Last updated at 11:09 04 February 2008

It's never miserable on Mars if this picture of smiley face on the planet's surface is anything to go by.

Perhaps this is finally proof there is life on the red planet and that the Martians enjoy a joke.

These amazing pictures were taken by the Mars Reconnaissance Orbiter, which is on a scientific mission to the planet.

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Experts say this is just a bizarre bump in the landscape and have dismissed wild claims that merry Martians had been up to any high jinx.

The NASA Orbiter took the image on a special high-definition camera and has been studying the planet for signs of water since October 2006.

The happy face can be seen in a crater 3km wide in the Nereidum Montes.

The images come just a couple of weeks after a strange figure was spotted stalking the landscapes of the red planet.

The picture caused a stir on the internet as amateur astronomers speculated about the seated figure which appeared to be pointing into the middle distance.

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The photograph was taken by Spirit, Nasa's Mars explorer vehicle which landed there four years ago.

But again experts feel that it is simply an optical illusion caused by the rocky landscape.