When geologists first saw pictures of rock outcroppings at the Opportunity landing site on Mars, they thought the mini-cliff was perhaps as tall as a person. Some started calling it the “Great Wall.” Then the robot’s 3-D cameras, a pair of eyes standing as tall as a person, showed it was all a bluff. Seen in stereo, the stack of rocks shrunk to the height of a house cat and the public never heard the catchy nickname.