Mars MER-A what lies ahead sol 59 This map shows the path the Mars Exploration Rover Spirit will travel toward its future target, the large crater dubbed "Bonneville." The red line indicates Spirit's travels up to the 59th martian day, or sol, of its journey, and the blue line, the route it will follow. Engineers pinpointed the rover's exact location by comparing images taken by the panoramic camera on the rover (inset panels) to those acquired during descent by the descent image motion estimation system camera (underlying map).