Today's Mars Photo was taken by Mars Exploration Rover Opportunity on a rock being called Salisbury. Oppy been brushing this area clean of dust and drilling into it with its rock abrasion tool for the past few days. This allow the rover to get a view of the 'raw' rock beneath the weathered, dust-covered surface. The rover is continuing to use its microscopic imager to determine what the rock is made of and learn more about its past.
This photo was colored by The Road to Endeavour Blog, one of the leading authorities on everything related to MER Opportunity. Clicking on the image below will take you to the post where he discusses Salisbury in much more detail with numerous photos.