The stories are marked by attention to the detail of the alien ecosystems with which Weinbaum equips his planets.
In Weinbaum's Solar System, in accordance with the then-current near-collision hypothesis, the gas giants radiate heat, enough to warm their satellites to Earthlike temperatures, allowing for Earthlike environments on Io, Europa, Titan, and even Uranus.
Mars is also sufficiently Earthlike to allow humans to walk its surface (with training in thin-air chambers) unprotected.
By 1934, the Solar System was known to consist of the Sun, nine planets, 26 moons, and a few thousand asteroids and comets.
Weinbaum limited himself to planets and moons as settings, naming the following: (All entities mentioned are nonsentient animals unless otherwise noted)