Neptune Odyssey: why we need to visit an ice giant

Mat Kaplan: Building a path to Neptune this week on Planetary Radio.

Mat Kaplan: Welcome, I'm Mat Kaplan of The Planetary Society with more of the human adventure across our solar system and beyond. The Planetary Science and Astrobiology Decadal Survey recommendations for the next 10 years of exploration, will be released on April 19th. An enormous amount of work will have gone into this report, including the preparation of an ambitious concept study, titled Neptune Odyssey, a mission to the Neptune–Triton system. Though it may sound like one, it's not a mission proposal. Project engineer, Brenda Clyde and project scientist Kirby Runyon will join me in moments to explain and to help us understand why they and their international team hope the decadal will prioritize a trip like the one they describe. We'll also check on the night sky with Bruce Betts, the chief scientist has some cool random space facts to share, along with another great prize for the new space trivia contest.

Mat Kaplan: Yuri's Night is almost here. If you're hearing this episode soon after its release, you still have time to join the party, make that parties. The Planetary Society is once again a sponsor of the worldwide celebration of humans reaching space. Yuri's Night is a living expression of something Society CEO Bill Nye likes to say, "Space brings us together." Check the map at yurisnight.net to see if there's a gathering near you and to get tickets. I look forward to talking with many of the great guests who will be under Space Shuttle Endeavor at Los Angeles's California Science Center on the evening of Saturday, April 9th. A lot of my Planetary Society colleagues will also be there, that's yurisnight.net for the LA and all the other parties.

Mat Kaplan: Does that Pluto image that tops the April 1 edition of the down link look a little duller than some? It's not an April fool's joke, it's Pluto without the false color enhancements that reveal more about this world, I don't think it's any less spectacular. You'll find it at planetary.org/downlink along with these headlines, the Hubble Space Telescope has detected the light of a star, a single star that radiated outward more than 13 billion years ago. That makes it the farthest and oldest individual star ever seen.

Mat Kaplan: Don't count out the European Space Agency's ExoMars mission just yet. ESA says it will consider other partners after it lost its ride on a Russian booster. The Rosalind Franklin rover will go into safe storage at a corporate site in Italy while the search continues.

Mat Kaplan: We heard a quick overview of NASA's new budget request last week when Casey Dreier stopped by, Casey, Brendan Curry and I will go much deeper in the April Space Policy Edition of Planetary Radio, watch for it in your podcast feed on Friday, April 8th.

Mat Kaplan: Brenda Clyde and Kirby Runyon have a lot in common, they both work for the Johns Hopkins University Applied Physics Lab where both contributed to the New Horizons mission and many other projects. Brenda is part of the principal professional staff at APL while Kirby is a senior research scientist. If you stay till the end of my conversation with them, you'll learn that Kirby also has had a long, long relationship with a certain podcast and public radio series about space exploration. They joined me online a couple of days ago.

Mat Kaplan: Brenda and Kirby, welcome to Planetary Radio, I am so glad that you are here to talk to us, not just about this concept study that you helped to lead, but about this whole process which is going to reach climax in just a few days, as people are hearing this. Welcome, first of all.

Kirby Runyon: Thanks so much. I'm excited to be here Mat.

Brenda Clyde: Thanks for having us.

Mat Kaplan: I was hoping that the Planetary Science and Astrobiology Decadal Survey covering the next 10 years of NASA work in space, would be released before our conversation, but we learned last week that it's not going to become public until, I think the date is April 19th. There are a lot of hopes and maybe even careers riding on this big, influential release, aren't there?

Brenda Clyde: Yes, I believe that's true.

Kirby Runyon: Yeah.

Mat Kaplan: What is a planetary decadal mission concept study, which is what you have submitted with this concept called Neptune Odyssey?

Brenda Clyde: The decadal studies come out roughly every 10 years, they're not quite perfectly on the decadal. What they are is they're a place where NASA reaches out to the community to find out what the community thinks is important for planetary studies, astrobiology studies, going forward to give NASA guidance on where it should invest its money and plan for the future, to get the best science return.

Mat Kaplan: We have talked about decadal studies, I mean, we just had the astrophysics decadal released not too many weeks ago. These really are, I mean, I use the word influential, that's right isn't it, Kirby?

