Ganymede (moon)

Ganymede[p]  is the largest of the 95 known moons of the planet Jupiter. It is also the largest moon in the Solar System. Ganymede is larger in diameter than the planet Mercury, but has only about half of its mass as Ganymede is much less dense. Ganymede is part of a group called the Galilean Satellites. These also include Io, Europa and Callisto.

Galileo Galilei discovered this moon in 1610.Galilei, G.; Sidereus Nuncius  (March 13, 1610) Simon Marius suggested the name "Ganymede" soon after. In Greek mythology, Ganymede was Zeus' cup-bearer.Marius, S.; (1614); Mundus Iovialis anno M.DC.IX Detectus Ope Perspicilli Belgici , where he attributes the suggestion to Johannes Kepler This name and the names of the other Galilean satellites were not favoured for a long time, and were not put into common use until the mid-20th century. Instead, it is simply referred to by its Roman numeral designation (a system that was introduced by Galileo) as  or as the "third satellite of Jupiter".  Ganymede is the only Galilean moon of Jupiter named after a male figure.

 Structure 
Ganymede is composed of roughly equal amounts of silicate rock and water ice. Its body has an iron-rich, liquid core, and an internal ocean that may contain more water than all of Earth's oceans together. Its surface has dark regions, with impact craters dated to four billion years ago. This covers about a third of the satellite. Lighter regions, crosscut by grooves and ridges and only slightly less ancient, cover the rest. The cause of the light terrain's disrupted geology is not fully known, but was likely the result of tectonic activity caused by tidal heating.Tidal heating: the huge force of Jupiter's gravitation deforms the satellite as it swings round its orbit. The orbit is not circular, and this sets up the stresses which cause the tectonic activity. Ganymede is also the only known moon to have a magnetic field of its own.

 Notes 
[p] ^ The name "Ganymede" is said as /Gan-ee-Meed/.

 References 

 Other websites 
Ganymede 

Category:Jupiter's moons