2. Monolith on Mars
For quite some time there has been speculation about the existence of various structures on Mars that seem to have been made by intelligent life forms, but most of these – such as the Mars “face” – have been thoroughly debunked. However, the Mars monolith still remains a mystery. Discovered after photo of it was taken by the Mars Reconnaissance Orbiter, it is a rectangular object that measures 16.4 ft (5 meters) wide. Even weirder is a similar monolith on the Martian moon of Phobos, which measures 278 ft (85 meters) across! The fact that Buzz Aldrin himself asked the question, “Who put that there?” is enough to make us wonder.