NASA scientist and astrobiologist Dr. Steve Vance tells us about the Europa Clipper mission, the spacecraft that will explore Jupiter's moon Europa in the next decade in search of life beyond Earth.
Guest | Dr. Steve Vance, Deputy Manager Planetary Science Section NASA Jet Propulsion Laboratory [@NASAJPL]
On Twitter | https://twitter.com/Steven_D_Vance
On LinkedIn | https://www.linkedin.com/in/steve-vance-12780825/
On Facebook | https://www.facebook.com/steve.vance1
Host | Matthew S Williams
On ITSPmagazine 👉 https://itspmagazine.com/itspmagazine-podcast-radio-hosts/matthew-s-williams
______________________
This Episode’s Sponsors
Are you interested in sponsoring an ITSPmagazine Channel?
👉 https://www.itspmagazine.com/sponsor-the-itspmagazine-podcast-network
______________________
Episode Notes
NASA scientist and astrobiologist Dr. Steve Vance tells us about the Europa Clipper mission, the spacecraft that will explore Jupiter's moon Europa in the next decade in search of life beyond Earth.
Scientists have been waiting for decades to get a closer look at Europa and other "Ocean Worlds" in our Solar System to see if life has made a home beneath their icy surfaces.
______________________
Resources
NASA's Europa Clipper Mission: https://europa.nasa.gov/
______________________
For more podcast Stories from Space with Matthew S Williams, visit: https://itspmagazine.com/stories-from-space-podcast
The Europa Clipper Mission | A Conversation with Dr. Steve Vance | Stories From Space Podcast With Matthew S Williams
Matt: [00:00:00] The authors acknowledge that this podcast was recorded on the traditional unceded lands of the Lekwungen peoples.
Good morning, and welcome back to Stories from Space. I am your host, Matt Williams. Today, my guest is none other than Dr. Stephen Vance, a NASA scientist with NASA's Jet Propulsion Laboratory, the former supervisor of the Planetary Interiors and Geophysics Group, and the current deputy manager of the Planetary Science Section at JPL. Dr. Vance, welcome aboard.
Steve: It's great to be here. Thanks for having me.
Matt: Well, thank you for coming on. So, as my listeners may recall, in a previous episode, we discussed ocean worlds, referring to icy moons in the outer solar system that have interior oceans and could possibly harbor life. And Dr. Vance, this is your specialty, isn't it?
Steve: That's right. That's what I do. I study the interiors of ocean worlds. I started my career thinking about Europa. I've since extended my interests to Jupiter's moon Ganymede and [00:01:00] Enceladus and basically anywhere there's liquid water under ice in the solar system.
Matt: Now, looking at your JPL page, it is really quite impressive here. You've worked on a number of missions, including the Cassini Huygens orbiter and lander. The Mars Insight Lander and the Mars Exploration Rovers. And that would include NASA's Spirit and Opportunity Rovers.
Steve: So yeah, I've had some tangential involvement in some stuff there, but, and an interest generally in what Insight did, but my, my main role is on Europa Clipper and I make use of Cassini Huygens data to think about what the interiors of Titan and Enceladus in particular might be like, but yeah, my main mission involvement is with Europa clipper.
Matt: And that certainly came up in our previous episode. Now, before we get into all that though, I'd like to have you tell us a little bit about yourself. What was the road that brought you to NASA JPL and to the position of deputy manager of the planetary science section?
Steve: Sure, yeah, it's a common trope [00:02:00] in planetary science. A lot of my colleagues were influenced by Carl Sagan, and I am also part of that trope. So I work with people who, you know, worked with him, or just simply were inspired by him. And so I felt like I was in good company stepping into an interest in planetary science, being someone who was really excited about the Contact movie and book in the 90s.
Contact being a fictional work in which Sagan and co authors imagined receiving a coded message in radio from an exoplanet, or at least from beyond our solar system. Yeah, you know, so, so that kind of, Interest in eventually contacting intelligent life really fed into my already growing interest in the nature of the universe and how the planets work.
It just happened that when I was completing my undergraduate degree in physics at UC Santa Cruz, NASA inaugurated the field of astrobiology after the discovery of possible life in the ALH84001 meteorite, that is the Allen Hills meteorite [00:03:00] discovered in Antarctica.
So there was a lot of fertile ground for me to develop my interest in planetary science and the search for life in the universe.
And it also just happened that Galileo, the NASA spacecraft was exploring the Jupiter system around that time and had just returned really strong evidence for an ocean currently. present in Europa. That evidence coming mainly from Europa's magnetic field, which was gen is generated in response to Jupiter's changing magnetic field.
So, so that, that was the thing that got me into planetary science. And so in my graduate work at the University of Washington, I studied astrobiology, just thinking about the possibility for life elsewhere, how we might imagine life elsewhere might Get by based on the extremes of how life works on Earth.
