After astronomical observations proved that Mars and Venus were thoroughly uninhabitable, science fiction storytellers applied the tropes of Planetary Romance to imaginary worlds outside of the solar system, as seen in Ursula K. Moore's Northwest Smith series, and other works of Planetary Romance - a subgenre of science fiction focused on humans having adventures on extraterrestrial worlds with alien cultures and ecosystems.
The John Carter series went on to inspire Leigh Brackett's Eric John Stark series, C.L. Related: John Carter: Every Failed Attempt At Making The Disney Movie There, he embarks on a long, fruitful career of warlord slaying and planet-saving, pursuing a tempestuous romance with the Red Martian princess Dejah Thoris and trouncing armies of foes thanks to his soldier's training and "heavy-worlder" super-strength. The titular John Carter is a Civil War veteran from Virginia who travels via astral projection to Mars (called Barsoom by its natives), an arid, dying world of feuding Martian species and city-states. The Planetary Romance genre as we know it was codified by pulp writer Edgar Rice Burroughs (of Tarzan fame) and his long-running John Carter of Mars series. Like stories and games in the steampunk genre, classic planetary romance narratives such as the John Carter books of Edgar Rice Burroughs are gloriously anachronistic blends of science fiction and fantasy tropes. Gamers who are fans of this retro genre of fiction should check out the following tabletop RPGs, set in universes where Mars is crisscrossed with canals, Venus is covered with jungles, and heroes wield ray guns and sabers with equal aplomb.