Kirby Runyon: Yeah, these are absolutely influential. I mean, I think Casey Dreier has probably been on the space policy version of this podcast, talking about how that's the guidebook, or maybe like the Bible for NASA for the next 10 years. Not that NASA is legally obligated to follow it, but the decadal surveys really get the will of the people in the community and are very influential at the level of the National Academies of Sciences and also very influential in Congress. These really have a very strong effect in guiding what kinds of missions get flown, what kinds of research get funded, really at the top level. And then how that trickles down into individual research grants, individual groups of scientists might want to lead. It's a very influential document, really guiding exploration of the solar system for the next 10 years.

Mat Kaplan: I read that there were 11 concept studies selected for development. This was back in 2019, so this is not something you've just spent a few weeks working on, since your project is one of these. I found nine of the resulting papers in The Planetary Science Journal, and we will put up a link to that because they're all open access, people can take a look at them. We'll put that on this week's show page of planetary.org/radio. Quite a variety there, two each for Ceres and Mars, a Pluto orbiter, a Mercury Lander, a Lunar Geophysical Network, the Orbilander concept, which is an orbiter and a lander for Enceladus, which is something that's been mentioned in at least one previous episode of our show. And then there's this study that you two are part of, Neptune Odyssey. How did this get started? When did you become involved in it? Brenda, I'll go to you first.

Brenda Clyde: Well, whenever NASA does the decadals, they try to pair concepts with what they call design labs. APL is one of their design labs that they use so they reached out to us. We actually did more than just the Neptune Odyssey, we had two other decadal studies that we worked on at the same time. Then we put together a team of scientists and engineers to go through and develop what we call a point design that allows us to prove that a mission is possible, and that it reasonably closes to achieve the science that the community is interested in.

Mat Kaplan: Kirby, how did you get involved?

Kirby Runyon: Back in 2018 or 2019, NASA put out a solicitation for proposals, to propose to do a mission concept study. And the PI the principal investigator for this report, Dr. Abi Rymer, put in a proposal with quite a number of us on the team, not just at APL, but really around the country from different institutions. Fortunately our concept study was selected for funding from NASA to look into what it would take to send an orbiter to the Neptune system. I have a background working on New Horizons during the Pluto and [Erikof 00:08:37] flybys. And I worked very closely with Abi, becoming the project scientist, this interface a little bit between the science and the engineering teams, working with Abi and Brenda on this project. We were selected end of 2019, going into 2020, and we started doing things in person and then of course the pandemic hit, and so the vast majority of the study got done from our bedrooms and dens with pets roaming around.

Mat Kaplan: Such is life, right, in this part of the 21st century? And by the way, Abi, who was unable to join us today, I'm told that she's still putting in some time at NASA headquarters right now. We sent our regards to her and she was thrilled to know that the two of you would be joining us on the show today. We've heard from so many guests who want to see a mission to one or both of our solar neighborhood's ice giants, and that's exactly of course what is written about here in this study. It bears repeating, why is it so important that we return to one or both of these worlds, Uranus and Neptune, that have only been visited really once ever by spacecraft? And that was of course by Voyager.

Kirby Runyon: Yeah, that's right. You hit the nail on the head right there Mat, it's because we've only been visited each of these planets, Uranus and Neptune, once, and it was just with a flyby. And Voyager 2, for its time, especially was a very capable spacecraft, and the science we got at Uranus and Neptune is revolutionary, but the science you can get with just a quick flyby is certainly not the level you can get if you hang out in the neighborhood for a long time and do multiple orbits, and image things from different perspectives, and fly through different parts of the magnetic field. And maybe even observe some small seasonal changes while you spend time looking for changes on the surfaces of Triton or the moons, or in the atmosphere, or changes in the rings, that would be exciting to see as well.

Kirby Runyon: We've had an orbiter at a dwarf planet, at Ceres, that's already happened, and so really the ice giants are the last category of planet that has never had an orbiter. Our exploration of the solar system is far from complete until we are able to get the type of data that you can only get from an orbiter mission. I'll also add that many, many of the exoplanets that we're discovering around other stars, tend to be in this Uranus to Neptune mass regime. By understanding ice giant planets in our own solar system, we can use them as analogs or analogous to the similarly massed exoplanets around other stars, and then really have a better, more broad, general understanding of planets in general. Understanding planetary systems not just as they are in our own solar system, but understanding planets in general, around the galaxy and cosmos.

Mat Kaplan: That's such an important point and one that has been made several times on Planetary Radio. You already indicated that this is much broader than studying the planet itself, you've got those thin rings that are worthy of exploration, a whole bunch of moons, but one in particular that you haven't mentioned yet, Triton right?