So, you know, thinking about life at the bottom of the sea floor on Earth and hydrothermal systems thinking about life living in ice in Antarctica, that sort of thing. Yeah, so I did a lot of research as an undergraduate, a lot of fun studying different fields, [00:04:00] science related to astrobiology and long story short, ended up with a postdoc at JPL.
That turned into a job and I continue to do things that build on the work that I did as a graduate student. So I'm lucky that I developed that fertile ground on which I started and continue to do work that I'm really excited and passionate about.
Matt: Yeah. Well, I'm glad you mentioned contact by Carl Sagan because yeah, me too. Seeing that in the nineties was a really major boost to my interest in all things space related. And yes, if anyone has not either read the book or seen the movie, yeah, I'd recommend doing both. Yeah. And the sci fi holds up even after 20, 30 years. Yeah. So in terms of Europa itself, it was a long road getting to this point, wasn't it?
Where we would send a mission out there to explore it directly rather than an orbiter that was just passing through the system or [00:05:00] one that was like the Galileo probe studying Jupiter and Juno as well, but making flybys of European and gathering new data.
Steve: Yeah, it's, it's been, it's been a really long road, you know, starting with the antenna failure on the Galileo spacecraft, Galileo was meant to have a high gain antenna to beam lots and lots of data back to earth.
And if that had opened, I think Galileo would have. Given us a similar sense of the Jupyter system, the same volume of data, a similar volume of data to what we got from Cassini, which, you know, globally mapped Titan at fairly high resolution using its radar, gave us a whole lot of data relevant to Enceladus.
By contrast, all of the information for Europa can fit on a CD ROM, less than a gig, less than a gigabyte. So, you know, just during the Galileo days, there were on one hand some exciting, compelling discoveries that we made. And on the other hand, a sense of frustration with what we might have had. And so people were [00:06:00] already busy formulating mission ideas as early as 1999.
There's the name Europa Clipper, in fact, is on record back in 1999 for studies people were doing of a follow on mission to the exciting discoveries of an ocean at Europa. So yeah, I got into helping out with that effort when I came to JPL in late 2007. And at that time, I thought we were going to have our flagship mission to go and orbit Europa.
Within a few years, that was kind of the general feeling from the community, but instead we ended up working on lower cost, more effective mission studies and didn't get going on the main flagship mission until 2015 by then we had arrived and instead of an orbiter. At a multiple flyby mission, because it turns out because of Europa's radiation environment, you can do a lot more with your available hardware by flying by Europa a bunch of times in an elliptical orbit that keeps you out of the radiation environment and allows you to beam back.
Lots of data to earth [00:07:00] while you're on the long part of your orbit around around Jupiter. This is similar to the strategy that Juno employed with its soon to be concluded exploration of Jupiter. And you might have seen the exciting images of Io that were just sent back in December from Juno. So Juno is part of that long road as well.
You know, we've learned a whole lot about Jupiter in the meantime. And Juno gave us some some updated images of Europa, kind of a teaser for Europa Clipper
Matt: Oh, yes. Well, and I'm glad you mentioned IO and also the nature of the orbits, how those play a role. Yeah. For those who haven't seen those images, they were just stunning infrared images of the surface of IO and showing just how volcanically active it is.
Just looked like a whole bunch of embers and a fire. Oh, it's beautiful. And so Jupiter's radiation environment in this, in fact, Not just it's powerful magnetic field, but the magneto tail that the moon's pass through this makes the prospect of humans [00:08:00] living there pretty limited right , pretty bleak.
Steve: Yeah, I I wouldn't I wouldn't want to live on on Jupiter just to Yeah to elaborate on some of what you were saying Io spews a bunch of materials into space because it's so volcanically active.
Jupiter has an immense magnetic field, the influence of which would be larger than, would appear larger in the sky than the full moon, if we could see the magnetic field of Jupiter, despite Jupiter being so far away. So, that magnetic field grabs onto solar wind particles, and the field environment ionizes the stuff coming out of Io.
And so altogether you have a really intense radiation environment in the region at the orbital distance from Jupiter that Io and Europa sit at. So, yeah, that really intense radiation environment is bad for spacecraft, even worse for people. And so, yeah, maybe, maybe, you know, in the long distant future or in the imagination of a science fiction author.
We can easily embed ourselves just a few meters below [00:09:00] the ice where we would be protected from that radiation, you know, and then you'd have lots of ice to work with, but, you know, the idea of walking on Europa's surface for more than a minute or two, and even
then, you know, in a really thick Iron Man suit is not very appealing. It's a dangerous environment.
Matt: And so, yeah, in fact, proposals for settling on any of Jupiter's moons, which was the subject of another previous podcast, settling on the Jovians, in the case of just about everywhere but Callisto, it is strongly recommended that if there's going to be any human settlements, they need to go beneath the ice. And so, in a way, we'd be taking a bit of a page from what we hope is the life that exists there right now.
