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n 1976, one of the first images from the Viking 1 spacecraft showed a formation in the Cydonia region of Mars that NASA said resembled a human face. NASA scientists quickly interpreted the image as having been caused by the angle of the sun and the resulting shadows. But that didn't prevent claims that the "Face on Mars" proved there was intelligent life on the Red Planet.
The European Space Agency's Mars Express, equipped with its High Resolution Stereo Camera, revisited Mars' most famous feature in 2006.
Zooming in on the "face" resolves the mystery. The ESA describes it as a "remnant massif thought to have formed via landslides and an early form of debris apron formation. The massif is characterized by a western wall that has moved downslope as a coherent mass."