Kirby Runyon: That's right. Triton is one of my favorite places in the solar system. It is a captured dwarf planet from the Kuiper Belt. It is the only large moon in the solar system that orbits its primary planet backwards with regards to the primary planet's rotation direction. That combined with its eccentric orbit is a dead ringer that it did not form with Neptune, that it was captured into orbit at some point in the solar system's past. It in some ways, is like a big sister to Pluto. It's twice as massive, but it's just a little bit larger. It's roughly the same distance from the sun as Pluto, about 30 astronomical units, or about 3 billion miles, 5 billion kilometers.

Kirby Runyon: We think its surface composition is the same. Voyager did not have an imaging spectrometer on board, so we don't have as good of compositional information on the surface of Triton that we do from New Horizons at Pluto, but from Earth-based spectroscopy we've got nitrogen, methane, carbon monoxide, water on the surface of Triton. And the way the geology manifests on Triton, even though it's at the same distance from the sun, roughly as Pluto, and we think made out of the same things, the way the geology manifests is very different from Pluto. It's its own exotic little planet, orbiting a giant planet that's worthy of study. As a planetary geologist, personally, who uses images of other planetary surfaces to do his science, I'm really excited just thinking about further exploration of Triton.

Mat Kaplan: It's a nice opportunity to study a Kuiper Belt object without having to go as far as New Horizons did, one of many successful missions to come out of APL.

Kirby Runyon: That's right, yeah. Actually it is traveling about as far. At the time of the New Horizons flyby of Pluto, Pluto and Neptune are roughly the same distance from the sun, so we got to go the same distance as New Horizons went, basically, but we have to slow down to go into orbit with a much larger and more capable spacecraft. Not to take away from New Horizons, but it is a small little spacecraft and our mission concept spacecraft is quite a bit beefier.

Mat Kaplan: I want to pick up on that exact point. This is a flagship mission, the one that you have developed this concept for, and we also have to explore what we mean by a concept study a little bit further. And make sure people understand this is not a mission proposal, this is not going to NASA and say, "Hey, give us several billion dollars to build this flagship mission." When I look at what you've come up with, Brenda, you and the engineering team, and the scientists you've been working with, it's very impressive. I think I see some heritage there because it looks like, well, I'll let you say if I'm right about that, but I do see some resemblance to very successful missions of the past, maybe one in particular. Is this just an example of form following function?

Brenda Clyde: It does have some similarities to previous missions, but this was designed quite a bit differently to try to take advantage of certainly some differences in power, because NASA is working on refining its nuclear power systems. We were hoping to actually use the Next-Gen RTGs, but timing of that and when we would want to fly a mission like this, may or may not work out that you would be able to do that. A lot of what was done here was really constrained by a couple of things. It was constrained by power.

Brenda Clyde: The real thing we were trying to get was lift mass such that we weren't constrained on our launch windows. We really worked hard to find a mission design that would allow us to use a launch vehicle that we have today without having to be constrained with planetary flybys and very limited launch windows for doing that. We've come up with a unique mission design capability, and then we worked to refine the mass on the spacecraft to be able to make it fit, right? The launch window constraint, as well as having sufficient power when we wanted to do the tour, were our two big driving constraints.

Mat Kaplan: The answer to this next question may be obvious, but flagships of course, easily the most expensive class of planetary science missions, always well over a billion dollars. Why was it important in this case? And this is for either of you, to have a flagship that has just this wonderful collection of instruments attached to it, rather than a smaller, less expensive New Frontiers or Discovery mission, like well, New Horizons?

Brenda Clyde: One aspect of that is because we really wanted to do science for all, right? If you're going to do a flagship mission or a mission to the outer planets and to the ice giants, this is a long mission, you're talking multiple decades of work. You're going to have a multi-generational team, the science and stuff is going to be dynamic and changing, so doing a flagship offers you a lot more to be able to do that over the long periods of time that we're talking about, and in a changing environment.

Kirby Runyon: Brenda, you really said something key there, that this is a mission for everybody, and our science team was very multidisciplinary. I'll speak for the planetary geologists first, but we had the imagers and imaging spectrometers on board to really study Triton and the other moons, especially Proteus. Proteus is a prominent small moon of Neptune, but we had atmospheric scientists [Kunio Sayanagi 00:17:20] down in Virginia led the effort on a lot of the atmospheric science for studying Neptune, studying the deep interior. I mean, this concept has an atmospheric probe that would detach from the orbiter and enter into Neptune's atmosphere on the way in.

