It's almost embarrassing to see all these 'believers' that have no justification for their belief in extra-terrestrial life other than the but-there-have-to-be-aliens-because-of-all-the-planents/solar systems/galaxies/etc. argument.
Has no one even bothered to see if there's a scientific method or theory that may be able to prove "life-out-there"?
Three words: the Drake equation. Look it up.
Anyway, aliens' relationship to Earth's religions; how would religion be affected at all? Half (maybe more) of the bible has been systematically proven false, and still people cling to their belief in a Higher Power. The proof of life in the universe does nothing to dispute the Bible, other than Genesis (which much of the Christian community consider to be highly metaphorical, not literal).
I don't know where in the Bible it says that humans can't leave our planet, but if anyone can point me in the right direction, please do.