During an American space shuttle mission to the International Space Station in 1998, this photograph of a strange black object was captured outside of the Earth's atmosphere, and the conspiracy theorists loved it.
NASA's best explanation for the phenomenon is that it's a piece of space debris, but not everyone is satisfied with the official party line.
UFO enthusiasts swear the dark mass is alien in origin and have christened it the Black Knight Satellite. Some even believe it's been orbiting the Earth for 13,000 years.
Renowned space journalist James Oberg has also weighed in on the mystery, claiming that the object NASA photographed is in fact a thermal blanket that was lost during an EVA mission by Jerry L. Ross and James H. Newman.