Planetary Radio • Sep 15, 2021

The Case for a Return to Enceladus

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Morgan Cable

Research Scientist and Group Supervisor, NASA Jet Propulsion Lab Astrobiology and Ocean Worlds Group

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Kate Howells

Public Education Specialist for The Planetary Society

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Bruce Betts

Chief Scientist / LightSail Program Manager for The Planetary Society

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Mat Kaplan

Senior Communications Adviser and former Host of Planetary Radio for The Planetary Society

Morgan Cable of NASA’s Jet Propulsion Laboratory is lead author of a paper that makes a compelling argument for a mission to Saturn’s small but dynamic moon Enceladus. She and her stellar co-authors believe it is among the best and easiest places in our solar system to look for evidence of life. Morgan has also been involved with the synthesis of organic crystals that could exist on Titan. What would they mean for possible biological activity on that big moon? Bruce Betts shares his excitement about the current night sky in What’s Up.

Approaching Enceladus' plumes
Approaching Enceladus' plumes On May 18, 2010, as Cassini approached for its 11th targeted flyby of Enceladus, it stared directly toward the little moon's active south polar geysers. This four-frame animation was taken from a distance of about 15,000 kilometers.Image: NASA / JPL-Caltech / SSI / animation by Emily Lakdawalla
Color view of the plumes of Enceladus
Color view of the plumes of Enceladus A true-color view of Enceladus' southern plumes.Image: NASA / JPL-Caltech / SSI / Kevin M. Gill
Highest-resolution mosaic from Cassini's 31 October 2008 flyby of Enceladus
Highest-resolution mosaic from Cassini's 31 October 2008 flyby of Enceladus Four high-resolution images are pieced together atop a lower-resolution image to make this composite mosaic of part of Enceladus' enigmatic south polar terrain. The fissure crossing the center of the image is Baghdad sulcus. To the right of center, along the fissure is the source of one of Enceladus' plumes, plume source VI, through no plume activity is obvious in this image. The resolution of this mosaic is a mere 12.3 meters per pixel.Image: NASA / JPL-Caltech / SSI
Titan beneath its atmosphere
Titan beneath its atmosphere In this image from NASA's Cassini spacecraft, you can see beneath the atmosphere of Saturn's moon Titan to its surface features.Image: NASA/JPL/University of Arizona/University of Idaho
Dragonfly artist's concept
Dragonfly artist's concept NASA's Dragonfly mission will explore Saturn's moon Titan to study the possible starting ingredients for life.Image: Johns Hopkins APL

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Mat Kaplan: Making the case for a return to Enceladus, this week on Planetary Radio. Welcome. I'm Mat Kaplan of The Planetary Society with more of the human adventure across our solar system and beyond. NASA Jet Propulsion Lab researcher, Morgan Cable balances a lot of tasks, and sometimes she balances herself on a mountain unicycle. You'll have to listen to the end of our recent conversation to learn about that.

Mat Kaplan: Along the way, you'll hear her passionate plea for a mission to Saturn's tiny, but very active moon. Morgan is lead author on a paper that lays out the reasons. She'll also tell us about fascinating work with organic crystals that may be common on Saturn's biggest moon, Titan, the target of the upcoming Dragonfly mission.

Mat Kaplan: How many spaceships are parked at the International Space Station? That's space trivia quiz from Bruce Betts has generated some very entertaining answers and a first time winner.

Mat Kaplan: And we'll talk in a minute or so with my Planetary Society colleague, Kate Howells about the brand new issue of our magazine, The Planetary Report that you can read at Kate also helps pull together our weekly newsletter, The Downlink. There's a stunning picture of galaxy, Centaurus A at the top of the September 10th issue.

Mat Kaplan: It combines images taken at x-ray, optical, infrared and radio wavelengths. Below it are these and other headlines. Perseverance, the 2020 Mars rover has now collected two samples from the rock dubbed, Rochette. Exploration of Jezero Crater really roll it along now.

Mat Kaplan: China's Chang'e 5 is on the move again. It may be headed back to orbiting the moon after returning lunar samples to Earth, or it may head to a near-Earth asteroid. Nice to have choices, I guess.

Mat Kaplan: Cosmonauts and astronauts are staying busy outside the International Space Station activating the new Nauka module and preparing to install huge new solar panels. And you may have heard that launch of the James Webb Space Telescope is targeted for December 18th. Godspeed JWST.

Mat Kaplan: Kate Howells is the communication strategy and Canadian space policy advisor for The Planetary Society. I reached to her this week at her home near Toronto. Kate, it is always great to see The Planetary Report show up both in our website, but also because I'm a member and I get that beautiful print edition of the magazine. I love to see that in my mailbox beginning with the piece that you contributed, which is sort of the lead article in the September Equinox edition. And it is titled The People Space Telescopes.

Mat Kaplan: You opened by saying that there are things we can only appreciate it in the abstract, at least for now, things like the oceans of Jupiter's moon, Europa or the interior of a black hole, God forbid. But a space telescope like the Hubble gives us something a much more tangible and frequently quite beautiful.

Kate Howells: Absolutely. My experience through my own journey as a space enthusiast and just from talking to other people is that often one of the easiest ways to get into space is by seeing images. I mean, it's something that you don't need to have any science background to appreciate. You don't need any context to understand. If I show you an image of a Nebula, I don't have to explain what it is for you to say, "Wow, that's gorgeous."

Kate Howells: What I think is fantastic about space images is that once you are hooked in by how beautiful space is, then you can start to get some of the science, some of the explanation of what it is that you're seeing and what's going on under the surface. And that just, I think is a great way to lure people in and sort of cultivate that appreciation for space that we already enjoy so much.

Mat Kaplan: No question about it. And it is hard to believe that at any time in the past, there were people who doubted the power of images taken from space of our solar system, even of our own planet. This is a great opportunity. I never miss one to talk about our co-founder, Bruce Murray.

