The Ending and Radiation - Serious Spoilers
I wouldn't have included the very final shot of the alien squid, I think it made the movie seem immediately silly.
They should have ended with the tentacles in the ship - that shot was enough of an indication of what was below the ice. Then the movie could have continued as it did (but kept some dignity), or better yet have announced a return trip to Europa to find out more about this unknown life form.
Also, was the radiation being emitted by the life beneath ice?
When probing beneath the ice, they say that radiation from Jupiter would be blocked by the ice, and that the radiation affecting the probe was being emitted from below the target zone. The effects of radiation are also always a factor whenever the characters encounter the bio-luminescence, but no character ever acknowledged this connection as far as I can recall.