Finding aliens on icy moon Enceladus

Hi everyone and welcome to Space Cowboys. Today with me, Thijs, your host, and Juri. Hi there, Thijs. Hi, Juri. Herbert is off today. We're going to have a great conversation today with Jonathan Lunine. Do you know who he is, Juri? I've heard about him. He's a big shot, right? Yes, in the preparation of this show you definitely heard about him. Yeah, so I talked to him four years ago at Cornell University in New York, New York State. Well, he has worked on Cassini, the mission to Saturn that was there for, I don't know, almost like a decade. The Cassini-Huygens mission. Actually, there was a Huygens probe named after a Dutch astronomer, Christian Huygens, that landed on Titan, one of the moons of Saturn. But also this Cassini space probe. Flew through plumes of Enceladus. And, yeah, you're going to learn a lot today. So Enceladus you know, right? Yeah. What is Enceladus? Enceladus is one of the moons of Saturn. And I think it's famous because of the plume where they found some organic compounds in it. Exactly. Yeah, it's like an ice ball. It's like an ice ball that goes around Saturn. And there's another ice ball in the solar system and it's Europa. That's usually a more well-known ice ball for some reason. It's bigger and it's, I don't know. Yeah. It's just for some reason its celebrity status is a little bit bigger. But Jonathan Lunine that we're going to talk to today has worked on Enceladus. So we're going to talk about astrobiology, finding life in the universe, and why NASA's priorities are sometimes a little bit weird so that we don't know the answer yet. To that eternal question, are we alone? Is there life out there? Are we excited? Yes. Looking forward. Jonathan Lunine, welcome to the show. Glad to be here, Thijs. Thank you. Hi. Well, let me give you a proper introduction for those of our listeners who don't know you. You are a planetary scientist, physicist, and director of the Cornell Center for Astrophysics and Planetary Science at the Carl Sagan Institute at Cornell University. Did I get that right? That was pretty good. Okay. I'm glad. And today we're going to talk about, well, your past, present, and future astrobiology missions because you've worked on quite a few. First of all, you're a principal investigator in the Enceladus LifeFinder mission. You've worked on the Cassini mission as well. But we had a very hard time figuring out what you were doing in the 80s and 90s. So could you please enlighten us? Sure. So I was actually working on Cassini. I was working on Cassini in the 80s and 90s. You know, Cassini, and it's really Cassini-Huygens because the European part of the Mission European Space Agency included a probe that landed on Titan's surface in 2005 called the Huygens probe. And in the 1980s, after the Voyager 1 and 2 flybys through the Saturn system, a lot of scientists on both sides of the Atlantic became interested in, going back to Saturn, orbiting it, and putting a probe into either Saturn's atmosphere or into Titan and to its surface, or do both. And there were many studies that were done. I was involved in those studies. I had finished my graduate work in 1984 and officially finished in 1985. So I began to have some involvement in various kinds of studies. And I was involved in a number of other research projects that eventually led to what was the Cassini-Huygens mission, which officially got started in 1989 and 1990 and, of course, was launched in 1997. Oh, that's when it started. Oh, yeah. Yeah. The official start, when the science instruments and the science teams were selected, was really spanned between 1989 and 1990. But there were six or seven years of study before that. And some would argue that missions like Cassini were even being talked about. Yeah. Some were being talked about in the 1970s. Oh, really? Yeah. That's quite a long time. Yeah. And how much did we know about Saturn back then, before Cassini? Well, we knew a fair amount about the rings from the Pioneer missions. We knew a little bit about the satellites, but very little, in fact. Nonetheless, there were a lot of very good papers that were written. John Lewis was a famous scientist. He was a famous cosmochemist in the early, well, 1960s and 70s. He wrote a paper in 1971 in which he talked about Titan having methane gas hydrates or clathrate hydrates in its crust because it was known that there was methane in the atmosphere. That was the discovery of Gerard Kuiper, the Dutch-American astronomer in the 1940s. Yeah. And so John Lewis followed the chemical implications of that. Yeah. Yeah. Yeah. Yeah. Yeah. Yeah. Yeah. Yeah. Yeah. Yeah. Yeah. I think his work, which, of course, predated the Voyager flybys by nine years, is actually quite relevant today. There was work in the 1970s by other scientists, Don Hunton at University of Arizona and Daryl Strobel at the Naval Research Lab on the atmosphere of Titan, Sushil Atreya in Michigan. All of these were actually pretty prescient in establishing that nitrogen might be present in the atmosphere of the atmosphere of the atmosphere of the atmosphere of the atmosphere. And also how the methane might be broken up by sunlight into other organic molecules. Oh, yeah. So, bottom line, we knew, we really didn't know very much about Titan, the other moons, a little bit about Saturn and its rings. But from the little that was known, there were some brilliant scientists who made some very, very good, I would say, either educated guesses or inductive discoveries, whichever you like, which helped to lay the groundwork. Yeah. After Voyager for Cassini. Oh, yeah. Would you call it astrobiology back then? Was that the name for it? No one used that term back then. So, everybody was, in a sense, still is a planetary scientist in terms of studying the nature of the planets. Those who are interested in the question of life out there would have called themselves exobiologists, primarily. Exo. Exobiologists, yes. So, life outside. Life outside the Earth. Yeah. But the term astrobiology had been used occasionally in the middle part of the 20th century and even earlier than that. And it was, I would say, it was captured by those who were trying to create not simply a subdiscipline of astronomy and planetary science, which exobiology was, but a whole field unto itself. And so, by, I would say, exhuming the word astrobiology. And so, by, I would say, exhuming the word astrobiology. From some obscure literature in the 50s, they were able to bring forth the idea that this was kind of a field unto itself of how planets are habitable, how life began on Earth, whether there's life elsewhere in the cosmos, and what is the future of life on Earth. We last spoke in 2015, Jonathan, when I visited the Carl Sagan Institute. Yeah. It was wonderful. Such a fantastic location there as well. So beautiful in Ithaca. Yeah. Yeah. Yeah. Yeah. Yeah. Yeah. Yeah. Yeah. Yeah. Yeah. Yeah. Yeah. Yeah. Yeah. Yeah. Yeah. Yeah. Yeah. Yeah. Yeah. Yeah. Yeah. Yeah. Yeah. Yeah. Right? Yes, it has. Yeah. Yes, it has come to a close. Yeah. Do you still have work? I'm still employed. That's nice. Actually, which is good. You never know. You never know. That's right. But on a more serious note, it was the end of what was, in a formal sense, a 20-year odyssey in space. Cassini was launched in 1997. 