Just putting in a quick note about this picture of a river in Titan. It came in today just as i was in the early onset of reading this book, Design in Nature, about the Constructal Law which not only explains, but predicts the formation of patterns, such as river flows and other fractal patterns in nature. If you ask me, this is constructal idea is a pretty monumental claim of answering the question of how patterns arise. For a while now, I've always been fascinated about the similar patterns that are visible all around us, like trees, spiral patterns of galaxies and hurricanes, and so on. Well, it's worth writing about this river in Titan because what flows in that river is not water but liquid methane. It just stikes me with awe that on an alien world with a wildly different chemical make up could produce a pattern that is so familiar to us. Should we then expect to see the familiar patterns we see right here on earth, or should we still expect something different on really alien exoplanetary worlds?