Titan (moon) Titan (moon) Titan is the largest moon of Saturn. It is the only moon known to have a dense atmosphere, and the only object in space, other than Earth, where clear evidence of stable bodies of surface liquid have been found. Titan is the sixth gravitationally rounded moon from Saturn. Frequently described as a planet-like moon, Titan is 50% larger than Earth's moon and 80% more massive. It is the second-largest moon in the Solar System after Jupiter's moon Ganymede, and is larger than the smallest planet, Mercury, but only 40% as massive. Discovered in 1655 by the Dutch astronomer
Fictional planets of the Solar System fragments of a single planet was gradually abandoned over the course of the middle decades of the 20th century in favor of the conclusion that no planet had ever accreted in the region of the asteroid belt in the first place. In fiction, various other names were given to the same or similar concepts. Fictional planets in our Solar System beyond the orbit of Neptune have been employed many times as settings or references in science fiction. Following the general reception of Pluto as the ninth planet of the Solar System in 1930, a hypothetical additional planet was sometimes called