At the dawn of the third millennium, planet-sized Titan stood as one of the great mysteries of our Solar System. Large enough to be counted among the planets, Saturn’s huge, orange moon cocooned itself in an opaque blanket of fog and mist (Fig. 8.1). Despite returning some images with resolutions better than 650 m per pixel, the best efforts of Voyagers 1 and 2 failed to gaze upon the moon’s face. There were no breaks in the clouds, no clear skies. Scientists had already come to realize that surface conditions there hovered at the triple point of methane, meaning that the pressure and temperature were just right for methane to exist as a liquid, ice or vapor (Earth’s environment is at the triple point of water). Was Titan graced with a global sea of liquid methane? Was it a desert, a version of Mars in cold storage? A wilderness of solid water ice? What lay beneath those frustrating clouds?