Kate Howells: Bruce Murray is a legendary figure in space exploration. And he was one of the people who really first championed including cameras on space missions. Specifically, he had this idea for the Mariner fleet of spacecraft that NASA sent to Mercury, Venus and Mars in the 1960s to include cameras saying that at the very least, this would have benefit to the public for engagement in this mission.

Kate Howells: NASA agreed and put cameras on the spacecraft. Now, you would never imagine sending a spacecraft to another world without cameras on it, because not only does it engage the public in a way that would otherwise never be possible, it also does have a lot of science and engineering usefulness.

Mat Kaplan: I think of the Juno mission as a great example, because it was not originally envisioned with a camera, but Scott Bolton and others definitely wanted one, Juno cam, the people's Jupiter camera. And it turns out to have contributed very greatly to the science that, that still active orbiter is doing. Of course, your piece is largely about the Hubble space telescope.

Mat Kaplan: There is no better proof. I think of the popularity of the Hubble than the grassroots effort that saved it a little more than 15 years ago. Talk about that campaign.

Kate Howells: In 2004, NASA announced that Hubble was not going to receive its last servicing mission. There were a couple things wrong with it. Its batteries were running down. Some of its instruments were failing and NASA said it was just too risky to send astronauts to go fix it because it would have required, a crew of astronauts.

Kate Howells: The Space Shuttle Columbia disaster had just happened. So I think that the risk tolerance for crude missions was a little bit lower than it had been previously. So the announcement came down that Hubble was just going to have to end its life as a spacecraft. The public outcry was enormous. People love Hubble. I mean to this day, Hubble, I think is one of the most popular spacecraft because it does, it delivers these undeniably gorgeous breathtaking images.

Kate Howells: So people took it upon themselves to save this mission. Planetary Society of course, was deeply involved in this. We had members sending letter to congress. We coordinated with other campaigns that popped up online around the world.

Kate Howells: So people in the US could contact Congress directly, but people around the world were writing to the US government, urging them to support a mission to save Hubble. And it worked. The government heard loud and clear that this is something deeply meaningful to people and absolutely worth the risk.

Kate Howells: I think NASA astronauts and or astronauts around the world embrace that risk as well in the job they take on. So they sent a servicing mission in 2009 and fixed Hubble. We're still getting images back from Hubble to this day. So it's just a beautiful story of people really showing how much they care about a particular mission.

Mat Kaplan: It is a heroic story, I think. It was only last week as you and I speak that we got the announcement of a launch date finally, for the follow-on to the Hubble Space Telescope. That leads us into talking about the main piece, the terrific feature that is at the core of this new edition of The Planetary Report.

Kate Howells: Yes, James Webb Space Telescope launching is an extraordinarily exciting thing because it has been coming up soon a few years anytime now for such a long time. Pretty much as long as I've been interested in space, I've been looking forward to this mission and I'm sure many people can say the same.

Kate Howells: So the fact that it's actually launching in just a couple of months is very, very exciting. It's going to knock our socks off I'm sure in terms of what it's going to show us in terms of imagery, but also what it's going to teach us about the universe. So if you read the latest issue of The Planetary Report, which you can find online for free at, or if you're a member, you'll get it in the mail.

Kate Howells: We have a fantastic article from Nancy Atkinson talking about basically everything you would want or need to know about this mission. So sort of the whole history of how it came to be, why it's taken this long, what it's going to do, what we can all look forward to discovering.

Kate Howells: It's such a great overview of a very exciting mission. And I think if you already were excited after reading this, you'll be even more excited for this mission to finally launch in November.

Mat Kaplan: It's another terrific article by Nancy. She's such a good writer, but it is also full of terrific images of the development of the telescope and what we expect it to do. There's much more in this quarter's edition of The Planetary Report that we don't have time to mention, but I hope you can say something about how we've once again, put the A in stem, making it STEAM with work from another great space artist.

Kate Howells: Yes. One of the best things about my job is that I receive all the emails of Planetary Society members sending us their artwork. So all you out there listening, whether you're a member or not send us your artwork. It's such a delight to see how space inspires people. One of the recent submissions we got was from a Planetary Society member named Barbara Fee Sheehan. She does unbelievable paintings inspired by Hubble imagery.

Kate Howells: We have one of her paintings on the back cover, and then we have another little feature showing her standing among several of her paintings and a little article from her talking about how she was inspired. Her story is just so inspirational to me as well. In 2015, she was 71 years old and she for the first time came across this Hubble space telescope image. And it just fascinated her so much that it inspired her to start painting these images.

Kate Howells: She has a huge collection of work. It's absolutely gorgeous. It's just wonderful to see that at any time in your life, you can become inspired by space and take whatever it is that your strength is, whether it's science or art or writing or anything else. And you can use space as something to inspire you.

Mat Kaplan: You can see Barbara's gorgeous work at If you want to go directly there, for The Planetary Report. It is in itself, a gorgeous edition of our quarterly magazine from The Planetary Society. Kate, thank you for giving us a little tour and we'll talk again soon.

Kate Howells: Always a pleasure, Mat. Thank you.

Mat Kaplan: Kate Howells is The Planetary Society's communication strategy and Canadian Space Policy advisor. Who isn't in favor of a return to Enceladus? Probably no one listening to this show. And certainly not Morgan Cable or the many co-authors of her recent paper on this topic. Morgan is a research scientist and group supervisor in the astrobiology and oceans worlds group at the NASA Jet Propulsion Laboratory near Pasadena, California.

Mat Kaplan: She worked on the Cassini mission as a project science systems engineer, and is now part of the Europa Clipper mission that will visit that ocean moon of Jupiter. Her work and research have taken her from Iceland to the Atacama Desert in Chile with a stop at the summit of Mount Kilimanjaro.

Mat Kaplan: In 2018, she was named by the American Chemical Society as one of the talented 12 rising stars in chemistry. Morgan, very generously made time to talk with me a few days ago on what was her birthday.

Mat Kaplan: Morgan Cable, welcome to Planetary Radio for a long overdue conversation. Very happy to have you on the show.

Morgan Cable: Thank you so much. I'm really happy to be here.

