Snow--well, yes, thought Ray, it was snow of a sort. All the water on Ganymede was of course solid ice. So were the carbon dioxide and ammonia. But the temperature often dropped low enough to precipitate methane or nitrogen. The moon's atmosphere what there was of it, consisted mostly of argon, nitrogen, methane, and vapors of the frozen substances--not especially breathable. The colonists used the standard green-plant air-renewal system, obtaining extra oxygen from its compounds and water from the ice-strata, and heated their dwellings from the central atomic-energy units. Ray hoped the ship's equipment was in working order. There was native life out there, a few scrubby gray-leaved thickets, a frightened leaper bounding kangaroo-like into the hills. The biochemistry of Ganymede was a weird and wonderful thing which human scientists were still a long way from understanding, but it involved substances capable of absorbing heat energy directly and releasing it as needed. The carnivores lacked the secretions, obtaining them from their prey, and had given the colonists a lot of trouble because of their fondness for the generous supply of heat a human necessarily carried around with him. "And now what do we do?" asked Ray. Dyann's eyes lit with a hopeful gleam. "Hunt monsters?" she suggested. "Bah!" Urushkidan snaked his way to the small desk bolted to the cabin floor and extracted paper and pencil from the drawers. "I shall debelop an interesting aspect of unified field teory. Do not disturb me." Ray looked around the ship. Behind the forward cabin, which held bunks and a little cooking outfit as well as the controls, there was a larger space cluttered with assorted physical apparatus. Beyond that, he supposed, were the gyros, airplant, and misbehaving engines. "Is this a laboratory boat?" he inquired. "Yes," said the Martian. "I chose it because tey are always kept ready to go out for gibing field tests to new apparatus. Get me a table of elliptic integrals, please." "Look," said Ray, "we've got to do something. The Jovians will be combing this damned moon for us, and it's not so big that we have much chance of their not finding us before we can clean out those tubes. We've got to prepare an escape." "How?" Urushkidan fixed him with a bespectacled stare. "Well--uh--well--maybe get ready to flee into the hills." "How long would we last out tere?" The Martian turned back to his work and blew a cloud of smoke. "No, I will debote myself to te beauties of pure matematics." "But if they catch us, they'll kill us!" "Tey won't kill me," said Urushkidan smugly. "I am too baluable." "Come on, Ray," said Dyann. "Let's go monster-huntin." "Waaah!" The Earthman blew up, jumping with rage. In the low gravity, his leap cracked his head against the ceiling. "Oh, my poor Ray!" Dyann folded him in a bear's embrace. "Let me go! Damn it, I want to live if you don't!"