Nasa's Curiosity rover has found a ball on the surface of Mars. The Mastcam on Curiosity snapped the spherical object sitting on a flat rock on the Red Planet.

mars ball
Have the Martians been practising for the Ryder Cup? A camera on Nasa's Curiosity rover photographed a spherical rock on the surface of the red planetNasa/JPL-Caltech/MSSS

Nasa experts say the ball is not anything too exciting – it is probably just one centimetre wide and an example of a geological process called concretion.

The rover also took a photo of what looks like a set of traffic lights protruding from the ground.

mars traffic lights
Traffic lights on Mars, as captured by Nasa's Curiosity roverNasa/JPL-Caltech/MSSS

Over the years, conspiracy theorists and bloggers with over-active imaginations have spotted all sorts of things on the Red Planet, including a fossilised dinosaur thigh bone, a military helmet, several rats and an iguana.

These are all examples of Pareidolia, the psychological need to see significance in random data, such as seeing faces in clouds.

face on Mars
Way back in 1976, the Viking 1 Orbiter photographed this face on Mars, launching countless theories of intelligent life on Mars. It turned out to be a mesa (or hill) in the Cydonia regionNasa
smiley face on Mars
Viking Orbiter 1 spotted another face on Mars in 1976. This smiley in Galle crater was imaged at higher resolution by the Mars Global Surveyor in 1999Nasa
woman on mars
In 2007, Nasa's Mars Exploration Rover Spirit captured this famous image of the figure of a woman sitting on the Red Planet. The Internet, predictably, went ballistic. Just a rock, said NasaNasa
rat on Mars
An eagle-eyed space enthusiast, poring over Curiosity images, spotted this rat. Or lizard. Or rat-lizard. Some people suggested it was the result of Nasa experimentation on the Red Planet. Others suggested some people should step away from the computerNasa
elephant on Mars
Is there life on Mars? Yes, herds of smiling elephants roam the Red Planet. (Well, it's actually a Martian lava flow)Nasa
thigh bone on Mars
OK, this one really does look like a bone on the surface of Mars (if not the fossilised dinosaur thigh bone imagined by some over-eager Mars fans)Nasa
iguana on mars
A rock that looked like an iguana was spotted by Curiosity in January 2013Nasa
helmet on Mars
A discarded World War Two military helmet on the surface of Mars? No, just a rockNasa
finger on Mars
A finger, complete with fingernail? No, just a rockNasa
penis on mars
Of all of the odd things spotted on Mars, the best one has to be this giant penis accidentally drawn on the surface of the planet by the tracks on one of Nasa's Mars roversNasa