Mat Kaplan: I think I already told you that your colleague at JPL, Linda Spilker has been telling me for ages that I should get you in front of a microphone as our guest. My fault it wasn't until I saw a recent article in Wired Magazine that I thought, "Oh, Morgan Cable. Yeah, Linda said I should talk with her." That article was about some recent work that you have led about so-called co-crystals on Titan. But we're going to come back to that because really where I want to start is another article that you did recently for The Planetary Science Journal. You were the lead author among many distinguished colleagues, including Linda, and our past guests, Carolyn Porco, who is listed as the second author.

Mat Kaplan: We will provide a link to the science case for return to Enceladus on this week show page at But I want to thank you for it. I read it. It is a compelling case that you build for Enceladus and even a very exciting one. So congratulations on that and thank you as well.

Morgan Cable: Oh, thanks so much. It was a pleasure to write in many ways. Enceladus makes that case beautifully on its own. It's a wonderful story to be able to tell.

Mat Kaplan: How important to this effort is what we learned from Cassini over it's 13 years in the Saturnian system in helping you to build the case that you make?

Morgan Cable: Cassini is the reason that we now have these incredible insights into Enceladus, as well as many other moons, the rings and knowledge of Saturn itself. It's such an incredible, almost a mini solar system in and of itself. The complexity, the diversity of worlds that we see there. Before we built and launched Cassini, we thought that many of the places in the outer solar system were just cold, dead, boring worlds.

Morgan Cable: We got that notion completely turned upside down thanks to the amazing discoveries that Cassini made.

Mat Kaplan: Don't you love how the solar system just has an endless series of surprises for us?

Morgan Cable: It's fantastic. It's one of the reasons I love my job so much.

Mat Kaplan: One of the things that came out in your article, we all know the great success that Cassini had as it flew through those plumes, rising out of the surface of Enceladus, those wonderful tiger stripes so-called, and that it found some simple organics. It really wasn't equipped to do more than that, but something that really struck me in your paper is the work that indicates that even the more complex organics that Cassini was able to detect could be fragments of much more complex organics that have simply broken down. I found that very striking.

Morgan Cable: Yes, this is very exciting work that's done by the leads of two instruments. One of them is called the Cosmic Dust Analyzer. And another one is called the ion and neutral mass spectrometer. These two instruments were aboard Cassini and that the PIs, the principal investigators of those instruments came together to work on this analysis. One of the cool things that Cassini did, as you mentioned, it was brave enough to fly through this plume of gas and ice screens skewing out of Enceladus as South Pole.

Morgan Cable: It did that multiple times and at different speeds. Now, this is really cool. You can sort of picture maybe, if you grew up in a place where it snows, I did not. I grew up in Florida, but I can still picture sticking your head out of the car window and trying to catch a snowflake, right?

Morgan Cable: So that might be easier to do at, say, 10 miles an hour than 50. But now imagine you're going seven to 17 kilometers a second, which is many times faster than a speeding bullet. That ice grain, that snowflake will go poof essentially at those speeds. So you can then analyze the bits that are inside. But depending on how fast you're going at some slower speeds, you can volatilize which means get into the gas phase, something going from solid to gas, and you can also ionize the things that are in there.

Morgan Cable: Now, that's important because a lot of these instruments that I've mentioned, they can only see things that have a charge, things that are ions. So at those slower speeds, we could look at sort of the bigger molecules that are there, but at these faster speeds, we noticed that we had more smaller bits.

Morgan Cable: So you're exactly right. That tells us that potentially some of these larger molecules are breaking up those really fast speeds. That gives us some hints and some clues as to the larger molecules that are outside of the mass range, that these instruments were capable of seeing. Because when Cassini was built, we didn't think that liquid water was out this far.

Morgan Cable: Cassini was not meant to be a search for life mission. So its instruments were geared towards looking at small molecules that we wanted to characterize and understand, not things like proteins or bits of cells. And hopefully a future mission we'll be able to tackle that problem.

Mat Kaplan: Proteins and bits of cells. Okay. That's a nice little tease for what we may be reaching in this conversation. If we were building Cassini now, and in a sense we are because the great Dragonfly mission is currently being put together and Europa Clipper is even farther along, but if we were doing this now, do we have the instruments? Could we build the instruments that had they been on Cassini would have detected these much more complex compounds if they're there?

Morgan Cable: We think so. A lot of development has gone on to mature instruments to address this question of, are we alone? Is Earth the only place that's inhabited or are we just one example of many different inhabited worlds in our own cosmic backyard and beyond? We've seen a lot of these instruments tested on Mars, which is a great proven ground, but now thanks to discoveries of Cassini and other missions like Galileo and even the Voyagers, we now know liquid water exists in a variety of different places in our solar system.

Morgan Cable: One thing we've learned is that if you follow the water, you can look for signatures of life in these environments that we call habitable environments. That means that they may have the conditions suitable for life as we know it. Potentially life as we don't know it too, in some cases. So that's why we're developing these instruments to search these habitable environments for evidence of life.

Mat Kaplan: I'm going to come back to that question of weird life, life as we don't know it as well. With what we know of Enceladus' history. And I know there's still a lot, we don't know. Can we say that it's been around long enough and that may be the liquid water under that ice has been there long enough for us to think... I mean, using Earth as an example, because it's the only one we have that there has been enough time for biological activity, if it has happened on in Enceladus or under that ice?

Morgan Cable: That is a great question. And that's something that many scientists have been working on understanding for Earth for a long time. We still don't know how long it takes for life to emerge. All we can do is take the one example we have, which is life here on Earth and dig through the record as far back as it goes to see if we can bound that question.

Morgan Cable: We've had a lot of really smart people looking at the most ancient rocks that we can find here on Earth for evidence that can help us do that. We've found so far, the best we can say is that it takes no more than a billion years.

Morgan Cable: So 1 billion years is the data point that we have on Earth saying that life definitely formed within that time period. It could have formed in a much shorter timescale, but those records have been lost because as you know, Earth is very active. Tectonics have recycled a lot of those previous bits of evidence here on Earth.