Steve: Yeah, that last point. I'm hopeful there as well. I don't know what we'll find at Europa, but you know, there's an outside chance that there's, there's something there that we might find some, some [00:10:00] biosignatures, even, even with Europa Clipper, although I want to emphasize that's not the main goal of Europa Clipper mission, that search for life is deferred to a future mission that has instruments specifically designed for life detection.
All that said, Europa Clipper will bring with it a really, really capable mass spectrometer. And a whole lot of imaging instruments that will be able to characterize the chemistry of Europa's surface and the composition of materials that are ejected from Europa's surface, either by Impacts, including, you know, micro meteorites, dust, that's constantly bombarding Europa's surface, or even by plumes, if eruptive features exist.
Matt: Well, thank you. That's actually my next question, which is, what exactly will the Europa Clipper do? And, well, you just summarized it there. Basically, it's going to examine the surface. Study the chemical composition of the ice sheet and learn more about the interior ocean, right? And now if the mission [00:11:00] goes well and the mission does in fact find evidence of potential biosignatures, biomarkers, so what then?
Are we talking a Europa lander?
Steve: Yeah, Europa Lander is something that's been studied. Actually, that big effort almost led to a flagship mission to follow immediately on Europa Clipper. That did a lot to quantify what it would take to thoroughly search for life. They had an approach. that would have had a lot of redundancy in a good way.
That is, multiple instruments trying to provide multiple lines of evidence for possible biosignatures. That if you were looking for life on Earth in Antarctic ice, you would have a reasonable chance of finding it by sampling a reasonable chunk of ice and, and looking for amino acids, looking for cells that had been the remnants of cells that were deposited, and for polysaccharides, the remains of metabolism, I'll say.
And so And you could also look [00:12:00] for isotopic signatures in organics embedded in the ice. So those are the sorts of things that the Europa Lander was going to do. And that effort also spurred a lot of activity in terms of NASA funded efforts to develop the next generation of mass spectrometers, advanced Raman sensors, things that would give better fidelity in terms of distinguishing different organic molecules, developing really capable cameras that would allow you to do a lot more than current microscopic imagers can do.
And packaging them in really small packages that would allow you to get a really capable payload into a really mass constrained setup. So all that being said, while we've had a lot of progress in in the field of astrobiology in that sense, just from this vision of landing on Europa, at the same time there have been efforts toward thinking about drilling through Europa's ice, or the ice of Enceladus, I should say.
You know, this is something that Stone Aerospace has proposed doing for quite a long time. But anyone who's tried to drill through Antarctic ice will [00:13:00] tell you that those efforts usually take massive equipment, more akin to what you use for oil drilling with lots of diesel generators and lubricants on your drill bits, things that you wouldn't want if you're looking for life and things that are prohibitive to a space mission where you have to be as mass efficient as you can, and you wouldn't be able to bring that sort of equipment with you.
So there's interest nevertheless, in how we might autonomously drill through the ice. And I'm excited to see where that goes in the next, next decade or so in the timeframe that we might consider taking another shot at, at developing a Europa lander, you know, maybe, maybe we'll be able to get further into the ice with this next effort, or maybe we'll continue with the previously studied Europa lander.
Those are both really great efforts. All of that is to say that there's continued work on this topic.
Matt: So Europa Clipper will be launching on October 10th, 2024. That's what the current schedule indicates. And we'll be arriving around Jupiter in 2030, at which point it's going to commence [00:14:00] orbiting Jupiter and making multiple flybys of Europa.
Steve: Yeah, that's right. So, so the launch window for Europa Clipper opens on October 10th. I think we've got about a month, if there's any kind of launch problems on the first day or two. I'm really hoping we're going to launch on the first day or two, because that's when I'll be there. And then we've got a really long cruise.
We'll, we'll pass by the Earth, we'll pass by Mars. We'll use those to slingshot ourselves to Jupiter. Arriving in Jupiter around 2030, as you say, and then we'll spend about a year getting into position to fly by Europa. As part of that, we'll fly by Callisto and Ganymede as well. So yeah, it's, uh, it's going to be a long journey.
On the science team, we're thinking about what we're going to do with our time for the next six Seven years or so. I've got a lot of research planned and it's okay. The time will go by fast, given that we've been, a lot of us have been thinking about this for 20 years or more, but once we get there, the overall goal of Europa Clipper is to both explore Europa and investigate its habitability.
That exploration in part includes thinking about that future [00:15:00] lander that you mentioned, but it also involves looking for. What kind of geological activity is happening on the surface, thinking about the time scales over which Europa's surface evolves, and overall thinking about confirming that the ocean exists and trying to figure out its composition.
