NASA’s Mars Rovers, Spirit and Opportunity, carry pieces of metal recovered from Ground Zero.  Both rovers are equipped with identical parts.  This image, provided by NASA, is of the rover Spirit, and was taken by the panoramic camera on February 2, 2004.  The piece of metal with the US flag emblem is aluminum recovered from the World Trade Center, after the September 11, 2001 attacks.

Image: NASA. Click on the image to go to the NASA site.