A 'cannonball' on Mars has UFO hunters excited

Some are convinced there was once life on Mars

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Mars is apparently fully inhospitable now but based on certain images, some think it was quite different in the past.

One alien hunter says the 'cannonball' is evidence of a war that ultimately ended life on Mars.

However, NASA says the ball is a rock that has turned round following a natural process. Find out more in the video above.

See also: UFO spotted in sky moments before motorway crash

See also: Is this evidence of an alien civilisation on Mars?

Where to go to spot a UFO

Where to go to spot a UFO