Mart Wells shut off the alarm buzzer and jumped out of bed—much to his regret. He cussed and then grinned sheepishly as he brought up with a thud against the fortunately unbreakable glass of the window. A year on Callisto, and he could still forget that he weighed only thirty-six pounds and couldn't take a normal step without neutronium-weighted shoes. Regaining his balance, he yawned and looked out over the rough Callisto landscape beyond Comprotown. Then he yawned again and reached for his uni