From the web page;

NASA's Mars rover Opportunity appears stuck in a rainbow instead of snagged wheel hub deep in a sand dune on the plains of Meridiani Planum.

In this mosaic of navigation camera images taken by Opportunity, the terrain around the rover has been color-coded based on height. The red regions are the highest areas, while the green spots indicate low terrain. The difference between them is about 28 inches (70 centimeters).

Opportunity sunk into the elongated sand dune, or ripple, on April 26, 2005. But over the last 11 days, the rover has managed to move about 10 inches (27 centimeters) after spinning its wheels enough to drive across 157 feet (48 meters) on firm terrain. Mars rover engineers are confident that the rover can pull itself out of its predicament in about two weeks or so.

(While you are on that site, check out Titan's Weird Red Spot)