The video shows a huge black shadow moving upwards from the bottom of the Moon towards the centre before it drifts off into space.
The camera then zooms in on the object, the tip of which has been described as “constantly spiralling.”
It has also been described as a triangular, black shape with a trail of fumes coming from it.
The footage was posted to an Arabic news site and was reportedly filmed in Oman’s astronomical observatory.
But, now sceptical UFO investigator Scott Brando appears to have cracked the case and identified what it is.
He concluded it was just the silhouette of nothing more than a plane and its contrails passing the Moon just above the earth.
After looking at the footage, he tweeted: “Guys, of course this is not a mystery #UFO crossing over the #Moon but contrails from an airplane crossing the lunar disc.”
He pointed to a photograph of a plane and contrail in an almost identical shape, saying: “This is the a similar perspective from which the airplane and contrails were filmed.”
The footage was gained using a high-powered telephoto lens.
More than 100,000 viewed the video in the first day it was uploaded.
It prompted many theories from it being a hologram of the NASA logo, to aliens, or a mystery “space squid.”
One YouTube user wrote: “Maybe a UFO took out North Korea’s missile after it launched from the test pad?
“Alien’s trying to save us from WW3?”
But, others had been more sceptical even before Mr Brando stepped in.
Another said: “It’s probably just an optical illusion coming from clouds.”
And before Mr Brando spoke out, they added: “that or chemical trails from a plane.”