Kirby Runyon: We also had planetary scientists who study planetary rings, Neptune has these enigmatic ring arcs that they don't seem to be complete rings around the planet, we'd like to understand what's going on with that. And we also had space physicists to study Neptune's very strange, off-center, my grandma would say [squidge odd 00:17:52] magnetic field around the planet. Studying also how Neptune's magnetic field and atmosphere interact with the solar wind. There are ultraviolet auroras, ultraviolet Northern and Southern lights around Neptune. We'd like to understand how the dynamo inside Neptune works, how it's magnetosphere works.

Kirby Runyon: It's not just Triton or the planet, it's really the whole Neptune system, the entire space environment from where Neptune's magnetic field first encounters the solar wind. Depending on how the orbit around Neptune works from the spacecraft, we could fly down the tail a little bit maybe of the magnetosphere and look at turbulent eddies in the magnetic field and the plasma environment. Which I know nothing about because I'm just a planetary geologist, and...

Mat Kaplan: But you're a fan.

Kirby Runyon: I'm a fan. I'm a fan. Yeah. All the space physics I know, I picked up on the street. It's really a broad multidisciplinary mission, and that's why it has to be flagship is because it's hard to get to Neptune, it takes a really long time to get to Neptune, so you want to do as much as you can while you're there.

Mat Kaplan: I was so pleased when I saw the website for this study, a Neptune Odyssey. And first of all, it's a beautiful website and you have a terrific animation. And again, we'll put a link to that on this week's show page planetary.org/radio [crosstalk 00:19:13].

Kirby Runyon: I want to give a call out to [Mike Yakaflaf 00:19:14] who made that beautiful animation, Mike Yakaflaf in our comms department at NPL.

Mat Kaplan: Good, kudos there, well deserved, it really is beautiful. One of the things that I love seeing though, really warm my heart because Margaret Kivelson, the pioneering astrophysicist, was our guest on the show just two weeks before this. And when I saw that long boom with the magnetometer out there, I knew Margaret would have to be pleased when she saw this study. You really are in very good company, I mean, you've talked about the team that's been put together. It's kind of a who's who of planetary science and to a large degree, these other fields that you've talked about, with the two of you and Abi up there leading the way, I suppose. But it must be a point of pride to have so many terrific people, many of whom, who've been guests on this show.

Kirby Runyon: It's certainly humbling to be around so many smart and accomplished people. You mentioned Margaret and that magnetometer boom, one of the reasons we want to fly that is not just to study the magnetic field around Neptune, but also to study the induced or any intrinsic magnetic field around Triton. Because we have a lot of reason to believe that Triton is an ocean world with a subterranean liquid water ocean, that is probably habitable, that's not the same thing as being inhabited, but I believe that Margaret was instrumental in discovering that induced field around Europa, if I'm not mistaken.

Mat Kaplan: Yes, absolutely.

Kirby Runyon: This is where the astrobiology and the habitability comes in, of understanding Triton as a potentially habitable ocean world. And indeed not just Triton, but Triton as somewhat of an analog for other Kuiper Belt dwarf planets, the most common type of planet in the solar system. A lot of these small little planets probably could've started off being at least somewhat habitable in the first half billion to billion years of the solar system's history. Understanding this interaction between ice, water and rock, three plus billion miles from the sun, is really important and really exciting.

Mat Kaplan: I'll be right back with Brenda Clyde and Kirby Runyon, after we hear a few words from the boss.

Bill Nye: Greetings all, Bill Nye here. Missions of discovery are underway right now thanks to The Planetary Society, the world's largest independent space advocacy organization. Now is the time to join our space advocacy network to keep NASA's planetary science going strong, help us fight for missions that mater. First visit planetary.org/takeaction to make your donations. Right now your gift will be doubled thanks to a generous member. US residents can also sign the petition, asking your representatives to support space science and exploration. With your backing, we'll keep advocating for space. Please go to planetary.org/takeaction today. Thank you.

Mat Kaplan: I've mentioned the website and some other stuff, but there is the complete study, which is also available for folks to read and we'll link to that as well. Brenda, as this was being put together, from the engineering standpoint, is it going to require big, new technologies or approaches, or is this... Because the comparisons to Cassini, I think are obvious, it seems like such a similar mission in many ways, does the success of that mission... Did that basically prepare you for this?

