PathfinderSojourner, the original Mars rover, rides out on the Martian surface, getting close-up looks at nearby rocks and demonstrating technologies that are vital to upcoming Mars missions, including automatic hazard detection and avoidance. Sojourner’s ability to “see” obstacles and navigate around them without advice from ground controllers will be essential to later Mars rovers, since it takes seven minutes for a signal to reach Earth, and seven more minutes for instructions to return. The rover captures the public imagination and is even immortalized as a Hot Wheels toy.