Father Gabriel Funes, director of the Vatican Observatory, has said that there could be life on Mars, and if there is, that doesn't contradict Christian belief.
(Well, yeah. Can't see why it would.)
This is the part that put me in mind of the C.S. Lewis book Perelandra:
Just as there are multiple forms of life on earth, so there could exist intelligent beings in outer space created by God. And some aliens could even be free from original sin, he speculates.