First: good work! I quite liked this once it got going - the intro was interesting and did a good job of grabbing me, issues (which others have pointed out) notwithstanding. The background about Europa I didn't find particularly engaging, but once you'd dealt with that and started to focus on the crew I began to enjoy it a lot more.
I'm often a fan of prologues like this, provided they're clearly relevant and enjoyable in their own right. Also, even if you do cut the prologue from the final work, it'll help your understanding of the setting to have written it!
Just two things I want to pick on:
Quote:
Originally Posted by TomS  Jupiter’s ruling presence dominated the sky, its washed out colored bands and storms clearly visible in Europa’s nearly atmosphere-free sky. |
This seems awkward to me because of the repetition of 'sky'. I'd write 'clearly visible through Europa's thin atmosphere.'
Quote:
Originally Posted by TomS “Good afternoon, sir,” said Karen. “Quite a trick of engineering to haul this enormous rig over 400 million miles along with all the-“ |
This stood out to me. What's she on about? It seems like she's about to launch into a massive info-dump, which is a bit of an odd thing for her to do to her commander!