I don’t think it would affect our faith (i.e., what the Church teaches) in any negative way whatsoever. God is still the Creator, and He can create as many worlds as He wishes.
(It might cause trouble for someone who does not understand the Faith very well and thinks it is tied to a geocentric world view.)
It would, however, raise some interesting issues.
Suppose, for example, that it were proven that the planet is not only inhabitable, but inhabited by intelligent creatures. Clearly, intelligent aliens would be just as much in the image and likeness of God as we are. But there are interesting things to speculate about:
*]Is this species of intelligent creatures also subject to Original Sin? If not, do they still retain their integral (i.e., unfallen) nature? If yes, is it through the sin of their own “Adam” or through ours?
*]Should they be evangelized?
*]Could they receive Baptism?
An interesting take on this topic is C.S. Lewis’s Space Trilogy (especially the first two, Out of the Silent Planet and Perelandra.)