Morgan Cable: So we can maybe assume that is an upper bound. And then the question is, "Okay. Well, if it takes a billion years for life to form, presumably our world like Enceladus old enough and have had habitable conditions, things like liquid water and energy source, molecular building blocks, have those things been around long enough. We're not really sure, but we're not going to know if we don't go and test that and try to find out,.

Mat Kaplan: Let's talk about what a mission, a return to Enceladus might look like? In the piece that you were lead author for, you talk about different approaches to this, landers, orbiters. Whether an orbiter should orbit Saturn as Cassini did or whether it should orbit Enceladus. I mean, what would your preference be?

Morgan Cable: Oh gosh. I would love to do all of those things because you learn different things at different stages of a mission. So a few other studies have looked at different mission architectures. In fact, there's one in that same issue of The Planetary Science Journal talking about something called an Orbilander. This is a joint orbiter that then would land on Enceladus.

Morgan Cable: The interesting thing is you can get a lot from orbit, especially at Enceladus or even by flybys. You don't even necessarily need to land to collect some of that precious ocean material. Enceladus is the only world where we know for sure it's spewing free sample from its ocean into space.

Morgan Cable: So there's a lot that you can do by scooping up some of those grains and sampling the gases to understand that environment. Ultimately, it would be great to also land. You can collect more sample that way. For some of these sensitive instruments, if you're looking for trace species that can be important to do.

Morgan Cable: At JPL, we're even developing some concepts that could get down into those crevasses and potentially reach the ocean directly, which in my book that would be the home run. But I think we've got a lot of exciting concepts that depending on what we can afford to do with the timing, there are a lot of different places to explore in the solar system. We've got a menu of options we could choose from.

Mat Kaplan: As you and I speak. I learned anyway, just a few minutes ago that perseverance on Mars just made its second successful collection of material from Jezero Crater. And we-

Morgan Cable: Woohoo.

Mat Kaplan: Yeah, I know. And especially with whom we someday get them back here on Earth into laboratories. What I'm really thinking of in this case is planetary protection and everything that had to be done to make sure that those sample tubes were maybe the cleanest things humans have ever created on perseverance and that the rest of the spacecraft, we minimize the chance for contaminating anything that might be on Mars.

Mat Kaplan: Well, okay, here we are talking about Enceladus, whether it's a lander or... And I would guess an orbiter that's orbiting in Solidus might cause even more concern because you probably wouldn't have the chance to crash into Saturn as Cassini did. Are these concerns also for the community as you talk about learning what we can about Enceladus?

Morgan Cable: Absolutely. What would be worse than finally finding life for the first time in human history, somewhere else, and then realizing that we put it there, that we had accidentally brought it with us. It's definitely a concern. That's one reason why flyby type missions that still orbit around Saturn in some respects may be the safest because you can still fly through the plume and sample it, but then you can do that spacecraft disposal, as you mentioned, somewhere else, somewhere that is less habitable.

Morgan Cable: Maybe Saturn itself or some of the other moons that don't have any evidence of liquid water oceans. So that's an option. Anything that would land on a place like Enceladus would have to have some way to guarantee that it would not contaminate that subsurface ocean for a certain period of time.

Morgan Cable: There is an international agreements through something called a COSPAR where we have planetary protection requirements that each mission has to meet. And given that we found all these amazing habitable worlds, of course the scientists want to go there, but then Planetary Protection says, "Well, you've got to go there carefully and not contaminate that world."

Morgan Cable: So there are negotiations and agreements that take place for each mission to determine how it will satisfy those strict requirements is that we all definitely want to search these worlds for evidence of life, but we need to do so safely so that they're preserved and kept pristine.

Mat Kaplan: We know how almost ridiculously complex a sample return from Mars is, and yet it's underway. Have you considered getting material back from Enceladus to labs on Earth?

Morgan Cable: Oh, yes, we have considered several return. At least a couple of concepts have been proposed and I encourage you... I think we cited a couple of those papers in our report, but there are other places online where those might be available.

Morgan Cable: The one issue with Enceladus is time, right? Space is big. Saturn is 10 times further out than Earth is from the sun. It's massive distances. And that takes a while to traverse. Cassini took about seven years to get to the Saturn system. You can imagine a sample return mission would be about double that.

Morgan Cable: There is work underway for cryogenic sample storage, such that we could have that option. So that's definitely something to consider because we have worked very hard to advance a lot of these instruments to be able to send them on these robotic explorers. But of course they're not going to be quite as good as the massive instruments we have here in laboratories that are too large to send on a spacecraft.

Mat Kaplan: You mentioned that great Orbilander concept. What is the current status? I mean, as I said, you make this compelling case, but it's going to take a good deal of money and commitment to send even an orbiter much less a lander back to that icy moon. What's your evaluation of the current outlook and the interest in doing this at NASA?

Morgan Cable: Oh, boy. Well Orbilander. The Enceladus Orbilander concept was one of many that were funded by NASA through something called the planetary mission concept studies. And the point of doing these now is that every 10 years, the National Academies of Science Engineering and Medicine puts forth a document called the planetary science and astrobiology this time. It's the first time they have astrobiology in the title. Decadal Survey.

Morgan Cable: That means once a decade, this recommendation comes out that basically says, "NASA, if you want to do cool science, these are the things that we recommend doing." That also includes some recommendations of different missions, flagship missions like Cassini, like the Mars 2020 rover, but also some smaller missions as well.

Morgan Cable: That is currently underway. I'm grateful to be a part of that process. So the Enceladus Orbilander concept along with many others, these reports gave us a lot of information that now this panel of... or many panels actually, excuse me, of experts in science and engineering will take to make those recommendations about what NASA should do for the next 10 years.

Morgan Cable: That process is underway right now. And the draft report will be out in March of 2022. At least that's the current plan. Maybe you can have me on again and we can talk about all of the exciting developments from that report at that time.

Mat Kaplan: That's an excellent suggestion. Thank you. Rest assured that all of us at The Planetary Society will be looking forward to that a Decadal Survey report and hoping that it includes one of these mission profiles for Enceladus.

