 What and where is Ganymede?
The glowing semi-disk of Jupiter was more than half a million miles distant. It had been built for Ganymede, but not for Jeffers. Tolliver began to have his doubts the next day; which was "Tuesday" by the arbitrary calender constructed to match Ganymede's week-long journey around Jupiter. "Ganymede's only about the size of Mercury, something like 3200 miles in diameter, so things get heaped up at steep angles. "Daddy gave me the title of tenth vice-president mostly as a joke, when he told me to find out what was wrong with operations on Ganymede. In the gravity of Ganymede, the man was knocked off balance as much as he was hurt, and sprawled on the floor.
 It’s a moon close to Jupiter.
 It’s a planet close to Earth.  It’s a planet close to Jupiter.  It’s a moon close to Mercury.  It’s a moon close to Jupiter.