Planetary Radio • Dec 20, 2023

Dragonfly soars to final design phase

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Robert braun portrait

Robert Braun

Head of the Johns Hopkins Applied Physics Lab's Space Exploration Sector

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Elizabeth "Zibi" Turtle

Planetary Scientist at Johns Hopkins Applied Physics Lab and Dragonfly Principal Investigator

Ken hibbard portrait

Ken Hibbard

Dragonfly Mission Systems Engineer at Johns Hopkins Applied Physics Lab

Bruce betts portrait hq library

Bruce Betts

Chief Scientist / LightSail Program Manager for The Planetary Society

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Sarah Al-Ahmed

Planetary Radio Host and Producer for The Planetary Society

NASA's Dragonfly mission to Saturn's moon Titan has been authorized to proceed with work on final mission design and fabrication, known as Phase C. This week on Planetary Radio, we get an update on the mission's progress and new timeline. You'll hear from Bobby Braun, head of the Johns Hopkins Applied Physics Lab's Space Exploration Sector, Elizabeth (Zibi) Turtle, the principal investigator for Dragonfly, and Ken Hibbard, mission systems engineer for the spacecraft. If that doesn't convince you that Dragonfly is one of the most epic things humanity has attempted to date, stick around for What's Up with Bruce Betts as he shares even more reasons for us to explore Titan.

Dragonfly In-Flight artist's concept
Dragonfly In-Flight artist's concept This artist’s impression of NASA's upcoming Dragonfly mission shows the spacecraft flying over the dunes of Saturn’s moon Titan. NASA has authorized the mission team to proceed with final design and development, aiming for a July 2028 launch date.Image: NASA / Johns Hopkins APL / Steve Gribben
Dragonfly on the surface artist's impression
Dragonfly on the surface artist's impression This artist's depiction of NASA's Dragonfly mission to Saturn's moon Titan shows the spacecraft preparing to sample and examine the material at its new landing site.Image: NASA / Johns Hopkins APL / Steve Gribben
Titan Chamber
Titan Chamber In order to test the upcoming Dragonfly spacecraft, set to launch to Saturn's moon Titan in 2028, the mission team at Johns Hopkins University Applied Physics Lab needed a new kind of environmental simulator. At 4.6 meters (15 feet) tall, wide, and deep, the Titan Chamber is the largest environment simulator ever built at JHUAPL.Image: NASA / Johns Hopkins APL / Ed Whitman
Dragonfly Mission Concept
Dragonfly Mission Concept Dragonfly is a dual-quadcopter lander that would take advantage of the environment on Titan to fly to multiple locations, hundreds of kilometers apart, to sample materials and determine surface composition to investigate Titan's organic chemistry and habitability, monitor atmospheric and surface conditions, image landforms to investigate geological processes, and perform seismic studies. It was selected as one of two possible missions for the next New Frontiers launch opportunity in 2017.Image: NASA


Sarah Al-Ahmed: Dragonfly soars to final design phase. This week on Planetary Radio. I'm Sarah Al-Ahmed of The Planetary Society with more of the human adventure across our Solar System and beyond. NASA's Dragonfly mission to Saturn's moon, Titan, has been authorized to proceed with work on final mission design and fabrication known as Phase C. Today we get an update on the mission's progress and a new timeline from some of the amazing people at the Johns Hopkins University Applied Physics Lab. We'll hear from Bobby Braun, who's the head of the APL Space Exploration sector. Elizabeth, also known as Zibi Turtle, the principal investigator for Dragonfly, and Ken Hibbard, a mission system engineer for the spacecraft. If that doesn't convince you that Dragonfly is one of the most epic things humanity has ever attempted to date, stick around for what's up with Bruce Betts. He'll share even more reasons why we should hoof it to Titan along with a new random space fact. If you love Planetary radio and want to stay informed about the latest space discoveries, make sure you hit that subscribe button on your favorite podcasting platform. By subscribing you'll never miss an episode filled with new and awe-inspiring ways to know the cosmos and our place within it. Let's face it, humanity has pulled off some seriously astonishing feats in recent times, but let me tell you, NASA's Dragonfly mission to Titan is absolutely next level. It's the kind of cool that makes me want to call up everyone I know and ask them if they've heard about this thing. Have you ever wondered why NASA's twin Voyager spacecraft didn't both visit Uranus and Neptune? I know this sounds like a tangent, but stick with me. We had the chance to revisit those distant worlds, so why did Voyager 1 take a detour? The answer Saturn's moon, Titan. That world lit so many imaginations on fire even with our limited understanding of this Saturnian System, that Voyager 1's trajectory was explicitly altered to get a closer peek at that moon. In 1980, it gave us our first close-up look at what is still one of the most mysterious worlds we've ever discovered. Over a billion kilometers from our sun, cozying up to Saturn was this world shrouded in a thick atmosphere. Its air was thick in nitrogen, much like our Earth's, but with a twist of methane and this orange haze that kept the moon's surface a total mystery analysis of Voyager 1's data threw us a curveball though. That haze, it's chock-full of complex organic compounds. This finding had scientists around the globe slack-jawed. Titan was practically screaming mysteries into the void. Flash forward a few decades. It's 1997 and the Cassini-Huygens mission, which was a joint endeavor between NASA and the European Space Agency, or ESA, launches on a journey to learn more about the Saturnian System and delve deeper into Titan's secrets. The spacecraft consisted of two main parts, the Cassini orbiter managed by NASA and the Huygens probe, which was an ESA project. While Cassini was going to orbit Saturn and study the planet and its moons from above, the Huygens probe would venture where no craft had before and dive headfirst into Titan's atmosphere to touch down on the surface that no one had seen up close. Finally, after years of sitting on the edge of our seats, on January 14th, 2005, the Huygens probe made its historic descent. It parachuted through that thick atmosphere and down to the surface and then beamed us back its findings. What it saw was a landscape eerily similar to Earth's, a world with river channels, lakes and seas, but with a twist. They were composed of liquid methane and ethane, not water. Meanwhile, Cassini continued its mission from orbit. Its instruments allowed us to peer through Titan's atmosphere down to the vast seas, the lakes of hydrocarbons and river networks carved by flowing methane. In all of our space travels, we've never seen anything quite like Titan. Liquid on the surface, a dense atmosphere, dunes of organic sand on water-ice bedrock and get this, there might be a liquid water ocean hiding underneath the surface. But here's the real kicker and why this should matter to all of us: Life as we know it needs three things, an energy source, a liquid solvent like water, or in Titan's case, methane, and the right chemical mix. We found all three of those things on Titan. Keep in mind that before life started on Earth, our atmosphere was a lot different. Much like Titan, there was hardly any oxygen and a lot more methane. So Titan isn't just some wild out-there place, it's got a vibe that's strikingly similar to primordial Earth, so saying that we could learn a lot by studying this moon is putting it really mildly. The groundbreaking discoveries made by Voyager 1 and the Cassini-Huygens mission laid the foundation for the next step: Dragonfly. This mission is spearheaded by NASA and crafted by the folks over at the Johns Hopkins University Applied Physics Lab in Maryland, USA. It's going to get the answers that we all crave, but in one of the most awesome ways I can possibly imagine. Think of NASA's Ingenuity Helicopter on Mars, but bigger and bolder. Dragonfly is a dual quadcopter that's about the size of a Mars rover and it's set to take on Titan's thick atmosphere by flying around and answering our burning questions. The mission was planned to launch in 2027, but it's now slated to blast off in 2028. Our guests today are going to fill us in on the timeline and tell us what's next for the mission team. So we have three brilliant minds from the Johns Hopkins Applied Physics Lab joining us today, Bobby Braun, Zibi Turtle and Ken Hibbard. Dr. Robert, or Bobby Braun, is the head of the space exploration sector at the Johns Hopkins Applied Physics Lab. He's held executive positions at NASA's Jet Propulsion Laboratory right in my backyard here in Pasadena, the University of Colorado, Boulder and NASA. Dr. Elizabeth or Zibi Turtle is a planetary scientist. She's the principal investigator of the Dragonfly mission and the third woman in history to become a PI on a NASA planetary mission. She's worked on a bunch of space missions including Cassini. Last but definitely not least is Dr. Ken Hibbard. He's a Dragonfly mission systems engineer. He's been involved with multiple missions, development, integration, testing, launch and orbit operations. He also has a passion for understanding Titan's Mare in more detail. Are you ready to dive deeper? Let's get to it. It's really hard for me to pick favorite spacecrafts. There are so many cool ones out there, but selfishly, I feel like Dragonfly is the one that I'm most hyped about right now and that's really hard because things like Mars sample-return are phenomenal, but Titan is such a fascinating world that is so Earth-like I'm really glad that I have you all here to give us an update, because it's been a while and I'm clearly not the only person that is super excited about this. We do have a lot of Planetary Society members who wrote in questions that they wanted me to give to you all on the team. So as we're going, I might be giving you a few questions from our members online.

