Aston Zehemerata gave a loud squeal of delight and bounded from her window seat to the main door of her family home. “They’re here, Mima! They’ve arrived!” Bouncing up and down with excitement, the child flung open the heavy wooden door, allowing the swirling mists of snow to enter and shower both her and the entry landing with wet, sparkling flakes. Just as she made to dash outside in her small stockinged feet, her father appeared behind her and gently pulled her tiny form back inside.

“Not yet, Aston,” he said. “It may be a while yet before the landing scouts allow the Altairs permission to leave their vessel. Once...