The use of autonomous rovers to carry out dangerous or exploratory tasks is well documented, especially in the field of space exploration. For example, NASA has successfully sent four rovers to explore the surface of Mars. The rover Spirit landed on Mars in 2004 and, after five years of service, became stuck in a sand trap. Despite numerous attempts, Spirit could not be dislodged, and the mission ended when scientists could no longer communicate with it. To overcome this issue for future Moon and Mars rovers, a group led by Siddharth Shrivastava and Andras Karsai from the Georgia Institute of Technology, in collaboration with NASA Johnson Space Center and the Jacobs Engineering Group, have been modeling and experimenting with the wheel geometry and locomotion of autonomous rovers. The researchers tested different wheel configurations for slopes of various steepness to determine which locomotion strategies worked best in which situations. They found that for hills of loosely consolidated granular material with slopes greater than 15 degrees, a technique of agitating and cyclically reflowing the grains under the rover allows it to paddle through granular material and “swim” up the slope, thus avoiding spinning in place and getting stuck in the substrate. The ability to modify their locomotion depending on terrain could help prevent future rovers from suffering the same fate as Spirit. READ MORE