'Flowing water' on Mars may actually be sand

MARS — New research from the U.S. Geological Survey has found that the mysterious streaks once thought to be proof of water on Mars are probably just sand flows. Sorry NASA!

According to NASA, recurring slope lineae or RSL are long, dark streaks that expand on the slopes of Mars during warmer seasons, and retract when the temperature gets colder.

RSL served as compelling evidence of water on Mars. It looked similar to features on Earth formed by water flows, and contained molecules that help water stay liquid. But a closer look reveals behavior that's unlike flowing water.

Streaks existed only on the tops of steep slopes, and all settled at the angle of repose — the maximum slope at which loose solid material can be piled without slumping.

Based on the findings, researchers concluded that the markings weren't created by water, but by dry grains like sand and dust that accumulate and flow down the slopes.

The RSL may still contain water, but probably not enough to sustain tiny microbial critters, more so human life.