1997 and ended in 2017. And if you count the development time, really a 27-year odyssey, but I like to think of it as 30 or 35 years if you count the time to develop the mission concept and sell it and get it going. So what's happening now is that the science teams are actually still partially funded through the end of the summer to complete the closeout on some of the science data products that are being put on the planetary data system, which is a NASA public archiving system for data. Some are still being analyzed as well. And people nonetheless are transitioning either to new missions or to research funding that will allow them to continue the analysis of the data for many years. Typically what happens with a very large mission like Cassini is that although no more data are coming back to the ground because the spacecraft no longer exists, it's now atoms in Saturn's atmosphere, a lot of the analysis, a lot of the detailed analysis and interpretation of the data actually is done after the mission is over. Because when you're still receiving the data, you know, you tend to, there's always the next change. Wonderful batch of data coming down so you don't have a chance to analyze the previous batch in detail and you don't have the full data set available. So the period, I would say, five or ten years, sometimes even 15 years out from the end of a mission, some of the most valuable science is done because the whole data set is available. There's a chance for not only experienced scientists but new graduate students with lots of energy and new ideas. Right. To get involved in analyzing this data and the deepest insights often come during that period of time after the mission is over. And that's why it's so important for NASA to continue funding and what's called its research and analysis program, the analysis of these wonderful data sets from Cassini. And so you're thinking that maybe this, the Cassini mission will, years from now, maybe suddenly its data will give us something that we hadn't looked at. Right. That's a good point. That's a good point. That's a good point. That's a good point. That's a good point. That's a good point. That's a good point. That's a good point. That's a good point. That's a good point. That we didn't think about yet or some emergent truth. I think that's almost certainly the case. I know there are scientists who are working on the analysis of data on Saturn's rings, which will gain new insights for us. There's new results coming up that actually have been published about a month or so ago from two groups on the lakes and seas of Titan and composition of the lakes and seas from the Cassini data. But I think that I would probably not be risking too much by predicting that if you look 10 years from now, there will be students who will be working, I would say, both on data on Titan, as well as data on the other satellites and on Saturn, who will produce entirely new insights. And there are an awful lot of questions that are remaining. We still don't know where the methane comes from. How could Titan sustain methane on its surface today, four and a half billion years after it formed, when in fact all the methane in the atmosphere will be destroyed in a few percent of that time, 10 to 30 million years? I would like to ask you, that's strange. Why is that? But you're saying that we don't know yet. We don't know yet. And, you know, whether the answer to that is contained in the Cassini data or will require a separate mission is to be determined. But certainly locked into those data sets, there has to be some perspective that we haven't quite understood yet because the modeling that is required along with the data themselves hasn't quite been done. Oh, yeah. And when it comes to habitability? And Cassini, did Cassini say anything more about how if it's habitable or not or if there's anything really living in these methane oceans or lakes? Yeah. For Titan, you know, what Cassini did is it took the supposition that there were bodies of methane and ethane lakes and seas and it made them into a reality that they really do exist. And it was able to determine that most. And this is something that we have done over the years,studies, research, but it's also about the fact that most of the large bodies of liquid are actually largely methane with only a small amount of ethane, the exception being Ontario locus in the south, which seems to have perhaps an equal amount of methane and ethane. That's actually not so good for life because these exotic kinds of biochemistries that one might imagine in the liquid methane seas depends on other molecules dissolving in the liquid methane. Yeah. Yeah. Yeah. Yeah. Yeah. Yeah. Yeah. Yeah. itself. That's certainly the case for oceans and lakes on the earth made of water where there are soluble organic species. Methane, it turns out, does not dissolve these heavier molecules, these polymers of HCN or acetylene or other things, as well as ethane does. So a nearly pure titan methane C is probably not as friendly an environment as, let's say, a mixed methane-ethane C would be. And so maybe in the north, like Ligia Mare, Punga Mare, maybe they're not so good as sites for life. But in the south, Ontario Lachis, which seems to have a larger amount of ethane in it, maybe that's a better place to go. Of course, we have to remind everyone who's listening that we're talking about life in a methane-ethane liquid, and we have no experience with that on earth. So the biology of such a system, if we could imagine that it has a biology, would be really, really different from that on the earth. I'm always imagining sea monsters, like something really Loch Ness-like. I don't know why I would start there, but for some reason I always have this image in my head. Well, I would probably reserve the sea monsters for Europa or Enceladus. Oh, really? Yeah, I mean, where you've got liquid oceans. Now, we also should not forget that Cassini discovered in two different ways that underneath this ice crust of Titan and underneath all the organics on the surface is a liquid water ocean. And that ocean appears... You said Titan. Titan. I said Titan. Really? Yep. That was not a mistake. So in addition to Europa and in addition to Enceladus, Titan as well has a liquid water ocean. Now, that ocean... You're kidding. I'm not kidding. No, you're the expert. I know. No, people forget about this. Absolutely. I've never heard about this. They fixate on the methane seas, which is fine. Yeah. But so there were two... Let me just tell you very quickly the two observations. So the first of them was that the... And this is not in order of time, but in order of kind of simplicity of explaining. So Titan has an orbit that is not circular. It's eccentric, slightly eccentric. It has an eccentricity of a few percent. And so it experiences a different tidal force when it's closer to Saturn, a stronger tidal force than it does when it's farther away, because the tidal force goes as a stronger power of the distance, the inverse distance than just the gravitational force itself, the plane gravitational force does. As a consequence of that, Titan's shape changes when it's closer to Saturn versus when it's farther away. So it's a different force than it is when it's farther away. So it's a different force than it is when it's farther away. It's pulled, if you imagine it like taffy, it's pulled more in the direction towards Saturn when it's closer to Saturn. Now, if Titan is just a body of rock and ice with no liquid at all, that amount of distortion would be very small because it's solid. On the other hand, if there's a liquid water ocean underneath a relatively thin ice crust, you would see more distortion because there would be a liquid layer that would not have any strength and would tend to be pulled, and the ice crust on top being thin would tend to go with it. So the bottom line is, you know, if we could observe the shape of Titan, that would be great. We can't do that because it's covered by a thick atmosphere. Yeah, it's super cloudy almost, right? Yeah, super