Ken Hibbard: It's our pleasure.

Zibi Turtle: Yeah, happy to be here.

Sarah Al-Ahmed: So I'm going to angle this one at you, Zibi. There's so much to talk about, but before we get deep into it, I wanted to ask you why is Dragonfly so important? What is its primary goal and why is it so amazing that you all are dedicated to spending so much of your time to the creation of this mission?

Zibi Turtle: That's a great question. We think about that a lot. Titan is a really key destination in our Solar System and that's because the chemistry at Titan's surface has a lot of similarities to the types of chemistry that might've occurred here on early Earth before life developed, and we can't really study those early chemical steps here on Earth. We've got biology overprinting everything, but on Titan that may be exactly what we have, the formation of this primordial chemical soup on the surface of Titan and that is what Dragonfly is designed to study. It's primarily a chemistry mission designed to measure the composition of the materials on the surface of Titan and see how far organic synthesis has been able to progress in this cold world in the outer Solar System.

Sarah Al-Ahmed: I've wanted to ask this one for a while because I'm not a chemist, but whenever we're talking about this world, we talk about how there's a whole liquid cycle going on with methane on this world. I like to call it a hydrological cycle, but that might technically not be true because it's methane. Is it a methodological cycle and what is the technical terminology there?

Zibi Turtle: On the Cassini mission, as we were learning about the Titan system and the hydrological process that the methane cycle with methane clouds and rain and rivers and lakes and seas on the surface, just like we have water playing that role here on Earth, we actually had a lot of debate as to whether hydrological cycle was the appropriate terminology, and in the end that was the most natural term, and so that's typically what is used for the methane cycle on Titan as well.

Sarah Al-Ahmed: Yeah, that means I don't have to change my terminology in my brain. It's a little challenging.

Zibi Turtle: Yep.

Sarah Al-Ahmed: Bobby, I wanted to ask you. When last we had members from the Dragonfly team on our show it was 2019, so quite a lot has happened in the intervening years and I wanted to ask how the Dragonfly team and APL's broader space exploration sector has adapted during this COVID era. How are you all doing?

Bobby Braun: Yeah. Well, that's a great question. I'm glad to answer that, although I'll point out that in 2019 and in several the years since then I wasn't at APL, so a lot's happened for me as well as I traveled around the country and learned things in different organizations. The Dragonfly team has done, in my view, a fantastic job of staying focused and staying on point and getting the flight system, the instruments, the science rationale, the whole mission, maturing it through a very difficult set of changes that were forced upon the program as it matured. But the team has hung together. They've shown tenacity, perseverance, they've been innovative, and frankly, I've found this particular team to be among the most inspiring of teams that I've seen in planetary exploration. They've done a great job.

Sarah Al-Ahmed: And earlier this year, Dragonfly passed all the successful criteria for the preliminary design review, so you guys are in a good place and now you're officially authorized to push forward and proceed into that final mission design and fabrication for the fiscal year of 2024. I was going to ask, Ken, since you're so into the systems on this thing, can you give us an update on where we are with the mission planning and testing and all of the instruments?

Ken Hibbard: So we're in the stage now where we're finalizing the design, so specifications will be written, final flight drawings are being produced and we're making progress in developing engineering model hardware. That hardware is going through testing and it's going to inform the final flight fabrications. We've had several great milestones lately. APL was gracious enough that they funded what we call the Titan chamber, and so it's roughly a 15-foot by 15-foot by 15-foot chamber that we can get down to Titan temperature at one atmosphere, which is very rare. Normally to get down to those temperatures you have to go vacuum. And just a few months ago we completed our first full-scale thermal test in that chamber. We have a full-scale mock-up of the lander and we're testing out the convective properties, and these tests go towards informing our modeling and our analysis that feed into the design. We've done parachute drop tests. We have a half-scale integrated test platform. Think of it as a half-scale drone that we fly around locally. We've also taken it out over dunes in Yuma, and so we have a lot of hardware that we are now testing with and using that testing to inform the design and the models that will feed forward into the final critical design that is planned for late next year before we start actual flight system fab.

Sarah Al-Ahmed: It's got to be really fun seeing this version of it kind of coptering around. I mean, we've got a lot to go, but that's got to be really fun to test.

Ken Hibbard: It is. It's really exciting when you see your algorithms actually work. And so our integrated test platform flies itself. We have a pilot there, but they're there purely for safety and so we've demonstrated that it takes off, it navigates, it finds safe landing sites and lands all autonomously now, and so we're making huge strides with our software and our algorithm development. We've been able to test with all of the sensors other than a LiDAR that we're still building the EM for, and so to see that come to fruition has been really exciting. And again, getting full-scale models, people don't appreciate how sizeable Dragonfly is. I mean it is comparable to Curiosity or Perseverance, so it's the size of a small car that we're going to fly on an alien moon. I think intuitively when people think drones, they think small and we are anything but, and so most people, when they see the full-scale models and test platforms we have, they're like, "Oh my god, this thing's huge," and so just the magnitude of what we're trying to do is very exciting.

Sarah Al-Ahmed: I think the first time someone actually made me grapple with the size of this thing, they described it as like a mini-bus flying around on another world. I imagined it would be Ingenuity-sized, but in fact it is ginormous and you're going to be sending the stuff go fly on another moon. That's so wild. So I'm glad you brought that up.

Zibi Turtle: It speaks to physically how much easier it is to fly on Titan than it is on Earth or on Mars. Titan's atmosphere is denser than Earth. It's four times denser than the Earth. The surface pressure at Titan is one and a half times that here on Earth and the gravity is 1/7 that here on Earth. So physically it's actually easier to fly there and a person could put on wings and soar over the surface, which would be pretty spectacular way to explore Titan.

