Anaglyph

"Since settling in on the red planet, the Mars Exploration Rovers Spirit and Opportunity have sent back a number of 3-D postcards to countless fans outfitted in red- and blue-tinted spectacles. To some, the realistic pictures of the rocky martian terrain may seem magical, but the concept behind the illusion is in fact quite simple.
"Basically, 3-D pictures trick your brain into doing what it does all the time in the real world," says Zareh Gorjian, a graphic artist at NASA's Jet Propulsion Laboratory who makes 3-D pictures and animations of Mars for a living, both the black-and-white kind and the more advanced color versions.
The key to 3-D imaging lies in simulating a left and right eye. For the Mars Exploration Rovers, this is accomplished with the aid of a left and right camera eye. Images from the rovers' stereo camera lenses (either the hazard-avoidance cameras, the navigation cameras or the panoramic cameras) are tinted in red and blue, then merged into one blurred picture, which pops off the page when viewed through a pair of red- and blue-tinted glasses.
"Your brain thinks it is seeing two separate left and right images and so does what it always does -- combines them into one picture," says Gorjian."