cloudy. But Cassini could measure the change in the mass distribution because the gravitational field, if you will, of an obliterated mass is a big problem. So it's a big problem. So it's a big problem. So it's a big problem. So it's a big problem. So it's body is different from that of a spherical body. And that's exactly what Cassini did. And so, led by the group at the University of Rome that was involved in the gravity part of the radio science experiment, Luciano Yes and colleagues, those measurements were made by Cassini. And lo and behold, Titan is squishy. It's quite squishy, in fact. And so at least part of that, and maybe all of that, must be due to the presence of a substantial liquid layer beneath the ice crust, maybe 50 or as much as 100 kilometers, but more likely 50 kilometers below the surface. Now, the second piece of evidence came actually from the Huygens probe. And that technically came first, but it was easier to interpret. Yeah, take us back to that probe anyway, because we haven't even talked about it yet. No, we haven't. And that was such a marvelous part of the mission, you know, to engineer a probe to plunge into a relatively unknown atmosphere and survive to the surface and return data was really remarkable. Take a picture also. Lots of hundreds, 300 pictures. Yeah. And make measurements in the atmosphere. That was a remarkable achievement that was thanks to the European Space Agency and the ESTEC, the Space Technology Center. Yeah. So, okay. So, Huygens descended under parachute and it landed on the surface. And it landed on the surface of Titan. And in addition to the camera and the chemical measurements and so forth, there were measurements of the electric field around the probe itself. The hope was that it would detect lightning. There were no lightning strikes, but the electric field itself, there was one. There was a non-zero electric field in the atmosphere. And what was interesting about that field is that it was most intense at higher altitude. And it gradually decreased in intensity as the probe went to the surface, but it didn't go to zero at the surface. There was still a non-zero electric field at the surface. Now, everybody who's listening has to take out their electromagnetic textbooks from college and go through them. But, yeah, okay. So, you have that. So, you know, how could you have this electric field that's sort of just sitting there? Well, one way to get it is to have a dielectric, something that is partially insulating, sandwiched between two conductors. The outer conductor on Titan is the ionosphere. It's the part of the atmosphere that has charged particles. It was actually discovered by Voyager and measured by Cassini. And if you simply extrapolate the data on the electric field, the electric field is strong in the upper atmosphere. It's getting weaker, weaker, weaker. If you extend that line below the surface, you reach zero electric field at about 50 or 60 kilometers below the surface. And what they reasoned was that there, 50 kilometers below the surface, was a salty ocean. A salty ocean, of course, is a great electric conductor. And that that would be the bottom conductor in this cavity that they referred to. The technical term is it's a Schumann-like resonance that is maintained between the two conductors. And that's what they referred to. And that's what they referred to. So by itself, that seemed to be a rather speculative conjecture. But remember that completely independently, the gravity data showed that Titan had a liquid water ocean about 50 kilometers below the surface. And so these two independent data sets, one from measuring how squishy Titan is, that was from the orbiter measuring the gravity field at different points as Titan moved, and the other one from measuring how squishy Titan is, that was from the orbiter measuring the gravity field at different points as Titan moved. And so these two independent data sets, one from measuring how squishy Titan is, that was from the orbiter measuring the gravity field at different points as Titan moved. And the other, the electric field from the Huygens probe, give the same result, that there's an ocean at about 50 kilometers under the surface. And more detailed analysis of this change in the mass as Titan experienced variable tidal forces by another group showed that probably that ocean is a little bit denser than liquid water. And how do you do that? Mm-hmm. You make it denser with salt. You put salt in it. I am. So, you know, these two independent measurements both come up with salty, a substantial body of salty liquid water about 50 or 60 kilometers below the surface. So that's, I think, extremely strong evidence coming from two different kinds of analyses from the two different spacecraft. And that leads to the question, could that ocean support life? Yeah, exactly. You know, the Europa Ocean and the Enceladus Ocean having life. We wanted to talk about that, but now we're suddenly talking about Titan Ocean. We are. Yeah. So here's the one question about Titan's ocean. If you model the interior of Titan, which several groups have been doing now for many, many years, I've been involved in some of that, what you find is that Titan is so massive and has so much ice in it that the ocean is not bad. It's not bounded at the bottom by rock necessarily. In the simplest model, it's bounded at the bottom by high-pressure ice, which is simply a form of ice that has a slightly different crystal structure, is denser than liquid water, so it sinks rather than floats. There's a lot of familiarity with this. People make high-pressure ices in the lab all the time. But if that is the case, then the ocean… Titan is what's called a perched ocean. What does that mean? Or a sandwiched ocean. Perched, as in something that's on a perch, like a bird sitting on a perch. Okay. Meaning that it's sandwiched between ice at the top and ice at the bottom. And that's not so good for life because life in an ocean, as we understand it from the Earth's ocean, really benefits from having water cycle through rock, have minerals extracted, heat extracted. All of that could be blocked. If there's a very thick layer of high-pressure ice. Yeah, exactly. Now, before we close the book on Titan, though, there's one other piece of information, which is something that dynamicists call the moment of inertia of Titan, which actually seems to be a bit larger than expected. And one way to get a… And what that means is that Titan isn't as centrally condensed. As, for example, Ganymede. It's not as tightly layered with the densest stuff being, let's say, metal at the very center and then pure rock and then pure ice. It's a little bit less concentrically organized in that way. So how do you get that in a physical model? Well, one way to do that is to assume that the rock core of Titan, we know that it must have a lot of rock from its density. The rock core is… The rock core is what's called hydrated. It has a lot of water in it. The water has combined with the rock. And hydrated minerals, as we're familiar with on the Earth, are less dense than rock that doesn't have water in it. So rock that is anhydrous might have a density three to four times that of liquid water. Rock that's hydrated might have a density between two and a half and three. So it's actually not as dense. And when you put a model together of Titan's interior with that stuff, the rocky core extends far enough out that it actually either completely eliminates or makes very thin this high-pressure ice layer. Now, all of this is, you know, in a computer being done by some scientist somewhere who is trying to fit the Cassini data so we can actually look at the entire… the