... B efore the Galileo encounters with Ganymede it was thought that Ganymede and Callisto were composed of a rocky core surrounded by a large mantle of water or water ice with an ice surface (and that Titan and Triton were similar). ...
... Some surface detail is visible in the infrared with HST. T itan is similar in bulk properties to Ganymede , Callisto , Triton and (probably) Pluto . ...
... 61 identified moons in the solar system, only three other satellites are known to have atmospheres: Jupiter's volcanically active moon Io (sulfur dioxide), Saturn's largest moon Titan (nitrogen/methane) and Neptune's largest moon Triton (nitrogen/methane ...
... rose to 31 (almost doubling the 17th century total): Neptune 1846 Johann Gotfried Galle , Urbain Jean Joseph Le Verrier Triton 1846 William Lassell Hyperion 1848 William Cranch Bond Ariel 1851 William Lassell Umbriel 1851 William Lassell Phobos 1877 Asaph ...
... The blue planet was encircled in diffuse, dusty rings and six new moons were discovered orbiting along with the two that were already known, Nereid and Triton . ...