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 structures in nature. If you ask me, this constructal idea is a pretty monumental claim of answering the question of how patterns and 'design' arises. For a while now, I've always been fascinated about the similar patterns that are visible all around us, like trees, and bifurcating networks, spiral 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 and ethane. It stikes me with awe that on the surface of 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 on other planets the familiar patterns we see on earth, or should we expect something different on truly alien exoplanetary worlds?