The first two rock samples examined by NASA's Mars rover Perseverance give scientists a firm belief that water inundated Jezero Crater for a sustained period of time, the agency announced Friday. "We determined salt granules in the rock indicate it was exposed to water," Julia Goreva, a NASA scientist for the rover program, said in a news conference from the Jet Propulsion Laboratory in Pasadena, Calif. The rocks, drilled Monday ...