Bobby Braun: Right. And that means for us, we can carry a full set of science instrumentation and we can be a science vehicle that's flying across this expansive world.

Ken Hibbard: Yeah, we refer to it as a relocatable science platform, but it's a fully instrumented science platform. So you get the benefit of all those instruments being able to go to different geologic settings and be able to go explore Titan in a way that we've never been able to do. I mean, I like to talk to people. If you imagine you've never been to Earth and you sent one probe to Earth and it landed in the Sahara, you'd get one impression of what our planet is. If you had a different probe go to Hawaii, you get a totally different impression of what our planet's like. Dragonfly is a singular system that we're trying to get to at least three different geologic settings so that we don't get false assumptions about what the moon is, but instead can actually really go and search and research across different parts of the moon to get a holistic view of what it really is like.

Sarah Al-Ahmed: And that really is the benefit of being able to fly. Our rovers have managed to go pretty far on Mars, but in order to grapple with all the different types of terrain on a world like Titan, flight is really key. Of course, you're trying to kind of stay in certain terrain. I feel like one of the most interesting places might be the lake districts and the way north, but you might get yourself in trouble up there. So my understanding is you're staying in the lower latitudes, is that correct?

Zibi Turtle: We are staying in the lower latitudes in large part because at the time when Dragonfly will arrive at Titan, it will be northern winter and Titan seasons are very much like Earth's, the tilt to the system is actually a little larger than the tilt of the Earth-moon system, and so in northern winter the north pole is not illuminated at all. The difference of course between Earth and Titan's year being that the year is much longer at Titan, so it will be several years of darkness at the Titan north pole. And if the sun isn't up in the sky, neither is the Earth, and one of the enabling aspects of the Dragonfly mission is that we do direct-to-Earth communication from the surface of Titan. So we would not be able to do this mission at the north pole in this epoch simply because we wouldn't be able to do the direct-to-Earth communication from the surface. The other aspect, of course, of the area that we're going to is that it has a variety of materials that we want to understand better. One of the big questions remaining after the Cassini mission is what is the composition of the solid-surface materials? We really don't know that. It's very hard to study that from orbit because of Titan's atmosphere, and so this gives us access to these different types of materials, the organic sand dunes on Titan, for which the sand may be very widely sourced regionally or even globally across Titan, the interdunes, which have a waterized composition on Titan and this composition may be representative of the primordial crust of Titan, and then eventually progressing into deposits associated with an impact crater, and that's where things become particularly interesting because this really complex carbon-rich molecules on Titan that have fallen out of the atmosphere onto the surface at the site of a large impact crater, like the salt crater we're going to explore, have had the opportunity potentially to mix with liquid water for an extended period of time, and so that's why you get this really fascinating chemistry that we want to study.

Ken Hibbard: Just to draw upon the Earth analogy, we have the benefit of knowledge from Cassini that we have a good sense of where we're going and the different kinds of geologies that are there. So just like there are certain places here in the US, you could think California or even right here in Maryland, we're hoping to travel dozens of kilometers and in that kind of distance you can get to very different kinds of terrains. You can get to the beach, you can get to mountains, you can get to plateaus and areas in between. So we have that same expectation on Titan and it's well-informed by data that we're privileged to have from Cassini. So that all factored into choosing where we were going on the surface.

Sarah Al-Ahmed: What I thought was really interesting actually, looking back at what happened with Cassini and Huygens, was that the Huygens probe actually landed on Titan in the same season as this spacecraft will be landing, and I was actually concerned because I know recently there was the announcement that the spacecraft was going to be launching about a year later than originally anticipated in 2028, but thankfully the seasons on Titan are so long that it's still going to be the same season by the time we reach there. So hopefully that'll help us prepare ourselves for the seasonal conditions.

Zibi Turtle: Exactly. Yep, absolutely.

Sarah Al-Ahmed: How has the team adapting to this change in the timeline now that we've got an extra year to prepare?

Zibi Turtle: Well, there's a lot of work to do and we're really keeping focused on those activities, as Ken was describing. It's not really extra time because the change in the schedule is driven by budget constraints that we're all living under, and so we don't have additional funding in that sense, so we're doing the same amount of work but stretched out over a longer period of time, but there's a lot of good progress and momentum and so we're really excited to be continuing to build on that momentum toward our critical design review next year.

Bobby Braun: If I could add to that for a moment, just to make it more clear, the Dragonfly team's budget in 2024 is actually less than it's budget in 2023 in the president's budget request. That's what I'm basing those numbers on. And so the team had to stretch out the work and the launch date is a year shifted to the right, but because the workforce profile goes with funding, the amount of work that that team can accomplish, and here I'm talking about the integrated team, APL, Goddard, Lockheed Martin, Sikorsky, all of our partners around the country, they have to fund that activity or staff that activity in a more stretched out way, and that leads us from the '27 launch to the '28 launch opportunity.

Ken Hibbard: From a technical perspective, we're fortunate that the design parameters don't change too much year-to-year. So our delta-v was bounded by where we were before. The environments that we are designing to are benign and consistent year-to-year. There aren't a lot of ripples that go through the technical implementation, where some missions are really driven by their launch window and their opportunities and if you shift them, they have much more disturbances in the design. We're fortunate to not have to worry about that. And in fact, things like our delta-v went down from 27 to 28, so it actually improved our margins some, and so there were some technical benefits that come with the shift in the launch. So from a pure implementation perspective, the team just rolls with it and they have a job to do and they're going forward and doing good work, and they've just accepted the change and going about their business.

Zibi Turtle: Yeah, it's a spectacular team and everyone is really dedicated and focused on continuing the great work to get to Titan.

Sarah Al-Ahmed: I'm just personally on the edge of my seat wanting it to get there. We're going to have to wait for the spacecraft to reach Titan after actually launches, so I'm just impatient.

Zibi Turtle: The outer Solar System is a long way away, yeah.

Sarah Al-Ahmed: It's so far away, but going there is absolutely worth it, particularly for this moon. We've learned a good amount about it from Cassini and Huygens, but there's so much we don't know about other terrestrial worlds that have these hydrological cycles. So there are so many interesting places in our Solar System in the search for life, but most of the ones that we talk about are places like Enceladus and Europa places with subsurface liquid water oceans, and I think people discount Titan in this where they really shouldn't because it is quite possible that this moon also has a subsurface liquid water ocean underneath all the interesting organics and methane going on on the surface. What can this mission potentially tell us about that subsurface ocean?

Zibi Turtle: Yeah, we're really lucky in our Solar System in the diversity of objects that we have to explore and the different things they each tell us, they each have to offer us in terms of understanding planets and planets as systems as well as to understand origins. Titan does indeed have a deep interior liquid water ocean, and one of the instruments that Dragonfly will have on it is a seismometer to be able to listen for Titan quakes. So this will give us information about the level of seismic activity on an icy moon in the outer Solar System, which is going to be really exciting.

Bobby Braun: Dragonfly is NASA's only mission to the surface of another ocean world, and that to me is just fantastic. So yes, Enceladus is interesting, Europa is interesting. There are many interesting worlds in our Solar System and throughout our universe, but if you want to go to the surface of one, Dragonfly is doing that. We're going to the surface of another ocean world, we're going to be able to touch that surface. We're going to be able to smell it, taste it, and decipher the origins of life by doing so, and that to me is just remarkable.

