Since 2011, scientists have wondered about the hundreds of dark streaks that appear seasonally on steep slopes on Mars. But it wasn’t until last year, after detecting salts in the streaks from orbit, that researchers were finally confident enough to say they were wet with salty brines. Now, scientists have found that the boiling action of just a little bit of briny water beneath the surface could be responsible for creating the hillside flows. In the barely there atmosphere of Mars, liquid water is unstable. Researchers mimicked these conditions in a chamber experiment on Earth, and covered a block of frozen brine with sand. When the brine was melted, the water boiled immediately, percolating up through the sand with enough force to send grains into the air and downslope, the team reports today in Nature Geoscience. The resulting shape of the flows (pictured) is similar to the streaks seen on Mars, and the experiment demonstrates that boiling seeps below the surface could be responsible for significant surface changes on Mars.