Alternate Worlds

Other worlds are a huge part of both Science Fiction and Fantasy. When writing them it is a good idea to look at existing ecosystems for inspiration. For the science part we are not even limited to good old Earth anymore. Essentially all of Mars is mapped, the moon has been photographed in every imaginable way, and even Mercury and Venus hold few secrets from our probes. Of course there is the problem that all of these extraterrestrial locals cannot host life as far as we know. A story is not much of a story without living beings to motivate it. But the are a good start and the best bet we have at the moment.