So we have goals to figure out Europa's salinity to within some constraints, and to figure out the transport of materials between the ocean and the surface, both materials coming out of the ocean and materials going into the ocean. Since one of the really exciting things about Europa is that the radiation environment generates oxygen at the surface by breaking up water, and that oxygen might be a source for life, so the overturning rate of the ice then becomes a proxy for the delivery rate of oxygen into the ocean.
So then you can imagine if we have that constraint on that rate, then we can think about how the ocean might have changed through time. And by measuring the chemistry of the surface and the chemistry of material coming out of the ice, we can put direct constraints on the pH of the ocean, [00:16:00] also the salinity of the ocean, and thereby get a sense of the availability of oxygen, the chemistry of the ocean, what kind of metabolisms might take place in the ocean.
Matt: And that, in fact, the nature of the icy crust there and the evidence that there is resurfacing, this is part of what led scientists to theorize about the interior ocean in the first place, isn't it?
Steve: Yeah, let's, so yeah, I'd love to, to step back in history a little farther to the, to the 80s, even the late 70s, when the Voyager spacecraft launched, and there were two of them, it's a different time for NASA.
These two very capable spacecraft that had the goal to explore each of the large planets. It happened that at that time, some researchers, Stan Peel and others, who were thinking about tidal interactions, that is, how different bodies orbiting a large planet interact. realized that there might be a lot of tidal energy due to the eccentricity of Jupiter's moons that might lead to volcanism on Io.
And then lo and behold, Voyager observed that [00:17:00] volcanism. So that was a really, that to me is one of his favorite story of science that people were able to use basic physics and some simple observations of a system to make some pretty profound predictions that immediately turned out to be verified. But the Voyager flybys of Jupiter, that confirmed the volcanism of Io, they also revealed Europa.
They transformed Europa from being a blurry point of light in the sky, as seen through telescopes, to being this really curious looking icy ball crisscrossed with fractures throughout its surface. If your listeners have not seen pictures of Europa, I encourage them to immediately go and search for it online, and they'll see this wonderland of geophysics and geology.
One of the remarkable things, though, about that first detailed observation of Europa is that it has strikingly few craters, and you can imagine craters being a convenient marker for how geologically old something is. Um, so crater counting and crater statistics, that is the numerical distribution of crater size, [00:18:00] counts of the number of craters of a given size. Those are used, um, with some informed models for how cratering might work through time, uh, basically the statistics of how frequently a given body might be impacted relative to its place in the solar system and its size.
That gives you a sense, the number of craters gives you a sense of how old the body is. And so the fact that Europa has only a few large craters has been used to infer that Europa's surface age is probably no greater than 200 million years. So Europa has been basically erasing evidence of past impacts. The ice has been overturning. It's a geologically active place. And so the geological activity was immediately jumped on to to infer that there's likely to be.
The ice is not that thin, they're not that thick rather, because it's easier to churn about and move the surface if the ice is active, and it's easier for the ice to be active if it's thin. Now there's some nuance there, in that the ice can actually [00:19:00] be quite a lot thicker if it undergoes solid state convection, but generally you still need Heat to cause the ice to be mobile in the first place, and the amount of heat observed at Io can be scaled to Europa based on the title parameters, the lower eccentricity of Europa, and you get a pretty high heat flow just from your prediction there, and that heat flow, you can model how thin the ice has to be to get that heat out, and it can't be more than, you know, a few tens of kilometers, even if convection is happening.
So again, a thin ice shell suggests that there's an ocean, but the naysayers can still. respond and say, well, yes, you need, you need to have had a thin ice shell at some point to get that activity. But what if that activity happened some time ago? And since then the, the ice is frozen. So all of this is to say that the young surface age itself isn't definitive evidence for an ocean.
So it was really critical. to have that follow up with Galileo to observe the changing magnetic field. That was the thing that really [00:20:00] gave us a compelling sense that there is an ocean currently at Europa. Nevertheless, as I said, a goal of Europa Clipper is to confirm the presence of an ocean at Europa.
And with, after that confirmation, which I'm pretty confident we'll get, We have a lot that we can do to characterize that ocean and understand its habitability.
Matt: Yeah, in fact, that's a fair point. At this juncture, we can't say with absolute certainty, yeah, Europa has an ocean in it. Much like many of the ocean worlds, it's modeling simulations and all these hints that point towards the existence of it.
But, yeah. Like, well, we haven't exactly seen it with the naked eye or what have you. Now, you mentioned, of course, Carl Sagan being a big inspiration. Does Arthur C. Clarke ever enter your mind when you're talking about missions to Europa?
