In the 1970s, NASA launched two spacecraft called Viking 1 and Viking 2 on missions to Mars. Both spacecraft photographed the surface of Mars and sent images back to NASA. In one photo, a hill on Mars' surface looked a little like a face. Author and conspiracy theorist Richard Hoagland went a step further and said that it didn't just look like a face, it was definitely a face. Hoagland theorized that an alien civilization colonized Mars and that the face was evidence of an alien city in the Cydonia region. When other satellites photographed the surface of Mars, the pictures of the Cydonia region revealed that the face was just an eroded mesa. Hoagland argued that the equipment NASA used to take the subsequent photos wasn't as accurate as the Viking equipment. He also claimed that NASA doctored the images, making them look less like a face [source: Hoagland].