Where ever we find water on Earth we find life. And so, it makes sense to search throughout the Solar System to find water. Well, here’s the crazy thing. We’re finding water just about everywhere in the Solar System. This changes our whole concept of the habitable zone.
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Female Speaker: This episode of Astronomy Cast is brought to you by Swinburne Astronomy Online, the world’s longest-running astronomy degree program. Visit astronomy.swin.edu.au for more information.
Fraser Cane: Astronomy Cast episode 352: Water, Water Everywhere. Welcome to Astronomy Cast, our weekly facts-based journey through the cosmos. We’ll help you understand not only what we know, but how we know what we know. My name is Fraser Cane, I’m the publisher of Universe Today, and with me is Dr. Pamela Gay, a professor from Southern Illinois University Edwardsville, the Director of CosmoQuest. How are you doing?
Dr. Pamela Gay: I’m doing well; how are you doing, Fraser?
Fraser Cane: Good. Have you got anything interesting to say about CosmoAcademy?
Dr. Pamela Gay: We have a bazillion classes going on, so sign up now, please, please, please.
Fraser Cane: Yeah, I don’t think I’ll do the long version of this, where I, like, just, like, “Listen everybody. CosmoAcademy is the greatest thing you could ever want. And you get to have these classes with amazing PhD researchers, and they’ll teach you everything about black holes, and observational astronomy, and it’s the best. And it’s a reasonable price, and you can learn from these brilliant minds. So if you haven’t already, go sign up. Why wouldn’t you? All right. Cosmoacademy.org?
Dr. Pamela Gay: Yes.
Fraser Cane: Okay.
Female Speaker: This episode of Astronomy Cast is brought to you by 8th Light, Inc. 8th Light is an agile software development company. They craft beautiful applications that are durable and reliable. 8th Light provides disciplined software leadership on demand and shares its expertise to make your project better. For more information, visit them online at www.8thlight.com. Just remember, that’s www dot, the digit 8, T-H, L-I-G-H-T, dot com. Drop them a note. 8th Light: software is their craft.
Fraser Cane: So wherever we find water on Earth, we find life. And so it makes sense to search throughout the Solar System to find water. Well here’s the crazy thing: we’re finding water just about everywhere in the Solar System. So this changes our whole concept of the habitable zone. All right Pamela, you put this one on the docket. What were you getting at?
Dr. Pamela Gay: Well, so – it used to be – like when we started this show, when people started talking about habitable zones and stuff they were figuring, well, like that Goldilocks place where it’s not too hot, it’s not too cold, and you’re able to support liquid water on the surface of the world. Well, we’re now kind of finding liquid water everywhere in the solar system, and it’s appearing more and more that what’s actually required is something to prevent it sublimating away into the atmosphere, and a good case of gravitational squishing.
Fraser Cane: Right, which giant planets provide that in spades.
Dr. Pamela Gay: Yes. And then we’re also finding places with water that I know I never expected. It looks like the world Ceres, formerly known as a planet, now known as the largest asteroid, still getting called a planet by some –
Fraser Cane: It’s a dwarf planet.
Dr. Pamela Gay: It’s a dwarf. So Ceres is – it’s starting to look like, even though it’s not exactly undergoing tidal heating from anything, it looks like it might have cryovolcanism, which means maybe it also for some weird reason has sub-surface oceans. So it’s getting to be a pretty watery Solar System out there.
Fraser Cane: Right. So in the olden days, seven years ago – well, older than that, astronomers figured the water was on Earth; the Earth is where the water is, that’s that. Maybe Mars, but probably not. That’s the – we can see that Mars has some ice caps, so maybe there’s some water there.
Dr. Pamela Gay: Dry ice accounts for that quite nicely.
Fraser Cane: Yeah. But isn’t there, like, water – couldn’t they sense – detect water mixed in the atmosphere?
Dr. Pamela Gay: The atmosphere, yes.
Fraser Cane: Yeah, but that’s it. And then – but now – and then they know that there was icy moons around Saturn, and there’s comets and all this good stuff. But it’s all frozen snowballs. No water – no liquid water to be had. So what is our new understanding, and how are people sort of discovering this?