Sarah Al-Ahmed: It really is when do you get an opportunity like this and we don't have to dig and drill kilometers beneath the surface to actually get to some interesting chemistry going on here, because it's interesting from just the top to the bottom.

Zibi Turtle: Exactly. Exactly. There's been incredibly complex chemistry right at the surface, and so the materials that resulted from that are accessible at the surface and protected by the atmosphere of Titan, so they can persist for long periods of time, which is also important.

Sarah Al-Ahmed: I love that you brought up the seismometer because just a few weeks ago I was talking with Ben Fernando who works primarily with the seismometer on InSight on Mars, but also works with the Dragonfly team, and so I got to speak with them a little bit about that seismometer and it's really exciting that it will be able to tell us more about the subsurface ocean, but that's just water and things that we are familiar with. I want to know more about this methodological cycle and what's going on with the organic compounds. Even the dunes that you're going to go visit are made out of these organic materials, right?

Zibi Turtle: Exactly. Exactly. The sand grains on Titan are about the same size as sand grains here on Earth, but they're very different in composition, and we actually don't know how Titan forms organic sand grains. Titan clearly does because there are sand grains that have saltated to form vast seas of longitudinal dunes, absolutely spectacular landforms, but we don't know how the sand itself is actually formed, and so it's going to be very interesting to understand that. And to understand the materials on the surface and how those materials are mixed, modified, transported across the surface. Dragonfly has a suite of different instruments to be able to investigate Titan as a system. So in addition to the mass spectrometer that will be able to measure in detail the compositions of samples of the solid surface materials, we also have a suite of cameras to be able to observe the terrain at different scales, very high resolution imaging of the sampling site and then panorama imaging and aerial imaging, which is going to be really exciting, and then we have gamma-ray neutron spectrometer that'll give us the bulk elemental composition of the surface beneath the lander and inform different measurements that we'll make as well as the geophysical suite that includes the seismometer and the suite of meteorological sensors as well. And so one of the things I'm really excited about is that we get to put the very detailed chemistry measurements into the context of Titan as a system and understand the environment and how that environment has modified the chemistry and different places on the surface.

Ken Hibbard: We're taking the latest versions of these instruments, so just thinking about the mass spectrometer, the detection range it has is one of the widest that I'm familiar with. It has the full range of the Sam instrument from MSL combined with the MOMA instrument that is going on ExoMars and it's really married those two. Our friends at Goddard have done a fantastic job in developing this instrument, and so we're going to get a compositional range that exceeds what we've been able to measure with similar instruments on other machines because we're taking the latest version of it with us. And so the capability of the instrument suite is phenomenal.

Zibi Turtle: And we were able to base the design of the instruments on the information that we have from the Cassini and Huygens measurements at Titan.

Sarah Al-Ahmed: And of course you have the benefit of another copter going around another world, and what I think is interesting about this is that the last time you specifically were on the show, Zibi, you were talking about developing this mission in tandem at the same time as the Mars 2020 mission and Ingenuity, but in the intervening time, it's already gotten to Mars, started flying around, I believe we're at its 68th flight on Mars at this point. I wanted to ask, what have these flights taught you that you're going to be carrying forward to Titan?

Zibi Turtle: It's been so exciting to see Ingenuity fly on Mars. What a great achievement and demonstration of this kind of technology and this exploration strategy for other planets. There are a lot of aspects that we can bring into our design, not only in terms of hardware design and testing especially, but also in terms of planning our operations. And in fact, we just had a meeting last week with members of the Ingenuity team talking about the kind of things that they've learned in terms of planning observations or planning activities, I should say, with Ingenuity at Mars. Even though Mars is a lot closer, Ingenuity still needs to fly entirely autonomous, and so we have a different timescale in terms of the difference how much time it takes information to get between Titan and Earth and Mars and Earth, but at some level it's really the same issue. The system needs to be autonomous and needs to be able to make decisions on its own.

Ken Hibbard: Yeah, and we've benefited a lot from our colleagues at JPL. They've done a phenomenal job. It's super exciting watching all the success they've had, but we are fundamentally different problems that we're solving too, right? They're working in a very thin atmosphere, we're working in a very dense atmosphere. The scale of the vehicles, as we've discussed, are dramatically different. So while there are similarities in the algorithms and the con ops and the autonomous flight, the design of the rotorcraft or vertical flight system, if you will, are dramatically different. We also have the challenges where our environment helps us fly and it makes it very conducive to flight. It's also very cold, and so it makes some of our thermal challenges different than what a Mars mission would've to go through, both in good ways and in bad. I mean, we also have a very stable environment. Our temperatures vary by about one degree Kelvin over the course of a day where they have much wider swings between daytime and nighttime. So we're more stable, but we're stable at a very cold temperature. So there are a lot of differences in the problem sets that the respective missions are trying to solve.

Sarah Al-Ahmed: One of our Planetary Society members online noted that this spacecraft is named for a flying creature, a dragonfly, and want to put this question to you: How are these designs clearly different? How are the actual rotors placed on this craft and what is its maneuverability like?

Ken Hibbard: So we're dual quadcopter. So we have four hubs and each hub has an upper and lower rotor. The diameter of the rotors is about 1.4 meters, and so they're obviously larger. To deal with the temperature effects, right now we're planning on our rotors being made out of metal as opposed to composites because there are fatigue factors we were concerned with, whereas the Ingenuity rotors could be composite materials, and so it makes them lighter. So ours are a little larger, they need stronger motors. In terms of flight, they had one pair directly over the top of the vehicle. So in many ways it's more akin to a helicopter in terms of its control laws, we have four, so we're kind of in this X configuration as a dual quadcopter, and so we use variable speed control in order to maneuver the vehicle. And so our rotor pairs are contra-rotating rotors, and we vary the speed that different blades spin at in order to maneuver the vehicle. They're canted slightly, so you get force vectors on each of the major axes. And so we are not a nimble... If you think a small toy drone, we don't zip around. We kind of lumber through the atmosphere, but that is okay because we're not going for speed records or maneuverability. We have well-defined flight profiles. We're looking for a robust system that allows us to move from place to place and then safely get down on the ground because the preponderance of our science is done on the ground, and so we view ourselves as we're facilitating the relocation of the science platform and we want to do that in as robust and resilient to manner as possible.

Zibi Turtle: And we really do spend almost all the time on the surface, more than 99% of the time is on the surface. The plan is to fly probably every other Titan day, and a Titan day is 16 Earth days, so that's about once a month, and then the rest of the time we're on the surface making measurements, communicating with Earth and sending back data.

Ken Hibbard: But we fly roughly 10 to 12 meters per second. If you think about that, when you account for density variations and things like that, it's kind of like 40 miles per hour in a car in terms of air effects and all of that. Our nominal cruise altitude is about 400 meters above ground level, so we climb, we cruise out to different places, we can drop down for scouting and imaging, we elevate back. We're able to go over dunes, we pre-scout where we want to land and have the ability to send those images to the ground so the scientists and the engineers can decide where we want to go and plan out our flight path. So there's a lot that goes into it, but all-in-all, it's going to be super exciting to just be able to maneuver this vehicle so far away from the Earth.

Sarah Al-Ahmed: We'll be right back with the rest of my interview with Zibi Turtle, Ken Hibbard and Bobby Braun after the short break.

