Planetary Radio • Dec 23, 2020

Astronaut Stephanie Wilson Might Walk on the Moon

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Stephanie Wilson

NASA astronaut chosen for the Artemis Team

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Linda Spilker

Voyager Mission Project Scientist at NASA's Jet Propulsion Laboratory

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Bruce Betts

Chief Scientist / LightSail Program Manager for The Planetary Society

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Mat Kaplan

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

Engineer and astronaut Stephanie Wilson was a toddler when Neil Armstrong and Buzz Aldrin visited the Moon. She may someday almost literally walk in their footsteps. Stephanie is one of 18 astronauts--9 women and 9 men--chosen for the Artemis Team. We also welcome back Cassini-Huygens project scientist Linda Spilker for another update on the discoveries still being made thanks to that flagship mission. Linda also looks ahead toward more missions in the outer solar system. Did you catch the great conjunction? Mat and Bruce did, and they’ll talk about it in What’s Up.

Stephanie Wilson in the Cupola of the International Space Station
Stephanie Wilson in the Cupola of the International Space Station NASA astronaut Stephanie Wilson, STS-131 mission specialist, poses for a photo in the Cupola of the International Space Station while space shuttle Discovery remains docked with the station.Image: NASA
Titan beneath its atmosphere
Titan beneath its atmosphere In this image from NASA's Cassini spacecraft, you can see beneath the atmosphere of Saturn's moon Titan to its surface features.Image: NASA/JPL/University of Arizona/University of Idaho
Infrared views of Saturn's Moon Enceladus
Infrared views of Saturn's Moon Enceladus These views of Saturn's moon Enceladus were created using infrared data collected by NASA's Cassini spacecraft during its 13-year mission at Saturn. The red regions correspond to warmer surface temperatures. The bottom-right image shows Enceladus' south pole, where subsurface ocean water vents into space. These warmer regions could indicate hotspots on the ocean floor, along with conditions favorable for life as we know it.Image: NASA/JPL-Caltech/University of Arizona/LPG/CNRS/University of Nantes/Space Science Institute

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Mat Kaplan: She could become the first woman on the moon. This week on Planetary Radio. Welcome, I'm Mat Kaplan of The Planetary Society, with more of the human adventure across our solar system and beyond. Stephanie Wilson is one of the 18 astronauts just chosen for what NASA calls the Artemis team. It moves her one step closer to walking on the moon. We'll meet her in a brief conversation, then we'll turn to another pioneering explorer, Cassini project scientist, Linda Spilker is back to tell us about the most recent science from the mission that spent so many years circling Saturn. Linda also has thoughts to share about our exploration of the outer solar system and the current planetary science decadal survey.

Mat Kaplan: Speaking of Saturn, did you catch the great conjunction? Though I wasn't all that excited when I first heard it was coming, I have to admit that it was thrilling to see our solar system's two biggest worlds sharing the eye piece of my telescope. I'm sure Bruce Betts was also watching this once in many lifetime's event, so we'll ask him about it when we get to what's up. The conjunction also tops the December 18 edition of The Downlink, our weekly newsletter that you'll find at Just below is some lovely coffee colored dirt. That's not just any dirt, it is material gathered in 2019 by Japan's Hayabusa2 spacecraft that has safely dropped it off on Earth.

Mat Kaplan: The same goes for regolith brought back from our moon by China's Chang'e 5. Over now to Israel, where nonprofit SpaceIL has announced it will once again try to land on the moon. The Beresheet 2 mission is set for launch in 2024. We've got links to our coverage of Beresheet 1 on this week's episode page at All that and more are in The Downlink. The latest of my monthly newsletters is also out. You can subscribe to it for free at Here is NASA administrator, Jim Bridenstine, talking at the December 9th meeting of the United States National Space Counsel.

Jim Bridenstine: Welcome to the Artemis generation. A lot of you in this room, you've heard me talk about the Artemis generation. I'm the first NASA administrator in history that wasn't alive when we had people living and working on another world. Of course, it is our goal that I'm the last NASA administrator in history that wasn't alive when we have people living and working on another world. Our goal is to go to the moon sustainably to learn to live and work on another world so that ultimately we can take all of that knowledge onto Mars.

Mat Kaplan: One of administrator Bridenstine's tasks at that NSC meeting was to introduce the 18 astronauts named to the Artemis team. One of them is Stephanie Wilson. I don't want to call her an overachiever, but like all her colleagues, her resume is impressive. Stephanie spent 42 days in space on three space shuttle missions, beginning in 2006. That was after working for NASA of the Johnson Space Center at the Jet Propulsion Lab, and for Martin Marietta. She has engineering degrees from Harvard and the University of Texas in Austin, and she currently serves as the astronaut office mission support crew branch chief.

Mat Kaplan: I was all in when NASA announced opportunities to talk with members of the Artemis team, and Stephanie was at the top of my list. Ms Wilson, Stephanie, thank you so much for joining us on Planetary Radio, and congratulations on your selection as part of this new Artemis team.

