The nine stories in Earthmen And Strangers include "Life Cycle" by Poul Anderson and "Out of the Sun" by Arthur C Clarke. Both of these stories are set in the twilight zone of a Mercury still believed to turn only one side towards the Sun but also to librate, thus causing a local sunrise and sunset. Anderson's characters encounter Mercurian life whereas Clarke's encounter Solar life. Anderson's Terrestrial characters are accompanied by a feathered, owl-faced Martian who sounds familiar from other Anderson works.
Anderson devises an ingenious life cycle in which hive-minded Mercurian females inhabit the Twilight Zone but must risk the dangerous heat of Dayside in order to be fertilized, as they believe, by their gods. Since females past the age of fertility return to Dayside to die, it does not take long for the Earthmen to deduce that the females apparently going to their deaths are in fact going to be transformed by the heat into the males of their species.
There is an eerie moment when the Earthmen, disguised as females, having entered the Dayside temple, see the gods approach:
"...tall lizardlike forms, in burnished coppery scales, wreathed in silvery vapor - they glowed, walking dragons, but they did not burn. They advanced...Their beaks gaped..."
- Poul Anderson, "Life Cycle" in Robert Silverberg, Ed., Earthmen And Strangers (New York, 1966), pp. 91-116 AT p. 111.
Having visited Greystoke and Hadrian's wall yesterday, today we visited the Lake District town of Keswick where I bought Earthmen And Strangers as a second hand paperback in a charity shop.
