Source : INDIA TODAY NEWS
Nasa’s Perseverance rover has uncovered evidence that rocks at the edge of Mars’ Jezero Crater were altered by water on at least three separate occasions, offering new clues about the planet’s ancient climate and potential habitability.
The findings, published in Communications Earth & Environment, come from the rover’s exploration of a region known as the “Margin Unit,” which stretches along the shoreline of an ancient lake.
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Scientists initially expected to find sedimentary rocks formed from layers of material deposited by the lake. Orbital observations had also detected strong signatures of carbonate minerals, which on Earth commonly form in shallow water environments.
Instead, Perseverance discovered igneous rocks. These rocks formed from magma deep underground and later became exposed as the Martian surface eroded. Their mineral crystals preserved evidence of several episodes of interaction with water.
The rover used its SuperCam instrument to analyse more than 185 bedrock targets across the Margin Unit. SuperCam can fire a laser at rocks from a distance of up to 6.5 metres and analyse the resulting plasma to determine their chemical composition.
At higher elevations, Perseverance found coarse-grained rocks rich in olivine that showed little evidence of water interaction. Lower down, however, the rocks had been dramatically transformed, with fractured olivine grains surrounded by silica.
Scientists identified the first major water interaction as carbon-dioxide-rich groundwater reacting with olivine. This process produced carbonate minerals that filled fractures in the rock.
A second episode may have occurred when the ancient lake occupied Jezero Crater. Some rocks contain silica, particularly those that appear to have been below the former waterline.
The third event appears to have involved much hotter water. Mineral veins containing calcium sulfate and fluorite were discovered in part of the Margin Unit. Fluorite is typically associated with hot water circulating through volcanic rocks, suggesting a later episode of heated underground-water activity.
The exact ages of these water interactions remain unknown. However, the findings suggest that Jezero Crater experienced a much more complex history of water than previously thought.
The discovery is significant for the search for ancient life because water-rock reactions involving olivine can produce hydrogen, potentially providing an energy source for microbes. Carbonate and silica can also preserve chemical traces of past environments.
Researchers say the results could help reconstruct how water, climate and habitability changed on early Mars.
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SOURCE :- TIMES OF INDIA