Stephanie Wilson: Well, thank you for having me, and I thank you for the congratulations. I'm very excited.

Mat Kaplan: I bet. I had several reasons for asking to talk with you specifically, but two stand out. Please forgive the first one. I'm hoping that unlike a lot of your colleagues on the Artemis team, you're old enough that you may actually remember the last time humans walked around up there. Am I right?

Stephanie Wilson: You are correct, and I do have vague, vague memories of Neil Armstrong and Buzz Aldrin landing on the moon. I was about three-years-old, and I remember hearing it and watching it on the black and white TV with a lot of snow in the background. But I do have a vague, vague memory of that.

Mat Kaplan: Do you remember the end of the program, Apollo 17, any better? I mean, you were, what, six by that time?

Stephanie Wilson: Yes, true. Not that I can recall. I remember the first mission because of course my parents were there with me, and so it was a big moment to watch it together, or at least to try to have me pay attention to what was going on.

Mat Kaplan: That's tough with a three-year-old. This is the second question. I loved that before you started going up there yourself, you worked at the Jet Propulsion Lab, contributing to the robotic exploration of our solar system. Can you talk about your part in the Galileo mission to Jupiter?

Stephanie Wilson: Yes. I worked at the Jet Propulsion Laboratory from 1992 to 1996. I was a member of the attitude and articulation control team responsible for the orientation of the spacecraft, and in particular, pointing Galileo so that the assigned instruments could take the particular readings and collect the data from Jupiter. So, it was a wonderful opportunity to be part of a mission control team, which I think really helped my work at the Johnson Space Center. I became an astronaut of course working in mission control and working with the mission control team and being the representative of that team to the on orbit crews, and then of course the robotic missions are the pre courses to human missions collecting the data and giving us good insights into potential opportunities for human missions. All of that tied together very nicely.

Mat Kaplan: Did you develop a sense of being an explorer, being a part of that mission that continues today?

Stephanie Wilson: I did. I also had an early interest in science and engineering and in aerospace in middle school as a result of a school program talking to a local area astronomer, and really then developing or starting to be aware of the opportunities in science and engineering and exploration. At that time, I was interested in astronomy, and my exploration interest started then.

Mat Kaplan: I read that that astronomer that you're referring to, I think it was Jay Pasachoff, who happens to be a good friend.

Stephanie Wilson: Yes, and he is still a professor at the Williams College and working wonderfully well and vibrantly in the area of astronomy. He's still a contributing member to that field, and he has done wonderful work over the years, and has been a wonderful friend and mentor.

Mat Kaplan: And still chasing those eclipses around the world. Let me switch gears. I just read that the Artemis 3 science definition team released its report just a few days ago. I was very impressed by its long, very comprehensive list of recommendations, including the call for the Artemis astronauts, you and your colleagues, to have the same kind of intensive geology and planetary science training that the Apollo astronauts have. Does that option make this experience even more interesting or exciting?

Stephanie Wilson: It does. We, of course, as part of our astronaut candidacy training, have some training in geology a few weeks or so. Of course, mine was some time ago, and at that time, we took a field trip to Colorado and New Mexico, and I have since participated in some other analog training in the Arizona area, and undergone some other geology trainings, like an in depth course to prepare us for these missions to the moon would be welcomed and is certainly a great opportunity.

Mat Kaplan: Our time is so limited because you're talking to a lot of folks like me today, so I've got just one more for you. There were also recommendations made by that science definition team for leaving a suite of instruments on the surface just as the Apollo guys did, like that all set package, and a call for a rover. Can you see yourself kicking up some dust as you roll across the moon?

Stephanie Wilson: I can definitely envision myself kicking up some dust and participating in whatever way helps the mission as far as doing the field geology and the sample collection and return, and deploying experiments and driving a rover. All of that sounds wonderful to me. It's a great opportunity to represent the astronaut office and to work with my team members there to accomplish the mission objectives and to contribute to the Artemis program.

Mat Kaplan: Stephanie, I wish you the greatest of success and luck, and I look forward to watching that video of, I hope it'll be you, but certainly among your colleagues, seeing that video come back from the moon with humans up there for the first time since you and I were very young.

Stephanie Wilson: Yes. We look forward to it as well, and it'll be a wonderful opportunity, whether I am selected or another of my colleagues, I will be excited either way.

Mat Kaplan: Artemis team astronaut, Stephanie Wilson. I'll be back in moments with the news from Saturn, delivered by Linda Spilker. This is Planetary Radio.

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Mat Kaplan: Welcome back to Planetary Radio. Maybe one of you can help. I've lost track of how many times Linda Spilker has been heard on our show, not just in sit down interviews like you're about to hear, but in our coverage of milestone events and the great Cassini-Huygens mission that ended in September of 2017, when the great robotic explorer plunged into Saturn's atmosphere. Or did it end? The science enabled by Cassini is still very much a work in progress. Linda, welcome back to Planetary Radio for the umpteenth time. As I said, you still hold that title of the most frequent guest on our show.

