There is absolutely no doubt in my mind that life exists on other planets. Space is massive enough that we could easily consider it infinite and that assumption would fail us only when the mathematics get so large that the numbers are expressed in exponents of exponents. For the average person, skittering around on the face of this planet, believing the universe to be infinite is the ultimate in “close enough.” Go outside tonight, or right now if it happens to be night time. Go outside and look up. When you suddenly realize that you can’t even see a mere fraction of the way to the boundaries of our galaxy, let alone the cosmos, then the idea that we’re alone in space becomes incredibly absurd.
We’ve only begun to catalogue the planets we’ve discovered orbiting other stars. Astronomers have long known those planets were there, but like all good scientists, they needed proof. In science, the act of assuming anything is a dangerous business, even when the odds are so wholly stacked in your favour. So we waited, and technology eventually caught up with our desires, and we started finding planets, lots of planets. We live in an exciting time where we know about more planets than people have ever known about before. For the longest time, our ancestors knew only of six planets; Mercury, Venus, Earth, Mars, Jupiter, and Saturn. Now we know of the existence of over 300 planets and we know that there are many more planetary bodies in our own solar system. We may not call them planets, perhaps they’re dwarf planets, but we know they’re there.
So what about life?
Well our knowledge of those exo-solar planets is woefully limited. We’re doing the best we can, but you can only learn so much about something that’s so far away. Indeed, that we know about the atmospheres of some of these planets is amazing. It’s like someone standing in San Francisco and telling you how much condensation occurred when someone exhaled in Stockholm. But, you know, maybe we don’t have to look so far away. Our solar system has eight planets, 178 known moons (or satellites if you prefer the true scientific term), and not a single one is like another. Even moons circling the same planet are all different, each one a unique place with a unique makeup. With that much diversity, could there be life closer to home?
Well, maybe. Let’s look around a bit, shall we?
Now first off, when someone starts mentioning extraterrestrial life, the idea of life on Mars isn’t far behind. Heck, it’s usually the next sentence. The thing is, when you get right down to it, Mars could be a really lousy place for life to develop. I’m not saying it’s impossible, but for a change, let’s look at other places and have a comparison to Mars. At the very least, maybe you’ll look at the possibility of life on Mars in a whole new light.
So, what’s the one thing that seems to be needed for life? Air? As in oxygen? Well, no. There are plenty of organisms that don’t need oxygen to survive, and they’re closer than you may be comfortable with. Crawling around in your digestive track are a bunch of anaeorbic bacteria that not only don’t need oxygen, but die in its presence. There are also specimens of tube worms living at the bottom of the ocean near volcanic vents that don’t require oxygen to live.
Fine, how about light?
Turns out, humans are light-chauvinists because we, as a species, prefer light. We live in the light, do our business in the light, and when it becomes dark, we make artificial light. That’s us, what about sea life living miles below the surface of the water, where the sun never shines? There are plenty of creatures in caves that haven’t a clue what this whole “light” thing is. So no, light really isn’t a neccessity.
When you get right down to it, there’s one thing that we know of that really kicks off the whole “life” game, the one thing that needs to be present for life to get its start and keep going.
Solid water is okay, gas can work in some circumstances, but if you can get yourself some liquid water, then you’ve got the primary thing. After you find liquid water, the rest of life is literally organic chemistry. As it happens, organic chemistry isn’t all that complex (on its surface) and all the building blocks you need to start things along to making a living creature are well scattered throughout the universe. And the bonus is this — if you have water, then chances are you’ve got the rest. Organic building blocks and water have this habit of showing up in the same places.
So have a look around us, at the various places in our own little solar system. Who has the water?
Well, obviously we do, but that’s not interesting. Where else?
If you look at Mars, you see a very Earth-like landscape in many regards. The problem is, when I say “Earh-like” I mean “like Death Valley.” Mars can be divided, simply, into four geological areas:
Barren, sand blasted deserts where the winds driving the sandstorms can encircle the entire planet with gusts around 120 miles per hour (192 km/h).
Olympus Mons, the largest volcano in the solar system.
Valles Marineris, a canyon so large it makes the Grand Canyon look like a gulch.
None of those options really bespeaks of our need for running water. Sure, there’s water there, but its locked up in the frozen polar caps. Valles Marineris could have been carved by flowing water, like canyons here on Earth, but if so, that water is nowhere to be found today. So you’re left with a dormant volcano and deserts.
Oh, and there’s this problem with the temperature. Your average, sunny day on Mars means temperatures around -55 degrees Celsius, or -67 degrees Fahrenheit. Since the freezing point of water is 0 degrees C, then I bet you’re already starting to see the problem. We’ve observed tantalizing evidence of the sudden appearance of what looks like water in some of the ravines on Mars, and then that water (if it is water) freezes solid in seconds. Could there be subsurface water, hidden below the freezing deserts and kept liquid by the insulating nature of the sands?
Maybe, and I hope there is. The issue is, we just don’t see a lot of it. While you can get life from a puddle, you’ll find far more in an ocean, and you get better odds.
