IAU Dwarf Planet



At last, on July 1, 2004, the Cassini spacecraft fired off its breaking rocket, glided into orbit around Saturn, and started taking pictures that left scientists in awe. It wasn't as if they hadn't been prepared for such wonders. The weeks leading up to Cassini's arrival at Saturn had served to intensify their already heated anticipation. It seemed as if each approach-picture taken was more enticing than the one preceding it. Titan orbits Saturn once every 15 days and 22 hours. Like Earth's large Moon, in addition to many other moons in our Solar System, Titan's rotational period is precisely the same as its orbital period. This means that Titan only shows one face to its parent-planet, while the other face is always turned away. The scientists also considered other possible sources of hydrogen from the little moon itself, such as a preexisting reservoir in the icy crustal shell or a global ocean. Subsequent analysis indicated that it was unlikely that the observed hydrogen was obtained during the formation of Enceladus or from other processes on the moon-world's surface or in the interior.