This pair of pieced-together images was taken by the Mars Exploration Rover Spirit's rear navigation camera on March 6, 2004. It reveals the long and rocky path of nearly 240 meters (787 feet) that Spirit had traveled since safely arriving at Gusev Crater on Jan. 3, 2004.
The lander can still be seen in the distance, but will never be "home" again for the journeying rover. This image is also a tribute to the effectiveness of the autonomous navigation system that the rovers use during parts of their martian drives. Instead of driving directly through the "hollow" seen in the middle right of the image, the autonomous navigation system guided Spirit around the high ridge bordering the hollow.
In the two days after these images were taken, Spirit has traveled roughly 60 meters (197 feet) farther toward its destination at the crater nicknamed "Bonneville."
Image credit: NASA/JPL