“Tidal Moon” is a science fiction short story by Stanley G. Weinbaum and Helen Weinbaum that first appeared in the December 1938 issue of Thrilling Wonder Stories and was reprinted in the collection Interplanetary Odysseys (2006).
Sam Moskowitz stated that Stanley G. Weinbaum completed only a page and a half of the story before his death, and that his sister Helen Weinbaum completed the story on her own. “Tidal Moon” is the only story by Weinbaum to take place on Ganymede.
Ben Amherst is a cree collector on Ganymede in the year 2083. Although he normally operates alone, he finds himself accompanied on one of his rounds by a tourist from Earth named Kirt Scaler. Scaler plans to travel with Amherst to the village of Aquia, then remain there for two months while Amherst continues on his rounds. Amherst finds Scaler strangely knowledgeable about conditions on Ganymede for someone who claims never to have left Earth before.