Linda Spilker: Matt, it's a pleasure to be here.

Mat Kaplan: I am so glad that we still have lots of new stuff to talk about. This time, not just Cassini, but I think that's where we'll start. There are two recent press releases that I got that I'm hoping we can talk about. One of them begins with some revelations on that big cloud shrouded moon titan having to do with the impact craters there. We know from talking about other bodies how important craters can be for telling us about the past and much more about those worlds. I didn't know this would apply to Titan until I saw this announcement made in October. I mean, what's going on here? Could you describe it?

Linda Spilker: Absolutely, yes. Titan is a very interesting world. As you said, it has this very thick, opaque atmosphere, and so it's very hard to see through to the surface. That was one of the goals of the Cassini mission. That thick atmosphere, you can think of it as a protective shield, so any meteoroids that come into the system usually are vaporized or burned out before they get to the surface, just like happens here on the Earth. But some of the larger objects do make it through, and they make craters, and those craters you can think of excavating the material on the top and revealing what's underneath. For this particular paper, what the authors did is they studied nine different craters at different locations on Titan.

Linda Spilker: There were some craters around the field of dunes that are there in the equatorial region. There are these particles from the upper atmosphere form and rain down and form these very thick dunes.Then they studied another set of craters at the mid latitudes, and what they found is that these craters tell you a lot not only about the surface underneath of Titan, but about the processes that happen in the atmosphere than can change the surface. This was some very fascinating results while you're looking at these two kinds of craters.

Mat Kaplan: Knowing that Titan as we've talked about in the past is such a dynamic place, all that weather going on, does this mean that craters generally are, at least in geologic terms, fairly fresh on Titan because they get worn away?

Linda Spilker: That's' exactly right, Matt, that the craters on Titan do tend to be young in geologic terms. What was so fascinating about the difference is is that the craters in the equatorial region, and the dunes were made up completely of organic material, probably these particles that form when methane is broken apart in the upper atmosphere and methane fragments grow into larger and larger molecules until they're big enough to actually fall to the surface. But when you look at the craters that are in the mid latitude range, there there are a mix of organic material, but they have a lot of water ice and a small amount of methane ice. So, it looks like the mid latitude is this methane rain that we know happens on Titan is cleansing or sort of washing away the organic particles so you can still see the ice. This is telling us about the weather on Titan, as you said, and what we can see now through and looking at these craters to understand the weather on Titan.

Mat Kaplan: Here's just a random possibly unwelcome thought. I mean, wouldn't it be great if methane rain... I imagine it's transparent just like rain here, but wouldn't it be great if it was purple rain? Tribute to Prince there.

Linda Spilker: Well, it really does show up. We saw a big methane rainstorm had occurred on Titan, and we looked at a place on the surface that looked wet. It looked darker. It looked different. Then we flew by Titan, Cassini actually flew by Titan over 120 times in the 13 years it orbited Saturn, and we actually watched as that place on the surface of Titan as that methane evaporated, and then we could see the surface going essentially back to normal over a period of months.

Mat Kaplan: You've mentioned that this is revealing the presence of organics yet again on Titan. Is this adding to the body of knowledge that leads us to think there may be a lot more going on underneath the surface?

Linda Spilker: That's exactly right. In fact, Titan is an ocean world, and we think it has a sea of water and ammonia underneath its icy crust, and there might be pathways for this water plus ammonia to get to the surface of Titan. Titan joins Enceladus as an ocean world, and we wonder what kind of prebiotic chemistry, that chemistry that could potentially lead to light might be going on in the ocean and perhaps sometimes expressed on the surface of Titan.

Mat Kaplan: I'm not constrained by being of science, so I'm going to say we wonder about biotic activity as well as prebiotics. But you don't have to agree with me.

Linda Spilker: Oh, it would be tremendously exciting if that was the case, tremendously.

Mat Kaplan: Wouldn't it be? One of these nine crater is called Selk. Does it have special significance?

Linda Spilker: Yes. Selk is one of the younger craters on Titan. It's well defined. What's so interesting is it's the target of the Dragonfly mission to go to Titan. This is an octnocopter that's going to actually fly to different places around Self crater, perhaps in the crater itself, and actually take samples of the surface. When the quadcopter is flying across, it can use its cameras to look at the landscape and to see what's going on. Very exciting mission that's set to launch in 2027.

Mat Kaplan: What an amazing progression. I mean, here we're talking about this extremely exciting mission, Dragonfly, which is going to build on Cassini. Of course, Cassini maybe didn't just build on Voyager, but actually happened because of Voyager.

