It was a hard life. Crystalline rock was cut by machines at the mine-faces, and by the time other machines had brought it up the shafts to the surface-level in the domes, it had become amorphous and powdery, its crystalline structure destroyed by being heated to twenty degrees below zero Centigrade. When you repaired machinery below the surface, you wore sixty kilograms of spacesuit (Earth weight), and a failure of any item of equipment or a fumble by any member of your crew might mean sudden death. The walls of the dome shut you in from the sky, for the vacuum out there was death too; when you did get up to the observatory to see the sky, you saw Jupiter, weirdly streaked with brilliant color--if your dome was on the side of Callisto toward Jupiter. Otherwise, you looked across twenty million kilometers of vacuum to the nearest star.
It was a hard life, and no life for a lone wolf. There were no homestead farms to be settled by lonely pioneer families. Callisto was a sterile place, and to keep life going there at all men had to work together. Cooperation was a lesson Earth civilization had learned only after thousands of years of oppression and war; a lesson that had to be learned before men could cross space; and a lesson that was very difficult to forget on Callisto. At least for most people.
Rita and Cliff Belden had control of the trade between Callisto and the inner planets. It didn't start as control, though; the way it began was this: Once the colony had been well established, its operation was left completely up to the Callistans, who shipped as much of their goods to Earth as they could manage, and requisitioned as much food and supplies from Earth as they needed--which was really the best way. The inner planets could not very well take part in the planning of Callisto's activities, since there was no radio contact and the trip took over two months by freighter even when the relative positions of the planets in their orbits was most favorable. One freighter shuttled back and forth between No. 2 Dome on Callisto at one end and any of several inner-planet ports at the other. Rita and Cliff Belden were the two Callistans whose job it was to run that freighter.