Lord Lenox Redgrave
The wealthy builder and commander of the Astronef, confident in both invention and social authority.
Lilla Zaidie Rennick
An American heiress whose engagement, marriage, and curiosity give the planetary tour its human center.
Mrs. Van Stuyler
Zaidie's chaperone, scandalized by the unconventional courtship but ultimately supportive.
Murgatroyd
Redgrave's loyal engineer, committed to the ship and his inherited duty even at the prospect of death.
Professor Rennick
Zaidie's father, whose discovery of the R. Force makes the Astronef possible.
The Martians
Technically capable but hostile inhabitants whose attack prompts Redgrave's devastating response.
The Venusians
Peaceful birdlike people presented as a harmonious contrast to Mars and Earth.
The Ganymedians
Advanced hosts who welcome the travelers into their crystal cities beneath Jupiter.