Linda Spilker: It's so incredible to look back and think about the Voyager mission. A Voyager 1 first flew by Titan a little over 40 years ago, 40 years ago in November. It found a smog enshrouded world with this thick, dense, opaque atmosphere. One of the goals of Voyager was to see through to the surface of Titan. What did Titan look like? We just didn't have the instruments. I was part of the Voyager team at that time to see the surface. After that close fly by, we came within about 2,500 miles of Titan's surface. Plans immediately were underway to have another mission to go back to Titan and to carry a probe and to actually look at and understand the surface of Titan. That mission was Cassini.

Linda Spilker: Cassini carried the ESA provised Huygens probe. That probe parachuted down and landed softly on the surface of Titan. We carried radar instruments and instruments looking in the infra red windows on Titan to help reveal it, as well as infrared windows in the cameras. Now we see that globe of Titan and understand it is a very, very interesting world with many similarities to our own, methane rain in stead of water. Raining [inaudible 00:18:36] has lakes and seas of liquid hydrocarbons. Such an interesting world with a first close look by Voyager 1 in 1980.

Mat Kaplan: Quite an anniversary. Speaking of infrared, let's jump over to that other fascinating little world, much smaller world of Enceladus. There was another press release I got back in September of 2020, and it has these gorgeous infrared images. Tell us about these.

Linda Spilker: A global map was made of Enceladus. It's a tiny world only about 300 miles across, and so combining the images taken by the cameras with the infrared images taken by the visual infrared map and the spectrometer created some of the highest resolution most complete maps that we have of Enceladus. These maps, the influx is in the spectral region, so the false colors that you see in these very beautiful maps actually indicate different compositions on Enceladus. What we find is that those colors correspond to some of the ages of the surface of Enceladus as well, Enceladus' intriguing little world with active jets shooting out of the south pole, with water vapor, with organics, also icy particles all coming from a global ocean underneath Enceladus' icy crust.

Linda Spilker: Looking at these maps where you see fresh surface where these particles have fallen back to the south pole, it's colored in a reddish color and looking at these maps, and this is the water ice. What's interesting, what's new from these maps is if you look in the northern hemisphere, there's a large region that also has this reddish color, fresh water ice, fresh in geologic times in the northern region of Enceladus as well. What's so interesting is it's telling us in some way, Enceladus, either through perhaps icy vents coming up and putting material there on the surface, or maybe ice creeping up through the cracks coming from this sub surface ocean potentially in the northern hemisphere as well, so a very exciting new result. It took building a global map to really reveal it.

Mat Kaplan: We will put up a link, of course, on this week's show page, You really have to see these. Yes, they're false color images, but they are just so stunning, especially the image, this map of the south pole of Enceladus. Is it possible, sounds like you're saying it is, that maybe at some point in the not too distant past, that the north pole of Enceladus may have had these jets just like we still see at the south pole, or maybe it's just oozing up. I think you've said both of those were possible.

Linda Spilker: Right. Somehow resurfaced, it's not quite at the north pole. It's more in the mid latitudes on Enceladus. But it's just a very intriguing result composition wise, which is also we know an indication of age because we know the south pole is active. To see this region that looks so similar, it's just very, very intriguing.

Mat Kaplan: You mentioned Dragonfly going to Titan, of course. It's not going to tell us anything in particular new about Enceladus. I'm sure you would still love to see a mission head for this other small node.

Linda Spilker: Oh, an Enceladus mission would be fantastic. It could be just flying through the jets at the south pole multiple times and collecting material. It could get more exciting potentially landing on the surface, or maybe from an Enceladus orbiter and actually taking your little laboratory down to the surface and making those kinds of measurements and looking for any kind of chemistry going on, fatty acids, amino acids, maybe even carry a little microscope to look and see if perhaps there's evidence of life as we know it. What's so interesting is Enceladus is essentially coated by snow.

Linda Spilker: It's very bright and white like an icy snowball, at least most of these particles that shoot out of the jets fall back onto the surface and coat Enceladus' surface, so you can land in multiple places. You wouldn't have to go right to the tiger stripes. You could land in multiple places perhaps and get samples, and even perhaps even at some point maybe we'll get a sample of Enceladus and bring it back to the Earth, and then use all of the laboratories we have here to analyze that sample. That would be tremendously exciting to at some point bring back a sample from Enceladus and actually do a lot of studies on that sample.

Mat Kaplan: That truly is extremely exciting to think about. I mean, I guess in some ways, it might be easier than getting a sample back from Mars. I mean, you have to come a lot farther, but at least you don't have to deal with that gigantic gravity well that Mars has. I guess we can hope that the sample return from Mars proves itself out. Maybe that will lead to getting material back from elsewhere around the solar system. If you were talking about just an orbiter for Enceladus, could you send the kinds of instruments that everyone hopes will be headed for Jupiter's moon, Europa, soon? Same sort of instruments, but you wouldn't need as much radiation shielding, would you?

