Northbound

Commander Hollis did not like surprises, which was an unfortunate trait in a man who had volunteered to live on a moon of Jupiter.

“You’re telling me it’s repeating,” he said, for the third time.

“It’s not just repeating.” Anjali put the spectrogram up on the big screen. “Look. Prime numbers. Two, three, five, seven, eleven. Then it stops. Then it starts again.”

The other four members of the crew crowded into the control room in varying states of dress. Mei still had her toothbrush. Tomasz was holding a mug that said WORLD’S OKAYEST GEOLOGIST.

“Could be ice cracking,” Tomasz offered. “Tidal stress. It does weird things.”

“Ice doesn’t count,” said Anjali.

Nobody spoke. Somewhere under their feet, under the station and the ice and the long black column of water, something went on counting in the dark.

Hollis rubbed his face with both hands. “Nobody transmits anything,” he said at last. “Nobody tells Earth. Not until we know what we’re dealing with.”

“And how do we find out,” Mei asked around her toothbrush, “without answering?”