"--ten. All right, Bo." Lundgard started moving up the slope, light and graceful as a bird. It was wide and open, no place to hide and sneak up behind him. * * * * * Figures reeled through Bo's mind, senselessly. Mass of the asteroid, effective radius, escape velocity only a few feet per second, and he was already on one of the highest points. Brains! he thought with a shattering sorrow. A lot of good mine have done me! He prepared to back down the other side of the hill, run as well as he could, as long as he could, until a bullet splashed his blood or suffocation thickened it. But I want to fight! he thought through a gulp of tears. I want to stand up and fight! Orbital velocity equals escape velocity divided by the square root of two. For a moment he lay there, rigid, and his eyes stared at death walking up the slope but did not see it. Then, in a crazy blur of motion, he brought his wrench around, closed it on a nut at one side, and turned. The right hand air tank unscrewed easily. He held it in his hands, a three foot cylinder, blind while calculation raced through his head. What would the centrifugal and Coriolis forces be? It was the roughest sort of estimate. He had neither time nor data, but-- Lundgard was taking it easy, stopping to examine each patch of shadow thrown by some gaunt crag, each meteor scar where a man might hide. It would take him several minutes to reach the hilltop. Bo clutched the loosened tank in his arms, throwing one leg around it to make sure, and faced away from Lundgard. He hefted himself, as if his body were a machine he must use. Then, carefully, he jumped off the top of the hill. It was birdlike, dreamlike, thus to soar noiseless over iron desolation. The sun fell behind him. A spearhead pinnacle clawed after his feet. The Southern Cross flamed in his eyes. Downward--get rid of that downward component of velocity. He twisted the tank, pointing it toward the surface, and cautiously opened the blow valve with his free hand. Only a moment's exhaust, everything gauged by eye. Did he have an orbit now? The ground dropped sharply off to infinity, and he saw stars under the keel of the world. He was still going out, away. Maybe he had miscalculated his jump, exceeded escape velocity after all, and was headed for a long cold spin toward Jupiter. It would take all his compressed air to correct such a mistake. Sweat prickled in his armpits. He locked his teeth and refused to open the valve again. It was like endless falling, but he couldn't yet be sure if the fall was toward the asteroid or the stars. The rock spun past him. Another face came into view. Yes, by all idiot gods, its gravity was pulling him around!