Planetary Radio • Sep 09, 2020

A Planetary Mystery is Solved, and it’s Bill Nye’s Anniversary!

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Jennifer Vaughn

Chief Operating Officer for The Planetary Society

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Bill Nye

Chief Executive Officer for The Planetary Society

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Marc Rayman

Chief Engineer for Mission Operations and Science, 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

JPL’s Marc Rayman, former Dawn mission director, reveals the secrets of those bright spots on dwarf planet Ceres. First though we celebrate Bill Nye’s 10th anniversary as CEO of The Planetary Society. Chief Operating Officer Jennifer Vaughn is followed by the Science Guy himself. And there’s a Nye invention at the heart of this week’s What’s Up space trivia contest.

Ceres' bright spots in Occator Crater
Ceres' bright spots in Occator Crater This mosaic created by images from NASA's Dawn spacecraft uses false color to highlight salty water that was pushed up from a reservoir beneath the dwarf planet Ceres' crust.Image: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA
Global View of Ceres in False Color
Global View of Ceres in False Color Dwarf planet Ceres is shown in this false-color rendering—created using images from the Dawn spacecraft—which highlights differences in surface materials. Occator crater and its mysterious "bright spots" are clearly visible near the center of the image.Image: NASA / JPL-Caltech / UCLA / MPS / DLR / IDA

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At Home In Space: Dawn Mission's Marc Rayman Takes Us on a Tour of His Home Dawn Mission Director Marc Rayman is a lifelong space enthusiast. His tasteful home provides the evidence.

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Cheers to 10 Years of Bill Nye as The Planetary Society's CEO Robert Picardo toasts Bill Nye on his 10th anniversary of being CEO of The Planetary Society.

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Trivia Contest

This week's prizes:

A Planetary Society Kick Asteroid rubber asteroid.

This week's question:

Bill Nye holds 3 patents. One of them relates to shoes. What kind of shoes?

To submit your answer:

Complete the contest entry form at or write to us at [email protected] no later than Wednesday, September 16th at 8am Pacific Time. Be sure to include your name and mailing address.

Last week's question:

What is the only spacecraft that launched with solar system escape velocity?


The winner will be revealed next week. 

Question from the 26 August space trivia contest:

Assuming a combined Greek and Roman pantheon mythology, within this mythology, which planet (in our solar system) is named after the earliest (oldest) god?


Assuming a combined Greek and Roman pantheon mythology, within this mythology, the planet in our solar system named after the earliest or oldest god is Uranus…or not.


Mat Kaplan: A planetary mystery solved, and a science guy's anniversary celebrated 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. JPL's, Marc Rayman is back. His retired Dawn spacecraft discovered and has now enabled us to explain those brilliant white spots on dwarf planet Ceres. We'll talk to Marc in a bit, but first, we'll mark Bill Nye's 10th anniversary as leader of The Planetary Society. Society Chief Operating Officer, Jennifer Vaughn will join us before we hear from the science guy himself.

Mat Kaplan: The celebration will continue as Bruce Betts introduces a nice centric space Trivia Contest that is going to win someone a rare and valuable Rover asteroid. Did you know that Martian dust devils can reach eight kilometers into that pink sky? The little devil captured recently by a camera on the Curiosity Rover isn't nearly as ambitious, but it still tops the September 4th Edition of the Downlink. And here is some of the space news in that week's newsletter beginning with the ongoing saga of the mole, the InSight Mars lander's burrowing heat probe is fully buried for the first time.

Mat Kaplan: Thanks to help from the spacecraft's robotic Scoop. Keep digging little one. Artificial intelligence has helped discover 50 more exoplanets. This pioneering achievement was accomplished with data from the Kepler space telescope. Northrop Grumman has successfully test fired a solid rocket booster for the giant space launch system. The huge five segment engine will help get later SLS missions off the ground. You'll find much more at It has been 10 years since Louis Friedman, The Planetary Society's Founding Executive Director, literally, handed the keys to someone who was till that transition, vice president of the nonprofits board of directors. Bill Nye became a charter member of the society at the invitation of his Cornell professor, Carl Sagan. Chief Operating Officer, Jennifer Vaughn has probably worked more closely with Bill than anyone else. We'll hear from the science guy himself after Jennifer reflects on the age of Nye. Jennifer, welcome to the show. I am really glad to have you on because I think you are the very best person to help us celebrate this a 10th anniversary of our CEO.

