If you want to import terrestrial snowballs, you're going to have to design a method for keeping them spherical under liftoff pressures. Wouldn't do to arrive on Europa with a ton or so of compressed snow all over the rear bulkheads of your spaceship, now would it?

Annotated bibliography, yes please. And provenance for whatever you pull off the Internet as opposed to raiding the library or the journal databases.

Have fun! :)