I believe you can hear the miltitary helicopter coming in when they embrace, so one must assume they were knocked out/beaten unconsciously somehow.

But you're right, it didn't seem clear. Not much of this film did. I'm still trying to understand why he and his wife would agree to such an absurd experiment with the result being either he dies from the tests or him leaving for another planet!

@cpheonix said:

I'm still trying to understand why he and his wife would agree to such an absurd experiment with the result being either he dies from the tests or him leaving for another planet!

I saw that as a case of "wide-eyed optimism." I thought the bigger issue facing the test subjects was that the transformation might kill them. The long-term proposal seemed to be they would be "super-human" and able to live on another planet (inferring for a while?). I dunno, that's how I saw it. The result just seemed silly.

@spirit-with-a-vision said:

Wouldn't it be 100 times easier to recruit individuals with no family responsibilities in the first place? And keep the changing individuals in a locked facility, rather than in open homes with kids and spouses? Would cut 100 % of the drama, and possibly make a watchable movie.

They explained that those chosen were because they survived extreme conditions, so being single / having no family would severely limit their choices.

I suppose once the subtle changes started happening they couldn't suddenly lock them up. Although you're right, they should have definitely kept them quarantined once one of them they started showing signs of aggression (killing their spouse would be a good indicator that something wasn't right with the changes...).

Although it goes back to why would someone with a family (Sam Worthington's character) - who clearly loved his wife and kid - essentially sacrifice himself when they themselves wouldn't even be saved unless they could be experimented on and live on Titan?!

@spirit-with-a-vision said:

...and possibly make a watchable movie.

I'm not sure I agree with this bit, but everything else you said is spot on!