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Sarah Al-Ahmed: I was going to ask a bit about the workflow there because you're, what, about 70 minutes or so communication time away from this thing, so you're going to need to be able to wait for it to do its own thing and then give it instructions. So what is that full workflow like?

Ken Hibbard: As Zibi mentioned, with the cadence of a Titan day to an Earth day, 16 Earth days is roughly one full Titan day, it allows us to stay on a nominal schedule for the operators here where we have one week of kind of daylit operations on Titan that we can have the vehicle execute and send down data during normal hours, and then when the vehicle is essentially hibernating over the Titan night, we can plan the next week, and so it's like a week-on, week-off where you're executing planning, executing planning. In terms of executing out the flights, we're building up a library of flight sequences. What is a climb? What is a cruise? What is a descent? How can you do a hop or jump or pivot? And so we build up a library of flight sequences and then an actual traverse flight or an actual end-to-end sequence has these building blocks stitched together. And so every one of them is pre-tested and thoroughly vetted and lives on-board, and then when we upload a sequence to the vehicle, we stitch them together and we tell it roughly, "Go this distance, go to this heading," and then it just executes out of the library of onboard sequences in order to do that. In terms of what it does autonomously, it doesn't really quote, unquote, navigate autonomously. We're telling it where to go, but as it's going, it collects images of the terrain beneath it, and so it's tracking the terrain beneath it, and as it does so, it is able to also identify safe landing sites. And so ultimately, it will traverse out to a landing zone that is a fairly large area and it will scan that zone and within that zone it will look to identify the best landing sites within and it prioritizes the top three. And so as it goes along, if it finds one that's better than another, it re-ranks it in priority. So it's kind of keeping a running tally on where it could land and then it says, "Oh, I'm in the right general area, here's the safest spot. I'm going to go land there," and then it will settle down on its own. In many ways, it's similar to a lot of the capabilities that have been demonstrated on Mars. We're using a LiDAR, it's a scanning LiDAR it and we're doing a lot with optical navigation. I think the biggest difference that we have on Dragonfly is we don't have detailed elevation maps. We don't have a high-rise imaging system that tells us all the information about the surface, so there are no onboard maps that we're correlating to. It's doing it all real-time in image-to-image correlation, and it can correlate against images from previous flights or images that took just a few moments earlier in the same flight, but it's all data that we will have collected ourselves once we get out to Titan.

Sarah Al-Ahmed: It sounds like it's going to be really interesting for the spacecraft to try to determine where it is because you don't have robust maps. It's not like it can peer through Titan's atmosphere to use stars to determine its location, and it's not like there's GPS on this world, so it's going to be really interesting, but I'm sure the spacecraft will figure it out. We've even seen Ingenuity figure out its location based on local markers in imagery, so I think it'll be okay.

Ken Hibbard: Yeah, we've always said we don't have requirements for absolute precision. We will do radiometric tracking after the fact every time we've landed in a new site, and we will use our partners at JPL and their navigational expertise to help identify against the Titan global map precisely where we are combined with the data we take real-time and so with the IMU and other things, you can assess your movement from a known point to another point, and then you redefine your new known point and you kind of stitch it together from there.

Zibi Turtle: It's relative navigation, as you were saying. We don't need the absolute precision. What we're doing is navigating relative to our location to progress from the dunes and inner dunes toward the deposits associated with the crater, and we have maps from Cassini that we'll be able to locate ourselves in.

Ken Hibbard: Yeah, so that reminds me, what I was going to say is the other analogy I like to give people. So we live near Washington D.C here, and let's imagine we wanted to travel up to Philadelphia. It's no different than you would do in a small airplane. You could just get up in the air and fly over I-95. It doesn't matter if I'm exactly over I-95, slightly east of it, slightly west of it, I can follow the road and I know if I keep going up, I will make my way from D.C to Philadelphia. Once I get to the Philadelphia area, I've been given a rough destination. I want to go to a particular parking lot outside of Lincoln Financial Field, right outside the football stadium. So I navigate to the parking lot and then I want to look for safe landing spots. So if there are scattered cars inside the parking lot, I don't care if I land in spot number 17 or spot number 324, I just want to land in a spot that I'm not near another car, so I'm not at risk of hitting it. And so our system enables that. So that's where it's really centered on robustness and resiliency, not precision, because for the measurements we want to take, the precision doesn't really matter at that level.

Sarah Al-Ahmed: When you do land at a site, what are the first steps in testing the site? What are the first measurements you're going to be taking or the first samples to get into its little instruments?

Ken Hibbard: From a technical perspective, when we first touch down the surface, we'll immediately get IMU measurements and we will also get feedback through our landing gear and the inertia changes in the vehicle. And so we'll be able to detect contact of the surface, and that feedback will also give us some assessment of the rigidity of the surface, how hard is it versus how soft it might be. From a science impact, I'll defer over to Zibi, but I think we're going to pretty immediately take images of the new terrain around us and we'll be able, just from those basic measurements, get an idea of stability and position and some sense of the terrain that we've landed on.

Zibi Turtle: And then the next step is to understand what types of measurements we want to make. And so if we've pre-scouted the site, we'll have some data from that pre-scouting images of the landing zone, and from that we'll be able to understand where we are within the landing zone. The images will also tell us information about the different material. Are we in a place that has material that's different from the kinds of places we've seen before or are we in a place that has sand and we've measured sand before? And that will kind of tell us which sequence of measurements we want to make. As Ken was saying about the flight, there's kind of a library of different commands of different activities, and we have the same thing on the science side, on the science operations side, in terms of which measurements do we make with the different instruments. Do we want to sample at this site? Is it a type of material we haven't seen before? And if we want to sample what different kinds of measurements do we want to make with the mass spectrometer? And so there's a whole series of observations that we'll make to inform each of the observational decisions and the specific measurements.

Sarah Al-Ahmed: One of our members, Sabine Vollenhofer-Schrumpf from Austria, was most interested in knowing whether or not you've already created a plan for where you think you're going to be landing and what order and how much we might be able to veer off of that course if we find something that really sparks our imagination.

Zibi Turtle: We do know roughly where we expect to land on the surface. There's a landing ellipse on the surface and there's kind of a probability distribution within that landing ellipse depending on the Titan winds, et cetera. And so there's an area just south of the impact crater that's defined by this landing ellipse that we're targeting on the surface. We have such a wealth of experience at this point with mobile in situ operations at Mars. We know that you don't always find what you're looking for, you find something new and different to explore and that you need to build flexibility into your operational and exploration sequences to be able to adjust and adapt to the discoveries you make. We fully expect Titan to come up with surprises, and we have worked to make sure we have the flexibility in our exploration plan to be able to adjust as we learn new things about Titan.

Ken Hibbard: I think we're also working to build models and tools that facilitate the discovery nature that this mission has. We have a tool that we've developed, it's called DRAMPACT. I don't remember the acronym, but fundamentally it allows us to plan out the entire surface mission and then model it in hours to days depending upon the level of fidelity we want to go to. And so that can be updated almost real-time as you learn new information and then it can re-sequence your science activities and so you can feed into it which measurements you want to do, and then it compares that against the requirements that we're trying to satisfy aggregately over the lifetime of the mission and then allows you to replant it. So it allows us to very rapidly re-optimize the surface mission from making sure we're achieving the science perspective because we're very attuned to that's why we are going. I mean, it's going to be super cool flying on Titan and the engineers are really geeked out by all that, but we very much know that we're going for science and we respect that, and so we're trying to make sure that we can maximize the science return for the mission that we have.

