Memorial Image Taken on Mars on Sept. 11, 2011

This view from NASA rover Opportunity, of an American flag on metal recovered from the site of the World Trade Center towers shortly after their destruction, was taken on Mars on Sept. 11, 2011, the 10th anniversary of the attacks on the towers.

This view from NASA rover Opportunity, of an American flag on metal recovered from the site of the World Trade Center towers shortly after their destruction, was taken on Mars on Sept. 11, 2011, the 10th anniversary of the attacks on the towers.