Jupiter has many moons, but none are quite like Europa: it has a thick crust of ice and a huge amount of liquid saltwater underneath its surface. In fact, many believe it’s the best place in the Solar System that we could find other lifeforms. To dive deeper into the mysteries of this icy world–and how we plan on exploring it–Miles sits down with Kevin Peter Hand, Deputy Project Scientist of NASA’s Europa Mission on this episode of Miles To Go.
Help us improve this podcast: take our short survey.
Miles O’Brien: Hello and welcome to another edition of Miles To Go, I’m Miles O’Brien.
Now, imagine, if you will, a landscape. Think of a seafloor, pitch black, miles of saltwater above you working overtime to crush your submersible. It’s cold–barely above freezing–except around towers rising from the seafloor, which are belching out superheated water and gases.
No way anything could live down here, you think. But, when you turn on your ship’s night vision camera, you see bizarre lifeforms scurrying around, especially around those towering hydrothermal vents.
Now–if you’re picturing something like that in the Mariana Trench at the bottom of the Pacific Ocean, you’re not wrong… But, I was actually taking you somewhere else. I was thinking of Europa, a moon of Jupiter.
Scientists have known for decades that Europa is a world with a thick, icy crust hiding a massive saltwater ocean underneath. This could theoretically sustain life, right? After all, everywhere we go on Earth that has liquid water, we find life… Everywhere.
The task of getting to and exploring Europa is a daunting one, to say the least–but the possible reward of finding alien life has kept a cadre of scientists pushing for a mission… or two.
Even some politicians have seemingly caught the alien bug: the proposed Europa Clipper mission is the only one it is illegal for NASA not to fly! The Congressman who pushed that piece of legislation through, John Culberson of the Houston area, just got voted out of office after nine terms. But the law still stands. For more on that, check out a PBS NewsHour piece I did last year. It’s called “What do the stars hold for the Trump administration? Here’s how NASA’s mission could change”. We’ll put a link on our website, milesobrien.com and you could check that out.
For that segment, I also interviewed Kevin Peter Hand, Deputy Project Scientist of NASA’s Europa Mission. Though the Jet Propulsion Lab in Pasadena where we met is more oftenly known for its Mars rovers, Kevin has his sights set firmly on that snowball circling Jupiter…
Miles O’Brien: Let’s first off all just talk about Europa for a moment. Why is Europa such an interesting target for astrobiology?
Kevin Peter Hand: This moon of Jupiter is fascinating in the context of the search for life elsewhere because if we’ve learned anything about life on Earth, it’s that where you find the liquid water, you generally find life. And out at Europa we have really good evidence for a global, roughly 60-mile deep liquid water ocean beneath Europa’s ice shell. And with that much water out there today in our solar system, that begs the question: could there be life within that ocean?
Miles O’Brien: Okay. So NASA has for years and years said, “Follow the water.” You know, everywhere we go in this planet, deepest part of the ocean, acid springs of Yellowstone up in high altitude, dew drops in the Atacama Desert, there’s always life there. So, why have we been going to like one of the driest places we can imagine, Mars, to find water when there’s water there at Europa, right? If that’s the goal.
Kevin Peter Hand: Mars is kind of more of the traditional habitable planet, potentially. We think Mars may have looked somewhat like the Earth in that you’ve got an ocean on the surface and you’ve got continents. And that’s our, sort of, traditional perception or conception of a habitable world.
With a place like Europa, you’re talking about kilometers, miles of ice over an ocean. And so, this kind of challenges our fundamental conception of habitability. We’re not talking about a world where the liquid water is maintained by energy from the parent star, from our sun. That’s the case for the Earth and that would have been the case for Mars in the past.
Out at Europa, we’re talking about an ocean of liquid water that is sustained and maintained through tidal energy interactions, that tug and pull that Europa feels as it orbits Jupiter. Mars is a great place to search for evidence of life as preserved in the rock record from life that may have existed in ancient oceans on Mars.
But, I’m really captivated by the prospect of finding extant life, living life, life that we can poke and prod at and understand its fundamental biochemistry and to understand life at that level requires finding a living sample.
And so, Europa and the other ocean worlds like Enceladus, and Titan and possibly Ganymede, Callisto, et cetera, these are worlds with oceans where life could be existing today, and they could represent a second independent origin of life, separate trees of life that are popping up in our solar system beyond Earth.
