Ganymede This is one of the four moons Galileo observed, discovered January 7, 1610 (by a Westerner.

Ganymede This is one of the four moons Galileo observed, discovered January 7, 1610 (by a Westerner.  It is thought Ganymede was observed as early as 365 BC by Chinese astronomers).  Ganymede is larger than Mercury, with a large amount of water trapped beneath the surface.  The dark regions you can see in the picture above are dated 4 billion years old and are covered with impacts from the early formation of the solar system.  The lighter area is slightly less old, and its causes are not yet fully understood, however, it’s thought to be due to some sort of tectonic activity caused by tidal friction.  This moon has a thin oxygen atmosphere which possibly includes ozone-a constituent of our own atmosphere.  Here’s a gif showing how Ganymede orbits Jupiter: And here’s a picture of Ganymede’s internal structure: Anything you want to see?  Message me! -- source link

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