Sarah Al-Ahmed: And this spacecraft is going to be powered by an RTG, so it's got nuclear power. We don't have to worry about it getting solar power, but that means necessarily it only has so much time to operate. How long do we think the optimal lifetime of the spacecraft will be?

Ken Hibbard: So Dragonfly's life is probably going to be driven more by the waste heat out of the MMRTG than the power. So just looking at the normal degradation curves of the RTG, we should get years beyond the proposed primary science mission, so we should be able to execute the whole science mission and go beyond that from a power perspective. The thermal output in the unique Titan environment is more uncertain, and so that is probably going to be more of the discriminator. There's no concerns that it should get us through the nominal mission and probably into multiple extended missions. It's how far beyond that is unknown.

Zibi Turtle: And then the nominal mission itself is a little over three years.

Bobby Braun: Yeah. I mean, it's a lot like the Mars Rover missions. So both Curiosity and Perseverance had RTGs or have RTGs. They were each designed for a baseline science mission and Curiosity has gone many times beyond that baseline science mission. Our baseline science is 3.3 years, Earth years. I wouldn't be surprised if this mission is not flying around for a decade.

Sarah Al-Ahmed: I mean, it is a New Frontiers class mission and as we've seen with all the others in that class, New Horizons, Juno, Osiris-Rex, now Osiris-Apex, you always get some really exciting new extended missions. So I'm hoping that this fits the pattern as well, and then we can do something even wackier with the future extended mission. Fingers crossed. But if we were to get an extended mission, is it conceivable that we might end up closer to those upper latitudes, maybe seeking out a pool of methane here or there?

Zibi Turtle: Yeah, so we're targeting three different types of, or materials with three different geologic histories, but Dragonfly actually has 40 landing sites at least. So there'll be a lot of different sites that we're exploring and we'll get measurements to really understand the diversity of the surface materials even in the region we're exploring. What we'll do in an extended mission really is going to depend on what we discover in the nominal mission and where the biggest questions lie that we'll be able to answer, and while it's thrilling to think about flying far north and dipping the skids in the edge of a methane lake, the range to the lakes is not really conducive to being able to get up to even the southern tip of Kraken Mare or something like that. It's really quite far away. I expect we would stay in the same region and explore other terrains nearby to the impact crater or study different aspects of the impact crater itself depending on what we learned in the first part of the mission.

Bobby Braun: Dragonfly has a tremendous science mission in its own right, but I think one of the legacies of this mission is going to be proving a nuclear-powered flying science platform to do planetary exploration. And so we will accomplish our baseline science mission, but one of the things that I'm excited about is all the platforms, all the aerial platforms, that this will enable. Just as Ingenuity has enabled the advancement of flight on Mars, this mission will do the same at Titan and perhaps elsewhere.

Sarah Al-Ahmed: Yeah, unfortunately we're limited by the number of worlds that have atmospheres, but that doesn't mean there aren't plenty of places we can drop one of these. Imagine trying to put one up in the atmosphere in Venus or something, although it's got to land at some point, so that might get a bit hairy.

Ken Hibbard: It doesn't necessarily have to land.

Sarah Al-Ahmed: I love that answer.

Ken Hibbard: You could do a different mission. That's an all-aerial platform and does science, particularly a Venus, just without ever touching the surface.

Bobby Braun: Yep. You could do the same at Mars, frankly. I've been on several proposal teams that have proposed just that to fly around on Mars and do science there without touching the surface. They were never selected for flight, but they were still great missions to be a part of.

Zibi Turtle: Yeah, long-lived aerial exploration has a great potential.

Ken Hibbard: Yeah, absolutely. I would also add that beyond advancing flight capabilities, I think we're going to make huge strides for different kinds of thermal environments and the exploration it can take place there. The fact that we are designing a system that will survive and conduct science in a cryogenic environment is absolutely transferable to other destinations in the Solar System, and so I'm hopeful that the advancements we make from a thermal perspective with our instrumentation, with our spacecraft accommodations, will feed into past efforts that NASA's done like COLDTech where we can take lessons learned from Dragonfly and feed it forward into other different thermal environments. And so flight is the obvious benefit of this mission, but I think we're going to touch into design aspects and engineering capabilities that will go far and beyond just the flight capability, and the thermal aspects are some of those.

Sarah Al-Ahmed: I wanted to ask a little bit about the weather conditions on Titan because we aren't going to be purposefully venturing near pools of methane, but it does rain liquid on this world, and I'm wondering what your team is trying to do to try to weatherproof this thing and if there's any concern that it might be in trouble if a big rainstorm comes by.

Zibi Turtle: Absolutely. Titan has a very dense atmosphere and it has a long day and a long year, and that combination means that there's a lot of inertia in the atmosphere and the weather systems are much more sluggish than what we're used to here on Earth. So we don't have these very large temperature gradients driving the kind of weather we have here on Earth. The day to night, winter to summer temperature variation at the surface of Titan is about a degree, compared to here in Maryland where yesterday it was 60 and today, this morning, it was in the lower 30s and there was snow on the ground. It's a very different environment in that context. There's just not the same degree of dynamics in terms of the weather. But that being said, there's absolutely weather. There are methane clouds. Cassini did observe evidence of methane rain. Cassini was in the Saturnian System for 13 years, so it's almost half a Titan year, and Cassini made observations of the weather patterns over that time and we could see that the weather systems follow the Subsolar point. So when Cassini arrived, it was late southern summer and all of the activity we saw in the atmosphere, Titan was at just above the south pole. It was several years after that before we started to see weather systems at the lower latitudes, and in fact, it was more than a year after the Vernal Equinox before we even saw a storm at 30 degrees south latitude. So when Dragonfly arrives again, it will be late southern summer and we expect most of the weather to be at the south pole, far from where Dragonfly is just north of the equator. We would expect it to be several years before one would predict rain at the latitude that we're exploring with Dragonfly. That being said, we all know you can't always predict the weather, and so Dragonfly absolutely has to be designed to be robust to weather systems, and so we have indeed done testing of different components to make sure that they are robust to getting rained on if it were to rain on Titan.

Ken Hibbard: Yeah, so we've done material testing to make sure all the materials are resilient to liquid methane. We should remind everybody the lander, it's coated in foam for thermal reasons, and so most of the components are internal and we have tortured paths. So even if it does rain, it's difficult for liquid to get in. Nonetheless, it is not hermetically sealed and so should liquid indeed get in, it actually sublimates pretty quickly. We don't think that it's going to persist in a liquid form and as soon as the storm, quote, unquote, passes, we expect that it would effectively evaporate and we've tested to make sure that that is not a concern from a safety perspective. It translates into something we have to watch from a thermal perspective because it will cool the lander much like the human body if you sweat and you cool off as it evaporates off your body. So our components would cool off, but that falls within the balance of the thermal ranges that we're designing to. And then the external components are equally resilient through the materials and component testing that we have done and continue to plan over the coming years. We plan on doing health checks prior to a flight, so we probably would not actively fly if it was raining at the time. So that is the safeguard we have in place. But in many ways it would be super exciting to actually experience rain on Titan. I mean, one, you're getting rain on another world, but because of the atmospheric differences and the gravity differences, it rains at a different rate. We have a microphone, we'd be able to listen to what it sounds like as the rain hits the exterior of the lander and just imagine how cool it would be to get that sound file back and actually listen to rain on Titan, and especially if it's a gentle storm, how slow it actually rains because of the gravity difference.

