New Scientist is carrying this article on the six "great" unknowns of the solar system. Some of the answers (such as the one re: relative sizes of the Moon and Sun) seem to rely on some awfully convenient coincidences.
Hey, man, don't look at me. I live on a planet where one of the greatest empires in history originated on an isthmus shaped like a human boot, complete with heel and calf bulge, that's kicking a football. It's all sitting at nearly the middle of a giant lake, which ensures it's even visible from space. If a planet like that had been put in a science fiction movie, nobody'd believe it. And that's just the start of the coincidences of this place. Don't even ask me about the triple alpha process.