entire material. But the constraints that we get from Cassini suggest, at least to some of us, not everyone, but some of us, that if you looked inside Titan, that high-pressure ice layer would be either very thin or maybe even just intermittent. And there might be places where the ocean, even today, is in contact with a rocky core, a fluffy rocky core that extends further out than in the simplest manner. Yeah. So that's the whole point of this model. So that would, of course, make Titan's ocean look a bit more attractive again for life. Yeah. Because in what way does it make it more attractive for life? Could there be hydrothermal vents, for example, as well? Exactly. That's… In fact, if water is reacting with rock to make these hydrated minerals, that very process would be part of a hydrothermal system. And what would be powering that system would be a little bit of leftover energy from formation, and then the radioactive decay of some of the elements in the rock, the uranium, the thorium, the potassium, and a little bit of tidal heating from that non-circular orbit that Titan has. Exactly. Yeah. And so, I mean, this is all about Titan. It's also a really good introduction to Enceladus and Europa. Absolutely. Yeah. Because it's sort of the same model. I had never… I was never aware of the fact that Titan was so similar, actually, to the other ones. That's a first. First… I'm glad I'm able to tell you something new today. Definitely. Definitely. So then I think… I have two questions. One is, have we detected any sort of plumes coming from Titan as well? Or is maybe the atmosphere too thick so that we can't see them or witness them in a certain way? So we have not definitively detected plumes, but there have been a few cases where clouds or ground fog have been seen in the atmosphere that have been interpreted… Yeah. …either as just weather clouds or some sort of methane that's being outgassed. I mean, one can't rule out water plumes coming up. Yeah. And in fact, there may have been epochs on Titan when there was a lot of water volcanism, water ammonia, water sulfur spraying out onto the surface. Such a nice environment. Cassini… Yeah. But again… Absolutely. …it would be hard to see underneath this atmosphere that's hundreds of years old. Yeah. And these methane lakes that we talked about, is there any way that life produces them? And how would you know? Yeah. It would be very difficult to know, but there is this one mystery that I think analyzing, reanalyzing the Cassini data will help us with. The hydrogen that is being produced from the methane in the upper atmosphere, methane is broken apart by sunlight. Some of the hydrogen escapes. Even Voyager saw a corona of hydrogen around Titan. It was looking in the ultraviolet. All that's fine and good, but there's also a weak indication from the Cassini data that hydrogen is being lost at the surface, that there's a sink of hydrogen that's being taken up. And some people have said, well, maybe that has something to do with life. Maybe there's a kind of metabolism occurring. And while that would be the extraordinary explanation, you'd want to rule out the more mundane ones first, there could be a system where energy is being extracted from these hydrocarbons and methane is being recycled again by life. And indeed- It just bubbles up? It just bubbles up and is produced in that way. Now, personally- It's a theory. I think it's a theory. And the other theory is that, as John Lewis said- Yeah. As John Lewis said almost 40 years ago, 39 years ago now, the crust is suffused with methane in the form of gas hydrates and that it's just bubbling up from the gas hydrates. So, it would take a future mission to tell us which of those is right. Ah, a future mission. That's something I- Yeah. Yes. So, I would love to talk about the Enceladus Life Finder mission because- Let's talk about Enceladus. Yeah. Let's talk about Enceladus because it's- Okay. It's very close. Yep. And so, now I know, pretty similar. And you have worked on this since when, on Enceladus itself? Yeah. So, I've worked on the Enceladus Life Finder mission since 2015. So, for our listeners, you know, let's leave Titan, let's zoom in closer to Saturn. There's Enceladus. It's a tiny moon. It's a thousand times smaller in volume than Titan. It's a thousand times smaller in volume than Titan. It's a thousand times smaller in volume than Titan. It's a thousand times smaller in volume than Titan. It's a thousand times smaller in volume than Titan. It's a thousand times smaller in volume than Titan. Wow. But it has more tidal heating because the orbit is closer to Saturn and so it gets tugged and pulled more. And of course, that produces the famous plume that we see coming out of the South Polar region. The Cassini first saw? Which Cassini first discovered. Yeah. There is one image from Voyager that might possibly show that plume, but it's controversial as to whether it does. But certainly in terms of the aha moment when people said, oh, there's a plume there, it was Cassini in 2005. And then Cassini proceeded to fly through that plume many times, a dozen times making measurements. It luckily carried some compositional detectors called mass spectrometers that were not intended for the plume, but they worked very well. So we know that there are organic molecules. In addition to water, there's organic molecules, carbon-bearing molecules. Some are quite heavy and complex. There are grains of water with salt in them, up to 1% or 2% salt, which is not too far off from the 4% saltiness of the Earth's ocean. There are tiny silica grains pouring out of Enceladus. These silica grains are really quite pure. And what they almost certainly tell us is that water is a very, very small amount of salt. So water is cycling into the rock at the base of Enceladus' ocean. It's leaching out the silica, and then that's getting blown out into space. And that is then a signpost of hydrothermal activity. And if that's happening, then there should be hydrogen produced from this chemistry between the rock and the water. And in fact, on the very last fly-through of the plume by Cassini, there's a lot of hydrogen. Cassini, in, oh goodness, when was that? 2015, I guess. Hydrogen was discovered. It took a special way of operating one of the mass spectrometers to detect it, but lo and behold, the hydrogen was discovered. So all of the ingredients that would point to Enceladus' ocean having hydrothermal activity, and being a place that could feed life. So they are all there. And the one thing that Cassini could not do for us was to actually detect, definitively detect biomolecules. And that's what we want to do next with Enceladus' life finder. And what's the, about organic molecules? Yeah, because you mentioned organic molecules. That triggers me because then I think organic molecules, that's life. But what's the difference? Yeah. So to a chemist, and I'm using the chemist terminology. An organic molecule is... Yeah. An organic molecule is a molecule that contains carbon and hydrogen. But it doesn't necessarily mean that molecule was produced by life. There are, of course, methane is an organic molecule. It's abundant throughout the universe as far as we know, but it's not necessarily made by life. And even the more complex organic molecules, things like polymers or strings of hydrogen cyanide. And things called polycyclic aromatic hydrocarbons. Those are very likely produced just by non-biological processes. But life of course itself produces organic molecules. It produces a narrow subset of possible organic molecules that chemistry could make. It makes the ones that are useful to it of course. And so for example, out of the