Miles O’Brien: That’s an important point, I think that people may not understand. Mars and Earth have been swapping rocks for billions of years. We could be a common genesis. In this case though, we could probably rule that out, right?
Kevin Peter Hand: Yeah. I try and avoid the word common genesis.
Miles O’Brien: Separate origin. If you find life on Europa, we can say pretty categorically that was a separate strain of life that began on its own separate from Earth entirely.
Kevin Peter Hand: The prospect of finding life on a world like Europa, an ocean world, provides the prospect of identifying a potentially second independent origin of life in our own backyard.
Contrast this with, say, finding fossilized life on Mars. That would be profound, and we need to continue with that exploration. But the biomolecules, the biochemistry of life is not very well preserved in fossilized life. So, we would have a fossil, but we wouldn’t know whether or not that life was based on DNA, or RNA, et cetera. And even if we did find life there, and let’s say we found it was based on DNA, we would say “Well, is that connected to life on Earth?”
Because Mars and the Earth had been transferring material for much of the history of the solar system and so, Earth could have seeded Mars, Mars could have seeded Earth, and we wouldn’t necessarily be able to identify that life as having come from a second origin.
Meanwhile, if you go out to the outer solar system, it’s much harder to get material ejected from Earth and eventually impacting Europa and seeding Europa’s ocean with life on Earth. And so, if we went to Europa and found life on Europa, that would in my opinion be a strong signal of a second independent origin.
And, interestingly, I think even if we found that life there was based on DNA, that would be incredibly intriguing from a fundamental biochemistry standpoint. It would point towards a convergent biochemical evolution to DNA as a fundamental biomolecule for life. Or maybe there’s some other molecule there or maybe there’s no life at all, which is also a profound result. What if we go to a world like Europa and the conditions are right for life, but there is no life?
That also informs us about our own origins. Maybe hydrothermal events, like we might expect to find on Europa are not a good place for the origin of life. Maybe the origin of life requires continents and warm tidal pools. By doing this exploration, by searching for life on these worlds beyond Earth, we learn not only about life beyond Earth, but it also points the lens back at us and our origins.
Miles O’Brien: So, if you want to try to really answer this question, there’s probably no better target when you sum everything together as far as proximity and capability and what is there, right?
Kevin Peter Hand: Europa and Enceladus both meet the criteria in my opinion of worlds where you’ve got liquid water interacting with rocky seafloors providing the elements and potentially the energy needed to build and power life.
And this is water and carbon-based life, life as we know it. Coupled with that, there’s also Saturn’s moon Titan, which is a fascinating world in the context of possibly harboring weird life, life that might have originated in these methane, ethane lakes that cover Titan’s surface. And so from the standpoint of intriguing chemistries in the oceans beyond Earth, Europa, Enceladus, and Titan rank highest on my list of prime targets for exploration.
Miles O’Brien: As a scientist, I know you don’t want to speculate too much, but do you think it’s likely there’s life on any of those places?
Kevin Peter Hand: The way I like to frame it is that we can make a prediction based on our knowledge of life on Earth. We don’t yet know how life on Earth originated, but we think that it involves some combination of bringing together liquid water, some key elements, some energy, some catalytic surface on which early molecules could have been templated. Maybe it was at hydrothermal events, maybe it was at hot springs, et cetera.
But we can put forth what I like to call the “biology hypothesis,” bring together those things and maybe life arises. And so, in our exploration of the outer solar system, we’ve found these worlds like Europa and Enceladus where to the best of our knowledge so far, they meet the criteria for the biology hypothesis. Does that mean that the origin of life occurred? Who knows? We just have to get out there and do the exploration.
Miles O’Brien: I know you can go on great detail about this, but give us the broad overview of what these — there are two launches now, one with an orbiter, actually of Jupiter, right, because of the radiation issue. Walk us through that and then what the lander would do.
Kevin Peter Hand: A mission that NASA currently has on the books and is moving forward at a great pace is the Europa Clipper Mission. This is a mission that would reach the launch pad in the early 2020s and it would orbit Jupiter and make over 40 flybys of Europa. And with each flyby, it would collect stunning imagery of Europa’s surface, spectroscopy to tell us about Europa’s surface composition, looking for things like salts and organic compounds and it would also do ice penetrating radar to kind of see below the surface of the ice looking for the ice-ocean boundary.
