I am asking because I don't know, but would dust kicked up by orbital bombardment stay up for an appreciable time in a vacuum? I guess it could be re-suspended if an atmosphere is created but more probably would form some sort of accretion if left in vacuum for a few months.
Perhaps some budding astronomer could provide an answer.
It shouldn't. Without air to hold it up the dust should be purely ballistic. Anything that doesn't achieve orbit* or escape velocity should fall within a couple of hours at most, depending on local gravity. A super-bolide like what killed the dinosaurs hitting a high gravity world like Earth can put up enough material that it takes a couple of weeks to clear, but an orbital bombardment shouldn't be anywhere near that scale.
That said, while I haven't tried it, I don't think that Aurora takes any of that into account.
*Orbit on airless worlds tends to mean 'high enough to clear obstacles'.
