NASA’s Perseverance rover has helped scientists reconstruct a more complicated history of water on early Mars than expected, with evidence pointing to ancient lakes, groundwater circulation and hydrothermal fluids in Jezero Crater.
The findings focus on the crater’s “Margin Unit,” a geologic area along the edge of an ancient Martian lake. Scientists had expected mainly sedimentary rocks, but rover observations revealed a mix of minerals and textures consistent with multiple episodes of water activity.
Why the Margin Unit matters
Carbonate-rich rocks in the area are of particular interest because carbonates can preserve information about the chemistry of ancient environments. On Earth, related environments can also preserve evidence relevant to past microbial life.
NASA’s Jet Propulsion Laboratory said the new study indicates that the unit was shaped not by a single lake episode but by a sequence involving surface water, groundwater and hot fluids moving through fractures.
A more dynamic early Mars
The work adds to evidence that Jezero Crater experienced long-lived and changing water conditions. That matters for Perseverance’s wider mission: identifying environments that may once have been habitable and collecting samples for possible future return to Earth.
The rover has been exploring Jezero since 2021, examining rocks and sediments across the crater floor, former river delta and crater rim.
Sources: NASA Jet Propulsion Laboratory, Sept. 21, 2026; TRT Haber, Sept. 25, 2026. Image: NASA / Wikimedia Commons, public domain.
