Weird Hexagon on Saturn's North Pole

One of the most recent bits of news from the Cassini Saturn orbiter is the weird (or in the words of NASA, "bizarre") hexagonal cloud pattern at the planet's north pole. Apparently, it's been there since at least the Voyager days. Why would clouds form a long-lived hexagon? Check out the video available with the press release. Is this one of the strangest (or really, most unexplained) things in the solar system? I can't think of anything that seems odder off the top of my head.

By the way, isn't it time we had a long-term ("permanent") robotic orbiter presence at each of the first 8 planets? You never know when you'll find something interesting. Sure it would cost money. Maybe we could cut back on manned spaceflight or something.