Linda Spilker: Yes. If you were to fly a Europa clipper like mission to Enceladus with a very sophisticated orbiter, that part would be much easier, and your orbiter at Enceladus, since you don't have the harsh radiation, Saturn's rings essentially act as a shield from the radiation, and so it's a very benign environment. Your orbit around Enceladus could last for a very long time. In fact, as part of the decadal survey, there was a concept for Enceladus called an orby lander, where you would have an orbiter and a lander that could go down to the surface of Enceladus.

Mat Kaplan: I've heard of that, and we will come back to the decadal survey that's currently underway in just a few minutes, actually. This is the first I've heard that the rings play a role in keeping the environment around Saturn a little more benign, at least in terms of radiation. I didn't know that. How does that work?

Linda Spilker: Well, Saturn's rings act as a barrier, that usually a radiation belt has built up as you have particles spiraling back and forth along the field lines from the north pole to the south pole, et cetera. These particles are what create the beautiful aurora at Earth, and Saturn also has aurora at its poles as well. The rings themselves then just stop that process from happening. You have this region that suspends the rings, which are quite extensive at Saturn, and that region is then radiation free, and so you don't have the huge, energetic radiation belts like you have at Jupiter.

Mat Kaplan: Fascinating. Before we move on, is there much other research still underway that relies on Cassini's 13 years at Saturn?

Linda Spilker: There's a lot of research still ongoing for Cassini. In fact, NASA has a data analysis program. It's the Cassini Data Analysis Program, and researchers propose to that program and are funded to continue looking at the Cassini data. There's so much more there. What's so intriguing is that the science teams are now starting to combine even more carefully the data from multiple instruments. I think there's a lot of clues and new science, and you can start to combine, say for Titan, you can take the radar data and the visible images and the infrared data and infrared spectra, and even into the ultraviolet, and combine all of those datasets to give you a more complete picture of any of these objects that we're looking at. That's the next step there.

Mat Kaplan: All right, let's broaden our view a little bit. Zoom out from Saturn somewhat, although it'll still be in the picture. You're vice chair of OPAG, NASA's Outer Planets Assessment Group. What is OPAG's mission?

Linda Spilker: The Outer Planet Assessment Group is a forum for scientists to come together and provide input for planning and also prioritizing outer planet exploration activities looking into the future over the next several decades. We have a chance to hear talks from various missions to present their ideas also from other scientists about what kinds of science they're looking at. We want to evaluate the outer solar system, not just the planets, but any of the objects in the outer solar system, and look at what measurements might be possible or what kinds of missions we would like to see in the future.

Linda Spilker: We provide input to the decadal survey. The Outer Planet Assessment Group wrote one of many white papers that were input to the decadal survey. We also work closely with another assessment group, the Small Bodies Assessment Group, or SBAG, and we have it as we're joint custody of Pluto and some of the [inaudible 00:28:01] Belt objects. There's some overlap in these assessment groups, but our goal is really to provide information to NASA that would help them in formulating their future plans.

Mat Kaplan: You have brought us back to the decadal survey. This is a very big deal, this project that's underway. Right?

Linda Spilker: Absolutely. This is a chance for the planetary science community to come together and to look over the next decade and evaluate the science that's already been acquired by the various missions, and then start to look ahead and say what kind of science and what kinds of missions we want to do in the next decade, and to prioritize to look at flagship missions, that class of missions like Cassini, where you have a very complex mission, perhaps maybe an ice giant orbiter with a probe would be an example of some kind of a future flagship missions, look at new frontiers missions, that's a little less expensive, the next class down. Those are [copeded 00:29:02] missions, or even discovery class missions. Basically, the decadal survey is this report that goes to NASA. Also, it's read by individuals in congress, it's the general public, and so it's basically a roadmap of what the Outer Planets community would like to see in the next decade.

Mat Kaplan: Does NASA pay pretty close attention to the recommendations made in the decadal survey? I know it's not absolutely required, but I think they take it pretty seriously, don't they?

Linda Spilker: Absolutely. NASA takes the decadal survey very seriously, especially in looking at missions and looking at any plans for ideas how to make various kinds of selections. This particular decadal survey based on so many of the discoveries and findings in the past decade also has a strong astrobiology component as well. There's actually separate groups as part of the decadal survey. Of course, there's a Giant Planet Systems group, and then there's an ocean worlds group that's part of the decadal survey. There are also groups for Venus and for Mercury and for the moon all to look and try and come up with the best possible science.

Mat Kaplan: Let's follow up on that mention of ice giants. You know that we regularly talk on this show about how important it is to get a dedicated mission to Uranus and/or Neptune, most recently with Heidi Hammel. I bet your feelings about this haven't changed.

