Mick Hartley

Is that a plank of wood in this Nasa picture? An old railway sleeper?

Don't be silly. Of course not:

The picture, which was taken as part of Nasa's Mars Exploration Rover mission in May 2004, has given excitable internet message board users reason to believe that a civilisation has formed on the planet.

Some of the more far-fetched theories over the object's identity range from a plank of wood to a giant flake.

However, Dr Jim Bell, an Associate Professor of Astronomy at Cornell University and the lead scientist in the development of the Rover project's cameras, has provided an alternative explanation.

He told the Universe Today website that "sadly" there was no wood in the picture, adding: "I say 'sadly' because personally I think it would be incredible and spectacular to find a wooden plank on Mars. However, in this case, it's just a trick of the lighting and the viewing angle.

He added: "What you're seeing is a piece of flat, platy, layered sulfur-rich outcrop rock … Sometimes, like in this case, those flat, platy rocks have been tilted or dislodged, this one probably from the forces associated with the huge impact crater that formed nearby.

But you notice how he says nothing about the tiles at the bottom of the picture, where someone's quite clearly been laying down a patio floor…