The north pole of Saturn is a gigantic hexagon easily capable of swallowing the entire earth. That the feature is so symmetrical and of at least twenty years standing has become a great mystery of the solar system. The hexagon is made up of swirling gasses, but we know of nothing that would cause a cloud to form a hexagonal shape and remain like that for an extended period. The cloud could be much older than 20 years. That’s simply when we discovered it.
Here’s a nice video about it: http://www.youtube.com/watch?v=FOiV1RSfMnQ&NR=1
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