Theeeee Space Pope!
Sure, Martians, fine. Just not gay Martians.
I'm sure he's just trying to be nice and inclusive, but if there's anything that'll cause interplanetary war it's religion.
He'll baptize gay Martians, he just won't marry them. Which is going to get awkward really fast if it turns out that Martians are a species of hermaphrodites.
"they should be accepted with open arms"
Has he issued a ruling on performing an exorcism on their UFO? If so, can he also rid Scientologists of body thetans?
One of the theories for alien contact is the Prime Directive scenario where aliens exist and have a huge intergalactic community but you're not allowed in until you can prove that you can behave yourself. There would be a set of criteria that you have to pass before first contact is made. I've thought about what that list would look like and "giving up outdated superstitions" is one of the possibilities.
Generally it looks something like:
1. Developed a sustainable energy supply (green energy)
2. Developed a sustainable mineral supply (recycling)
3. Climate/pollution levels stable
4. Majority of planet's able population is productive and reasonably cared for. No such thing as the "third world"
5. No major conflicts, resource disputes are handled peacefully and fairly. (tribalism would have to become a relic of the past)
6. Some sort of world government is available -- Otherwise who do you contact?
7. Has something to offer on the galactic stage -- This is a real wildcard, since we would likely be many thousands of years behind technologically, but it's not impossible that we went down some branch that most everybody else did not. Maybe our silicon based electronics are unique in the universe (not likely) and can offer some advantages. More likely it would have to be art/music/culture instead.
Unfortunately a list like this means neither me nor my children are going to be around for first contact. All of these problems are way too big to deal with in my lifetime. But it's also completely and entirely reasonable I think. Nobody is going to give away Warp drives to someone who still thinks war is a reasonable option--that's just asking for trouble. And you don't want people who have not even figured out their own shit messing up other planets. Plus, the timescales involved are potentially huge. They may not even check but once every 1,000 years or more, especially if travel is expensive.
So that says if he would baptize alien converts, but that leaves the question of how. What do you do if they're aquatic? What happens if pure water hurts them, or they exist at temperatures or pressures where the liquid isn't stable? Do things like ammonia or vapor baths become acceptable alternatives, and how do you determine?
If we're exploring how theology holds up in hypothetical cases, that would seem to be a more interesting question than whether assumed-to-be-ensouled-creatures would be treated as such by people willing to make that assumption.
This pope is the "Who am I to judge homosexuals?" pope, though. He'd probably baptize them and marry them -- who is he to close doors?
What kind of gets in the way is some of the bureaucrats that are invested in the hateful status quo, but the dude on top seems like he'd be down with it.
Hmm, I wonder if he would be willing to marry a human and a space alien?
Might depend how different they are from us. If they look like Star Trek aliens that are just people with funny forehead bumps maybe it won't be so bad. Something like a Pierson's Puppeteer would be an entirely different matter. Or some being of pure energy that only partially exists in our dimension.
Those aren't really the hard questions. Over the centuries, Christians have many times found themselves in circumstances where it's impossible to do things by the book. Try bringing bread and wine into a prison some time - I dare you.
The hard question is the one Il Papa answered - what do you do if they aren't human? Long ago, somebody had to grapple with a harder question: what do you do if they aren't Jews? Inclusion wins in both cases.
EDIT: @wubfurradio That article is pretty awesome.
Out of curiosity, why would an alien necessarily require salvation? Did the original sin affect them as well? Only species within our light cone, or is it transmitted at superluminal speeds?
Solved or not, it's the question I would have been vaguely interested to see answered. It would maybe show some creative thinking about what converting aliens entails, give some hints about the sort of challenges that it would take to spread faiths between worlds, etc.
Whether people outside a particular genetic group might ever be allowed in an organization is less philosophically curious, on the other hand, is usually obvious unless you've decided to be awful. The pope announcing they aren't already planning to be awful to at least sufficiently human-like aliens, well...that's nice and all, but we'd see depending on what they're like.
Oh I know. But the answer wasn't obvious in the 1st C. and it took some wrangling to get there - kind of like today. I'm just drawing a parallel - to ancient Jews, Greeks were pretty damn alien.
As for creative thinking, there's been plenty over the last 50-70 years. CS Lewis asked the question of other planets long, long ago, and came up with some interesting answers. Teillhard de Chardin had some pretty weird ideas too.
I like to think that a sufficiently advanced race that can travel the stars would be at a point in their evolution that they've gotten past using mythology and fantasy to explain the world around them. With a little luck they'll find all of our world's religions amusing and quaint or it goes the other route and they think we're all a bunch of simpleton heathens that should be killed and our resources pillaged because we are not their gods "chosen people". I mean what are the odds of the history of human exploration repeating itself, only on a much larger scale where we aren't the ones holding the vastly superior technology and war-faring skills this time?