Gusev Crater's Horizon - Soles 497/500 (Approximate True Colors; credits: NASA/JPL-Caltech)

Original NASA caption:"In this case, scientists have also been studying the mineral and chemical differences, which show that some rocks have been more highly altered than others.
In the foreground, in the middle of the image mosaic, Spirit is shown with the scientific instruments at the end of its robotic arm positioned on a rock target known as "Ahab". The Rover was busy collecting elemental chemistry and mineralogy data on the rock at the same time that it was taking 50 individual snapshots with its five PanCam filters to create this stunning view of the martian scenery. The twin tracks of the Rover's all-terrain wheels are clearly visible on the left. This mosaic of images spans about 220° from left to right and is an approximate true-color rendering of the Mars terrain acquired through the PanCam's 750-, 530-, and 430-nnmt filters. Spirit collected these images from its 497th Sol, through its 500th Sol (May 27 through May 30, 2005)".