Oh yea, and drop that whole "all the planets orbiting one sun" nonsense since it isn't workable. Miranda would have been frozen ice-ball _or_ the "inner planets" would be molten slag.
It was their way dealing with the issue of no FTL travel. And a rather good one at that. Partly terraformed planets led to the many barren landscapes they visited, and they could get to another planet/moon within a reasonable amount of time (ie, before they run out of food and water).
The absent ones are always at fault.