Metal Object on Mars, Shaler Outcrop

The Curiosity Rover photographed a rock outcrop known as 'Shaler' on the 120th day of the mission, Dec 7th 2012. There are several objects of interest in this image apart from the rocks. Many of these objects look as though they have been manufactured or constructed, in other words they are not natural objects. One in particular stands out and it appears to be a metal box with holes drilled into one side of it. You can also see that the edge of the side with the holes in it has very distinct angles and curves. There are other less distinct metallic looking objects around it.

Original image taken by the Mast Camera (Mastcam) sol 120 (Dec. 7, 2012)
http://www.nasa.gov/mission_pages/msl/multimedia/pia16550.html