There's been another strange sighting on the surface of Mars and conspiracy theorists are convinced it shows evidence of aliens.
UFO hunters have spotted a bizarre dome structure in one of NASA's pictures beamed back from the Opportunity Rover.
They believe it is an artificial structure made by aliens at some point in Mars' past when water ran freely on the surface.
"The existence of domes on Mars proves that someone or something built them in the past," wrote conspiracy website, the Unsilent Majority .
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