Alien hunters believe they have discovered a door on the Mercury which could be an entrance to the planet.
Scott C Waring at UFO Sightings Daily first spotted the object in 2012.
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The rectangular shape appears in a photo taken by NASA.
But YouTube footage shared by SecureTeam10 shows that it may be a monolith.
According to the Daily Mail, Tyler Glockner from SecureTeam10 uploaded the video and said: "I took a really good look, it became clear to me that this is not an entrance at all. In fact, it's something much more magnificent.
"This is a shadow ... where is the shadow coming from?"
"That my friends, is this large, long rectangular object, monolith-looking structure towering up above the surface."
The video has been viewed over 290,000 times.