hundreds of amino acids that can be produced in nature, you can find a number of organic molecules. And so life is very selective. Life is, if you want to think of it this way, is a chemical system that has a very high information content, produces a very specific set of compounds, and is able to faithfully replicate those chemical factories over and over again. The factories that we call cells. So we want to look for the signposts of organic molecules that are produced by life and not merely organic molecules in general. Yeah. And so you have designed a mission, the Enceladus LifeFinder mission, that where Cassini just, well Cassini couldn't do it, but Enceladus LifeFinder could do it. Cassini was so close, then it's almost too bad that it wasn't able to catch these biosignatures. But what would Enceladus LifeFinder do different from Cassini? So if somehow you could have magically swapped out the 1980s technology mass spectrometers on Cassini and put in mass spectrometers that fly in space today, that would have done it. Oh wow. If you could magically beam it aboard Cassini, that would have taken care of the whole thing. Oh wow. It's such a profound question. It's so heartbreaking almost that, you know, if it's there, of course, right? If it's there, maybe there's nothing to be found. Right. But you know, the mass spectrometers that were flown on Cassini were marvels in their time. They were marvels of their time. And of course, no one knew that there was a plume and an ocean underneath the surface of Enceladus, such a tiny moon after all. Nobody thought of it. So no regrets. You know, it's a wonderful discovery. And you ask, what's next? So in our concept, which is Enceladus Life Finder... It must have been a little frustrating, Jonathan. A little. No? Well, probably more frustrating is that NASA has not chosen these concepts yet. Exactly. Yeah, we're going to talk about that in a second. But okay, so what's the concept? What's the concept? So my concept is take two or three of these mass spectrometers, go back to Saturn, do exactly what Cassini did, fly through the plume. We'd probably slow down the flybys a bit to preserve more space. And then we'd go back to the moon. And then we'd go back to the moon. Right. And then how you might start collecting hopefully more particles индue the�� analysis and the unauthenticated solutions that's in thatальноbubenAAs toZe fnhhastic listeners which is likely to help us become very mostrollers. And our science would then pretty much have done more than just that. Exactly. We studied galaxies восي-a diferente Package ofggerstrootATT li Katharine deciding whether those patterns were strong enough to indicate that the organic molecules are being manufactured inside Enceladus by life in the subsurface ocean of Enceladus by biology rather than by non-biological processes. And how much would this all cost? So in the original version, I believe when we talked, it was a discovery proposal that was $450 million. It didn't quite fit in the end. So we went again in 2017 for a New Frontiers-class mission. Yeah, which is bigger, right? Which is bigger. That's $850 million plus launch. NASA throws in the launch. Okay. But these are less than, yeah. So, you know, people say, wow, a billion dollars, that's a lot of money. Not for this. Not for this. And it's a fourth the cost of Cassini. And it's a billion. Between a fourth and, well, it's a twentieth the cost of developing a commercial jetliner nowadays, whether you're Airbus or Boeing. Yeah. So, you know, these are, I mean, look, this is a sum of money that Jeff Bezos could write a check for. Exactly. You know, it would put a little dent in his pocketbook, but he'd still have some money left over to eat. Or Uri Milner, because I think I read. Or Uri Milner. Yeah, he was talking about maybe funding it, no? He has been. And has he talked to you about funding it? Funding it? So, he has talked to me, but he's mostly been talking to a colleague of mine. Now, in the interest of full disclosure, the New Frontiers competition had two Enceladus missions in it. Enceladus Life Finder. And then a competitor from Goddard called ELSA, E-L-S-A-H, which was led by Chris McKay at NASA Ames. They had a slightly different approach where they used a wider variety of instrument types. And used a large collector in order to collect more molecules because the other instruments needed more molecules. But the basic philosophy was the same. Fly through the plume and collect the information needed to determine whether biology is at work in the ocean of Enceladus. And neither mission was selected for flight by NASA. Why? Do you have any idea? Well. So, here's where I start to choke up and cough. Right? Yeah, exactly. And I'm the same here. This must be painful. Yeah. Yeah. I'm banging my head against the wall. Well, so, first of all, I have to say that, you know, there were many excellent mission concepts. And, you know, here I am at Cornell. And, in fact, a mission to return a piece of a comet, a pristine piece of a comet from the same comet that Rosetta visited. That's a mission that was advanced on to step two. That's very exciting. Yeah. But we were wondering why this. Building blocks of life. Okay. And, you know, a Titan mission to fly around with a quadcopter was also selected. Yeah. A quadcopter on Titan. Right. A quadcopter on Titan. So, both of those are really meritorious missions. It was selected. Sorry. It was selected? The quadcopter on Titan? The two of them were selected for the next round. Oh. They were actually in competition with each other. And we'll find out in July which of those was selected. Okay. Good to know. For flight. Yep. So, going for a sample return mission from the same comet that Rosetta landed on. I'm just, I was a little surprised. Like, why would we visit the same comet twice? Oh, because by returning a sample from that comet, rather than analyzing the material in situ, we can actually do things in terrestrial laboratories like measure isotopic ratios and trace species that we simply can't do on the comet. Okay. Yeah. So, the genius of the CESAR mission. Yeah. And the other thing that we're really proud of is that we know enough from the Rosetta data that the mission can confidently land on the surface and collect this material and return it to Earth where we have across the world these exquisitely sensitive laboratory machines that will be able to really tell us what the nature of this material is like and what was going on in the outer solar system when the planets formed. Okay. So, I mean, you know, I am a planetary scientist at heart. And it's very, very cool. And that kind of information combined with the information we have from meteorites, for example, and even some asteroid return missions will give us a huge advance in understanding where we actually came from. What was the primordial material that the planets and life came from? So, it's all part of the same puzzle. And so, why wouldn't they pick three missions, right? I mean, they could have picked three. Do it all. Do it all. Yeah. And I have to say. I have to say that, to me, that makes perfect sense. But, you know, of course, NASA is an agency that has many different priorities and budgets. And, you know, there's just every New Frontiers competition, because of the budget that's available, has to end with just one mission selected for flight each five or six years. So, you know, New Horizons was the first, the one to Pluto. And then Juno. Which I'm involved in, which is doing great stuff at Jupiter. And then Osiris-Rex, which is currently at the asteroid Bennu to collect a sample. And, yeah. So, why not Enceladus Life Finder or ELSA? Yeah, exactly. I