Once Upon a Time, Long Ago.

Ganymede is larger than Mercury, and almost half the diameter of the Earth itself. It is the Solar System's largest moon. It is a moon, though, in slumber. It has a surface of ice mountains, often with long intersecting ridges. There are darker and light regions, all of them ancient. There are craters, but the older ones have not been left exactly as they were formed. Once upon a time, Ganymede did not sleep, but had an active surface. The ice moved. [ABSTRACT FROM AUTHOR]