Mat Kaplan: Much, much more from Morgan Cable is ahead including our truly fascinating discussion of a paper for which she is co-lead author with Tomče Runčevski. They and others are learning about organic co-crystals that just might be found on Saturn's big moon Titan. This is Planetary Radio.

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Mat Kaplan: Let's turn to a different world, a sister world of Enceladus, circling Saturn. This is the one that made me think slap my forehead and say, "I really got to get Morgan on the show." And it was a piece based on another article that you did pretty recently. It was in the accounts of chemical research. Titan in a Test Tube Organic Co-crystals and Implications for Titan Mineralogy. And we'll put a link up at from this week's show page, of course. First of all, can you tell us what a co-crystal is?

Morgan Cable: Sure. This is some really exciting work that we've been doing in the laboratory here on Earth to try to understand Titan. It's such a fascinating world. It's similar to Earth in some ways, and yet it's so very different. Co-crystals are a great example. The best way you can think about these is they're essentially minerals on Titan, but they're made of different stuff.

Morgan Cable: Most of the minerals we have here are made of rock, right? Silica, carbonates, minerals like that. But on Titan, they're made out of the building blocks that are more common on that world surface, which are organic molecules, things like acetylene, which you may be familiar with for acetylene torches or butane lighters. Even hazardous compounds like benzene.

Morgan Cable: So we always work with these very carefully in the laboratory. There's a saying, there are old chemists, there are bold chemists. There are no old, bold chemists. And I plan on living a very long time. So we work with these hazardous compounds in very small amounts and very carefully. But it's so fun to freeze these down to Titan surface temperatures, which are really cold. It's about minus 183 degrees Celsius. Don't ask me what that is in Fahrenheit. I'm a scientist. So I don't work in Fahrenheit.

Mat Kaplan: It's cold. It's very cold.

Morgan Cable: Yes, it is. And even just simple mixtures of these, we combine two chemicals, two gases here on Earth, but they're frozen solid on Titan and they'll rearrange and form these unique mineral structures that have different properties. We're just scratching the surface now of this new field that we call Titan cryomineralogy.

Mat Kaplan: I love that phrase. I love that title for this field, which I have not specifically heard of before, cryomineralogy. These crystals form because of these conditions on Titan. Would you find anything like these on Earth, at least made simple organic molecules?

Morgan Cable: So there are a few, I think one or two examples of organic minerals here on Earth. They're made out of larger molecules. So far, to my understanding they're pure. So they're only made up of one thing. Because of that, we don't have a lot of examples here on Earth to study them. Luckily though, the conditions of Titan are relatively easy to reproduce in the lab, assuming that you have access to liquid nitrogen. That's one of the ways that we can study and characterize these compounds.

Mat Kaplan: And I want to mention that if people take a look at that, that article, which we will put up the link to, it's more of the intersection between art and science, in my opinion, because there is an image of some of these co-crystals, which have now been created in the lab. And they're quite beautiful.And I will also add to my untrained and inaccurate eye, I could have confused them with biological activity.

Morgan Cable: Oh, gosh. Yeah. Some of them do have very interesting shapes. Some of them are blocky and square and look kind of closer to maybe table salt or sugar. Others are long needle like structures and they change over different temperature scales. One fun thing we'll do is we'll dump liquid methane or ethane on top of them to simulate a reign on Titan because Titan has methane and ethane rain. They'll change colors. Sometimes they'll become translucent. They're quite beautiful. It's very fun to be able to explore these in the laboratory and basically just play around and then shoot a laser at them and characterize what they are actually made of.

Mat Kaplan: What are these crystals mean, if anything, for the possibility of biological activity on... I almost said Enceladus, on Titan.

Morgan Cable: That's a great question. And something we're interested in exploring too. I'm actually working with a student at USC who is studying a certain type of microorganism that eats acetylene. Acetylene is one of these molecules that we found is really prevalent in Titan minerals. We know it's present in Titan's atmosphere and on its surface. So one idea is that these minerals could act as reservoirs. Basically ways to sequester away this particular molecule and make it available for communities of life that could sustain themselves, essentially eating it as food.

Mat Kaplan: Wow. So one woman's co-crystal is another other organisms lunch, it sounds like. What do you think of work by people like your colleague, Chris McKay, and many others that try to work out the chemistry of life, perhaps using these co-crystals, these compounds that you've been talking about? I mean, it would by definition be weird life, right? Life as we don't know it.

Morgan Cable: It's fascinating. It's one of the reasons that gets me really excited to get up and go into work because we still just have the sample size of one for life. As astrobiologists, as scientists, we try very hard not to let that bias ourselves because any life that we discover somewhere else could be made out of different stuff. It could reveal itself in different ways. But it's still going to follow the basic rules of chemistry and physics. And because of that, we can still do a lot to understand and bound these questions in the laboratory that as an experimental chemist, that's really exciting for me because the things I'm doing in the lab here on Earth have such broad implications when we're sending robotic explorers to extend our senses to the outer planets and beyond.

Mat Kaplan: I want to talk about that robotic Explorer that will in a few years be headed to Titan Dragonfly, of course. But I got to add somewhat reluctantly. You ever read or see The Andromeda Strain, that classic film?

Morgan Cable: I have, yes.

Mat Kaplan: Well, Andromeda Strain. That was a crystal.

Morgan Cable: It was, wasn't it? That's right. Very cool. Well, I promise if we do characterize any alien crystal in life in the lab, you'll be the first to know.

Mat Kaplan: Yeah. Don't let anybody in a little town in Arizona open up the return capsule, please.

Morgan Cable: Okay.

Mat Kaplan: Get to me first.

Morgan Cable: We'll do our best.

Mat Kaplan: Thank you. Let's talk about Dragonfly and why this kind of work that you're doing that may tell us what to expect on Titan, why that's so important.

