Today's "Astronomy Picture of the Day" is another shot of Saturn's North Pole and its bizarre cloud pattern in great detail, an image taken by the Saturn-orbiting Cassini spacecraft.
To me, it looks almost as if the hexagon itself rises well above the regular cloud surface, but I suppose that's just a optical illusion since the darker portion in the rear looks to be as flat as everything else.
No one has a clue as to how this cloud pattern was formed, how long its been around, or how much longer it will remain. Some may try to explain them as clouds produced by an atmospheric phenomenon known as "closed Rayleigh-Binard convection cells." That's a theory that's trying to explain some partially hexagon-shaped clouds on earth, but on a scale many magnitudes smaller.
Regardless, it has to be one of the most unusual structures in the solar system.