Steve: Yeah. And I was pleased to see that Arthur C. Clarke's 2001 featured in your zoom background when we met just a few minutes ago. Clark certainly figures into our [00:21:00] imagination and it's fun that both Jupiter and Europa. Featured in, in 2001 and 2010 and 2001, albeit it was Jupiter was, was the focus only in the movie and not in the book. I thought it was really fun to go back and read the book when I started at JPL and to realize that Iapetus was the target instead.
Matt: Yeah. I remember that wasn't, yeah.
Steve: So, but, but, you know, to your point about, about Arthur C. Clarke. Two fun points, you know, we, we spent a lot of time thinking about landing on Europa and it often came up during that study that 2010 we were instructed to attempt no landings there, but Arthur C. Clarke had a habit of dialing into planetary science meetings in the 90s and the early 2000s and we did get him on record saying that we had permission to land on Europa, you know, so for what that's worth.
It was a fun, fun thing to have and fun to have those interactions. I, I think science fiction feeds our imagination has a really vital role in feeding our [00:22:00] imagination and inspiring us to pursue these, these, these efforts. And, uh, you know, so much so that, uh, Arthur C. Clark's 2001 is, is a. Motif for our, our science team, we have the monolith as, as the mascot basically for our science team, such that we have a scale model, a replica of a monolith at JPL that was the first one that was built for our science team for our first science team meeting in 2015.
My wife actually had a role in orchestrating that construction, and she's someone in film here in LA, and then at our subsequent team meetings that we've had around the country. We've encouraged the organizers of those meetings to figure out ways to construct their own scale model monoliths. So, there are a number of those throughout the country now, which is really fun.
So as our knowledge grows, the number of monoliths also grows.
Matt: Yeah, in fact, I wanted to mention something for our listeners. So, 2001, a space odyssey. But yeah, 2001, a space odyssey. The film and book [00:23:00] were released in 1968. And Jupiter is featured pretty prominently in the film version, but as you said, yeah, the, the book version that it was around Saturn, around its moon Neapolitan, where the main character at this point in the story finds the larger monolith, the one that has been communicating with the one on the moon.
And so this was all written before the Voyager missions had passed through the system before they, there was any scientific speculation about a possible interior ocean. It's interesting because 2010, the next Installment which was also made into a film so in that film and the novelization of it, which, yeah, the film was the adaptation of Clark's second space odyssey novel, he made sure that the location was back to Jupiter and focused on Europa because, of course, at this point, he worked that into the script right here.
He [00:24:00] worked it into the book speculation about an interior ocean and how. If the surface ice were melted, Europa could become a habitable world, and That for me was a really, really inspiring, but a question I have for you is, let's assume that actually were the case that terraforming efforts were put into place.
The ice was melted to create an atmosphere, would that be able to let the life loose or would Europa simply fall to pieces because of its composition?
Steve: Oh, that's really an interesting question. Yeah, the idea of oceanic, you know, moons, including around exoplanets, it's a possibility. The thing is, the lifetime, I think, would be short.
You can imagine if Europa were a little bit hotter, it even might have been a little bit hotter in its earlier days, such that its ice were really, really thin. The ice could frequently break up. At least in places, and you could imagine generating [00:25:00] enough outgassing or, or loss of water that you develop an atmosphere.
The thing is, sustaining an atmosphere is difficult for a body the size of Europa, because as soon as the atmosphere is just a little bit warm, you know, imagine an atmosphere like ours, the individual molecules of water would have enough kinetic energy that they, they would, their, their average velocity would exceed the escape velocity.
And so you would lose the atmosphere pretty quickly. So this is a problem of having small moons. Now, you know, if Europa were the size of Ganymede, or even larger, that lifetime would be longer. I don't, I don't have the numbers off the top of my head. I would expect that you, you know, you're talking about tens of thousands of years at a minimum before you lose all the water, and it could be millions of years.
And for larger objects, it could be even billions of years. Yeah, so Arthur C. Clarke's idea of, of having a habitable Europa that's, I don't want to give away the ending, but, you know, a Europa that's warmed by a hot Jupiter, let's say, that, that would be a shorter lived scenario, at least in the geological sense, it would be short [00:26:00] lived. It's still of interest to think about.
Matt: Oh, absolutely. So if we could just speculate here for a second, let's assume that the Europa Clipper, it finds Potential evidence of biosignatures. The lander is sent there as well. It's dispatched to the surface. It's finding biosignatures in the water. If, in fact, there is life within Europa, I can only assume you've had fevered thoughts about what it might look like or what it might constitute.
Steve: Sure, sure. You know, we, we often as astrobiologists, we often answer these questions with a kind of a conservative view of, well, we think the amount of energy available for life is going to be less on earth. And so what we imagine is microbes, you know, really my thinking about what life on Europa might be like, since I tend to cleave to that more conservative answer, at least for now, while I'm sticking to that answer.
