NASA’s Perseverance rover has found evidence that rocks around Mars’ Jezero Crater interacted with water at least three separate times, offering new clues about the planet’s ancient environment and potential habitability. The findings, published in Communications Earth & Environment, come from the Margin Unit, an area believed to have bordered an ancient lake.
Scientists initially expected to encounter sedimentary rocks formed by material deposited in the lake. Instead, Perseverance found igneous rocks that formed from magma deep underground and were later exposed by erosion. Their mineral composition preserved evidence of multiple periods of interaction with water.
Using its SuperCam instrument, the rover analysed more than 185 bedrock targets. Researchers found relatively unaltered olivine-rich rocks at higher elevations, while lower sections showed fractured olivine surrounded by silica.
The first identified water interaction involved carbon-dioxide-rich groundwater reacting with olivine and producing carbonate minerals. A second episode may have occurred when the ancient lake occupied Jezero Crater, with silica found in rocks that appear to have been beneath the former waterline.
A third, later episode involved hotter underground water. Calcium sulfate and fluorite veins were detected, with fluorite suggesting hydrothermal activity linked to volcanic rocks.
Researchers say the timing of these events remains uncertain, but the findings point to a more complex history of water on Mars. Water-rock reactions involving olivine can generate hydrogen, potentially providing energy for microbial life, while carbonate and silica can preserve chemical evidence of ancient environments.
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