Orbiting Mars to scout landing sites, Viking 1 captured a low-resolution photograph of the Cydonia region showing a rock formation that appeared, in the image's harsh shadows, to resemble a face staring up into space. NASA released it as a curiosity, but it became a touchstone for fringe theories about ancient Martian civilizations, one that later high-resolution imagery thoroughly debunked.
The image, formally cataloged as frame 35A72, showed a mesa roughly a mile and a half across sitting amid the pitted terrain of Cydonia. Viking's camera resolution was coarse enough that shadows fell across the formation in a way that, to human pattern-recognition instincts primed to see faces everywhere, produced two eye sockets, a nose, and a mouth.
NASA's own press release at the time called it a "huge rock formation, which resembles a human head," formed by shadows giving "the illusion of eyes, nose and mouth," and noted it was probably a trick of light. That caveat did little to slow the image's cultural afterlife. Books, documentaries, and a cottage industry of Mars-anomaly researchers spent decades insisting the face was evidence of artificial construction, an ancient monument left by a vanished civilization.
When the Mars Global Surveyor and later Mars Reconnaissance Orbiter photographed Cydonia at far higher resolution in the late 1990s and 2000s, the face dissolved into an unremarkable eroded mesa, no different from thousands of other landforms scattered across the Martian surface. The episode became a favorite case study in how easily the human eye finds meaning in noise.