"Os—car" Assistant Navigator Andy Horn cocked an attentive ear and listened for an answer, but only the soft eternal moan of Io's restless winds came to his straining ears. "Dern that perfidious imp of Satan to hell and gone and back again," he muttered, stretching his red neck out like a turkey gobbler and squawking again. "Os—car.... Dern your flea-bitten hide. You better turn up." Gravel grated on a rock ledge not five feet above him and a Ganymedian honey bear stepped daintily into view. It