Brenda Clyde: There are some interesting things that we leverage... Like the probe for instance, is very much leveraged from Cassini. We learned a lot from the Cassini probe, but there will be some different challenges entering into the system with Neptune. We have solutions that we believe will work, but they're going to require further study. The big thing that is going to probably be an improvement over Cassini, is going to be the power, right? We will have a lot more power for a longer period of time. The other thing that was a particular challenge and was somewhat different than what Cassini was doing, the mission design for the orbit and the tour between Triton and Neptune. Trying to manage the launch of the probe as you're going in and getting captured into orbit, working the orbits to get far enough into the atmosphere to be able to take the necessary measurements and to make sure that you're getting the correct science from both Neptune and Triton. That was probably the most challenging piece of this and the place where new approaches to things had to be done.

Brenda Clyde: The other place in the early part of the mission design, coming out, we do some interesting things to give us the opportunity to lift a little bit more mass with a standard vehicle, in terms of being able to open up those launch windows and being able to launch pretty much any time, rather than being limited to very, very narrow windows.

Kirby Runyon: You mentioned the orbital insertion and delivering the probe, and that's a really exciting time/terrifying time in the mission concept, because after a 16 year long cruise from Earth to Neptune, with we don't even need gravity assist along the way, we can go straight there. All of a sudden you have to thread this needle, as I recall, between the rings and the planet, drop off the probe. The probe has to enter the atmosphere, take its measurements, broadcast back to the orbiter before the orbiter has even burned its engine to slow down to go into orbit. The orbiter has to receive the radio signal from the probe before the probe gets destroyed, stored on board.

Kirby Runyon: The probe then gets down to a certain altitude where the orbiter has gone below the horizon and also then gets crushed by Neptune's atmosphere. Then the orbiter has to burn its engine, go into a very long capture orbit that's many months long, and then broadcast the information back to Earth. Then we use Triton to shape the whole orbital tour around Neptune in a very similar way, at least on paper, to how Cassini used Titans gravity to shape its orbit around Saturn. It is a very complicated, not just orbital dance, but getting all the spacecraft systems to work at the right time, while we're collecting science.

Mat Kaplan: You still want to take this on after all that, Brenda?

Brenda Clyde: Of course, I love a good challenge.

Mat Kaplan: Of course. When you talk about a direct route, what are we talking about as a vehicle? What are you proposing if there's a mission like this that is actually funded someday? Are we talking Falcon Heavy or are-

Brenda Clyde: We've got two choices, you could do an SLS Block 2, or you could do a Falcon Heavy. With the SLS Block 2 we would use a Centaur upper stage to give us some extra kick. We would still need an extra kick if we used a Falcon Heavy, but it would be a little bit different because the two systems are not necessarily compatible, they're fueled a little bit differently and stuff. But either way we would be able to do a direct to Neptune.

Brenda Clyde: When the study was commissioned, the goal was to try to get there in 20 years, we're right at the edge of that. We get there right around at 20 years, doing the direct the way we want to do it. In order to get a little bit of extra mass, there are a couple of places where we optimized the mission design to be able to carry a little bit more fuel and things. Like I said, it's a point design that should close, but there's probably still a lot that can be done to optimize it and make it better. Right now the spacecraft design as it is, is about 3,800 kilograms, so that's how much lift we would need, that's wet.

Mat Kaplan: Wet, in other words, fully loaded with all its propellant and other consumables.

Brenda Clyde: Yep.

Mat Kaplan: Yeah. At least you have these choices of vehicles that were not available to previous missions like Cassini, and you can take full advantage of them.

Kirby Runyon: And I'll mention with the strong capability with the SLS or the Falcon Heavy, without having to do a Jupiter gravity assist, that frees us up to launch any year. You don't have to literally wait for the planets to align, to do this mission, so this is a fly any time mission concept.

Mat Kaplan: Which is great. You already mentioned this will obviously, over the time span that you're talking about, be a multi-generational mission. I mean, once you get there, let's all hope that a mission like this, if it happens, will have the kind of lifetime that Cassini enjoyed at Saturn. You're both in good shape, you might be around through the end of something like this, but really this is something that you address in the concept study as well. That, at some point, a lot of this work is going to have to be handed on to another generation.

Kirby Runyon: Princeton sociologist, Janet Vertesi was on the team. We're planetary scientists, she is a scientist who studies planetary scientists and understands the teaming in that, and even how people use their bodies to refer to different components of the spacecraft, they anthropomorphize the space robots, if you will. We have planned obsolescence in terms of the people in this team. I mean you can create a culture with traditions and ceremonies even, of passing knowledge, of having certain staffed positions on the mission that are only for X number of years, and everybody has an understudy under them, learning with them as they go along.