Dr. Pamela Gay: It’s really kind of shocking. What we’re now finding is Mercury doesn’t have liquid water, but it does have water in the permanently shadowed regions in some of its polar craters. We are finding Venus is still a nasty, acidic, don’t want to go there kind of place. We’re not gonna talk about it, because really it doesn’t have water.
Fraser Cane: Wait, but what about on the surface? I mean there’s more water on Earth below – there’s mountains and mountains of water below the surface – than we ever knew. And we’re finding these pockets ten kilometers down, mixed in with the rock. And so you get ten kilometers down on Venus, it’s a different place, right?
Dr. Pamela Gay: Well, and we don’t know. The crazy thing about Venus is it’s one of the weirdest surface in terms of not understanding its volcanic history. It looks like every large period of time that we don’t really know. It pretty much has a massive outbreak of volcanoes, the way a teenager might have an outbreak of acne. It just – the whole thing balloons up at once and resurfaces. Now the question is, in the process is it outgassing all of the volatiles that are stored deeper down? What exactly is going on during this massive process? We don’t really, totally, completely understand. So Venus, we’re gonna put into the “other” category. It’s not really well understood in that category, but covered in really gross, nasty gasses.
Fraser Cane: Put it in the “send more rovers” category.
Dr. Pamela Gay: I’m not quite sure we’re ready for rovers there, but balloons that circulate in the atmosphere, go for it.
Fraser Cane: No way, they – Geoffrey Landis came up with a sterling engine that could keep a rover going on the surface of Venus for months. Awesome idea.
Dr. Pamela Gay: Not planned to be built by anyone at the moment, though.
Fraser Cane: Yeah, but in my mind. In my mind, I’m speculating. Please continue.
Dr. Pamela Gay: Okay, so yes. So Earth we kinda know we’re kinda covered in water. The nearest asteroids we’re generally contending with, they rotate – they generally don’t have ices on them. You occasionally see evidence of volatiles have escaped, in the case of those that are really dead comets, more than they’re plain, old, rocky asteroids. But for the most part, near-Earth asteroids in the inner part of the asteroid belt is a dry place. This is because the sun baked everything dry.
I kind of bypassed Mars in there. Mars, liquid water is extremely salty, is what it appears. So it has briny water that is able to stay liquid at significantly lower temperatures than non-salt water can.
Fraser Cane: That’s good enough for life.
Dr. Pamela Gay: That’s – we sure have saltwater here on Earth that supports life, and so this salt water’s a bit saltier, more, I think, Dead Sea than Atlantic, but there’s potential there. So Mars has, it appears, sub-surface water in the form of briny water.
Then, moving outwards, as we move out through the asteroid belts, go past Vesta, past the – what we call the water line – the snow line in our solar system. This is that point in the solar system where the distance that you are away from the sun is such that things that formed during the early solar nebula formed with water and didn’t get baked to the point of not having water anymore. This is part of why we wanted to send the Dawn Spacecraft to both Vesta and Ceres, is they formed on either side of this line, we think.
Well, now it’s appearing that as we’ve been observing Ceres in the ramp up to getting the Dawn Mission there, it’s kind of looking like it may have cryovolcanism, which indicates water. That one’s kinda confusing. Then as we move out, we have Jupiter next. We already knew Europa has sub-surface water, ice on the surface. It’s kinda water in different phase states.
Fraser Cane: But it’s not the only one. I mean, that’s –
Dr. Pamela Gay: It’s not, no. It’s looking like Ganymede has water, Callisto has water, Io is another kinda baked kinda place, lots of nasty volcanism. Kind of awesome, but not really a watery kinda world. But then as we move out toward Saturn, we find the tiny worlds, like Enceladus, which actually appeared to also have these sub-surface oceans as well. and so it’s kinda like sub-surface oceans everywhere, and there’s the question of now what are we gonna find when we get to Pluto?
Fraser Cane: Pluto, right.