Zibi Turtle: Yeah, the raindrops fall at about the same speed that big snowflakes do here on Earth. It would be really spectacular to watch.

Ken Hibbard: Yeah, it's just something romantic about the idea of being able to listen to a rainstorm on Titan. So there's part of me that thinks that that would be really kind of a cool observation set to get at some point.

Sarah Al-Ahmed: I can already see the YouTube channels forming in my brain like, "Listen to Titan rain while you sleep." It would be amazing. I'm really excited to see what happens when you actually get to Selk Crater and see the aftermath of whatever happened there. If there was actually water that formed in this impact crater during that impact and then disappeared, what evidence might we find in that crater of that?

Zibi Turtle: So we know from models of impact cratering into targets that the energy deposited when the projectile hits the surface, a lot of that energy goes into melting and even vaporizing the target material, and of course the crust on Titan being made of water-ice, that impact melt will... At the Selk Crater, which is about 80 kilometers in diameter, so it's a good size crater. That impact melt will have been liquid water, and so there will have been a pool of liquid water on Titan's surface cooling over timescales of thousands of years, possibly longer. So what we want to study is the different chemistry there. What kinds of chemical components do we see there, how does that differ from the chemical components that we've seen previously in Dragonfly's exploration of the dunes and the interdune areas and finding places on the surface where there is exposed impact melt that may carry some of these chemical signatures and see how far that chemistry has progressed. It's going to be absolutely exciting. Fortunately, we have impact craters here on Earth, and so we can use those to understand the kind of distribution of materials after impact craters and use those to plan out observation strategies and exploration strategies.

Sarah Al-Ahmed: Before I let you all go, I wanted to ask which landing sites and what kind of terrain are you each most excited to go explore?

Zibi Turtle: Wow. That's a hard question. I mean, Titan is this alien world where the materials are all very different. The bedrock is water-ice and the rain is methane, and yet the landscape is so familiar. It's such a similar environment to Earth. So I'm really excited about all the places we're going to land, but in particular, being able to go beyond the horizon, to see what's out of the field of view of the Huygens Lander, that great scene that Huygens sent back from the surface, and I'm just really excited about all the things that we don't know that we're going to learn when we get there.

Bobby Braun: I'll throw in on that one. I'm most excited about the first landing site, because this team has worked so hard and they've worked for many, many years and they're going to continue to do so, and there's going to be something exceedingly special about landing on another ocean world for the first time. It'll be a milestone for humanity. I'm sure that that first site will have all kinds of scientific importance, but I think it'll be just a historically monumental event and one that I'm thinking about every day.

Ken Hibbard: Now, I guess Bobby took my answer. I'm super focused on arrival. I want to get there and know that the system flew for the first time, because you think about it, just we're going to be bundled up in an aeroshell for seven years, and then we're going to come and we're going to do a direct entry through the Titan atmosphere. It's like shooting a gun into a giant pillow, and so we got about two hours of a descent profile, and then we're going to have our lander literally free fall off the EDL back shell and transition into powered flight, which in many ways is recovering from a stall for a small aircraft, and it's then going to execute the first ever flight on an alien world of a vehicle of this size and this magnitude, and to know that that whole sequence executes and we safely arrived down on the surface. I'm going for the dunes and the first landing and seeing that whole sequence come together, and there's still part of me, we're a couple of years away from it, but there's still part of me who wants to figure out how to hide a GoPro somewhere on there to get an image of the first flight because I just think that would be spectacular and video that we would all cherish for a lifetime.

Sarah Al-Ahmed: I mean, we saw what that Perseverance landing did. The way that that video hit the internet, if it's at all possible to stick a little GoPro in there, I'm telling you it'll hit the internet like a ton of bricks. I would watch it over and over and cry.

Zibi Turtle: It'd be spectacular.

Sarah Al-Ahmed: Well, we do have to wait. It's going to be some years, but by the time this mission reaches Titan, it is going to be one of the most spectacular things humanity has ever done, and I don't think people are fully prepared. There's a lot of love for Mars and Venus and all these other worlds that we're intimately familiar with, but I think by the time Dragonfly is done with Titan, it's going to spawn a whole new era of sci-fi and movies, and suddenly everyone's favorite Moon is going to be Titan. That's what I think.

Ken Hibbard: I think we're right there with you. Titan is going to become the darling of the Solar System.

Sarah Al-Ahmed: Oh, I hope so. Well, good luck to all of you as you get toward this launch. You've got a few years, but you've got a lot on your plates before then, but I know you're all up for it because it's been spectacular so far. So when you actually get closer to that launch point, when the full mission is approved and ready to go, I would love you to all come back on and tell us about what that process has been like because I can't wait another bajillion years to talk about it. It's too cool.

Bobby Braun: It won't be that long.

Zibi Turtle: It won't. It'll go by fast, but it sounds great and we'll look forward to talking to you then.

Sarah Al-Ahmed: Awesome. Thanks so much everyone.

Zibi Turtle: Thank you.

Bobby Braun: Thank you.

Ken Hibbard: Our pleasure.

Zibi Turtle: Take care.

Sarah Al-Ahmed: So many of us are looking forward to the Dragonfly mission to Titan. In the event that Dragonfly doesn't get the approvals or the budget that it requires, rest assured The Planetary Society is already standing by to put our support behind the mission. We'll let you know how you can help us advocate. Go Dragonfly. Now let's check in with Bruce Betts, the Chief Scientist of The Planetary Society for What's Up? Hey, Bruce.

Bruce Betts: Hey, Sarah. How you doing today?

Sarah Al-Ahmed: Okay, so I feel like Dragonfly is a really cool and unique mission because there are so few bits of media in my brain that really allow me to understand what Titan is like. I know there's a good number of books about it, but as far as I know, the only thing in my brain that I can reference is Titan from Destiny 2.

Bruce Betts: Well, I mean, that's an entry point to learning about Titan. I shouldn't talk. I didn't make it past Destiny 1 and getting shot up on Mars.

Sarah Al-Ahmed: Still pretty sweet. I do like that you get the methane seas, that's pretty cool, but I feel like we need more imagery of Titan and more understanding so we can weave it into more pop culture so people understand how cool that world is. It's sweet.

Bruce Betts: It's really cool and weird because you got that thick atmosphere. The only moon with a thick... I mean, I'll state the obvious, the only moon with a thick atmosphere. The only atmosphere... Well, technically Triton with a thin atmosphere have nitrogen-dominated atmospheres like the Earth. It just happens to be really, really cold. You've got a whole fluid cycle with rain and dendritic patterns of rainfall carving things and lakes and seas and evaporation, and oh, by the way, the water's all ice and it's like a rock it's so cold, and so it's our fun friend. You mentioned methane along with some ethane, and methane and ethane on Earth is natural gas, and no, you wouldn't start a fire because there's no oxygen. that's usually the next question people ask me. But there are seas. There are cool seas, and it's all surrounded by this smog that makes it impossible to look through with typical visible imaging as Voyager found out. So we're dependent on so far on radar, carefully selected infrared bands and hopefully looking forward to getting on the surface and flying around. We also have the Huygens probe single image from the surface as well as descent. So it's a weird place. It's like, "Hey, that looks like Earth. That is not Earth. That is so not Earth."

