"There is no closed basin at Meridiani, and so formation of significant evaporite deposits there requires that it be a region of groundwater upwelling," Squyres said.
Andrews-Hanna said the finding does not imply that oceanlike bodies of water were never present on Mars.
"Large amounts of water on the surface of Mars were certainly possible early in the planet's history," he said.
But as the planet dried, he said, "water would have been present only where the global-scale groundwater flow brought the water table to the surface."
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