This top image is a panorama mosaic taken by the Mars Exploration Rover Spirit panoramic camera on sol 68 of the rover's mission (March 12, 2004). The southern end of the hills nicknamed the "Columbia Hills" can be seen on the left near the horizon. The middle image shows the same view, but the sky has been further processed to show contrast, bringing out a feature that dips along the rim of Gusev Crater. The feature, toward the right of the image, is a valley called Ma'adim Vallis that appears to go through the crater. In the bottom version of the image, the foreground is masked for better viewing of the Gusev Crater rim, which at its closest point is approximately 50 miles (80 kilometers) away from Spirit.
Image credit: NASA/JPL/Cornell