One thing I find consistently missing from these sorts of discussions: Sex.<p>I get that we have a social taboo against talking about it. But really, can we isolate small groups of humans in faraway places and not expect that this will become a major issue? Do we only send couples? What happens when couples split or one member dies? Or does NASA think they can find a perfectly asexual team to send to Mars? Or is this subject simply being ignored completely?