Originally Posted by
warty goblin
There was an entire not quite shared solar system of aliens and inhabited planets, which existed from let's say 1912 (publication of A Princess of Mars) to pretty much the minute the Viking spacecraft landed.
So you had Mars, dry and slowly dying, filled with dangers from its vast and often terrifying past. Venus, the jungle planet, inscrutable under the clouds, teeming with new and often primitive life, but with its own ancient dangers. Mercury, which was thought to be tidally locked to the sun, was a half frozen, half incinerated ball of rock, only populated along the twilight belt. Farther out, the asteroids were full of weird little worlds, and also space pirates or very alien things from still farther out. One of the oddities of this brand of sci-fi is that evolution often converges to human, or very nearly human, form, at least on the inner planets. The moons of Jupiter and Saturn are where you find very cruel and inhuman aliens.
But there was no effort to make these consistent between authors, they're really just conventions and broad tropes. Even within a single author's work things might vary enormously. In one Leigh Brackett story Venus is populated by dragon riding natives, in another its controlled by entirely native powers and also has a sea of breathable liquid where slaves labor in subaquatic mines. In yet another, most of the planet us covered in oceans of entirely normal water.
You could say these are on different parts of the planet, or at different points in the timeline, but I think that's a very post-hoc effort to jam disparate stories into, ugh, continuity when they don't need it. It'd be like deciding every story that had New York in it was in the same universe.