Morgan Cable: Yeah. Oh my gosh. I am so stoked about Dragonfly. So picture one of the big Mars rovers, Curiosity or the Perseverance rover. They're about the size of a car. Take the wheels off and put skis on and then give it four sets of two counter-rotating helicopter blades. That is Dragonfly, and it is amazing. I'm so excited to be a part of it as a co-investigator on this mission.

Morgan Cable: The reason that we're doing something that seems this crazy is because in a world like Titan, the gravity is much less than Earth. It's about the same as our moon. So picture of how light you would be there. Plus its atmosphere is denser. It's about one and a half times thicker. So that means that it's actually more efficient to fly and traverse the amazing terrains of this world.

Morgan Cable: In these series of hops. It's more efficient to do it that way than it would be to drive like a traditional Rover. Dragonfly is slated to land on Titan in 2034. And we'll make some amazing discoveries. Every time we send something to land on a world. In situ is what we call it. The measurements you can make, the images you can take. Everything is just so much more visceral and personal because you're there. You don't have to look at it from afar. You're in the environment, experiencing it for the first time.

Mat Kaplan: I cannot wait to see some of those images of seas of methane and ethane and canyons dug by the same materials. It is beyond thrilling.

Morgan Cable: It's going to be amazing. I should note that Dragonfly is not the first time we will have landed on Titan. The Huygens Probe, which was part of the Cassini mission. This was a contribution from the European Space Agency was the first Lander on Titan. We should get that out there. But it was battery powered. It was actually designed to float in methane or ethane, because at that time we thought that all of Titan was covered in a sea of liquid hydrocarbons.

Morgan Cable: We still don't know where all of those mysterious hydrocarbons went. There's a question about the missing ethane. We can talk about, if you want. So Huygens landed. It was battery powered. It lasted for a few hours and gave us some great images, but dragonflies scheduled or is planned to at least for its prime mission to be on Titan surface for two and a half years. So two and a half years versus just a few hours, we're going to learn so many incredible things.

Mat Kaplan: Big advantage of having a radioactive source of energy that can work for you like it's working for Perseverance and Curiosity on Mars right now, as well as the Voyager Spacecraft, still out there and still going strong. I was going to move on, but you've intrigued me now with your mention of the missing ethane. I know that we found that the methane. Where's the ethane?

Morgan Cable: That is one of the big questions. So we've got this thick atmosphere on Titan. It's mostly nitrogen, but it has a significant amount of methane about 5%. And because of photochemistry, so light from the sun, as well as some other processes, because of Saturn's magnetosphere, that methane is actually being converted primarily into ethane. So there are two big mysteries actually.

Morgan Cable: One of them is why is there still methane in the atmosphere? It should have been gone after I believe about a hundred thousand years. Titan is definitely older than that. So why is there still methane? It must be coming from somewhere. Also, where is this ethane? There should be an ocean.

Morgan Cable: Meters thick covering the entire surface of Titan. And there's not. So some scientists think that maybe it's been stuck down into the interior of Titan somehow. Some evidence for that is that all of the lakes in the Northern Hemisphere, in the North Pole, they're all exactly the same height, which is weird, which makes us think that maybe they're all connected by some sub-surface. They don't call it an aquifer because aqua is water. They call it an [alkanefer or alkanofer 00:41:18] because it's alkanes hydrogen. Excuse me.

Mat Kaplan: Easy for you to say. I'm not going to try

Morgan Cable: Yeah, chemist. They train you how to say these things before you get your PhD in chemistry. It's one of the fascinating mysteries and the instruments we had aboard Dragonfly and the many in-situ measurements that we'll be able to get with that mission should really help shed some light on some of these key mysteries.

Mat Kaplan: What do you think of this speculation that there could actually be two biospheres on Titan. One, that would be weird on the surface and maybe another one, maybe not too different from what we might someday find in the ocean under the ice on Enceladus.

Morgan Cable: Oh, it's one of the things that makes me so excited to work on Titan as a chemist because yeah, you have these two completely different solvents, right? One is polar, liquid water. Titan has a liquid water ocean underneath all the cool stuff happening on the surface. Deep down, it's got a liquid water ocean just like Enceladus, just like Europa and just like Earth.

Morgan Cable: And yet on the surface, it has this completely alien solvent. Non-polar. So that means that anything that dissolves in water is not going to dissolve in liquid methane and ethane. It'll solubilize and allow chemistry to happen for completely different molecules. It's something that we can study in the lab, but there's no way we're going to replicate the complexity of a world like Titan. We have to go there and explore these places ourselves to really wrap our arms around all of the amazing science that's happening.

Morgan Cable: But I have to say as a chemist, it's so cool to be able to bring in many of my colleagues who study polymer chemistry, organic chemistry, things like that who are now able to come in and really make significant contributions to planetary science and potentially to astrobiology too. It's a really fun way to engage that side of the community.

Mat Kaplan: So take note a science fiction writers out there, and I know a few of you are out there. Here's that story idea, the war of the Titanic biospheres. You can credit me when you write the book. Just one other thing about this work that you and so many others are doing to prepare for Dragonfly. It makes me think of what happened with Viking. Those utterly amazing missions from the mid 1970s that did such wonderful work. Such sophisticated machines way ahead of their time. But we just didn't know that much about the surface of Mars and that had a big effect on the science that they were able to do, and then send back to Earth. I guess this is in large part, an effort to avoid that problem.

Morgan Cable: Certainly. And back when the two Viking landers landed on Mars, we actually only knew about two of the three branches of life. Archaea hadn't even been discovered yet. So it's not only that we were learning about Mars and Mars is surface properties. We're also still learning about life and the extreme places where it can be found, things like hydrothermal vents, I don't believe had been discovered yet, or they had been recently discovered.

Morgan Cable: These are an excellent proven ground and potentially a great example of how life might emerge or subsist on a place like Europa or Enceladus. These communities of life that live off of geothermal energy at the sea floor. That's a great example of what we think might be possible at these ocean worlds. And Dragonfly luckily can build off of a lot of the amazing discoveries that Cassini made. So we have some ideas of the complexity of the organic molecules that are present on Titan.

