Ciaran Slow, of Waihopi School, asks :-

How did Jupiter get its Great Red Spot?

Alan Gilmore, an astronomer at the Mt John University Observatory at Lake Tekapo, responded.

The Great Red Spot is like a giant lazy whirlpool in Jupiter's atmosphere.

It is similar to an anticyclone in Earth's air. Anticyclones are the 'highs' on the weather maps in the newspaper. The Great Red Spot stands out because Jupiter's clouds get wound up in the circling gases.

Many small round spots are seen on Jupiter. They are also anticylones and depressions, similar to those we get on Earth. The Great Red Spot is the same as them but bigger. Because of its size it has lasted longer than the small spots do. It has been seen for at least a century. Jupiter is very cold and so its weather changes very slowly, much more slowly than the weather on Earth.

So it seems that the Great Red Spot is just a super-big anticyclone that formed by chance. Eventually it will fade away, just as they do on Earth.

The Great Red Spot is certainly big, about twice as wide as the earth. It isn't always red. Its colour changes slowly over months and years. Just now it is a cream colour, much the same colour as the cloud around it. This makes it hard to see in a telescope. At other times it has had a much more reddish colour.