NASA's Mars Reconnaissance Orbiter: Coprates Chasma dark streaks indicative of water

A portion of the Coprates Chasma showing dark streaks on generally north-facing slopes in northern summer and southern winter. 

Coprates Chasma is a huge canyon that forms part of the Valles Marineris system

Credit: Nature Geoscience | Alfred McEwen et al.

Dark seasonal streaks on slopes near the Martian equator may be a sign of flowing salt water on Mars, liquid runoff that melts and evaporates during the planet's warmer months, scientists say.

NASA's Mars Reconnaissance Orbiter spotted the dark streaks on Mars as they formed and grew in the planet's late spring and summer seasons, when the Martian equatorial region receives the most sunlight.

The streaks then faded the next season as cooler temperatures prevailed.

These seasonally occurring flows — known as Recurring Slope Lineae — were previously seen on Martian slopes at mid-latitudes, but the MRO spacecraft has now detected them near the equator of the Red Planet.

While there have been no direct detections of liquid water, the new findings hint at a surprisingly active water cycle on Mars today, said study leader Alfred McEwen, a professor of planetary geology at the University of Arizona in Tucson.

"Now we've found them in equatorial regions," McEwen told reporters. "This is more surprising, given peoples' expectations that the equatorial region was completely dry."

"It suggests there may be much more water in the near-surface crust than we imagined before."

Map of the confirmed locations of dark streaks, or recurring slope lineae, on Mars.

Credit: Nature Geoscience | Alfred McEwen et al