Following the above link will take you to an amazing photo mosaic showing the Mars Exploration Rover (MER) Opportunity on the 2847th sol (Martian day) of its mission, looking away from the Martian sunset to see its own shadow project on the rim of a crater.
The significan amount of Martian dust that has accumulated on the dorsal solar arrays is evident looking at the bottom of the picture. Yet, despite the environment, this rover (MER-B) has been operating on the Martian surface since 2004, almost eight years now.
MER was one of the first projects I worked on, and it is so cool to see the rover still rolling around on another world (well past its design lifetime of 90 sols on the surface). In fact, the level complexity and interconnectedness on the MER system, its resulting robustness and endurance, and its engaging WALL-E-like appearance make it a potential example of system elegance.
Here is some more info on Opportunity via Wikipedia.