Here’s an article by an atheist who bears an uncanny resemblance to Jack Chick. He theorizes on What Rome Is Up To when a couple of Catholic sources remark that the discovery of life on other planets poses no particular threat to the Catholic faith.

This piece is a classic example of how sin makes you stupid. Our Bright knows ahead of time that Catholics are censorious idiots who fear Truth. So it only stands to reason that Rome fears the discovery of life on other worlds because the first Vulcan we meet will conclusively prove that advanced civilizations have outgrown the god myth and Arthur C. Clarke's Childhood's End is the only truly prophetic book ever written. Therefore, it can only be that "Rome" is preparing a last-ditch spin defense for That Great and Terrible Day: the Definitive Eschatological Event when the Hope of Atheists is fulfilled as we make First Contact with ET and our Elder Intergalactic Brothers Who Have Outgrown god Reassure Atheists They Were Right All Along.

It really is remarkable how much atheists have in common with Fundies. The real Parousia is going to be quite a jolt for both camps.

In fact, of course, the possibility of extraterrestrial organic life—even intelligent organic life—is not a new thing for the Faith.

The best short essays I've seen on this question are from C.S. Lewis. One is called "Religion and Rocketry" and the other is "Will We Lose God in Outer Space?" Lewis points out several basic criteria that have to be met before organic life on other worlds would pose a theological problem to Christianity.

First, it has to exist, which we don't know.

Second, it has to be sentient. Alien oysters cannot sin any more than ours do.

Third, it has to have fallen. An unfallen race is not in need of redemption.

Fourth, we have to know that, being fallen, it has been denied the chance of redemption by God. How on earth (or Thulcandra) we'd ever figure that out beats me.

Fifth, we have to know that the redemption will be forever denied this hypothetically existent, hypothetically rational, hypothetically fallen race. After all, if you'd visited earth 10,000 years ago you would not have seen too many obvious clues that redemption was in the works for us. And since the only way to know that God has no plans to redeem them is to know the mind of God, this seems an especially tricky hurdle to get over.

Sixth, we have to know that redemption via an incarnation, death and resurrection of God the Son in this fallen alien nature is the only way in which God redeems fallen creatures and that such a redemption will never be granted such creatures.

As Lewis says, if our faith never encounters a bigger challenge than this, we are sitting pretty.

The curious thing is that atheist materialists, deluded by their fantasy philosophy, tend to inhabit a mental universe populated by creatures of Gene Roddenberry’s imagination rather than cold hard fact. As strange as it sounds to say it, the best thing these allegedly scientific atheists could do here is stop listening to fairy tales about Klingons and Vulcans and face the fact that the real non-human intelligences have been known to the Church since its birth. They are called "angels" and “devils”. The only thing the Church (and real science) is agnostic about is the existence of organic intelligent creatures. If it turns out God made those too, then glory to God! He can do as he likes. It is, after all, his universe.

That said, I would not be a bit surprised to discover that we are, in fact, alone. As Ward and Brownlee have done a fine job of demonstrating in Rare Earth, the Copernican Principle (i.e., the notion that planets like ours are dime a dozen in the Great Grand Scheme of Things) is waaaaaaay over-rated. I wouldn't be at all surprised if our planet is one of the few in the galaxy to have complex life and the only one with intelligent life. After all, all the hard evidence supports this view so far. If the universe is crowded with alien civilizations, then—as Enrico Fermi asked 50 years ago and projects like SETI are making more acutely felt with each day—where is everybody? But I won’t bet the farm on the proposition the we are alone. I merely note that what difficulties I have with the notion of extra-terrestrial intelligence have nothing to do with the Faith.

Finally, supposing, just for argument’s sake, Klaatu does touch down on the White House lawn tomorrow: should Catholics preach the gospel to him? Until Lewis' questions are answered I doubt there would be much point. Indeed, as Lewis’ Space Trilogy suggests (almost alone in the canons of science fiction that I know of), the reality may well be that an unfallen race would be way ahead of us in their knowledge of Maleldil, just as the angels are. That only stands to reason since the universal God who reveals himself to us in Christ Jesus would be present to the souls of unfallen rational creatures without the hampering effects of original sin. Missionaries to an unfallen planet might find themselves embarrassed by the knowledge of their students, who would all speak "with authority, not like the scribes and Pharisees."

I tend to side with Lewis in his speculation that, if there are any intelligent critters out there the vast distances of space are designed to be a quarantine. If we ever made contact with a technologically inferior race, we would murder and enslave them as we have murdered and enslaved weaker members of our own race. If they were technologically superior, they would very properly annihilate us in self-defense.

But, as I never tire of saying, that won't happen, because we are never getting off the earth in any serious way and we will never contact any aliens. It will be vastly simpler to erect a glittering metropolis in Antarctica then a self-sustaining colony on the Moon, much less Mars. And the irrational anger that cheery assertion typically provokes in our culture is, I think, one of the surest proofs that we have largely substituted a secular eschatology of the Glorious Ascension of Man for a Christian one.