think NASA is still struggling with the question of whether these types of measurements are enough to definitively say, yes, there's life. Oh, they're afraid it might not answer the actual question. They're afraid it might be ambiguous. And, you know, my answer to that is the following. That in either mission, ELSA or ELF, we will not give you a picture of a cell. You know, we will not collect a microbe and culture it. But in both missions, they're designed to give us an information. Indicator, a green or red light, if you will, of whether biology is actually going on there. And will tell us what kind of biology. Because the kinds of ingredients, the kinds of molecules, and the patterns of those molecules will tell us quite a lot about the biochemistry itself. And the environment that that life is operating in. And if either of those missions went and gave that green light that, yes, there is biochemistry going on in the ocean of existence. And that's what we're going to be doing. And if that's the case, that would create a huge pull to put together a more ambitious mission. A flagship class, Cassini class mission. To go and actually try to find and culture a microbe. That's very ambitious, of course. Yeah, of course. Or a bit like a sample return mission. Or a sample return mission. But, frankly, if you look at the amount of cells in the terrestrial ocean, for example. And you can see that there's a lot of cells. And you can see that there's a lot of cells. And you could then compare that to what is coming out in the plume itself. It's a little bit of a needle in a haystack. You would have to design very, very sophisticated ways of collecting enough material from the plume. And probably by landing on the surface that you could be assured that you had collected a cell or a microbe. Flying through the plume once, you get a nanogram worth of material or tens of nanograms. And you can see that there's a lot of cells. And you can see that there's a lot of cells. And you can see that there's a lot of cells. Within that, you have the molecular signs of life. Sometimes I tell people you've got the waste products or the poop, if you will, of life. But the cells themselves are simply going to be too scarce to be collectible in one flyby. So that really is the challenge. And if we want to discover life on Enceladus, it's a one-stop mission. You do it with Elf or Elsa. Yeah. You determine whether life is going on. But then if you want to study that life, if you want to culture that life either in a spacecraft or back on Earth, that's going to require a second mission. Yeah. And some people say, well, why not just go for the second mission, the big one, the flagship? Right away. Right away. And I could make an argument in favor of that. But on the other hand, that's spending probably $3 or $4 billion without knowing. Whether, in fact, life is present. So either Elsa or Elf become the cheaper and faster way to get there. Tell us whether it's worth going there with a flagship mission and then go with the flagship after. And so what was Joeri Milonov saying, the Russian investor, billionaire? Well, so, you know, he had been interacting with various scientists. I can't speak for him. He was interested at one point, it seemed, in funding. All or a good part of an Enceladus plume mission. But on closer analysis, he seems to be interested in many different possibilities in space. And so, you know, I suspect, and this is only my opinion as kind of an outsider who had, you know, really one interaction with his planning team. I think they might be interested in supporting part of it and offsetting part of the cost of that mission. But not necessarily. Right. Not necessarily doing the whole thing. Well, let's hope so. And what's so interesting is that at the same time, right now, the Europa Clipper mission is in full swing. Being prepared for a launch in, what is it, 2020? 2022. 24. I think we're out at 23 now. 23. Okay. Yeah. Sorry about that. Yeah, no worries. It'll be a little bit. And it's in sort of heavy competition. Well, it's not in competition with your missions, so to speak. Because it is going. It is going. But the science, as you told me also in 2015, the science for it is not as definite. Sort of, if you have to check a whole bunch of boxes, then Enceladus has more boxes checked than Europa. Yeah, but still, there are two missions going to Europa. There's the Europa Clipper and there's the Jupiter IC Moons Explorer from the European Space Agency. Why Europa and not Enceladus? Well, so let me... Let me clarify a little bit of what I may have said in 2015. My point about Europa was that we know far more about the habitability of Enceladus' ocean than we do about the ocean of Europa for two reasons. One is that the Galileo spacecraft, which was the one that discovered the ocean at Europa, was not instrumented in a way that would allow for the kinds of measurements. that Cassini is making today, simply because Galileo is a much older mission. It was a mission designed in the 1970s and launched in the 1980s after a very long delay. The other reason is that Enceladus has this huge plume of material pouring out of its south pole that can be sampled directly. Europa, we have hints of plumes, but because of the higher gravity and the larger surface area of Europa, possibly for those reasons, the plumes are not quite as evident. Now, even if Galileo had arrived and seen this giant plume coming out of Europa, it didn't have the instruments needed to make the observations that were made of Enceladus by Cassini. And so the rationale of the Europa Clipper mission is to do those measurements, is to go to Europa and make the kind of measurements that will tell us, that we will be able to make the measurements that will tell us, that we will be able to make the measurements that will tell us, whether that ocean is habitable or not. If there are plumes, you know, then it's done just like Cassini and Enceladus, you fly through the plume. If there aren't any visible plumes, one can still do that with material that's been deposited on the surface and is gradually evaporating away. The mass spectrometers are sensitive enough to do that. In fact, the mass spectrometers on Europa Clipper are the next generation after Cassini. Those are the ones that are going to be used to make the measurements that we're going to make. Those are the ones that are going to be used to make the measurements that we're going to make. Those are the ones, essentially, with minor modification, that we would fly at Enceladus with ELF. So these are marvelous instruments and Clipper is a wonderful mission. It's the mission that you have to do at Europa before deciding, you know, whether to follow up, to try to detect life either in the plumes or in surface deposits on Europa. So by no means is it any sort of a judgment about Europa, versus Enceladus. It was what I was really saying in 2015. It is an accident of history that the mission that went and discovered the ocean at Europa just didn't have the kind of payload that, well, 10, 15 years later, Cassini would have at Saturn. Yeah. But then it would seem that you could maybe, well, flip some priorities around and say, well, we have some better evidence here at Enceladus. Let's just go to Enceladus. Well, I think that it's possible to do both. Okay. And our strategy with ELF was that, you know, look, Europa Clipper is a flagship mission. It was selected as part of the strategic planning that's done by NASA and the National Academy of Sciences every 10 years with a little bit of help from Congress. So it's a mission in the tradition of Galileo and Cassini. It's a flagship mission. It's a flagship