Fine, okay. Is there someplace besides Earth with liquid water?
The answer, I’m happy to tell you, is YES!
There is one place that fits our bill for liquid water and there’s another place that has a really strong chance of it too. Surprisingly, neither are planets, but moons orbiting other planets. In the realms beyond the asteroid belt, there are two candidates for life that, in my opinion, present a far more compelling venue for critters than Mars.
The first, in order, is Europa, a satellite of Jupiter. Europa is the smallest of the moons discovered by Gallileo when he peered through his telescope but, as they say, size doesn’t matter. When you look at Europa, you wonder how life could exist there. It’s cold, much colder than Mars which is downright tropical in comparison. The surface temperature of Europa hovers around -223 degrees C or -369 degrees F. The entire satellite looks to be covered in a sheet of ice. Since the water is solid, how is that helpful?
See, when you take a look at the surface of Europa, everything is new, or at least it’s all new on a geological and cosmological timescale. One way to tell the age of a planet’s or moon’s surface is to have a look at the number of craters from meteorite impacts. Take a look at the Earth and you’ll not find a whole lot of craters. Sure there are a few, Meteor Crater in Arizona being particularly famous, but here’s nowhere near as many craters as on our own Moon, which is only right over there. On the Earth, there are all kinds of processes to take care of impact craters. There’s the wind. There’s running water and falling water. There’s glacial movement, scouring the landscape like you might scour greasy pots in a sink. There’s tectonic action, where the crust is moving, falling, rising, and transforming itself. After a few million years, just a couple of seconds to the cosmos, those impact craters disappear.
Not so on the moon. Without air, there can be no wind to sofen the craters. Without water, nothing will wash them away. And we can see that there’s little to no tectonic action on our moon because there are so many craters and because they’re so old.
That’s far from the case with Europa.
Europa has very few craters. They’re gone. The ice near the surface looks fairly new, like it formed in the last few thousand years. There’s a very tenuous atmosphere on Europa, mainly oxygen, but it’s not enough to blow things around and rework the landscape. As it happens, it’s quite easy to account for the relatively new surface of Europa — it all makes sense if there’s a subsurface ocean.
Sure, the surface is frozen, but what about underneath? Gravity can do funny things. Look at the tides here on Earth caused by the Sun and the Moon. While our Moon and Europa are comparable in size, and while the Sun is much more massive than Jupiter, it just so happens that Jupiter is a lot closer to Europa and it exerts an incredible tidal force on the satellite. Take a stress ball, or a foam ball, just something round and soft that you can hold in your hand. Gently squeeze it between your hands. Notice how it bulge? Now, roll the ball between your hands while squeezing it. See how the bulges remain in more or less the same place, but the surface of the ball moves?
That’s exactly what’s happening on Europa and that tidal effect causes heat. Now it’s not the kind of heat that will melt an icey surface exposed to space, but it is the kind of heat that will keep water flowing underneath an icey surface acting as a layer of insulation. As the water temperatures rise and fall, that water flows up and down and creates a current. Those currents, running wide open in a subsurface ocean, would melt, uplift, crack, and rework the surface of Europa on a very regular basis. It’d be very similar to tectonic action on our own planet. A satellite wide iceshelf that doesn’t seem to be moving actually is, all be it a little too slowly for us to notice.
Better yet, according to research by Richard Greenberg, a scientist with the Lunar and Planetary Laboratory in Tuscon, that surface ice could be brimmng with all kinds of stuff needed not just for life, but for larger forms of life. The surface is getting bombarded with radiation. Jupiter itself has an intense radiation field around it but Europa is getting a big dose from the Sun as well. So what?
So this, all of that radiation could be striking the ice and liberating electrons, changing atoms, and basically causing chemical reactions to make oxygen. The oxygen remains trapped in the ice until the surface area shifts, which it seems to do fairly regularly. Then that surface ice contacts the ocean below, melts, and oxygenates the water.
Oxygenated water. Now we’re not talking microbes or bacterial life, we’re talking larger forms, like fish-sized life. I don’t imply there to be fish on Europa, but with an oxygenated water source, you’re more likely to find larger organisms. Who knows what could develop there?
The next thing for Europa is the JUICE mission by the European Space Administration. Short for Jupiter’s Icy-moons Explorer, this mission is scheduled for launch in 2022 to explore several of Jupiter’s moons, including an accurate measure of the thickness of Europa’s ice-crust. That’s nice and everything, but you won’t see a massive grin on my face until we somehow put something down on that surface and do some literally in-depth studies to find out what lies beneath.
Note: In my next essay, we’ll look further afield in our solar sytem towards another icy moon orbiting Saturn and, coincidentally, beginning with an E – Enceladus.
Daniel Messer is a librarian, technologist, digital creative, blogger, historian, podcaster, author, and cyberpunk. By day, he's a webmaster for a public library system. After hours, he's online and scanning the web for signs of intelligence.