You know, that, that line of thinking really keys into my wonder [00:27:00] for thinking about, you know, Earth as a, as another planet. But basically Earth existed for much of its history in an unrecognizable form from what we see it today. Right? The main form of life on Earth was single cellular. And so, you know, until 500 million years ago or so, looking for life on Earth would also entail looking for microbes.
Now, that being said, Earth also had Had photosynthesis, you know, it had a lot of energy coming from the sun, such that I expect that if you pulled up to earth with a spacecraft, you'd see the signatures of life from orbit in terms of signs of photosynthesis, you know, the green from the algae or from cyanobacteria anyway.
So, yeah, you know, I think it'd be really intriguing to find some kind of cyanobacteria or similar. at Europa. And, you know, that line of thinking makes me wonder, you know, would
it have DNA with the same base pairs, the A, T, G, C, that DNA on Earth uses? Or was there an entirely different origin for life on Europa?
And if so, might it have used [00:28:00] different base pairs? Is there some physical reason why the base pairs that life, Earth life uses, are preferred? So I think of this kind of thinking as really just fundamentals about how life forms, how common it is, and whether the rules for forming life are so strict or so, I want to say simple, that, that putting together the ingredients for life.
is almost always going to give you similar life to what you find on Earth. You know, these are the kind of things we can start to ask if and when we find life somewhere else. So in that sense, that's kind of what gets me most excited about looking for life on Europa. There's of course, I think what you're going for more, the wild imaginings of, you know, what else could be there.
If you go to the aquarium, there's a lot of weird stuff, even on Earth. And in Earth's history, There were a lot of other weird body forms that were tried out that didn't last, but just looking at the diversity of types of starfish, you know, there are a lot of things out there that, that you could [00:29:00] imagine existing on Europa, different types of jellyfish.
People have imagined different types of octopi. In fact, the movie Europa Report has a really nicely imagined octopus. I had the good fortune of advising on that movie, which is a whole other dimension to my science career. Yeah, so in my more optimistic moments, when I think about oxygen making its way into Europa's ocean, I imagine fish, I imagine an ecosystem with life clinging under the ice, scavenging the oxygen coming from, from through the ice.
I sometimes even imagine, given that the ice is possibly tens of kilometers thick, I imagine vertical rivers of meltwater generated by, by tidal heating. And these channels of water flowing through the ice and microbes living in those channels or even larger forms of life that are living off the oxygen, you know, there's all kinds of things that that might exist.
It really depends on how much chemical energy is available. And so what I'm excited about with Europa Clipper is that we're going to get. A sense of the [00:30:00] distribution of chemical energy around Europe, but the spatial distribution both laterally around the surface and then within the ice and within the ocean, that's, that's just going to be even more food for the imagination to think about what kind of ecosystems might exist, not just what kind of individual organisms might be there.
Matt: Yeah, in fact, a lot of the current speculation and sort of theoretical predictions, right, is that there's likely hydrothermal vents around the Coromantel boundary. That's, that would be what allows for ocean worlds to maintain their liquid water oceans. And that these call to mind hydrothermal vents on Earth, which, as I understand it, modern evidence suggests that the earliest life on Earth may have actually started around these vents, like fossilized bacteria that's billions of years old.
Steve: But yeah, those are, those are both some really, you know, interesting, compelling points about, about Europa and ocean worlds in general, Europa in particular, because of the analogy to IO and [00:31:00] the possibility of really intense tidal heating has the best chance
of having hydrothermal systems. That said, we don't understand where the exceptionally high heating in Enceladus is coming from and it's possible that that heating also attributes to a significant amount of heat in the silicates and in the rocky seafloor and below, and we're sort of trying to figure out how that might work, you know, at the same time, it's important to keep in mind that.
The shallowest parts of Europe's seafloor are going to be under immense pressures, higher than on average at the base of Earth's ocean. And so, so how geology works under those conditions, whether you can get low enough pressures to break the rock, to get fractures and fissures, and whether you can mobilize lava rather than keeping the rock in a frozen, hot, kind of more runny form rather than forming volcanoes.
Those are open questions, and, you know, some of that will remain to be seen. There's a lot of modeling work happening right now, suggesting that the high pressures are really, really making it really difficult to develop hydrothermal [00:32:00] systems. That said, yeah, so the seamounts on Earth, mid ocean ridge spreading centers in the middle of the Atlantic, these are places where you do have You know, volcanic activity, a couple of kinds of volcanic activity.
You know, you can have active volcanoes at the mid ocean ridges where you have basically lava just below the surface or very hot rock just below the surface. And the gradients and temperature are so extreme you end up dissolving iron and sulfur and things in a way that they're not chemically soluble at the lower temperatures in the ocean.
So you have these. plumes of black material spewing out of these, these systems, these chimneys and rapidly precipitating out so you can have these kind of clouds of material forming. Long story short though, you know, you have hydrogen sulfide and other basic molecules coming out of these systems and there are whole communities of organisms that are scavenging materials out of these chimneys.