Morgan Cable: So we've designed instruments that should be able to parse out from that complex chemical tapestry and pull out the bits of information that can tell us, is this environment habitable? Does it have the building blocks? And do we potentially see evidence of biosignatures. But that's not all of what Dragonfly' i going to do. We are also just pure chemists studying a new environment. Peer geologists, who are studying this alien world.

Morgan Cable: We're going to learn so much about all different aspects of Titan, not just whether or not it has a propensity to host life, but just how it got to be the way it is and how unique or how common a world like Titan might be in the sort of universal context.

Mat Kaplan: Do you have any doubt that what we are learning and will learn in the future about Enceladus and Titan will help us learn more about our own pale blue dot?

Morgan Cable: It is probably going to blow our minds in ways that we can't even predict now. Every time we send something somewhere else, it requires us to mature and advance, develop these technologies that ended up having some benefits here, as well as just the sheer knowledge that we'll learn.

Morgan Cable: Again, we only have a sample size of one when it comes to life. And as a scientist, that's terrible. Oh gosh, you can't make any real theories or anything based on that small of a sample size. You need at least three, right? Ideally tens or even hundreds of examples before you can draw a line or make a claim about a trend.

Morgan Cable: So by studying these other habitable worlds, we can see where Earth lies on the spectrum and where other places lie on the spectrum of habitability and really start to understand better the universe and our place in it.

Mat Kaplan: A lot of other world's out there waiting for us to find out more about them, aren't there? Outside our solar system, I'm talking about. Before we finish, I don't know where you find the time, but you obviously enjoy not just doing science, but sharing your love of it. I noted that you were in 2018, given the JPL Bruce Murray award, our beloved co-founder of Planetary Society for excellence in education and public engagement.

Mat Kaplan: You have a lot of these sorts of activities, these STEM activities on. But just as an example of one that made my eyes go kind of wide, what do you do in South Korea each year? Is that still underway?

Morgan Cable: Oh, gosh. Yeah. So the Bruce Murray award was a tremendous honor and it's such a privilege to be able to work in a place where I can do this outreach and help expand the excitement, the sheer excitement and love of what I do and inspire the next generation. I've been fortunate enough to help manage a space camp in South Korea at a Challenger Learning Center. This is a one of these places that was started by the families of the Challenger astronauts. And there are many throughout the US. There are just a few internationally.

Morgan Cable: As far as I know, I think this is the only one in Asia, that's in South Korea. They've got an observatory there. It's such an amazing place. And to be able to go and teach third through sixth graders, some of the amazing things that we're able to do as scientists and as engineers. Usually, it's just funny.

Morgan Cable: It seems to happen in the summer. Maybe I've been working in the lab and I haven't been able to get something going or the laser is broken or something. So I go to the space camp and these kids look up at you and they're like, "You work for NASA? You're awesome." And you're like, "You know what? I am awesome. This is awesome."

Morgan Cable: It really scratches that itch and makes me remember why I do what I do and how incredibly lucky I am. So I love it. Unfortunately, because of the global pandemic, we haven't been able to do the camp for the last two summers, but we're really hoping to pick up again where we left off and see some of those teachers and hopefully see some of those students again and find out what they've been up to.

Mat Kaplan: Well, of course, you're awesome. I've saved the most important question of the interview for last and here it is. Are you still mountain unicycling?

Morgan Cable: Yes, I might be. It's a really fun sport. Actually, not a lot of women do it. So women out there, if you're interested in learning how, mountain unicycling, it's a lot of fun. It's the only thing that I have found where I have to be completely focused on what I'm doing. I can't be thinking about that meeting I've got to go to, or that presentation I've got to work on. I have to be completely present because if you're not, if you let your mind drift, you tend to fall pretty easily and befit and that's no fun.

Morgan Cable: So yeah, there are a lot of great trails in the area here in Southern California, and I just really enjoy it. So that's my meditation in motion, I guess.

Mat Kaplan: Stay focused, Morgan, because we need you for many, many more years to keep conducting and leading this research and explaining it to us as well. Thank you so much. This has just been delightful. Best of continued success with all of this work. And yes, let's do check in after that Decadal Survey comes out, hopefully in spring of 2022. Best of luck with that as well.

Morgan Cable: Oh, that would be amazing. You're such a wonderful outreach, and the words are not here. Thank you so much. You're just amazing.

Mat Kaplan: Those words will do just fine. Thank you so much, Morgan. And by the way, happy birthday, Morgan. Time for what's up on Planetary Radio. Here is the chief scientist of the . He's been with me, well, we're going on 19 years now of doing the show together.

Bruce Betts: What?

Mat Kaplan: I know. I know the feeling. That's Bruce Betts, coughing into your ears there into your earbuds. Welcome.

Bruce Betts: Thank you, Mat. Great to be here for the last little while.

Mat Kaplan: No, no. We're going to stick around. I promise.

Bruce Betts: Yay.

Mat Kaplan: Because we're just having too good a time looking up at that night sky.

Bruce Betts: Oh, and I just can't get enough of your clean segues. It is cool in the evening sky right now having the two brightest planets up there. You have Venus in the west after sunset looking super bright and you got Jupiter over in the east looking really bright. Saturn is to Jupiter's right looking yellowish. Not as bright. And between Jupiter, Saturn, and then over to Venus, you got a bunch of constellations.

Bruce Betts: So you got Sagittarius, the teapot of the sky in terms of what it looks like as an asterism. You got the Scorpius with the bright reddish star and Terry's so a party in the evening sky.

Mat Kaplan: I had a conversation with my five-year-old grandson yesterday, and we were debating whether Venus is stuck because it appears to have been for months really high in that Western sky. But I told him that I would ask you about this. Is Venus stuck?

Bruce Betts: I can't tell you. No, Venus is most definitely not stuck, but the way the orbits work it has indeed been hanging out in a similar location in the sky. But it's because both Venus and Earth are moving. And so you get different patterns in the sky, depending on what's going on

Mat Kaplan: Someday, I'll really blow his mind and show him retrograde.