Linda Spilker: It's definitely time for an ice giants mission. The only flybys we've had of Uranus and Neptune have been flybys by Voyager 2. They were just glimpses into these very interesting worlds with their moons and rings, and so I think it's definitely time to go back. In the previous decadal survey, an ice giant's mission was third priority in the list of missions, and we just didn't get that far down the list in the last decade. Hopefully as the steering committee for the decadal survey meets, they'll put an ice giants mission in high priority, an ice giants orbiter carrying a probe that we could send into the atmosphere of Uranus or Neptune, or perhaps used to study Neptune's very interesting moon Tritan. I have a flight leaning toward Neptune, although either ice giant has compelling science for a visit. But Neptune had that interesting world, Tritan, and Voyager saw evidence of activity of these little tiny plumes coming from Tritan, so it would be very interesting to go back. Tritan is a captured object. It's in a retrograde orbit, and a very interesting moon to study in its own right, perhaps another ocean world.

Mat Kaplan: But maybe also something captured from much farther out in the solar system that is sitting there waiting for us to take a look.

Linda Spilker: Absolutely. Maybe it's a captured Kuiper Belt object out there in orbit around Neptune.

Mat Kaplan: You had mentioned to me that you worked on a mission concept study for Neptune that has seen some progress. Tell me about that.

Linda Spilker: Right. As part of the decadal survey process leading up to it, NASA funded a series of studies that would be input into the decadal survey. I had the pleasure of being part of the Neptune study to look at what might be possible, and actually going back to Neptune and studying Neptune's moon, Tritan. In the end as we were studying, we said, "You know, we can take a lot of lessons from Cassini and the Cassini orbiter with the Huygens probe, and we'd want a very similar kind of mission with very capable instruments. We could use Tritan, much as Cassini used Titan to shape the orbits as we would go around Neptune. We'd want a very long lived mission as well."

Linda Spilker: So, we took some lessons from Cassini and built on those. We also felt that international collaboration would be very important for any kind of ice giant mission as well, reaching out to ESA, to the Japanese Space Agency, other places to invite them to join us on a flagship mission to an ocean world.

Mat Kaplan: So, you would expect that any major mission like this probably would have international involvement. I mean, that seems to be almost the rule nowadays.

Linda Spilker: There's a tremendous advantage to having international participation to bring in additional viewpoints, additional scientists, also additional funding, because usually these giant flagship missions are quite costly and can spread the cost that way and just build on international cooperation and collaboration for an ice giant's mission.

Mat Kaplan: What is the expected timetable for the decadal survey? When can we expect to see its recommendations?

Linda Spilker: Well, right now, the various panels are leading, and they're getting community input, they have the white papers. Their input will then go to the Steering Committee, and the steering reports gets released in the spring of 2022. During that time, there'll be a chance for community feedback. There'll be community town halls on the decadal, with the final dissemination of the decadal report in the spring of 202. So, it'll cover the decade from 2023 through 2032.

Mat Kaplan: All right, little more than two years. Something to look forward to.

Linda Spilker: Yes, a lot of work going on in the meantime.

Mat Kaplan: Well, it's a shame that going to be so many missions scientists and others would like to see around our solar system, all of which have merit, and there just isn't enough money to go around. We will keep an eye on this, of course. It's something we talk about as well on the monthly space policy edition of Planetary Radio with my colleague, Casey Dreier. Linda, there's just one other thing that I wanted to cover in this conversation, and that is to congratulate you on completing your term as chair of the American Astronomical Society's Division for Planetary Sciences, DPS. I will note that another good friend of Planetary Radio and Planetary Society is now in that office, has followed you, your former JPL colleague, Amy Mainzer, who's now at the University of Arizona. How is your term at DPS? I'm sure the pandemic didn't make it any easier.

Linda Spilker: Right. It was a very interesting year for DPS. I was actually in this year the outgoing chair's three years term. The first year, you're incoming chair, then the second year you're chair, and I was chair for the meeting in Switzerland, and that was a joint meeting with the European Planetary Science Congress. Then there's outgoing chair, then there's a virtual meeting for DPS. I think the virtual meeting was a tremendous success, given the constraints that we had to live with, put together a week long meeting. The talks were recorded, and yet there was a chance to have discussion and focus groups on the various types of sessions that we would normally have at DPS. It was quite different. DPS is a large organization, and we really brought together, I think, a lot of planetary scientists for this particular DPS meeting. We're hopeful that next year, as we have more and more of the vaccine out, that next year for DPS we'll be able to go back to an in person meeting.

Mat Kaplan: Well, I would love that. I had a thrilling time with a couple of DPS meetings that I attended, although that was several years ago. I haven't been in quite awhile. I would love to have a shot at attending once more. I imagine you would also be there to spend time with your many planetary science colleagues from around the world.

Linda Spilker: Oh, absolutely. I wouldn't miss it. I really enjoy the yearly DPS meetings.

Mat Kaplan: Linda, as always, it is wonderful to catch up with you about Cassini and about so much more. I sure hope that we can continue to have these periodic meetings and talk about what's happening out there, especially in the outer reaches of our solar system, where Cassini has done such great work. We look forward to new from new missions.