mission that's embedded in the NASA program that will do fantastic science at Europa. At the same time, we could, if NASA were to select an Enceladus life finder as a New Frontiers mission, at the same time, we could be exploring Enceladus for life. And so… Yeah. You could have a definite answer on that question. We could have a definite answer. Yeah. Yeah. But it's too important to simply ignore. And so the strategy has to be this sort of two-step process where at Europa we're catching up and doing the kinds of observations that will tell us whether the ocean is habitable while at the same time we're following up Cassini at Enceladus by going back and looking for life. Yeah. And that to me from an astrobiological perspective, perspective of looking for life in the solar system, that's a strategy that makes immense sense. Unfortunately, we are still waiting for NASA to select either ELF or ELSA and we'll have to either wait for the next round or find out that Joeri Milner has a warehouse somewhere where he's actually built this thing and is about to launch it. When is the next chance for ELF or ELSA? So the next chance I believe will be between… Yeah. I think it will be between three and four years from now. So let's say… I can't wait, Jonathan. I know. I can't wait. Yes, well… And even though if it goes to your…if Clipper goes to Europa and says, well, here's and here…this is what you have to do in order to detect life, then it will take until the 2030s before an actual mission will be flown to actually answer that question on Europa. Whereas Enceladus, if you would…if they would fund ELF today, you can have it in the mid-20s. Yeah. Yes. Although there is one option that would compress the schedule for Europa and that is that NASA does have some advanced study money, significant amount, to do the preliminary development of something called Europa Lander… Okay. …which would land on a patch of material that has been released from the ocean and made it to the surface. That patch would be identified by Europa Cluster. Okay. And it would land with life detection experiments and it would analyze that material. Now, that mission was a particular favorite of one congressman in the U.S. in particular, John Culberson… Okay. …of Texas. He was not reelected, of course, and so I think that the momentum for the Lander mission has been slowed as a consequence. Yeah, it was budgeted out already, or not. No, there was some NASA research money for it. No, there's actually… There's actually a significant amount this year. Okay. Whether there will be a significant amount next year is unclear. Okay. And there is research money for the preliminary instrument development for that mission. So, you know, it is moving forward, but the big question is what will happen next year. And in two years, the community, the planetary scientists, will be working with the National Academy of Sciences and NASA on the next strategic planning exercise. The previous one was finished. The previous one was finished in 2013. And unless Europa Lander is somehow green-lighted to the status of a flight mission, it will probably be competed against other potential missions that will be evaluated by that so-called decadal survey process. Okay. And, you know, there are a number of other missions. One of the… You know, putting on my planetary… Putting on my planetary science hat as opposed to my astrobiology hat. Yeah. There have been so many remarkable discoveries made in the solar system that we just can't possibly follow up on even a small fraction of them. It's a money thing, right, eventually. In our lifetimes. It is… It all comes down to money in the end. Yeah. And I think that if we leave aside these very ambitious plans, you know, for putting humans back on the moon very soon and so forth… Yeah. …you only have to imagine… Let's not go into that. Yeah. Let's not go into that for now. All right. That's a separate radio show. Oh, yeah. All right. Fair enough. We talked about that for ages and we're all like, there's so many questions to be answered right now. There's so many other things to do. Yeah, yeah. Okay. But… So, let's go back to the space science budget. Yeah. So, you know, you would only have to double the planetary science budget, which is a lot from the point of view of, you know, NASA programs. But from the point of view of the federal budget in terms of the space science budget, you know, you would only have to double the planetary science budget. Yeah. Yeah. Yeah. Yeah. And if you double the federal budget in total, it's a tiny, tiny amount. If you double that, the pace of exploration of the solar system would increase dramatically. I mean, we would be able to go to the ice giants, Uranus and Neptune, which is a big goal. Yeah. We'd be going back to Enceladus to look for life. We'd be doing Europa Lander in parallel with Europa Clipper. Oh. We'd be accelerating the Mars sample return program, which, of course, is starting out now with Mars 2020. Yeah. And with ExoMars looking for life. But, you know, all these things would happen in a shorter time scale. And as someone who is going to be celebrating his 60th birthday at the end of next month. Congratulations. Thank you. But, you know, the horizons begin to look remarkably and disturbingly distant for some of these goals. And I think that, you know, the future of the space science is going to be a little bit different. Yeah. Yeah. Yeah. Yeah. Yeah. Yeah. Yeah. Yeah. Yeah. Yeah. Yeah. Yeah. Yeah. Yeah. Yeah. Yeah. Yeah. Yeah. Yeah. Yeah. Yeah. Yeah. Yeah. Yeah. Well, I'll make this one prediction that if these kinds of scientific adventures are compelling and important to people around the world, that the frustration of the time it takes to do these things will build to the point that maybe if we can deal with our other very, very deeply rooted problemsальных change, starvation war, et cetera, maybe we could songs Maybe we could spend more on the scientific exploration of our cosmic backyard and get the answers to these questions sooner. Yeah. The war in Iraq, I believe, was at a certain point $1 billion a day. So, you know, you have an Enceladus life mission on Monday. Elf a day. Yeah, an elf a day. I think the New York Times totaled up the wars in Iraq and Afghanistan, and it came out to between $2 and $4 trillion. I can't vouch for that number. No, but imagine. But that would be an interplanetary species by now. We would be sending humans to Mars and doing other things as well. Exactly. From an astrobiology standpoint, right, what are the Holy Grails? So we have Enceladus and Europa. We talked a little bit about Titan. Like, who knows? Then there's Mars. Anything else? Well, so let me return to Mars and Venus, actually. So the Holy Grail on Mars now is to determine whether life really did start on Mars early in its history when the planet was habitable, and also to really better understand in what way was Mars habitable. Was it habitable over a large geographic area or only localized areas? And how long did those habitable environments really last? Yeah. When did Mars? When did Mars finally become uninhabitable at the surface? We've made huge strides in answering those questions, but there's a lot yet to be done. And, of course, all of this comes down ultimately to the question of whether life began there. And, you know, did life begin on Mars and get transported to Earth? And, you know, did that kickstart things on Earth? Interesting question. Going to Venus, we have a sister planet. It is nearly the same size as the Earth and is just far enough inward of the Earth's orbit that it evidently lost its ocean sometime in its history, maybe very early on. That's the sort of