Rover photographs perfectly round ball on Mars surface

NASA's Curiosity Rover has sent back a photo from Mars of a perfectly round object that looks like a ball.

But sad news for conspiracy theorists: No one has been playing golf on the Red Planet.

Instead, experts told Discovery.com they believe the ball is an example of a geological process called concretion — when a mass of minerals embeds in a "host" sedimentary rock.

NASA said the sphere, which was photographed Sept. 11, is likely one centimetre wide.

It's not the first time a rover has photographed a similar phenomenon on Mars. In 2004, the rover Opportunity relayed images of a small grouping of concretions that looked similar to blueberries. The existence of the spheres suggests that area of Mars had groundwater at one point, the scientists said in a paper in Nature in June 2004.