Strange, sinuous gullies etched into the dunes of Mars are finally giving up their secrets. These gouges, new experiments reveal, are carved by the explosive sublimation of dry ice, burrowing down the slopes like a mole and blasting away sand as it goes. The new results finally account for all the curious features of Mars' mysterious squiggles. "It felt like I was watching the sandworms in the film Dune ," says Earth scientist Lonneke Roelofs of Utrecht University in the Netherlands. Related: