The strange ring, which has been branded an eroded rock formation by sceptics, was found in NASA images taken by the Curiosity Rover droid which is exploring the Martian surface taking samples and pictures.
Avid alien seeker Streetcap1, based in Scotland, was responsible for the find, before alerting Express.co.uk and other UFO websites.
His discovery has been picked up by various sites and YouTube channels, sparking the debate.
YouTube channel SecureTeam10 shared the find, saying: “This is a very strange formation of rocks put together in what appears to be a very artificial way.
“What we are seeing looks very different from the craters on Mars and the moon.
“It almost looks as if these rocks were arranged in this circular formation or this could potentially be some sort of ruin that’s part of some larger structure buried beneath the surface.
“I’ve never seen anything like it on Mars. That’s why it’s such a fascinating discovery.
“It looks eerily out of place than the rest of the terrain and surroundings.”
People commented on YouTube with various theories on what it could be.
One said it looked like a well while others said it could be a martian campsite or an alien UFO refuelling site.
Many were convinced it proves aliens are living on Mars.
Eric Hansen commented: “That formation is clearly not ‘natural’.”
While Layla Chester added: “Way to many strange formations on the moon & mars, when will people wake up & see what’s right in front of them??”
Others refused to believe the rock formation was a sign of alien life, saying it was a natural geological process.
One poster said: “That first rock circle you featured was not a stone circle.
“If you look closely you can see that they all belong together. It actually looks like it at some point in time was one big rock that now only has what you see left of it.”
And another wrote: “This round rock formation is probably a so-called lava bomb, came out of a volcano, landed and broke and later eroded.”