While Nasa rarely comments on these claims, in August of its scientists has provided an explanation for why so many people see strange objects on the red planet.
Some are heralding the discovery of an ancient 'Buddha statue' on Mars as proof the red planet one hosted an advanced civilisation.
The statue has got UFO hunters suggesting that intelligent life once existed on the planet, that may even have had a religion, reports the Daily Mail.
Scott C Waring of UFO Sightings Daily says: "This photo alone should be enough to convince the United Nations that intelligent life once existed on Mars.
"Nasa doesn't want anyone to know the truth, because they will be asked to share the info and technology that they have found.
"This shows a face and head turned to its right, with breasts and a plump stomach, shoulders. Very remarkable detail in this photo."
The rock was found by YouTuber Paranormal Crucible and highlighted by UFO Sightings Daily. The same site recently showcased a ghostly woman, a military bunker and President Obama's head on Mars.
Increase in 'sightings' of strange objects
Ashwin Vasavada, who works on the Mars rover project, says scientists are not trying to hide evidence of alien life from the general public.
His comments were sparked by an increase in 'sightings' of strange objects. In their latest 'discovery', for instance, a number of people said they had spotted the Star Destroyer from Star Wars on Mars.
And earlier this month, alien hunters claimed they had spotted a mysterious 'facehugger crab' on the planet.