It was Sunday, July 25, 1976. At that time, the Viking 1 spacecraft was orbiting Mars, the first of two ships sent into space as part of NASA's Viking program to deliver a lander to Mars. Viking 1 was searching for a landing site and taking pictures of the planet's surface. It also took a picture of a rock formation that sent shivers down the spines of NASA engineers. It strikingly resembled a human face.