Dr. Pamela Gay: So Pluto and Chiron are certainly close enough that perhaps, maybe, sort of you could end up with some kind of tidal heating. Don’t know. Probably not, but wow, what if? So yeah, the solar system is turning out to be much more watery than previously thought.
Fraser Cane: So of all of those places, which one is the best candidate? Which is the best place for us to look, do you think?
Dr. Pamela Gay: The one that I didn’t name: Titan. So Titan you actually have massive organics already in place. This is a world that has methane and ethane at the transition point where they can go from vapor to liquid to solid. And with that triple point in play, you end up with a whole weather system. You end up with lakes that, depending on where they are, are either methane or ethane. Majority – it’s looking like the majority methane.
But there is also water in this crazy environment. And so you know we have all the organics. You have a complex water cycle, or liquid cycle, rather. You do have water. So that’s an excellent starting point. And, as has been noticed before, it’s atmosphere is actually out of chemical equilibrium for what you would expect for a system that doesn’t have life at that particular distance from the sun. so there’s already this weird – okay, there’s either chemistry we don’t understand, or there’s life.
Fraser Cane: But it would be underground. But the surface of Titan is cold enough to freeze methane, and to have methane snow. So you got ammonia oceans. So you need to go underground, under the surface, and that’s where you could have these reserves of liquid water.
Dr. Pamela Gay: Well, and you can also have – perhaps we don’t know, life that lives in the methane and ethane.
Fraser Cane: Yeah, that’s a whole other kinda life.
Dr. Pamela Gay: Yeah. And we know our planet Earth had methanogens in the past, so the idea of a more methane-oriented life form isn’t even alien to our own world.
Fraser Cane: Whoa. And so then there’s this idea of Pan Spermia, right? We did a whole show on this. This idea that life is moving around the solar system. And we know this for sure. We’ve found meteorites from even Vesta, right, and Ceres, and from Mars and the moon, and we find these in Antarctica. We pick them up off the ice, and something’s been traveling around the Solar System for three billion years, since it was blasted off.
And this idea that every part of this journey, life can survive it. It can survive being blasted off the world, it can survive being in space for a few million years, it can survive re-entry, and theoretically – and so you could imagine, right? You took a meteorite, it made the journey to Europa, somehow got into that ocean underneath where it’s probably gonna be rich organics, heat sources – it could be happy.
Dr. Pamela Gay: Well, I – and it could also be a death plague. And that’s the weird thing to think about, and it’s why we keep sending spacecraft into the atmospheres of first Jupiter, and now we’re gonna do it to Cassini in four years with Saturn. There’s the concern that life may be able to form through cold processes, and clays, and ices. And there’s been some really interesting experiments.
There was a Radiolab on this a while back. And it could be that life independently arose in more than one place, and if we send a rock from here to Europa, or a spacecraft, or an under-sea probe, that it could have the same sort of devastating impact that, well, Europeans had on the new world when they came here. Different biologicals carry different bacterias with different immunities. And this is a serious concern. So yeah, there could be life everywhere, and then we could successfully kill it. One of my favorite –
Fraser Cane: Replace it with our locally grown bacteria.
Dr. Pamela Gay: The replacing involves killing.
Fraser Cane: We’re terraform – we’re terraforming these worlds.
Dr. Pamela Gay: We’re killing.
Fraser Cane: But you can’t terraform without killing everything that’s there already.
Dr. Pamela Gay: My favorite Scientific American capture of all time – I’ve brought it up before – is one where it discusses the impact that killed the dinosaurs. It created a shockwave that flung dirt, plants, and dinosaurs at escape velocities.
Fraser Cane: Yeah, the impact that terraformed the dinosaurs.
Dr. Pamela Gay: And flung them to other worlds.
Fraser Cane: And flung dinosaurs to other worlds, yeah. Can you just imagine some dinosaur just landing – entering the Martian atmosphere and just landing on the surface? Isn’t that an episode of South Park, where there’s a killer whale on the surface of the moon? Anyway.
Dr. Pamela Gay: So that’s how the whale got there in Hitchhiker’s Guide.
