HALE CRATER, MARS - UNSPECIFIED DATE: In this handout provided by NASA's Mars Reconnaissance Orbiter, dark, narrow streaks on the slopes of Hale Crater are inferred to be formed by seasonal flow of water on surface of present-day Mars. These dark features on the slopes are called "recurring slope lineae" or RSL. Scientists reported on September 28, 2015 using observations with the Compact Reconnaissance Imaging Spectrometer on the same orbiter detected hydrated salts on these slopes at Hale Crater, corroborating the hypothesis that the streaks are formed by briny liquid water. (Photo by NASA/JPL-Caltech/Univ. of Arizona via Getty Images)
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