canonical story. But maybe it wasn't so early on. And there have been some interesting recent models that suggest that Venus might have been able to hang on to its ocean for one or two billion years, which would be enough time for life to begin and perhaps to flourish. Yeah. And survive, maybe. And survive. Well, not survive today. Not anymore? Underground? Well, the surface is at the melting point of lead and the temperature increases as you go down. But if we could go back to Venus and determine how long that ocean existed, so we know the ocean was there based on the isotopes of hydrogen, the deuterium to hydrogen, the hydrogen ratio on Venus, which is much, much higher than it is anywhere else in the solar system and points to the loss of a lot of water, where the heavy water preferentially got left behind, and so it enriched the deuterium. So that's the signpost that there was a lot of water on Venus. But the whole surface today is covered with these basaltic lavas with only a few exposures of other things. Right. Right. Right. Right. Right. Right. Right. Right. Right. Right. Right. Right. Right. Right. Right. Right. Right. Right. Right. Right. Right. Right. Right. Right. Right. Right. Right. Right. Right. Right. Right. Right. Right. Right. Right. Right. Right. The ancient rock that was there early in Venus's history and determine whether it was in contact with an ocean. What kind of rock? Was it andesitic or granitic? If it was granite, then that meant that there was plate tectonics for a long time on Venus. If we could find out those things, it would tell us really where the inner edge of the habitable zone is for a system like ours. And we know really well the brightness of the sun with time. Those models are really quite accurate. And so given that, if we only knew when Venus lost its ocean, it would give us a very, very important ground truth for extrapolating to other planetary systems. Because right now, we don't really know where the inner edge of the habitable zone is, because we don't know, you know, did Venus lose its ocean in the first few hundred million years after it formed, or did it take two billion years? And depending on the answer to that, that either stretches or shrinks the habitable zone for all of the exoplanetary systems that are being discovered now by various telescopes. I know we're running out of time, but I do want to... I want to ask you one question about Juno, because we haven't heard so much about it. So if you have a couple more minutes to chat about that, that'd be great. Can you just give us, for those who don't know about Juno, just like a five, let's chat about it for five minutes before we end the conversation. Where is it now? Like how, what's your work on it? And where do you see it going? Sure. So Juno is the polar orbiting mission around Jupiter. And it's, it's designed to make very, very close flybys of Jupiter. It sort of shoots in through the intense radiation belts to the cavity between those belts in the atmosphere, where it makes these extraordinary observations and takes wonderful images and then shoots back out again on a very, very eccentric elliptical orbit around Jupiter. And we're, we're in the halfway point of the mission. It's a five-year mission, which began in 20... 2016. And we, or Juno, I should say, has been discovering that Jupiter is a much more dynamic and complex place than we had imagined. For example, the inside of these gas giants were always thought to have a solid or maybe liquid, but a heavy element core surrounded by hydrogen and helium. They're mostly hydrogen and helium, the primordial elements of the cosmos. Yeah. But this core... And this core in the middle made of other elements, carbon, magnesium, iron, silicon, et cetera, it doesn't seem to be discrete. It seems to have been almost melted and stretched out based on the Juno data so that it's, it just gradually grades into the envelope. And that must be telling us that the way that Jupiter formed, probably formed out of smaller planetesimals, things that were maybe... Yeah. ...pebble-sized rather than boulder-sized. And that material wouldn't quite survive all the way to the center of Jupiter during formation. I always hear it's a failed star almost. It's a long way from a failed star. We actually have better examples of that beyond our solar system. It would have had to have been 80 times as massive as... Yeah. So, but it is certainly in the sense of having mostly the same elements that the sun does. Yeah. So, it's a good example of something that just was too small to undergo fusion. That's certainly the case. Yeah. The other amazing thing about it is the atmosphere is so self-organized. You look at the equatorial and the mid-latitudes, you see the familiar belts and zones, but you go up to the poles and they look completely different. And Juno has analyzed those poles in great detail and you get these beautiful images of these regular patterns, of storms that kind of are fixed around the pole itself. And one hemisphere, the storms form an octagon and the other, they form a pentagon. That's so crazy. And it's just nature producing these regular structures out of very turbulent, very random processes. Juno's finding a huge amount of lightning, which is telling us a lot about the way that the water meteorology works. It's making these amazing pictures. I don't want to call them amateurs because they're really experts, but they're volunteers, are taking these images and enhancing them and posting them so that just looking at Jupiter is just an amazing psychedelic trip without the need for the psychedelic. But tripping nonetheless. Tripping nonetheless. And then Jupiter's magnetic field is showing interesting consequences. There's a blue spot in terms of magnetism and the mid-latitudes that hadn't been discovered before. So Juno is really providing us with a picture of Jupiter that makes it a much more intricate and dynamic and unexpected place, I would say. And what is your research on it? So I'm involved in a couple of things. One is that we are, I'm involved with the Italian instrument, GRAM, which has been making beautiful infrared images. And looking at the composition of the atmosphere. I'm involved with an instrument called the microwave radiometer, which looks very deep into Jupiter's atmosphere, where we are trying to measure the abundance of water below the level at which it forms clouds. Because by getting the water abundance, this gives us how much oxygen is in Jupiter. And that tells us a lot about how it forms. So that's ongoing. And finally, I'm sort of a gadfly, I think, on the interiors. I'm sort of a gadfly, I think, on the interiors. So I'm part of the interiors group that works out the mass distribution inside Jupiter from the gravity measurements. That's where the discoveries about the core have come from. So it's exciting. And it's a New Frontiers mission, the same cost class as ELF, which demonstrates that you can do, as New Horizons demonstrated, fantastic science at a relatively low cost. Thank you for that pitch, because I fully support it. And I think you do as well. We're all rooting for you. Thank you. Thank you so much. We'll definitely, when there's any news around ELF, we'll check in again. And thank you so much for this conversation today. It was wonderful, this. Yeah, really great. And thanks for the little journey that you took us on out into the solar system. Great pleasure to talk to you both. Thank you. Yeah, thank you. Good luck. And thanks to all the listeners. And see you next week. Joeri, see you next week as well. And then Herbert will be back. He will be back later as well. Okay, great. Good to hear. Thank you so much.