A special kind of tube worm. It's basically an aggregate of microorganisms, single celled [00:33:00] organisms that live in these worms that scavenge hydrogen sulfide and other materials out of the stuff coming out of the vents. You know, it's really amazing that you have these systems that, for the most part, thrive.
Just from the chemical energy from these, these volcanoes, not on photosynthesis, although there are also organisms that these systems that benefit from organic materials that are that are ultimately coming from the continents or or from the ocean. So, you know, they're scavenging materials that fall into the ocean.
So there, there is some connection between those. The subsurface ecosystem on earth and, and the surface ecosystem, but getting down to those depths that are more comparable to what you have on Europa, where the pressures are up to 10, 000 atmospheres, you do have organisms that survive and those are different communities.
And we still have a lot of exploration to do of our own sea floor, such that perhaps we will discover some kind of volcanic activity or. Or at least hydrothermal activity at greater depths, more comparable to what we find on Europa. [00:34:00]
Matt: And I'm glad you mentioned Enceladus too, because one thing that's, that's happened with ever since the Voyager missions buzzed through the Jupiter system, we've gone on to, to find similar Conditions, right, are similar lines of evidence for many, many other moons out there, hence the term ocean worlds, right?
It's, it's plural, and so that includes Ganymede, possibly Callisto, Enceladus, Titan, and the list goes on.
Steve: Yeah, I think you've got the main ones where we have really compelling evidence. Pluto, there, there's been, you know, there was a single flyby by the New Horizons mission, but the heart shape on Pluto is suggestive of a low density region that's in some models is interpreted to be a subsurface ocean.
And, uh, people have pointed out that the nitrogen on top of that, that layer, [00:35:00] which if you look at it, it's really cool. It looks kind of like the convection currents in your, if you put cream in your coffee, you can see stuff churning at the top of the coffee. There's something similar happening in the nitrogen and it's a similar physics.
It's, it's, it's basically, it's actively. Churning around because the nitrogen has a really, the solid nitrogen has a pretty low viscosity, but that's my point that the solid nitrogen has a low thermal conductivity, much lower than ice, and so it basically works as a blanket. And so, based on that, it's kind of reasonable to suppose that the despite being such a cold and small world, Pluto might have retained some enough energy to keep some liquid water underneath the surface.
So, yeah, the more we explore, the more weird stuff we find. And, and, you know, we're still thinking about. In fact, NASA has a priority to send a mission to Uranus where Miranda and Ariel and Iapetus and Titania are moons that are similar in their orbital distance and that is the orbital [00:36:00] configuration and in their size to some of the moons around Saturn.
So there's just, there's a lot more to find out. I can go on. There are other, there are others as well that are possible candidates. You named the ones that are biggest and for which we have the best evidence. Yeah, Titan and Ganymede are just other kinds of worlds. They're more comparable to the size of Mercury, right?
And we have good evidence for oceans there. And those oceans are probably hundreds of kilometers thick, hundreds of miles thick. And so thick at their base, they probably have compact forms of ice that are dense and sink to the bottom of the ocean. So they're sandwiched, the oceans are sandwiched between different types of ice.
Matt: Well, that too, that does make the possibility of life in hydrothermal vents rather bleak, doesn't it?
Steve: I don't know. There's been some, some interesting progress in that realm in, in the last 10 years or so. The thing about the high pressure ice layers is that at the top of the ice, It's not like, you can't, you shouldn't [00:37:00] think of it like a, like a rocky seafloor at the top of the high pressure ice.
Because what's different is that the high pressure ice at the top, where you start, where you interface with the ocean, is at its melting point. And so, if you had a rocky seafloor like that, You would have lava, you know, interacting with, with rock. And you could imagine that that's not a very stable situation.
And so what that means is that you probably have fluids percolating the upper part of the the high pressure ice. And what that also means is that you probably have fluids throughout the high pressure ice, because you basically have a hot thermal profile through the ice. And so It seems likely that any thermal anomalies you get underneath the ice would be adequate to to mobilize fluids.
And so in that sense, at least you have possibly like kind of low temperature hydrothermal interaction. That said, there isn't a lot of tidal heating in Ganymede. or Titan. Instead, they have oceans because they just formed with so much material that it was hard for them to get rid of all their heat.
Matt: So in the coming years, the [00:38:00] way I see it, Europa Clipper will be something of a trailblazer, a pathfinder, right? It's going to be conducting the science that scientists have been waiting decades to do. And currently there's only one other mission, as far as NASA is concerned, to investigate the ocean world, and that's the dragonfly. Is that correct?
Steve: That's right. Yeah. So NASA has on the books, the Europa Clipper mission, which will complete our prime mission around 2035 and around that time, with any luck, the Dragonfly spacecraft will be exploring Titan.