Kirby Runyon: The Voyager missions have been lasting for over 45 years and some of the team members are the original team members, and that's fine. Voyager accidentally lasted this long, this mission is designed to last pushing 30 years or so, very long lived mission. You cannot assume that everyone is necessarily going to be around at a later point in the mission. You need that continuity of corporate knowledge, and a lot of this stuff is tacit knowledge. It's experience, it's remembering the hallway conversation, stuff you can't capture, even in a Slack thread. It's the culture, it's how you handle your team meetings, it's giving a voice to early career scientists and having a culture where, maybe at a team meeting.

Kirby Runyon: This is something that Janet has done for another mission concept we've done, Interstellar Probe, where in a workshop you say, "Okay, anyone within the first five or 10 years of their career, you're the only ones allowed to ask questions right now." And that way it forces the more senior scientists to give a chance to the younger crowd and to embolden the early career people to be able to grow into being leaders.

Brenda Clyde: I will say this, even though you said I'm in good shape, I would be 88 when it got there if it launched in 2030 as we proposed, so I won't be in that good a shape then.

Mat Kaplan: Yeah well, join the club. But I wonder, everything that Kirby just said about the science side, mainly the science side, do you see this on the engineering side as well? I mean, you must have newbie engineers out there, not long out of school, who are pretty thrilled that they might be carrying this torch?

Brenda Clyde: Yeah, we do. The interesting thing on the engineering side that we struggle with a lot of times too, is getting people... These long duration missions, it's very hard for them to get a cradle to grave view of the engineering that goes into it. We like to mix, for our engineering staff, we like to put them on these long, big missions, but we also like to put them on smaller, quicker turn missions, where they can see the entire lifespan of the engineering. Because I was an engineer on the New Horizons mission before it launched, so I got to see all of the engineering, plus I was able to still be around when it got to Pluto, right? But there were a lot of engineers that didn't get to see that. They worked on the engineering part, saw it launch and then have either moved on or passed on. It's an interesting thing because some of the engineers tend to want to see cradle to grave, and these kinds of missions are hard to do that, they only get to see certain aspects of it.

Mat Kaplan: Of course, we're getting ahead of ourselves here, we got to get through this decadal release, first of all. And every one of the proposals that I mentioned, the nine that I was able to find, every one of these deserves its time in the sun, shall we say? But let's say that we come out, it comes out on April 19th, and it does say that up near the top, or maybe the top priority is a mission that could look like Neptune Odyssey, then what? What comes next? Will APL pursue this?

Brenda Clyde: APL may very well pursue it. One of the things that we've learned over the years with the decadals too, is something that's proposed in the decadal often will morph and become other types of missions. What you may see is a scaled back version of this that gets put in as New Frontiers or a Discovery class mission. There are a lot of options for where this might end up going. You may also see this stretched out and not done as part of this decadal, but maybe started under this decadal and then continued under the next. It's really up for NASA to decide at what level they would want to do a mission like this, and then as well, how they might approach it, or even combine it with other opportunities.

Mat Kaplan: Kirby, if you want to be in planetary science, it really helps to be able to play the long game, doesn't it?

Kirby Runyon: Yeah. I'm an impatient person by nature, and ironically, I chose a career path that forces patience. That's the only way to do it. I'm dying to see what the other hemisphere of Triton looks like that Voyager never got to image. I'd love to know more, I'd love some other pictures of Neptune than just what Voyager got back in 1989. I really want to explore the planets and see what's out there, and this is the only way to do it.

Mat Kaplan: Folks, I wish you great luck, at least in terms of the influence that this study may have on the decadal. I would wish the same to any of those other teams, but as I've said many times, we have talked to a lot of people on this show who want to see a mission to the ice giants and I'm one of those. Thank you so much for taking us through this study. I hope that there is good news for you folks and the entire team when that decadal comes out in less than two weeks, as people hear this.

Brenda Clyde: Thank you for having us.

Mat Kaplan: Kirby, I got to ask you one more question and it's loaded. When did you first become affiliated with this show or at least at the listener level?

Kirby Runyon: I think I go back close to the beginning of this show. I was in high school or early college. Were you guys doing this in 2003, 2004?

Mat Kaplan: We had just started, we got our start in late 2002 and that's when I think I started hearing from you.

Kirby Runyon: Yeah, that's around the same time, I've been listening to this show all that time. It's quite an honor to be on here, Mat. I remember when you and I got to meet for the first time, I was a little bit of a fanboy to be honest. I had some business at Caltech in 2013, and I remember you and I met up at Planetary Society Headquarters. Yeah, this is my go-to podcast to listen to, so it's fun to be on the other end of the mic right now.

