** spoiler alert **
If Europe Report had been Star Trek....
Assume no changes in the story until the ending. You have Kirk, Spock, and McCoy trapped in a lander about to sink into the ice. What happens?
Spock deduces what the Europans are attracted to: light, heat, vibrations, radiation, whatever. Kirk tells Spock and McCoy to repair the lander while he lures the Europans away, nobly sacrificing himself in the process.
Spock argues that he's the logical one to sacrifice himself, but Kirk won't have it. Spock stuns him, takes the equipment to lure the Europans, and heads off across the ice.
Kirk and McCoy repair the lander while cursing Spock's stubbornness and bemoaning his loss. But...as the creatures grab Spock, he mind-melds with them and convinces them he's a sapient being. They didn't realize it; they thought the humans were a weird natural phenomenon.
Just as Kirk and McCoy are about to abandon hope and blast off, the creatures return Spock to the ship. They share an interspecies moment of understanding before the humans depart. Voilà...mission accomplished, no more lives lost, and first contact with a new species established.
True, this wouldn't have been the most original episode of Trek. But with the movie's special effects, it would've been entertaining.
Heroes don't give up
I wasn't expecting exactly that...but at that point, the crew knew they were dealing with a living organism. I don't know if they could've distracted it or lured it away in the short time they had. Perhaps not. But at least a mention of the possibility would've been nice.
If you've watched a single SF show on your long trip to Europa, you know space explorers don't give up. Not until you've exhausted every option, and perhaps not even then. Creatures are attacking you for some reason, so figure it out!
At that point, no way do I step onto the ice without good reason. And they understood that. The two who went out were both acting like it was a death sentence. They thought something was stalking them.
So in that situation, you go into Kobayashi Maru mode. Even if you don't know what it is, something under the ice is threatening you. What can you do to distract it or lure it away?
Maybe turn off all your power sources. Or throw a power pack onto the ice. Worst case, one of the three of you sacrifices himself. Doing nothing and giving up is not an option.
Back to the future
And that's just an action-adventure story. They could've gone all science-fictiony at the end.
You want to use a flashback structure? With a sense of foreboding? Okay. You start the story 500 years in the future. On an empty news stage, kind of like how they did it with the Europa Ventures director. So no expensive special effects.
She tells the story of what happened to the doomed Europa mission 500 years ago. The mission has never been repeated because it was too expensive of a failure. In fact, the Earth turned inward after that. There's been no real space program since then.
Using the same footage but in a more chronological sequence, she recounts what happened. And she makes it sound like it's breaking news. So you're wondering: Why are they revealing the truth about this mission only centuries later? What horrible thing happened on Europa?
You go through the same events--except you don't need the year of radio silence any longer. The ship lands, people die, and the last image shows an alien being.
And now, the big reveal: Europa has contacted Earth after 500 years. Someone or something transmitted the "lost" footage back. And a light is flashing on the landing spot, inviting--or daring--the humans to return.
Boom! That's also ten times better than the actual ending. Score another one for Rob.
And I had vague thoughts along these lines while I was watching the movie. So I'm not just taking advantage of hindsight.
To make a long story short, it's my way of saying why I consider Europe Report merely good, not great.
Answer: The Europans kept the humans alive and bioengineered them into human/Europan hybrids. They've been living under the ice and working to repair their technology ever since. Now they're ready to resume contact with Earth. But...are they friend or foe?!
I'm pretty sure you can make a flashback movie compelling if you use the right cinematic techniques. Like Citizen Kane or Titanic. Heck, practically any sports movie where you already know the outcome.
I like your second idea better.
Of course in the sequel, the Europan octopods have rebuilt the capsule and are on their way to Earth...to take over!
My first version was trying to take their story and make it better without violating their basic premise or requiring expensive new scenes. But yes, my second version might be better, dramatically speaking.
Europa Report 2: Return to Earth could go in several directions. But yes, I'd save the octopods for the sequel. If you want Europe Report to go out with a bang, you end with a shot of the hybrid(s) or something equally chilling.