Mars may once have had an ocean -but only for a geological eye blink. This puts a dampener on Ideas that there is or was life on the Red Planet. That's according to a theory from Tim Parker of NASA's jet Propulsion Laboratory in Pasadena, California. Speaking at the Lunar and Planetary Science Conference in The Woodlands, Texas, in March, he argued that a sustained barrage of asteroids hitting the young Mars could have delivered short-lived water to the surface. Signs that Mars was once rife with water litter the surface. These include polygonal cracks seen by NASA's Opportunity rover. On Earth, these require evaporation to form, so Parker sees them as an indication that the rover is traversing what was once the edge of an ocean. 'The uniformity of the surface is much easier to explain in a shallow marine setting," he says.
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