In an interview today's L'Osservatore Romano (L'extraterrestre è mio fratello), Vatican astronomer Fr. José Gabriel Funes suggests that life on other planets might not be a problem for the Christian faith.
Obviously, this is all speculative, and there has been no magisterial pronouncement on the question. (I don't anticipate there will be until we are dealing with a real, as opposed to speculative, situation).
The indefatigable Fr. Roderick of SQPN (does he ever sleep?) has translated the relevant chunk of the article, which also covers things such as the Big Bang, and Evolution.