Bruce Betts: Retrograde. I know it's going backwards. Yeah. It's just because everything's moving rather than everything stuck. On to this week in space history, 1965, Mat. They named a show after you. Lost in Space premiered. Danger, Will Robinson, danger.

Mat Kaplan: I'm found in space. That's where I'd like to find myself actually.

Bruce Betts: We'd like to find you there as well. Two, amazing outer planet missions ended during this week. Galileo in 2003 and Cassini in 2017 both crashed intentionally into the giant planets they were exploring, Jupiter and Saturn respectively. We move on to [inaudible 00:53:44].

Mat Kaplan: That was a good way. Clever. I like that one.

Bruce Betts: Oh, yay. Finally, after 19 years. People need to know this. In orbital mechanics, there is a thing called a pork chop plot. I'm assuming some orbital dynamics guys were really hungry. They plotted something and they thought, "Hey, that looks like a pork chop." Kind of like in the cartoons where the other character turns into a steak, but a pork chop plot is a chart that shows contours of equal characteristic energy against combinations of launch date and arrival date for interplanetary missions.

Bruce Betts: So they're kind of like fuel efficiency maps to figure out when you want to launch and when you'll get there. If you squint and are really out of it, the plots look kind of like pork chops.

Mat Kaplan: This is another example of that lesson that we've been trying to teach people for years. Never ever put your science on paper just before dinner.

Bruce Betts: Oh, That's for sure. Also, tends to be wrong just before you eat. But that's another story. All right. Do we go on to the trivia contest? And I asked you as of September 1st, 2021, how many spacecraft are docked or visiting the International Space Station? How'd we do, man?

Mat Kaplan: Not the biggest response we've ever had, but one of the most entertaining though, I think.

Bruce Betts: Ooh, I'm excited.

Mat Kaplan: Yeah. Here's the answer from a Poet Laureate Dave Fairchild in Kansas. Northrop Grumman Cygnus freighter takes a docking port. Space x has a pair of ships, the crew and cargo of sort. Russia has a Soyuz and a Progress 78. If we send much more, they'll have to stand in line and wait.

Bruce Betts: Always impressive how it works, these answers. I wonder how long it takes?

Mat Kaplan: That's five, I believe. Is that correct?

Bruce Betts: Five is indeed correct. What's hanging out there right now? You named them all.

Mat Kaplan: Well, what a relief for you. [Glenn Beauzou 00:55:48] in New Brunswick, Canada, because Glenn, you were chosen by Sure enough Glenn said five ships as well. So congratulations up there in NB, Glenn. You are going to be getting yourself a Planetary Society Kick Asteroid, rubber asteroid. Congratulations. Like I said, we've got a whole bunch more of very entertaining stuff. I should add that Glenn says, "Love listening to the podcast at bedtime. But makes me forget to enter the contest the next. LOL." Hey, glad that you had, what, insomnia this time, Glenn. Did you stay up all night?

Mat Kaplan: Darren Richie in the state of Washington says, "Almost wrote two dragons docking." Because two of those Space X spacecraft. Two dragons docking, which kind of puts me in a holiday mood." You get it?

Bruce Betts: Ooh, dragons docking.

Mat Kaplan: All the friends in Sweden. I count five at the given time, but my eyesight isn't the best. God, I was going to say, wait for it. The pun master, Robert Klane in Arizona, "Musk, you give us such easy questions? I ask again, Soyuz is going to give us a tough one. This question is too easy to make progress with. Still working on that Cygnus pun. We'll get back to you on that."

Bruce Betts: I think he's got a pun Cygnus. He should go to the hospital.

Mat Kaplan: That's very good. Right off the top of your head. I'm impressed.

Bruce Betts: Thank you. I'm impressed of how you read those puns flawlessly into the dialogue. But I guess you're the professional.

Mat Kaplan: I am a pro. 19 years, actually more. Joseph Poutre in New Jersey. "Of course, none of us can see the cloaked alien spacecraft keeping an eye on. We evolved apes. The question is, how many are there?" Mel Powell in California. "There would be a sixth, but some selfish bone head left a shopping card in the middle of the docking port instead of returning the cart." Come on, space people, be calm.

Bruce Betts: Come on.

Mat Kaplan: And we'll close with this from our other major poet, Jean Lewin in the state of Washington. "Docking with the ISS requires the finesse found in valet. But with limited amount of parking spots, they may soon need a valet. There's been mentioned of a parking garage within a short space walk proposed, not yet reality. So far it's only talk. So five ships are currently parked in place with a few empty docking slots. So if you want a primo port, you currently have a shot."

Bruce Betts: Well, I was unaware of those parking plans for the future of ISS. People are really thinking that through.

Mat Kaplan: I was too. Ballet and valet, that's the winning rhyme, I think this week. What do you got for next time?

Bruce Betts: What was the largest telescope during the 19th century? So during the 1800s. At any time during the 1800s, what was the largest telescope by primary mirror diameter, the usual way telescopes are measured. Biggest telescope in the 19th century. Go to

Mat Kaplan: Gosh, I think I know the biggest one in the 18th century, but not the 19th. Great question.

Bruce Betts: I think the answer is interesting. It will lead in interesting directions.

Mat Kaplan: You've got until Wednesday, September 22nd at 8:00 AM Pacific time. And we'll go with that asteroid again, the rubber ones from the rubber. That's if you're the winner of this latest quiz from the quizmaster, the chief scientist. Bruce Betts, we're done.

Bruce Betts: All right, everybody. Go out there and look up the night sky and think about why a question mark looks like a question mark. Thank you and goodnight.

Mat Kaplan: I don't know. I think it looks like a pork chop standing on end to myself. Go have lunch. He is the chief scientist of The Planetary Society who joins us every week here for What's Up?

Mat Kaplan: Planetary Radio is produced by The Planetary Society in Pasadena, California, and is made possible by its members who can't wait to dive into our solar system's other oceans. The water is warm and inviting at Mark Hilverda and Jason Davis are our associate producers. Josh Doyle composed our theme, which is arranged and performed by Pieter Schlosser. Ad astra.