[ It isn't different at all. In fact, the only difference between this kiss and the last kiss they shared in Marina is that he's so much more aware of what it's like. In a way it's a lot like the first kiss they ever shared, or at least the first real kiss — on her bed, after a sci-fi marathon in a dome that for all they know no longer exist.
He soon parts his lips to deepen the kiss. There's nothing sexual about it, just a desire to make the most of it while they still can. ]