Images from NASA's Mars Reconnaissance Orbiter appear to reveal evidence of liquid water running downhill during the Martian summer. But a device on the orbiter called CRISM, built by scientists at Johns Hopkins' Applied Physics Lab, scanned the stains and found no sign of water.
A report in the journal Science Thursday said the MRO team's best guess is that the stains, which lengthen and darken in summer and vanish in winter, are caused by a syrupy brine that dries quickly on the surface.
"It's a mystery now," said Alfred McEwen, the mission's principal investigator. "But I think it's a solvable mystery." If the cause is proven to be liquid water, it would be the first ever found on Mars.
Watch the mystery flows: http://bsun.md/nfZ1bt