Kirby Runyon: But with The Planetary Society, I got started in the late 90s when I was helping to advocate as a middle schooler, for New Horizons. I sent in a $15 check to The Planetary Society and I called my congressman and said that the New Horizons mission just had to go forward, it's too important not to. Now I'm working on New Horizons itself, and I was there for the Pluto flyby. It's been an incredible planetary journey and I hope there's a lot more exploration still to go.

Mat Kaplan: Now here I was fishing for just a selfish little compliment, and you delivered so much with that little speech there. Thank you so much, Kirby.

Kirby Runyon: My pleasure.

Mat Kaplan: And I am just delighted that we have been crossing paths for so many years. And now I'm the fanboy for people like the two of you and your team, and everybody out there who's doing the work that we dedicate this show to. Brenda, not required to have been a almost 20 year listener to Planetary Radio, but again, delightful talking to you as well. And thanks for all your great work.

Brenda Clyde: Appreciate it, thank you.

Mat Kaplan: Time for What's Up on Planetary Radio. The chief scientist of The Planetary Society is here with us. That is Dr. Bruce Betts. Welcome. We have from [Keith Landa 00:35:27], he looked it up, Gilligan's Island season two, episode four, Smile You're on Mars Camera. Tells you what happened in the episode. I'd forgotten some of the details like the professor tried to make glue out of tree sap to glue the lens for the probe back together, hilarity ensues.

Bruce Betts: It's truly one of the most realistic depictions of a space probe that's ever been committed to the small screen or the large screen. We talked about that last week, by the way, for those who might be wondering why we started with Gilligan's Island.

Mat Kaplan: How dare you miss our discussion of the Gilligan's Island last week?

Bruce Betts: [crosstalk 00:36:12] I'm sure no one missed it.

Mat Kaplan: I am glad you're here for our discussion this week, beginning with what's up in the night sky?

Bruce Betts: All right, there in the pre dawn sky, you got those three planets hanging out. Low in the East you got super bright Venus and then to its upper right, you'll see reddish Mars and yellowish Saturn, which is now passing Mars and heading farther to the upper right. Mars varies a lot in brightness, but right now it's about the same brightness as Saturn, making for a neat view. Of course, Venus is just ridiculously bright and it's kind of obnoxious, but that's another story.

Bruce Betts: Oh, I wanted to mention one other thing, this solar activity, I don't mention the sun very often, because I always have to then say, "Hey, don't look at the sun or you'll fry your eyes out. Don't look at the sun with just sunglasses or anything other than appropriate solar filters," but if you look at the sun with a telescope these days, with an appropriate solar filter, you'll be seeing sun spots more and more as we go deeper into this new solar cycle.

Mat Kaplan: The big telescope I have, I don't have a sun filter for it. I may have to drag out the smaller telescope that has a big solar filter I can put over the lens. And now I'm intrigued, I may need to do this.

Bruce Betts: We move on to this week in space history, it was this week in 1961, that Yuri Gagarin became the first human in space. 1970, Apollo 13 was launched, they came back, they were safe. 2001, Mat, Mars Odyssey launched. Mars Odyssey is still working, odyssey around Mars. Let us go onto random space fact, random space fact.

Mat Kaplan: 19 and a half years, don't start forgetting now.

Bruce Betts: I'll try not to. This is a simple one, but I think it's good to be reminded occasionally, especially as we find more of these things, that the solar system's planets, just the planets, not counting asteroids or dwarf planets, just the planets have more than 200 moons. 207 and counting, depending on details of what you consider a moon.

Mat Kaplan: Hardly seems fair that we only have one, but then there's Venus to make us feel better.

Bruce Betts: Venus, you got no moon.

Mat Kaplan: No moons ha ha.

Bruce Betts: And we got the coolest moon, it's the moon. We go onto the trivia contest. The question I asked you, as opposed to the question I meant to ask you, was what was the first ESA, European Space Agency mission to use ion propulsion? A valid and intriguing question of which we got great answers, and I learned things from our listeners.

Mat Kaplan: Well, there was a cavalcade of errors here. I made an error when I listed the question on the entry page at planetary.org, all I said was, "What was the first European Space Agency to use ion or electric propulsion?" Well, it was the European Space Agency, as Bruce pointed out a few minutes ago. It turns out, I mean, what answer were you looking for?

Bruce Betts: What I meant to say was, beyond the Earth, and I was thinking it was SMART-1. And anyway, what I asked was the first ESA mission to use ion propulsion and hey, I learned stuff. Thank you, listeners.