That mission would also help guide us with a future Europa Lander. The Clipper mission would provide some of the data that we need to figure out where to land and where it might be safe and scientifically interesting to land.
And the lander is a mission concept that’s currently under study at NASA and we’re doing a lot of that work out at the Jet Propulsion Lab. The launch date for that is yet to be determined, but we’re working hard to try and turn that mission into a reality.
Miles O’Brien: So, if you land on the surface, can you get enough done to settle this question or don’t you have to have some way of getting below the ice melting through or some other means?
Kevin Peter Hand: The mission concept as currently envisioned, would have a robotic arm that allows us to get beneath the radiation processed and guarded regolith, that sort of surface slough on Europa and getting a little bit deeper into the ice, a few to ten or so centimeters below the surface.
Sure, we’d love to melt through the ice and reach the ocean directly, but based on the evidence we have, Europa’s ice shell does serve as a relatively good window into the ocean below.
We think we see salts on Europa’s surface. Those salts would most likely have been derived from ocean water beneath the ice shell. And so, if there are concentrations of salts on Europa’s surface, could there also be concentration of organics and any organisms that might live in that ocean? Potentially, yes. And so, we could perhaps by sampling the surface, also be sampling ocean material and thereby also be potentially grabbing a sample that could have some little Europa organisms.
Miles O’Brien: So, it’s kind of an enemy of the good lander. I mean, at least get to the surface, maybe we’ll get the answer. We don’t have to melt through?
Kevin Peter Hand: Exploration sort of goes in these stages, and before we say commit to melting all the way through in getting into the ocean, it will be good to know how interesting the surface chemistry is and whether or not there really are any biosignatures, any signs of life.
Miles O’Brien: What about if you could land right next to a crevasse that was off-gassing something?
Kevin Peter Hand: That would be ideal. And that’s where the funds of give and take between the scientists and engineers become critical. Because a science team as you can imagine, would be like: “Land there. Land right next to that plume and get the freshest stuff.” But, the engineers might say, “We don’t want to take a risk of say getting a bunch of that plume material onto the cameras as we’re coming in for a landing.”
And so, that’s something that we’re actually working on some of that kind of capability out at JPL. And then in the future when we really have to make those hard decisions about where exactly to land, those kinds of issues will be at the forefront.
Miles O’Brien: There’s no spot that we know of, of course, this might be discovered by the first mission where you could like drop something in these crevasses and go all the way down?
Kevin Peter Hand: At Enceladus, we think that the gravity is mild enough such that the tidal tug and pull can perhaps crack the ice all the way from Enceladus’ surface down to the ocean. Enceladus is only about 500 kilometers in diameter. At Europa, we’re talking about a much bigger moon and the gravity of Europa is such that the pressures within the ice shell are probably sufficient to resist tidal cracking all the way through from the surface to the ocean.
So, you might have networks of cracks. You might have material sort of rising up through the ocean. But the direct connection and how exchange occurs between the ocean and the surface is one of the things that the Clipper mission will help us figure out. And it’ll be able to guide us to the prime sites for ocean material.
Miles O’Brien: This is a mission that’s been around for quite a long time. I remember being at JPL really a long time ago, when I was still at CNN. I can’t remember when was it. It was around one of the landing maybe —
Kevin Peter Hand: I obviously wish we could be moving a lot faster, but at the same time, I feel thrilled to be alive at a time when we can make progress on these missions. These missions, these goals are not for the faint of heart. You have to be committed, you have to be obsessed, you have to be a little crazy to really set your vision on getting this kind of exploration done, and that’s been true throughout human history.
If you want to get anything great done, you have to be committed to it and it’s going to take some time. In the decades past, we had the Galileo mission, as you recall, in the late 1990s, early 2000s, and that provided us with much of the data about Europa and prospects for an ocean within Europa, and there were a lot of studies looking at sending missions back and one of the images that captivated my imagination as an undergrad in the mid to late 1990s was this NASA cartoon of a meltprobe going through the ice on Europa and the date on it was 2009. Well, 2009 has come and gone. I have now spent over 17 years working on Europa and we’re a bit closer to getting there but political whims and different goals and all those things kind of result in sort of a wavering focus on exactly where we should go and what NASA should be doing. But thankfully, the search for life elsewhere, astrobiology, is something that people love. The public gets very excited about this kind of exploration. The winds and waves have perhaps prevented us from getting there on the timescales that many of us would have liked to have seen, but public support has been tremendous and people continue to be advocates for getting out there and so, we’re just doing the best we can.
