From a glance through some
relevant pages, my impression is that most of the time, genre has more to do with the content of the story than merely its setting. Genre can be based on your audience, or who the main character is, the tone of the story, what happens over the course of the novel, the
reason behind writing the novel in the first place...
Haven't found anything that separates stories by whether they occur on Earth or a place other than Earth, which is probably just a well because there are so many other options that give a less general view of the plot.
You may as well say, "I'm writing an adventure/satire/Western/et cetera set on another world," if you want a way to describe it to people who want to help.
I dunno, hybrid genres can be a pain. I'm working on just one setting that can be classified as low sci-fi / social fiction / tragedy / bildungsroman / adventure / political / quasi-paranormal / travel fic...