The navigation camera on NASA's Mars Exploration Rover Opportunity recorded this view of the western edge of "Cape York" during the 2,761st Martian day, or sol, of the rover's work on Mars (Oct. 30, 2011). Cape York is a segment of the rim of Endeavour Crater. A bright vein, informally named "Homestake," is visible on the right side of the image. The vein is about as wide as a thumb and about 18 inches (45 centimeters) long. Opportunity examined it in November 2011 and found it to be rich in calcium and sulfur, possibly the calcium-sulfate mineral gypsum.