Miles O’Brien: So, in that 17-year period — I haven’t counted them up, quite a few, more than a handful of Mars missions. Why hasn’t there been just a crumb left for Europa over these 17 years?
Kevin Peter Hand: A key thing to appreciate is that it’s really hard. Getting to the outer solar system, doing missions in a Jupiter environment where the radiation is very intense, it’s a hard engineering environment. Landing on the surface of Europa is a hard challenge. And in fact, much of our exploration, or much of the capabilities that we’ll use eventually to land on Europa will be derived from Mars landings.
And I think Mars has captivated the public mind for a much longer period. Think back to War of the Worlds, Percival Lowell, Schiaparelli–it’s been in the public consciousness for well over a century.
Europa has been a point of light up until the Voyager spacecraft flew by and gave us those first images in the late 1970s. And it’s only been through our robotic exploration of the solar system that Europa as an ocean world has become a tangible place to explore. And so, I think that’s been one of the challenges in trying to push forward with the exploration of these moons of the outer solar system is that giving people a sense of these worlds as places that exist, as oceans that are there today and have persisted for much of the history of the solar system, communicating that and getting the word out about the prospect that these worlds pose in the search for life elsewhere. That’s part of the key.
People understand Mars and they can appreciate that it once had a wet, warmer past and life could have existed there. And so, we’re gradually permeating the public consciousness more and more and people are getting more and more captivated.
Miles O’Brien: So, if War of the Worlds had been Europans, you’d be in business, right?
Kevin Peter Hand: Perhaps.
Miles O’Brien: Part of the Mars allure is that it’s about science, but it’s also about as laying the groundwork for putting boots on the ground, and you don’t have this in this case. No human feet will set foot — how much of that plays into it? A big part of NASA’s mission is to put human beings in space and that has driven a lot focus towards Mars.
Kevin Peter Hand: That’s right. So, Mars brings together the robotic exploration side and the human exploration side, and that’s a wonderful thing. I would love to walk along Mars and see all those layers within the ancient lakes and ocean of Martian sediments and look for signs of life.
And so, from the standpoint of NASA’s focus on Mars, it makes a lot of sense. It’s a very scientifically compelling place to look for past and possibly even present life and humans could, someday, set foot on Mars both to pursue exploration and fundamental research and to potentially inhabit Mars. We’re not going to send humans to the surface of Europa. They would die relatively quickly because not only is it cold and low pressure but the radiation environment is going to cook you and then it’s not going to be pretty–it’s hard enough for robots to survive on Europa’s surface.
Now, that said, if you get below the ice and into the ocean, the temperatures and pressures within Europa’s ocean are comparable to the temperatures and pressures that we see within the depths of our own ocean here on Earth. And part of what excites me about exploring ocean worlds beyond Earth is that it also motivates a more detailed exploration of the ocean we know and love here on planet Earth. We know very little about our own seafloor. And I’m of the opinion that as we extend our reach into the outer solar system to explore these ocean worlds, we darn well better also explore our ocean here on Earth to understand the fundamentals of what makes it tick and how to protect it. And that will build a nice bridge as we try to understand whether or not these worlds beyond Earth are habitable or possibly inhabited.
Miles O’Brien: The fact that we even know that there is an ocean there, was that mostly Galileo data that got us there? I mean, how were they able to — it could be frozen solid, right? I mean, there’s got to be some way to determine that, right?
Kevin Peter Hand: Right. So, the Galileo spacecraft gave us most of the data that provides the compelling evidence for a subsurface liquid water ocean. And I like to break it in to three easy pieces — well, four pieces. The first piece, Galileo discovers Europa. The second piece is that in 1950s, 1960s, and 1970s, astronomers did spectroscopy of Europa and figured out that it was covered in ice. Then with the Galileo mission, the spacecraft flybys allowed scientists to figure out the gravity structure of Europa and determine that along with having a dense iron core and a rocky mantle, there needed to be a layer of water in either solid or liquid phase in the outermost reaches. And then along with those flybys or coupled with those flybys were measurements of Europa’s magnetic field.
