Curiosity spots mysterious 'UFO' zooming across Mars' horizon

While the images are certainly a curiosity, NASA and photography experts insist they are nothing more than blemishes on the images, picked up by the camera lens sitting on the rover at a distance of 350 million miles away.

NASA has not commented on any of the strange sightings so far, but alien hunters have suggested that these are alien ships monitoring humans' baby steps into the universe, the 'Daily Mail' reported.

YouTube user StephenHannardADGUK, part of a group called Alien Disclosure UK, spotted the anomalies on the NASA images, publicly available on the space agency's website, and applied a series of filters to try to shed light on the mystery.

"Four objects caught by Mars Curiosity, very difficult to make out on original image so I have used a few filters to highlight," the paper quoted him as saying, referring to the four pin-points of light pictured in the skies of Mars.

"What are these four objects? UFOs, Dust particles, or something else? As always you decide," the user said.

According to the Huffington Post, video analyst Marc Dantonio, who has worked on projects for the US government, said that these are simply 'dead pixels' in the image - a regular problem in the world of graphics.

Another video appears to show an object rising from the horizon, followed shortly afterwards by another small object.

Curiosity, a six-wheeled vehicle the size of a compact car, landed inside a vast, ancient impact crater near Mars' equator on August 6 after an eight-month, 570-million-Km voyage through space.