was altered by groundwater, lake water, and hot hydrothermal fluids in three separate episodes.

When Perseverance reached the inner rim of Jezero Crater in September 2023, mission scientists expected sedimentary rocks deposited along the shoreline of an ancient Martian lake. Instead, the rover encountered ancient igneous rocks that were altered by water on at least three separate occasions, according to ScienceDaily, citing NASA's Jet Propulsion Laboratory. The study, led by Candice Bedford of Purdue University and published in Communications Earth & Environment, describes the Margin Unit as a 'crossroads' for different aqueous systems — a place where groundwater, lake water, and later heated fluids each left their own chemical fingerprints on the same rocks.

The surprise cuts against the mission's core hypothesis. Before arrival, orbital observations had detected strong carbonate signatures in the Margin Unit, and the leading hypothesis held that those carbonates formed through interaction with Jezero's ancient lake. The rocks tell a different story. According to The Economic Times, the discovery means a carbonate deposit seen from orbit might not automatically indicate a former lake or shallow sea — it could instead record groundwater moving through rock. Because Jezero sits within one of Mars' largest carbonate exposures, lead author Candice Bedford says what the team learns here 'reaches well beyond this crater.'

Most of the evidence came from SuperCam, the laser instrument on Perseverance's mast, which analyzed more than 185 bedrock targets across roughly 265 meters of elevation, according to ScienceDaily. At higher elevations, the team found coarse olivine-rich rock barely touched by water, suggesting it cooled slowly from magma deep underground before erosion exposed it. Lower down, near the ancient lakebed, the olivine grains are fractured and filled with silica.

The chemistry matters for habitability, even though the study does not claim life ever existed at Jezero. On Earth, when water reacts with olivine, the process can produce hydrogen that some microbes use as an energy source, and the same reactions produce carbonate and silica — minerals capable of preserving traces of past microbial activity, according to ScienceDaily. The Economic Times notes the finding identifies chemical environments that could help scientists assess where ancient Martian life might have survived, and that the olivine- and carbonate-rich rocks around Jezero were already flagged by NASA as valuable targets for eventual sample return to Earth.

Researchers can establish the relative order of the three water episodes but cannot yet assign precise dates to each one, which The Economic Times flags as an unresolved part of Mars' water history. Perseverance itself has moved on: space.com reports that starting this year the rover began exploring 'Lac de Charmes,' west of the Jezero rim — an area the mission team calls the 'Wild West frontier,' home to some of the oldest rocks the rover has encountered, possibly formed when Mars was still a young, impact-battered planet. Meanwhile, mission scientist Eleni Ravanis, quoted by srpske.rs, underscored the broader lesson: rocks below the ancient waterline carry more silica, a clue that continues to sharpen how scientists read Martian carbonates from orbit.