A new study suggests that dark streaks on Mars represent flowing sand — not water.

Monday’s news throws cold water on 2015 research that indicated that lines on some Martian slopes were signs of water currently on the planet. Instead, Arizona scientists report in Nature Geoscience that these lines appear more like dry, steep flows of sand, rather than water trickling downhill, at or near the surface.

If water is present, they said, it’s likely a small amount — and not conducive to life.

The lead scientist for NASA’s Mars exploration program, Michael Meyer, points out that the latest study does not rule out the presence of water. But he acknowledges, “It just may not be as exciting as the idea of rivers going down the sides of cliffs.”

NASA’s Mars Reconnaissance Orbiter provided the images of these so-called recurring slope lineae, or RSL. Thousands have been spotted on Mars, from the equator midway to each pole.