The image, taken by Nasa's Mars Explorer Spirit, seems to show a figure on the surface of the red planet.
However the more sceptical have decided that it is just a rock.
At first astronomers were disappointed with pictures sent back from the surface of the Red Planet by the six-wheel robot four years ago.
But a space fan spotted the figure, which was just a pinprick in the original photograph. It was blown up and posted on a website.
One stargazer writes on the site: "My first thought - it's Big Foot! If you show me another rock in another photo from Mars or Earth that naturally looks like that, I will reconsider."
Another said: "I couldn't believe my eyes when I looked and saw what appears to be a naked alien running around on Mars."
Experts say that if the planet once had surface water, there was the potential to support life.
Analysis of soil showed it contained 90% silica - a concentration only likely to have formed when water is present.
But as to whether there are likely to be aliens moving around, opinion is clearly divided.
Courtsey: Sky News
