Titan is in diameter, 1.06 times that of the planet Mercury, 1.48 that of the Moon, and 0.40 that of Earth. Titan is the tenth-largest object in the solar system, including the Sun. Before the arrival of Voyager 1 in 1980, Titan was thought to be slightly larger than Ganymede (diameter ) and thus the largest moon in the Solar System; this was an overestimation caused by Titan's dense, opaque atmosphere, with a haze layer 100-200 kilometres above its surface. This increases its apparent diameter. Titan's diameter and mass (and thus its density) are similar to those of the Jovian moons Ganymede and Callisto. Based on its bulk density of 1.88 g/cm3, Titan's composition is half ice and half rocky material. Though similar in composition to Dione and Enceladus, it is denser due to gravitational compression. It has a mass 1/4226 that of Saturn, making it the largest moon of the gas giants relative to the mass of its primary. It is second in terms of relative diameter of moons to a gas giant; Titan being 1/22.609 of Saturn's diameter, Triton is larger in diameter relative to Neptune at 1/18.092.
