- Amanda Barton, heiress - Solving the mystery of her father's death / romantic interest.
- Andrea Walsh, secretary - The plucky assistant / romantic interest.
- Dick Reckard, mine foreman - Ruggedly handsome with a mysterious past (of course). I can only assume that's a toupee, it can't be his real hair...
- Doctor Grigori Hauser, Surgeon - Rum-sodden doctor, the best (and only) on Titan
Mayor William Richards - Mayor of the Titan colony, and commander of its armed forces (all four of them)
- Belle Nova, “Hostess” - A scarlet woman, of course.
The last one may be familiar, but I hope the rest are reasonably obscure actors / actresses.