Linda Spilker: It's been a pleasure to talk with you, Matt. I look forward to sharing more Cassini results and future results perhaps someday for other missions.

Mat Kaplan: Cassini-Huygens project scientist, Linda Spilker. Another scientist is coming right up. Stick around for this week's What's Up With Bruce Betts.

Jennifer Vaughn: Hi. This is Jennifer Vaughn, The Planetary Society's chief operating officer. 2020 has been a year like no other. It challenges us, changed us, and helped us grow. Now we look forward to a 2021 with many reasons for hope. Help us create a great start for this promising new year at When you invest in a planetary fund, your year year round gift will be matched up to $100,000, thanks to a generous member. Your support will enable us to explore worlds, defend Earth, and find life elsewhere across the cosmos. Please, learn more, and then donate today, at Thank you.

Mat Kaplan: Time for What's Up on Planetary Radio. The chief scientist of The Planetary Society is here. That's Bruce Betts. Were you out there? Did you see the conjunction?

Bruce Betts: I did see the conjunction. It was spectacular. I mean, it was two dots of light in the sky, but they were really close together and we knew they were Jupiter and Saturn, and that made it super cool.

Mat Kaplan: I took out the telescope, did my best to hold my iPhone up to the eye piece, and actually got an image that some of our colleagues were impressed by when I showed it to them. But it was so much more impressive just to put my eye against that eye piece and see those two giant worlds right next to each other without having to shift the telescope at all. It was pretty cool.

Bruce Betts: Very cool. You know they're not actually next to each other in three dimensional space, right?

Mat Kaplan: Did you see the cartoon that one of our aforementioned colleagues was passing around, where they're watching in the telescope and they smash into each other, and then the person at the telescope says, "Damn this 2020."

Bruce Betts: Fortunately, orbital dynamics does not seem to be affected by [inaudible 00:39:21].

Mat Kaplan: Yeah, thankfully.

Bruce Betts: So far, so good. We still have a few days left.

Mat Kaplan: What else is on? Tell us more about that.

Bruce Betts: It was the closest conjunction or getting close to each other in the sky in 400 years for the Jupiter and Saturn, but in another 20 years, there'll be nearly as close, and in 80 years, they'll actually be closer. Put that on your calender, Matt. I can give you exact dates.

Mat Kaplan: I'm penciling it in right now.

Bruce Betts: For this year and into the next, I guess, Jupiter and Saturn will be getting lower and lower in the early evening and dropping out of sight really soon. But you're going to have Mars still to keep you company in the evening sky looking still pretty darn bright and reddish high over head in the south in the early evening. In the pre-dawn sky, we've got super bright Venus over in the east, but it also will be dropping over the next month or so out of sight. We've got the hardest to pronounce meteor shower, at least for Bruce, of the year coming up. I know this always excites you when we try it. The Quantrandid. That wasn't terrible.

Mat Kaplan: That was maybe your best ever. I mean, so much for this Planetary Radio holiday tradition of hearing you attempt to pronounce it. I think you got it.

Bruce Betts: Okay. Well, I shouldn't say it again, but I'll try to amuse you anyway. The Quadrantid... dang it. That meteor shower names after a constellation that doesn't even exist anymore, meaning it's not one of the 88 officially recognized constellations, but the kept the name Quandrantid, that will be peaking on the night of January 2nd to the 3rd. More precisely, the peak is predicted to be at 14 30 UT on January 3rd, which is more important than with most meteor showers, because this one has a pretty sharp peak in terms of most meteors typically occurring within many hours as opposed to many days with the [persients 00:41:25] and geminants. But there's more bad news. It's going to be a very bright moon, which is good news for moon watcher, but bad news for meteor watcher. But anyway, night of 2nd and 3rd, you might get some meteors. Onto this week in space history, it was 1968 that the first humans went around the moon as part of Apollo 8. Then in 2003, Mars Express from the European Space Agency went into orbit around Mars, still doing great work all these years later. We move on to Ring of Space.

Mat Kaplan: That was a good test of your new microphone.

Bruce Betts: Did I break it?

Mat Kaplan: I think your voice broke.

Bruce Betts: It broke long ago. In honor of the Jupiter Saturn great conjunction, we're going to compare the two worlds. One and three quarters Saturns would fit into Jupiter.

Mat Kaplan: One in three quarters. Okay. That sounds about right. Yeah. Both big dudes.

Bruce Betts: I'm glad you think so. Yeah, they're both really, really big. That's the technical term. We'll come back to them in a little bit in the new trivia contest. But let's go to the old trivia contest. I asked you, what are the only two maria on the moon names after people? How'd we do, Mat?

