Christmas on Ganymede by Isaac Asimov

Olaf Johnson hummed nasally to himself and his china-blue eyes were dreamy as he surveyed the stately fir tree in the corner of the library. Though the library was the largest single room in the Dome, Olaf felt it none too spacious for the occasion. Enthusiastically he dipped into the huge crate at his side and took out the first roll of red-and-green crepe paper. 

What sudden burst of sentiment had inspired the Ganymedan Products Corporation, Inc. to ship a complete collection of Christmas decorations to the Dome, he did not pause to inquire. Olaf’s was a placid disposition, and in his self-imposed job as chief Christmas decorator, he was content with his lot. 

He frowned suddenly and muttered a curse. The General Assembly signal light was flashing on and off hysterically. With a hurt air Olaf laid down the tack-hammer he had just lifted, then the roll of crêpe paper, picked some tinsel out of his hair and left for officers quarters. 

Commander Scott Pelham was in his deep armchair at the head of the table when Olaf entered. His stubby fingers were drumming unrhythmically upon the glass-topped table. Olaf met the commander’s hotly furious eyes without fear, for nothing had gone wrong in his department in twenty Ganymedan revolutions. 

The room filled rapidly with men, and Pelham’s eyes hardened as he counted noses in one sweeping glance.

"We’re all here. Men, we face a crisis!"

There was a vague stir. Olaf’s eyes sought the ceiling and he relaxed. Crises hit the Dome once a revolution, on the average.