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Last Updated: Saturday August 01 2009 15:27 GMT

Spot on Venus puzzles experts

The feature can be seen in the bottom right of this picture Venus (Esa/MPS)

Space experts are baffled by the appearance of a bright spot in the clouds covering the surface of the planet Venus.

The spot was first sighted by an astronomer on 19 July and confirmed by the European Space Agency's Venus Express spacecraft.

It's thought it might have been caused by a huge volcanic eruption, but astronomers just aren't sure.

Whatever the spot is, it's spreading through the planet's dense clouds.

Venus is covered by thick clouds of carbon dioxide, which means an eruption would have to be very powerful to be seen from space.

Another possible reason for the bright spot is particles from the Sun reacting with Venus's atmosphere.

Or it simply could have been caused by winds forcing lots of brighter material together in one place.