question:  What and where is Ganymede?
context: By H. B. FYFE [Transcriber's Note: This etext was produced from Worlds of If Science Fiction, September 1961. The big moon-face of Jeffers, manager of the Ganymedan branch of Koslow Spaceways, glowered back at him. The glowing semi-disk of Jupiter was more than half a million miles distant. Maybe they live soft back on Earth since the mines and the Jovian satellite colonies grew; but they were out here in the beginning, most of them. It had been built for Ganymede, but not for Jeffers. How else can you get pilots out to Jupiter?" 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. His contract guaranteed a pilot's rating, but someone had neglected to specify the type of craft to be piloted. On the bulletin board, Tolliver's name stood out beside the number of one of the airtight tractors used between the dome city and the spaceport, or for hauling cross-country to one of the mining domes. He soon found that there was nothing for him to do but hang around the garage in case a spaceship should land. Sometimes there's no reason but them for sending a ship back with a crew instead of in an economy orbit. She was about five feet four and moved as if she walked lightly even in stronger gravity than Ganymede's. They found they could send back loaded ships by 'automatic' flight—that is, a long, slow, economical orbit and automatic signalling equipment. Then he headed the tractor across the frozen surface of Ganymede toward the permanent domes of the city. "Any square inch of Ganymede is likely to be dangerous." "Ganymede's only about the size of Mercury, something like 3200 miles in diameter, so things get heaped up at steep angles. "I'm retiring in six months if I'm still alive," he said bravely, edging the tractor into the airlock at their destination.
output:  It’s a moon close to Jupiter.
options:  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.