Mat Kaplan: We had the biggest response to this one that we have had in a long time, almost double our usual response. I suppose it might have been those prizes, that new Planetary Society baseball cap, and the copy of Teasel Muir-Harmony's great book, Operation Moonglow: A Political History of Project Apollo. Sort of an international political history of project Apollo. Teasel was our guest on the space policy edition, the most recent show that I did with Casey. I'm going to jump straight to a person I believe is our winner, first time winner and possibly a first time entrant as well, I think so, Mitch Stevens in Bellingham, Washington. Speaking of Casey, they must be neighbors out there.

Mat Kaplan: Mitch says, "The two lunar Mare were named after people are Mare Humboldtianum, named after Prussian explorer and scientist, Alexander von Humboldt, and Mare Smythii, named after English Royal Navy officer and astronomer, William Henry Smyth or Smith. Do you have any idea which it is, and are those correct?

Bruce Betts: Those are correct, and one of those pronunciations is correct.

Mat Kaplan: Okay. I'm going to go with Smith, even though it looks like Smyth, because I'm an American. Mitch, congratulations. He added, "Love all the work y'all do. Very proud to support such a wonderful organization. So, I suppose it sounds like he's one of our members as well. Thank you for that as well, Mitch. We're going to get your baseball cap and the book by Teasel out to you very soon. I have more. I always do. Norman Cassoon in the UK, one of our regulars, he said that Humboldt, very accomplished guy, he resurrected the use of the word cosmos from the ancient Greek and assigned it to his multi volume treatise, Cosmos. He also was the first person, at least according to Norman, to describe the phenomenon and cause of human induced climate change. He did this as early as 1800. How amazing.

Bruce Betts: Wow. They should name something after him.

Mat Kaplan: Well, actually, that's answered by Micheal Unger in British Columbia, who says, "The weather might actually be better at the sea of Humboldt, up on the moon, than Humboldt, Saskatchewan, which are both named after Alexander von Humboldt. Then Renee Christopher, big run of people up in Washington state this time, "I wonder whether you can get your wrought iron space ship prepared at Mare Smythii." All right, now it gets personal. Robert Clain, who we hear from pretty regularly from Arizona, "Though not official, there are also two very small Mare on the far side, Mare Betsy and Mare Cathlani.

Bruce Betts: Really? Wow, we should look into that.

Mat Kaplan: A Devanal Rorke in Colorado, he agreed with Betsy, same spelling that Robert used, but suggests Mare Cathlaniana. I like a lot. I think that has a nice ring to it. Mare Cathlaniana. Listen up, IAU. Here's an interesting one from June Chen, I hope I have that right, in China. The big prize strategy really works. Apparently that was what pulled her into this week's show. "Hello there. Been a proud member for just over a year, even though I don't always enter the contest. But I always listen. You've accompanied me on so many subway rides and airplanes and high speed trains." Well, we're glad you're out there, June. Then this from Mel Powell, "We really need..." uh-oh, Latin alert, a Mare [foreign language 00:46:41] in honor of Dr. Betts." Yes, per Google Translate, that is probably random space fact in Latin. He says, "I dare Bruce to use it as an intro once. I double [foreign language 00:46:57] dare him."

Bruce Betts: Well, we'll have to try that, and apparently we should not take up ancient languages.

Mat Kaplan: Speaking of ancient not quite dead languages, here is this week's input from our poet [inaudible 00:47:11], Dave Fairchild. "We named two lunar Mare for people, I have reckoned. Humboldtianum is the first, and Smythii, the second. Smythii has winkle ridges, like my brow, in truth, when forced to rhyme these Latin names. I need some English, Bruce."

Bruce Betts: I'm just going to do several weeks in a row of Latin.

Mat Kaplan: Oh, joy. All right, well, here's your chance. Take us into a new one.

Bruce Betts: I'm not.

Mat Kaplan: No Latin is required, at least, in the following.

Bruce Betts: Back to Jupiter and Saturn, here's your question. What is the approximate ratio of the average density of Jupiter to the average density of Saturn? In other words, how many times denser is Jupiter than Saturn? I find the answer rather interesting. Go to

Mat Kaplan: All right. You have until New Year's Eve eve. That would be December 30, Wednesday December 30 at 8:00 AM Pacific time to get us this answer. You can still win yourself the brand new Planetary Society baseball cap. You'll find it at, or just go right to

Bruce Betts: All right, everybody. Go out there, look up at the night sky, and think about what food you want to eat before the end of the year. Thank you, and good night.

Mat Kaplan: All of it.

Bruce Betts: All of it.

Mat Kaplan: He's Bruce Betts, the chief scientist at The Planetary Society. Hey, merry Christmas, happy holidays. Have a great one, Bruce.

Bruce Betts: You too, Mat.

Mat Kaplan: Planetary Radio is produced by The Planetary Society in Pasadena, California. It's made possible by the women and men who are both members and explorers. You can join the adventure at Mark Hilverda is our associate producer, Josh Doyle composed our theme, which is arranged and performed by Peter Schlosser. Ad astra.