I expect you've heard/seen/read about the crazies who are looking for a middle-aged couple to journey to, around and back from Mars, in a mission they reckon will take a year and a half!
Now, I'm no great relationship success story myself, but this looks like a project full of potential bear-traps!
This piece from the Guardian sort of hints at the pitfalls.
http://www.guardian.co.uk/scie...married-couple-space