2. "Face" on Mars
This hoax arose from a picture taken in 1976 by NASA's Viking 1 orbital spacecraft of a rocky outcrop in the Cydonia region of Mars. The appearance of what looks like a face (created by light and shadows) sparked discussions that it could have been some remnant of an ancient civilization. The "face on Mars" idea persisted even past 1998, when NASA and the European Space Agency began taking more pictures with higher-resolution cameras to show that the facelike shape on the planet's surface was a coincidence.
https://www.livescience.com/51996-mars-hoaxes-conspiracy-theories.html