And so that'll be, those will both be entirely different from missions from anything we've seen before. For Europa Clipper, in terms of the science organization of the mission, the kinds of things we'll be able to see with the really high fidelity instrumentation we have, and the way we've designed the mission for all the measurements to overlap.
And so we'll be able to compare and just get a whole lot of information out of all those measurements. So I just expect that my field, the study of ocean worlds, is going to be turned on its head by what we find from Europa Clipper. [00:39:00] And yeah, Dragonfly, you know, flying around the surface of Titan is just going to tell us a whole lot about Titan in the weird ways that its surface weather and geomorphology manifest.
You know, Titan is more like an Earth like world in that sense. But I also hope that as part of that mission we're going to learn a lot about How is ice shell works and how thick it's ocean is some of the same stuff that I'm excited to learn with Europa. I hope to learn about Titan using dragon fly.
Matt: Well, I hope to have you back on the show so we can discuss that because Titan itself is a very interesting and unique world within our solar system. As far as we know, and the implications of its existence here. We assume that there may be many more like it out there and there's speculation that there could in fact be exotic life there.
Steve: Indeed. Yeah, I'd love to come back and talk about Titan. It's a weird spot and it's a paradise for organic chemists for all the weird stuff that's there. Lots of, lots of long chain [00:40:00] carbon molecules and probably a lot of other stuff too that we haven't detected.
Matt: And of course, all this has implications for exoplanet research.
Steve: Yeah. Well, in general, I mean, even just with Europa, but with ocean worlds in general, you know, we're exposed to a great diversity of different types of planets, types of worlds, but Titan in particular, I think really points the way to, you know, maybe there are earth sized planets that are cold like Titan and similarly carbon rich like Titan that have similar stuff going on.
Matt: Yes. Exciting times. I'm very, yeah, I can only imagine how excited you must be with the launch of Europa Clipper just a few months away. Now, one other thing I wanted to ask is, the European Space Agency, they launched their Jupiter Icy Moons Explorer, or JUICE, back in April of 2023?
Steve: That's right. Yeah, yeah, JUICE is on its way.
Matt: Yeah, now it is scheduled to reach Jupiter by 2034. [00:41:00] Whereas Europa
Clipper is launching in about six months and it's going to get there at 2030.
Steve: So , so Europa Clipper is launching on a Falcon heavy vehicle, a pretty capable vehicle that's going to give us a lot of oomph and get there faster. It just happens that the, I think it's the Ariane 5 rocket.
That's the most capable rocket that ESA has. It'll take a little bit longer for them to get there. They're taking, taking a more scenic route, but they will get there. And in fact, they'll be, they'll be getting into their. main tour of the Jupiter system just a little bit after we start ours. And so. It's exciting to be, to, to be at a place where now that we're finishing Europa Clipper, we have the time to speak with the JUICE science team and get back to thinking about some collaborative science between the two missions, which it happens is something we were trying to do back when I started at JPL, when NASA was, and ESA were considering a joint set of flagship missions to, to orbit Europa and Ganymede [00:42:00] respectively.
It happens that JUICE , that ESA continued on that path and the mission that they were studying culminated in the Juice mission, which at the, at the latter part of its main mission phase will orbit Ganymede.
Matt: And so, yeah, in fact, Clipper and Juice will be studying these two ocean worlds separately, but there will be overlap too as well, yes.
Steve: That's correct. So Juice will have a number of flybys of Europa, some of them very close on with Europa Clipper. So we can imagine having datasets that are very comparable in terms of being able to look with similar sets of eyes at exactly the same behavior of Europa. So I'll leave the discussion of those details for another, another time, since some of them are subject to You know, making sure that our trajectories are exactly the same, but suffice to
say, we're really lucky to have two very capable flagship missions in the Jupiter neighborhood at the same time.
Matt: Absolutely. [00:43:00] Well, I want to thank you for coming on. And also I look forward to hearing of any information that starts coming back from these venerable missions. Yeah. Much like James Webb. It's like. Oh my God, it's actually coming together. It's, and when the scientific returns start coming in, holy.
Steve: Yeah, it's a really exciting time with, with James Webb. And, and yeah, Matt, thanks for having me on and I can't overemphasize how excited I am that we're about to launch. It's only seven years until we'll be getting our first data from Europa Clipper.
Matt: Well, best of luck to you and your colleagues. And like I said, I hope to talk to you again there and discuss more on this really fascinating subject, because there's just, there really is so much.
You can disappear down a dozen different rapid holes and still each one dealing with a separate icy moon and still barely just scratch the surface. But that's what subsequent episodes are for. So thank you once again Dr. Vance for coming on to [00:44:00] my listeners.
Thank you for listening. I'm Matt Williams and this has been Stories from Space.