Sarah Al-Ahmed: It's so strange though. I remember the look on my... Well, I remember the way I reacted when the Huygens probe went down and sent back those images from the surface. It's like we got so few shots and still to this day it's like there's no way that's real. We did that? We did that.

Bruce Betts: Yeah, amazing. And the shots coming down where they have, again, the rainfall pattern carved into the mountains, it was just hard to believe that that's what it was, but seemingly it probably is, and you've got the surface that looks like a bunch of rocks. Turns out those rocks are water-ice that's hard as a rock, and so it's also a very confusing single image because you have no scale. So the objects are generally smaller than one would imagine, and the little potion people that are... Well, actually you didn't see that version hopefully. Okay.

Sarah Al-Ahmed: They all hid behind the rocks the moment that the probe took the image. It is a bit of a bummer though that this mission might be delayed a little bit. I want to get there as soon as possible, and it's okay, we're going to get there, but I mean, what do you think are the biggest learning opportunities that we might be missing or be putting off as we're waiting for this mission to actually get to Titan?

Bruce Betts: Well, I think the most exciting thing is it's truly... Although we've been there in flybys and with a single atmospheric probe that made it to the ground, it is an exploration opportunity. I don't know. I mean, I'll tell you some things because I babble a lot, but we don't know what we're going to find because we have these very tricky... We have a lot of great data from Cassini, but it's very tricky in interpreting the radar data and infrared data and single points of data on the surface. So I think we'll get a lot of surprises, but basically the type of learning opportunity is to learn about this Titan equivalent of the hydrologic cycle on Earth, but it's not hydro, it's metho... I don't know what it is, but it's methane and ethane and how that interacts and what the variation in terrain looks like. I mean, it's like when you have one place on Earth. Because it's really varied terrain. I mean, it's not like you have vegetation, but you've got mountains, you've got plains, you've got seas, and so their ability to move around and show us, even though it'll be still a limited part of Titan, is a really exciting part of this, as well as of course, flying a giant drone on Titan, which is just inherently cool and terrifying. But if it works, it'll be awesome to get multiple sites that look different. So I think we're missing that ground truth, geologic evidence by and large, unlike Earth or even Mars where we've got a number of sites now, but still are lacking so much because of the limitations. And then the excitement. We're missing the thrill, the adventure. Sorry, I didn't mean to get enthusiastic. Back to you, Sarah.

Sarah Al-Ahmed: How dare you be enthused.

Bruce Betts: No, it's super cool, Titan. I'll just keep saying how nifty it is.

Sarah Al-Ahmed: I hope that when it actually happens that just the gravity of what we've accomplished actually hits people because people are familiar with Mars and Venus and all these other big-name planets, but I don't know if there's enough people that have that same passion for Titan that everyone will fully come to grips with how amazing it is when it happens. Maybe they will because flying a drone on another world is completely bonkers, but I hope. I really do.

Bruce Betts: I don't know what would get us out of this funk that you've put us in.

Sarah Al-Ahmed: I don't know, maybe something random.

Audio: Random facts!

Bruce Betts: All right, last week we talked about the International Space Station, it's 25th anniversary since its building, and I gave you some pretty standard information about launches and the like, but here's one I don't know if anyone's been weird enough to think about. Probably, but it came out of my head, which is you've probably... Maybe you've asked yourself, Sarah. What is the most common first name of people who've been to the International Space Station? Have you asked that? Has anyone asked that? Has everyone asked that?

Sarah Al-Ahmed: I mean, I have a really common name, so I do think about this sometimes, but not in the realm of the Space Station. Now I'm curious.

Bruce Betts: Yes, I have gone through the list of hundreds, pushing towards 300 different people who have gone to the Space Station either as crew or visiting, and I have an answer. We have a tie, but not really. So did you want to take any guesses? They're male names, to give you a hint.

Sarah Al-Ahmed: Yeah, it's probably probably a man, probably something really common like John or Matthew, or... I don't know.

Bruce Betts: Johns are popular. Matthews, not as much. James very popular, but it turns out it's one of the most popular names in the US, it is... Well, there are two, let tell you the two and then what breaks the tie. We've got the very common US name, actually much of the world in other permutations, of Michael, and then we have the very common Russian name Sergei. There are 10 Michaels and 10 Sergeis who have been to the International Space Station. But wait, don't order yet because Michael gets different permutations in different languages and is equivalent, I would say, people can debate that, with Mikhail. In Russian there are two Mikhails, so we have 10 Michaels, two Mikhails giving Michael-ish the victory over Sergei at 10.

Sarah Al-Ahmed: I think it counts as one nacho, just one bigger nacho. I think you're right. Michael wins.

Bruce Betts: Michael. Congratulations. So there you go. That is what I think is one of my truly more random random space facts.

Sarah Al-Ahmed: That is pretty random, but the next time I see a Michael on the ISS, I will know there's one more tick in the box.

Bruce Betts: It's probably all the people there right now are actually go by Michael. Hey, Michael. Hey, Michael. Hey, mike. Don't do that. Michael is what we're using. Okay.

Sarah Al-Ahmed: We're all going by Michael.

Bruce Betts: All right, fine. Mikhail, we'll cut you some slack.

Sarah Al-Ahmed: And then like 50 years we could do it again with the Lunar Gateway and see what the most popular name is. Then I bet the statistics will be a little different then.

Bruce Betts: Jennifer.

Sarah Al-Ahmed: Oh, wouldn't that be beautiful?

Bruce Betts: Sarah. It'll all be Sarahs. Everyone will change their name before going, men and women. Sarah.

Sarah Al-Ahmed: All of us. We are Sarah now.

Bruce Betts: See, you're moving on. Last week you were in someone else's cult, but Sarah. Sarah.

Sarah Al-Ahmed: Start my own cult on the Gateway. Here we go.

Bruce Betts: All right, everybody go out there. Look up the night sky, think about Sarah's cult. Thank you. Good night.

Sarah Al-Ahmed: We've reached the end of this week's episode of Planetary Radio, but we'll be back next week for a look back at all of the astounding feats of space exploration in 2023 with The Planetary Society team. You can help others discover the passion, beauty, and joy of space, science and exploration by leaving a review and a rating on platforms like Apple Podcasts or Spotify. Your feedback not only brightens our day, but helps other curious minds find they're placed in space through Planetary Radio. You can also send us your space, thoughts, questions, and poetry at our email at [email protected], or if you're a Planetary Society member, leave a comment in the Planetary Radio space in our member community app. If you're excited about the Dragonfly mission, let us know. I'll send your messages to the team. Planetary Radio is produced by The Planetary Society in Pasadena, California, and is made possible by our members who are willing to work decade after decade to build a future where flying space labs on other worlds are an actual thing. You can join us as we work together to make sure that missions like Dragonfly get the funding and support that they deserve. At Mark Hilverda and Rae Paoletta are our associate producers. Andrew Lucas is our audio editor. Josh Doyle composed our theme, which is arranged and performed by Pieter Schlosser. And until next week, ad astra.