Or maybe not. As SenseOfEventsBlog notes:
The Church first faced the question of life on other worlds oh, more than 800 years ago.
There was a push from the University of Paris in the late 13th century to have the Church make it dogma that there are no worlds other than our own and that life cannot exist elsewhere.
This push was condemned by Paris' Bishop Etienne Tempier and was condemned by France’s Council of Bishops in 1277. It never made it to the Vatican. The Church has never held that God has not or could not bring forth life anywhere that God chooses, including other planets.and of course, in case you didn't notice: Angels are non human extraterrestrials
So CSLewis could write science fiction with Mars not only populated with three types of intelligent beings, but a planet where they talked to their Eldil all the time...