Hello, friends! Let’s talk about aliens!
If we want to find alien life, where should we look? Well, if money were no object, I’d say we should look anywhere and everywhere we can. Phosphorous on Venus? Could be aliens. Let’s check it out. Melty zones beneath the surface of Pluto? Let’s check that out too. Ariel? Dione? Ceres? Let’s check them all for signs of alien life!
But money is an object. We simply don’t have the resources to explore all of these places. Space exploration is expensive. Space exploration will always be expensive so long as we’re stuck using rocket-based propulsion. The Tsiolkovsky rocket equation makes it so.
Whenever you’re working within a restrictive budget, you need to think strategically. With that in mind, astrobiologists (scientists who specialize in the search for alien organisms) have focused their efforts on four worlds within our Solar System. Their names are Mars, Europa (moon of Jupiter), Enceladus (moon of Saturn), and Titan (another moon of Saturn).
This month, I’m going to take you on a deep dive (no pun intended) into Europa. In my opinion, of the four worlds I just listed, Europa is the #1 most likely place for alien life to be found. I don’t mean to denigrate Mars, Enceladus, or Titan. There are good reasons to think we might find life in those places, too. But there are also good reasons to think we might not.
- Mars: Life may have existed on Mars once, long ago. But then the Martian oceans dried up. We’re unlikely to find anything there now except, perhaps, fossils.
- Enceladus: Enceladus’s age is disputed. She may be only a few hundred million years old, in which case she may be too young to have developed life.
- Titan: If you want to believe in life on Titan, you have to get a little imaginative about how Titanian biochemistry would work.
Europa doesn’t have those issues. Unlike Mars, Europa has an ocean of liquid water right now, in modern times. Unlike Enceladus, Europa’s age is not disputed; she’s definitely old enough for life. And unlike Titan, Europa doesn’t require us to get imaginative about biochemistry. The same carbon-based/water-based biochemistry we use here on Earth would work just as well for the Europans.
There are still good reasons to search for aliens on Mars, Enceladus, and Titan. Finding fossils on Mars would be super exciting! Enceladus’s age is, as I said, in dispute, with some estimates suggesting she’s very young, but others telling us she’s plenty old. And while life on Titan would be very different than life on Earth, scientists don’t have to imagine too hard to find plausible ways for Titanian biochemistry to work.
But if I were a gambler, I’d put my money on Europa. And if I were in charge of NASA’s budget, I’d invest heavily in Europa research and Europa missions. Europa just seems like the safest bet to me, if we want to find alien life. And in the coming month, I plan to go into more detail about why I feel that way.
WANT TO LEARN MORE?
If you’re interested in learning more about the Tsiolkovsky Rocket Equation, you may enjoy this article from NASA called “The Tyranny of the Rocket Equation” (because NASA is the American space agency, and anything Americans don’t like is tyranny).
As for astrobiology, I highly recommend All These Worlds Are Yours: The Scientific Search for Alien Life, by Jon Willis. Willis frames the search for alien life just as I did in this post: alien life could be anywhere, but you only have a limited budget to use to find it. So how would you spend that money?
Planet Pailly 
I think Mars gets a lot of attention because it’s a relatively easy destination to get to, at least in terms of the tyranny of the rocket equation. Europa, and any other outer solar system destination, is much costlier. But definitely it’s chance of harboring life today is much higher.
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That’s certainly true. Getting to Mars is a lot cheaper and easier. And if we focused on colonization rather than astrobiology, Mars is way more appealing than Europa. I think the interest in putting humans on Mars drives Mars research more so than the search for alien life.
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I think you’re right that colonization is a big draw for Mars. Unfortunately I think that motive is misguided, at least for some time. But Mars is a much easier place to put crewed research stations. Similar to Antarctica, it’s the closest we’re likely to get to colonization anytime soon. But a crewed search for life is going to be a lot better than a robotic one.
Although improvements in AI and/or propulsion technologies might eventually make Europa an easier call.
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I certainly think, if we want to go digging for fossils on Mars, we’ll need actual people there to do it. If nothing else, the speed of light delay would make rovers too cumbersome for that sort of work. But yeah, that’s a small research station like we saw in The Martian, not a full scale colony like we see in Ad Astra.
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You’ve got great points, and of all the 3 moons I’d definitely agree with you to choose Europa first. That being said, Mars is so much cheaper to go to and it has so many similarities to Earth, and I can’t see much thermal activity other than the very minimal tidal heating on Europa. Some important chemicals for life need a bit of heat to be made, so the life on Europa would need to work around that, plus minimal sunlight. Let’s hope JUICE and the Europa Clipper can provide some more insight!
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There are a lot of good reasons to explore Mars that have nothing to do with alien life. It’s cheaper and easier, for sure. And, as you say, Mars has more in common with Earth. Studying Mars can help us understand our own planet better. On top of that, there’s a lot of interest in colonizing Mars, so it’s smart to try to get the lay of the land before any humans try to go there.
With tidal heating, I tend to think Europa might be in a tidal heating Goldilocks zone. More heating, and she’d end up like Io. Less, and she’d end up like Ganymede.
I’m really looking forward to JUICE and Europa Clipper. When those two missions get to Jupiter, it’s good to be one huge discovery after another!
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