Fraser Cane: Yeah. No, that’s a different story, that the whale was part of the infinite probability drive that would essentially create – because it’s a very unusual thing. but I see what you’re saying. I see what you did there. So okay, so we’ve got this idea that there’s water, water everywhere. So how on Earth, or in space, are we gonna be able to study this? I mean we’ve got this situation where this water is below ten kilometers of ice. You’ve got cryovolcanism; you’ve got Enceladus. That’s tough.
Dr. Pamela Gay: So with Enceladus, it’s light enough with the cryovolcanism to flight ice water – ice, which is a phase state of water – up into the lack of air, where spacecraft can fly through this. And that’s actually one of the planned orbital passages of the Cassini Mission during its final four-year phase. They are going to fly through where the geysers give off all of their particles, and they have onboard instruments that are actually capable of capturing the particles and measuring what they’re made of.
So hopefully they’ll be some nice, big ice crystals that are captured, and we can look at the salt, we can look at what other materials are in the water, look at all of the impurities, confirm that it is H2O and not something else. It’s one of those awesome things when space flings things up into reach of spacecraft.
Fraser Cane: Perfect. And we’ve got something a little similar happening – I guess that’s gonna happen with Ceres – it’s a little similar with what’s happening on Europa – there’s plate tectonics – ice plate tectonics on the surface of Europa. So you have a situation where the plates are going to crack open, or they’re going to be sliding over top of each other, and potentially, material is gonna be at the edges of these – at the subduction zones, you’re gonna have material from deep underneath being brought to the surface.
Dr. Pamela Gay: And it’s weird trying to understand exactly how Europa’s surface works, and Enceladus is, because it’s a different mass, even weirder physics in some ways. You have the tiger stripes on Enceladus, which appear to be where the water’s escaping, and then with Europa, we actually can see all of the organic materials that get sprayed down as the water particles come back down around the cracks. And with Europa, it’s this mix of tidal tectonics and weird hydraulic effects that we’re only learning to understand by studying how glaciers are interacting with the seas.
Fraser Cane: Yeah, it’s like the plate tectonics on Earth, but as you said, it’s hydrodynamic forces not rock, which has different physics. So okay, so – and then Titan, how on Earth would you get at the stuff on Titan? Or, as you said before, what if there is underwater reservoirs on Venus? I mean, that’s just – forget it.
Dr. Pamela Gay: So sampling materials with Titan is another case of you just need a spacecraft to pass through one of the ash plumes. We’ve actually been able to see those in silhouette; that’s less of a stress. It’s actually when we want to get deeper samples that it starts to become problematic.
Fraser Cane: We need a sailboat on Titan.
Dr. Pamela Gay: Well – yeah, that would work. I heard this great description: Titan’s surface is such that you could pretty much send anything you wanted, and ideally, you’d want something that can go back and forth from swimming to flying to roving. And you the winds, you have the lakes, you have the, we think, mostly solid surface. And so you’re in this amazing situation where any spacecraft goes.
Fraser Cane: Well, you could fly on Titan. You have wings. You could fly around with your arm strength. The gravity is so low, and yet the density of the atmosphere is so high. It’s, like, twice as dense as the atmosphere on Earth. You don’t realize that there’s this moon that has this dense of an atmosphere that you could work – of course, it’s cold enough to freeze methane, but don’t let that worry about it.
Dr. Pamela Gay: And the reason it’s able to retain this atmosphere is because of that cold. The atmospheric particles are moving so slowly that they’re not randomly colliding and hitting escape velocity with their rebound velocities. So Mars is just enough warmer that it struggles a lot more to keep its atmosphere.
Fraser Cane: Yeah. So I guess it sounds to me like you’re saying – and tell me if I’m wrong – you think we should send spacecraft everywhere.
Dr. Pamela Gay: Well, yeah. Why not? I mean it’s an awesome solar system out there. Every world needs its own spacecraft. We should have high-rise clones and sent to orbit moons.
Fraser Cane: Curiosities on every place with solid surface.
Dr. Pamela Gay: Yeah. And unfortunately, the one frustration is, we’re kind of out of our nuclear sources for power. And Curiosity, it’s going strong, but what do we do further out? And we can’t go back to Spirit and Opportunity’s usage of solar panels, because as you get that far away from the sun you just don’t get a high enough density per square centimeter flux, basically.
