Water boiling under Mars's thin atmosphere could explain some of the planet's puzzling geological features, such as gullies (pictured) and hillside streaks, which some scientists have attributed to liquid water flowing today.

A team led by Marion Massé of the University of Nantes in France melted ice on top of a pile of sand in a laboratory chamber that simulated the Martian atmosphere. Water boiled as it seeped into the sand, causing grains to tumble downhill. Even with relatively small amounts of water, the flowing grains formed channels that were similar to those seen on Mars.

Credit: NASA/JPL-Caltech/Univ. Arizona

Earth-like quantities of liquid might not be required to form features on Mars, the authors say.

Nature Geosci. http://dx.doi.org/10.1038/ngeo2706 (2016)