Thanks to the Spirit and Opportunity missions, the public has a pretty good idea of what a rover is: essentially an electrically-powered cart that uses a set of wheels to move across the terrain. However, some JPL scientists have a very different vision of what a rover could be: essentially a beach ball blown across the surface by the wind. In late January those scientists tested out the aptly-named Tumbleweed rover: a ball about 1.8 meters in diameter that spent eight days rolling across the polar terrain of Antarctica, propelled by the wind. The device, which resembles less a rover like Spirit and Opportunity than part of the air bags that cushioned their landing, collected data on atmospheric conditions and transmitted them (via an Iridium satellite telephone) back to JPL. Scientists would one day like to deploy a similar rover on the polar ice caps of Mars and perhaps on other worlds, including Venus and Saturn’s moon Titan.