The details of this are beautiful but, suffice it to say, it’s almost like you walking through a metal detector at an airport, where if you’ve got a conductor in your pocket and you’re walking through that metal detector, the alarm goes off. And that has to do with magnetic field interactions.
The Galileo spacecraft detected an induced magnetic field at Europa. The alarm went off and the conductor in Europa’s pocket is a salty liquid water ocean. And so, that’s some of the best evidence for this subsurface liquid water ocean beneath the icy shell. It’s beautiful physics that everybody learns in college. It has helped reveal this global liquid water ocean that could harbor life.
Miles O’Brien: You’ve got to be pretty excited about what you’re reading about the current talk in Washington, the President’s budget of course, that’s just the beginning, but there’s a lot of support on the hill. Is this vision — I mean I just was briefed by Gerstenmaier and there was for the second SLS flight. Europa Clipper. It’s finally becoming real, isn’t it?
Kevin Peter Hand: We’re getting there. It’s an exciting time. We’ve been building towards this for many, many years, going on almost a couple of decades now. One thing to appreciate is that we really are at the footsteps of making this great discovery. If you look at NASA’s roadmap, be it exploring Europa, Enceladus, Titan, Mars, et cetera, within the next 20 years, perhaps 30, but within the next 20 to 30 years, we will do the exploration of our solar system that could reveal whether or not life exists beyond Earth.
That’s within our lifetime; that’s an incredibly exciting discovery to make. It’s a question that humanity has been asking since we first looked up at the night sky and here we are in these decades with the prospect of potentially answering that great question.
Miles O’Brien: Do you care to actually hazard a guess whether the question will be answered once and for all about life extant or past on Mars before or after you get to Europa? Or will Europa be the first time we get an answer?
Kevin Peter Hand: So interestingly, when you look at our exploration of Mars, we’re making great progress with the Mars Sample Return and Mars 2020 will go and collect some cores that will eventually come back to Earth.
I would love to see that mission find evidence of fossilized life and then we get those cores back and we can look at them in the lab. Parallel to that, we’ll begin our rigorous exploration of Europa with the Clipper mission and potentially following that on with the Lander mission and missions hopefully to Enceladus and Titan and elsewhere. And so in my sort of dream of dreams, by the year 2030, we’re discovering life on Mars, we’re finding life on Europa, we’re exploring the plumes of Enceladus, we’re searching for weird life on Titan, we’re doing all of these great things and we’re also further advancing our exploration and our understanding of planet Earth because it all sort of folds together.
Miles O’Brien: What’s it going to be like when that discovery comes in? I say when, I think one of these days we’re going to get that answer. How is that going to change us?
Kevin Peter Hand: The way I like to think about it, if we discover life beyond Earth, it’s not going to change the way you make your coffee in the morning, it’s not going to shorten your commutes. But what it will do and what I find particularly profound is that if you go back to Galileo and the Copernican Revolution, a part of what Galileo helped lay the foundation for with his observations of the moon, and Venus, and Jupiter and subsequent science after that, we came to appreciate that the fundamental science of physics works beyond Earth.
And then in the decades and centuries that followed, we would appreciate that the principles of chemistry work beyond Earth. And with robotic exploration of our solar system and looking at worlds like the moon and Mercury, et cetera, we have come to appreciate that geology works beyond Earth. But when it comes to biology and the phenomenon of life, we have yet to make that leap.
We have every reason to predict that life should work beyond Earth based on our study of life on Earth, but we don’t yet know whether biology works beyond the home planet. We don’t yet know whether or not the phenomenon of life is isolated to our planet or extends into a biological universe. And I love the prospect of pursuing that question.
Miles O’Brien: Thank you very much, Kevin. We’ll be watching these missions to our nearby–relatively–icy neighborhoods with great interest! Guess it remains to be seen if our robots will be greeted with Europan snow cones…
While I’ve got you, please rate and review this podcast, it would really help us out. And sign up for my newsletter! You’ll get my favorite science news of the week delivered straight to your inbox. Just once a week–one email, no spam, we promise.
Thanks for listening! I’m Miles O’Brien and this is Miles To Go.
Banner image credit: NASA.