Mat Kaplan: [Devin O'Rourke 00:39:43], he's a long time listener, first time winner, as far as I could tell. Devin is in Colorado, he said Eureca.

Bruce Betts: Eureka.

Mat Kaplan: E-U-R-E-C-A, which is short for European Retrievable Carrier. I brought this up with Bruce and you looked it up and looks like this is correct, right?

Bruce Betts: It does seem to be correct. It actually beat the other entries that you may discuss, by many years. In 1992 was the launch, '93, fascinating mission.

Mat Kaplan: A whole bunch of experiments were loaded onto this bus and it was delivered by a space shuttle and then brought back down to Earth, right?

Bruce Betts: By a different space shuttle after being exposed to the space environment for over a year. Then they saw what happened, they had a lot of experiments on board. It was huge, as you say, a bus is used in the technical term, but it was about the mass of a bus, 5,000 kilograms, so 1,000 times more massive than our LightSail 2 spacecraft, a random space fact of interest.

Mat Kaplan: I was going to say, a nice little extra random space fact bonus there. Devin, congratulations, you not only got it right, you taught us something. And for your trouble, we're going to send you that Planetary Society, your place in space, t-shirt from Chop Shop. Then you can take a look at it and all the other great Planetary Society merch at chopshopstore.com. About those other answers, there was a second spacecraft that ESA put up there in Earth orbit, not outside of Earth orbit, called Artemis, a telecom satellite.

Mat Kaplan: And that inspired [Gene Lewin 00:41:30] in Washington to create this poem. Certain types of energy drinks are said to give you wings, but wings within the depths of space are really not a thing. To elevate to distant heights you're going to need thrust, and if on launch, you just fall short, the mission could be bust. But when you pack an ion engine, not intended for a boost, you just may reach the altitude where you first were meant to roost. So ESA in 2001, employed a nifty trick and placed Artemis electrically, the problem thus was licked.

Bruce Betts: Impressive.

Mat Kaplan: And here from our poet laureate, [Dave Fairchild 00:42:08] in Kansas is one that honors SMART-1, the one that we all thought was going to be the correct answer. If you want it well done, and you know you are a SMART-1, then the answer to the trivia is very plain to see. Once the Ariane was flying, there could be no more denying that the Xenon and the thruster was an ion strategy. ESA launched it up to Luna, though it got there not as soon-a as it would if a rocket of the normal type had flown, then it curved from the ecliptic into [peralune 00:42:40] elliptic and the mission proof the concept that Smart-1 could fly alone.

Bruce Betts: Soon-a

Mat Kaplan: I love it. That was my favorite, though it got there not as soon-a.

Bruce Betts: Wait, isn't that a person from Oklahoma?

Mat Kaplan: Soon-a? Yeah.

Bruce Betts: Oh wow, I'm on fire with my humor today.

Mat Kaplan: Thank you everybody for providing these great answers for us. We're going to give you another opportunity right now.

Bruce Betts: Back to moons of planets. If you alphabetize the named moons of planets in our solar system, what moon is last? Go to planetary.org/radiocontest. Oh, and it's the English alphabet we're using.

Mat Kaplan: Ah, good point. You have until April 13, that would be 8:00 AM on Wednesday, April 13, to get us this answer. And here is that Chop Shop prize package. It is The Planetary Society's very own Kick Asteroid!, it's a whole set of stuff. An 18 by 24 screen print, a pin and four Kick Asteroid! stickers. As far as I'm concerned, it'd be worth it for the beautiful poster alone, that is about a $45 value. It's just marvelous. Get out there and kick some asteroid with us and we wish you good luck.

Bruce Betts: That's a really cool package, I love those things. All right, everybody, go out there, look up the night sky and think about the next bird you tweet, what is it saying to you? Thank you and good night.

Mat Kaplan: Is that you?

Bruce Betts: Yes. It's a hidden talent.

Mat Kaplan: That's Bruce who's actually tweeting at us right there. If you want to catch his tweets elsewhere, it's @RandomSpaceFact, right?

Bruce Betts: Yes, it is.

Mat Kaplan: Just like I'm @PlanRad, although I don't tweet nearly as often or well as the chief scientist of The Planetary Society, Bruce Betts, 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 ice giant loving members. You can become as cool and blue as them when you visit planetary.org/join. Mark Hilverda and Rae Paoletta are our associate producers. Josh Doyle composed our theme, which is arranged and performed by Pieter Schlosser. Ad astra.