Fraser Cane: Right. By definition, you’re out in the cold. And you need some – you need a nuclear reactor. I’m sure that someone will think of something. I’m sure someone’s gonna bring program back online.
Dr. Pamela Gay: You say that, and then congress gets involved. The problem is the word radiation is involved, and radioactive, and you have to –
Fraser Cane: They don’t mind building bombs.
Dr. Pamela Gay: They don’t mind building bombs, but they’ve actually even largely gotten out of the at business. So the question is, how do we turn on a facility to create all of the isotopes that are needed for these radio-thermal generators?
Fraser Cane: Well, the Chinese will do it then.
Dr. Pamela Gay: Yes, that’s probably true.
Fraser Cane: There you go, problem solved. All right, so but then there are some missions in the works right now, and there’s some stuff that’s heading out right now. So are there any missions that are even gonna get anywhere near trying to help us understand if there’s – to follow this trail and continue on this investigation.
Dr. Pamela Gay: We are looking at some European missions, JUICE in particular; basically we’re going back to Jupiter. And as we look more and more at Jupiter, as they plan out these missions, you always have to worry about losing your pet instrument, losing your pet probe. But I think that JUICE may be where our best new hope is at.
Fraser Cane: So what’s JUICE? If you haven’t heard of JUICE, because we haven’t talked about it much in this –
Dr. Pamela Gay: Well, it’s the normal missions are dead to me until they actually launch. But JUICE is a European mission that is going to go to the Jupiter system, and I have to admit that’s pretty much all I know right now, other than –
Fraser Cane: Jupiter, I-C–
Dr. Pamela Gay: I shall Google.
Fraser Cane: Yeah, I forget what JUICE stands for. But it’s crazy, because we don’t have anything at Jupiter right now.
Dr. Pamela Gay: No. So, when you Google JUICE, you get a very cartoonish diagram. It’s a European Space Agency mission, and it does have a Ganymede lander planned.
Fraser Cane: Cool.
Dr. Pamela Gay: And so it will do an inter-planetary transfer, Earth to Venus, Earth-Earth, so lots of orbiting. It will use Ganymede and Callisto for gravitational braking. Variety of different orbiters, but landing on Ganymede’s kind of the coolest part. It will do two fly-bys of Europa, and then linger at Ganymede and Callisto.
Fraser Cane: And there was the – so Juno was launched in 2011, and that’s going to get there in 2016. But I don’t think it’s gonna have the ability to study the moons.
Dr. Pamela Gay: It doesn’t have the budget for it.
Fraser Cane: No.
Dr. Pamela Gay: But JUICE is our next big hope for moon exploration.
Fraser Cane: Yeah, cool. And then does this, like tell us anything maybe about other worlds? Other star systems? Because this is this – we are at this point, and of course, wouldn’t it be great if there was such a thing as the terrestrial planet finder that would be able to look at the atmospheres of other worlds? But you see some of the characteristics, like water, in the atmosphere – water vapor in the atmosphere of another world – that’s another candidate for life.
Dr. Pamela Gay: And the thing that has me really excited is we’re at this point where if we find life – even at it’s lamest, single-celled possibility somewhere else here in the solar system – that has originated somewhere else in the solar system, that starts to give us a sense for how easy it is for life to come into existence. And we’re now finding the diversity of locations that life could exist is so much more than that Goldilocks band.
So the possibility that we’re alone goes down every new time we find a habitable environment. But the other side of that is if we start exploring these liquid environments and we never find life anywhere else, then maybe we do need to slow down and think that maybe it is harder to get life there than we’d hoped. So we’re at the point of being able to start getting better numbers for that Great Drack – sorry, not Drack –
Fraser Cane: The Drake Equation.
Dr. Pamela Gay: Drake Equation. The Great Drake Equation of how probable is life?
Fraser Cane: Yeah. All right, cool. Well, thanks, Pamela.
Dr. Pamela Gay: Thank you.
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