Fluorite veins in Jezero Crater reveal ancient Martian hydrothermal systems

The Perseverance rover has identified evidence of ancient hydrothermal activity in Mars' Jezero Crater, suggesting that hot water once circulated beneath the planet's surface. Analysis of the Margin Unit-a region previously thought to be a simple lake shoreline-revealed that minerals were altered in at least three distinct stages, leaving behind calcium sulfate and fluorite veins. This discovery shifts the understanding of Martian geology from a world of surface lakes to one with deep-seated energy sources capable of sustaining microbial life. Initial expectations for the Margin Unit pointed toward sedimentary layers deposited by water billions of years ago. However, the rover's SuperCam instrument detected igneous rocks formed from magma. According to geologist Aleksey Trofimov, the presence of volcanic rock where sand and clay were expected indicates a volatile volcanic youth for the crater, followed by chemical alterations triggered by fluids. Mapping 185 different points revealed a sequential transformation of the terrain. First, carbon dioxide-rich groundwater reacted with olivine to form carbonates. This was followed by the influence of lake waters, and finally, a surge of hot, deep-seated fluids. Chemist Ilya Safronov notes that the detection of fluorite acts as a thermal marker; on Earth, this mineral crystallizes when superheated water moves through volcanic rock, indicating a high-temperature "chemical kitchen" operating beneath the crater.