Ace Books Paperback No 01770; copyright 1963; no other dates EXCEPT the glossy-paper two page cigarette ad in the middle of the book references a 1976 FTC report. 147 pp. Size MMPB. Covers and pages clean and unmarked EXCEPT some shelf wear to spine edge and front cover edges and a small crease at the back cover lower corner; spine is not creased. Novel formed from two previously published stories: "The Ark of Mars" (Planet Stories, September 1953); and "Teleportress of Alpha C" (Planet Stories, Winter 1954/1955).