The idea that Mars could have once been home to intelligent life is a theory that has become very popular in recent years. Discoveries like the so-called "Face on Mars" and the occasional sighting of flowing water have only fanned the flames of speculation.
Chances are, however, that you've never heard of the best possible evidence of intelligent life on Mars: the monolith on Phobos.
This is Phobos, one of Mars' two moons. It's a small, potato-shaped rock that makes its way around the red planet once every seven hours.
During a Canadian Space Agency mission in 2007, a probe captured this photograph. Looks normal enough, right?
Well, that's where you're wrong. Upon closer inspection of the photo, researchers discovered this large monolith.
Astronaut Buzz Aldrin mentioned the monolith directly during an interview on C-SPAN, after which the object received even more attention.
Despite that bolstered attention, researchers haven't been able to determine what the structure is.
You can check out Aldrin's thoughts in the video below.
(via Cool Interesting Stuff)
What the heck is that thing? Well, it could just be a giant boulder on an otherwise flat plain, but that's boring! Let's just go ahead and attribute this thing to alien ingenuity.