Water systems on early Mars were complex and hot

The Perseverance rover has discovered that Mars once boasted a complex water system, complete with hot hydrothermal activity. This revelation, published on September 21, 2026 in Communications Earth & Environment, challenges previous assumptions about the Red Planet's hydrological history.

Initially, scientists expected to find sedimentary rocks at the Perseverance's landing site in Jezero crater, which could preserve traces of ancient microbial life. However, the rover instead found igneous rocks formed from volcanic activity. These igneous rocks contain clues to a past water system, as analyzed by the rover's SuperCam instrument.

The researchers identified three separate episodes of water interaction with Martian rocks. In the first episode, carbon-dioxide-rich groundwater reacted with olivine to form carbonate ridges at low elevations. In the second episode, water from the former lake deposited silica in rocks that sat below the water line. Finally, in the third episode, hydrothermal fluids created mineral veins containing minerals like calcium sulfate and fluorite.

The findings are significant as Jezero crater is home to one of the largest carbonate exposures on Mars. The existence of hydrothermal fluids suggests that Mars' climate and habitability changed over time. The presence of olivine, which formed underground in hot magma, further supports the idea of subsurface water in Mars' early history. This discovery underscores the need for further exploration of Mars' geological past.