This color view of a mineral vein called "Homestake" comes from the panoramic camera (Pancam) on NASA's Mars Exploration Rover Opportunity. The vein is about the width of 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.
"Homestake" is near the edge of the "Cape York" segment of the western rim of Endeavour Crater.
Exposures combined into this view were taken through Pancam filters admitting light with wavelengths centered at 601 nanometers (red), 535 nanometers (green) and 482 nanometers (blue). The view is presented in approximate true color. This "natural color" is the rover team's best estimate of what the scene would look like if humans were there and able to see it with their own eyes.
The exposures were taken during the 2,769th Martian day, or sol, of Opportunity's career on Mars (Nov. 7, 2011).