Jennifer Vaughn: Well, I don't know about that, but I certainly appreciate the chance to be able to be here and celebrate what is really an extraordinary period for The Planetary Society under Bill's leadership.

Mat Kaplan: I second that, and I will tell you that I've already had a conversation with him that we're going to be hearing a few moments. He gives the most credit for the success of those 10 years, as of course you would expect Bill would because he's not going to talk as much about himself. To you.

Jennifer Vaughn: Well, that's so very kind and so very Bill. So, he's always gracious and always very giving and generous to our team because it really is a team effort, but as everyone knows, it's starts at the top. And so that's Bill. Bill has done a lot for this organization to refresh and rethink about where we are headed and what we should be focusing on and giving us all the enthusiasm and the passion instill in the team and in our membership. So, he is so very gracious that way. And it's one of the things I think about first, when I think about Bill.

Mat Kaplan: How would you describe your relationship with him? This is something he also talks about, I'll warn you, as the CEO and you as COO.

Jennifer Vaughn: I think we've developed a really nice partnership and rhythm over the years. I think with all team members, what you look for is you want to lean into one, strengths and then balance appropriately. And I think that Bill and I are very nicely balanced. Bill is a visionary. He is an eternal optimism about all that, all the great things The Planetary Society can achieve. I want to say I have that too. I'm not trying to say that I'm not both things, but at the same time, I am also more of the pragmatic, I'm operations. So, I'm trying to figure out how we are going to actually implement these things. So, I think between the two of us where I'm focused more on the day to day implementation of activities, he is setting the goals, he is setting the direction. He is clearly raising the profile, he's making the relationships. So he is very much at the helm of the organization. And I, along with the rest of the team are working to make that vision a reality.

Mat Kaplan: We have mostly so far talked about organizational managerial considerations. I'd love for you to say something also about how Bill represents the society as our spokesperson extraordinarily.

Jennifer Vaughn: I'm not alone here. A lot of people like to ask what it's like to work with Bill Nye.

Mat Kaplan: I don't know-

Jennifer Vaughn: [crosstalk 00:05:40] Exactly. I often say, "Well, probably exactly what you think it's like." Because the Bill Nye that people got to know on TV is really an extension of Bill Nye, the human. He is a teacher, he is enthusiastic, he is empowering, he is fun, he is friendly, he is thoughtful. He is all those things all the time. And so it's such a wonderful environment to be around. It starts with this kind of warm, friendly, encouraging team environment, but that just spreads out into all that we do. So, I think as a leader, he's always been one to live by his motto of everyone you meet, something that you do not.

Jennifer Vaughn: So, he treats everyone with tremendous respect and empathy. He is always a very curious person who wants to know, wants to know about you, wants to know your perspective, wants to know your, your experiences and does not pretend that he knows better. So, I think for all those reasons, he's not just the right person for the organization, but he's the right person for today as well. I think that's what the world needs more of, people who are willing to listen and build teams and bridges versus what we are experiencing a lot with the divisions. So, we're lucky to have him.

Mat Kaplan: I see, and that's lovely. It may be too much to hope for, but I'm going to hope for anyway another 10 years much like the last 10 with Bill and with you, Jennifer. And I hope I'm around for most of that too as part of the organization, because it's been a swell time.

Jennifer Vaughn: I hope so too, we are having a really good time together. And organizations, they're always growing, they're always developing. Clearly, we've had a gross batch because there was new leadership. That's what happens. It's just, you have new people, new things happen. We've had that excitement. We're not done. We have a lot more lined up for the next five to 10 years. So, I hope to see all this continue as well with many of the players that we have right now as the organization grows.

Mat Kaplan: Thank you, Jennifer.

Jennifer Vaughn: Thank you, Mat.

Mat Kaplan: That is the Chief Operating Officer of The Planetary Society, Jennifer Vaughn. And now, let's hear from the CEO. Bill, I was there for the start and I am so glad to still be with you and the society 10 years later to celebrate this auspicious occasion. Happy 10th anniversary.

Bill Nye: Thank you Mat. 10 quick years.

Mat Kaplan: [inaudible 00:08:27].

Bill Nye: What in the world? No, it's very surprising result as we say in geometric proofs. No, I did not anticipate being around the society as the CEO for 10 years. But, boy, time has flown. And speaking of flying, something we did do the last 10 years is get two solar sail missions up on orbit and we got down some fantastic pictures. We moved from a pretty cool, a pretty nice site for nonprofits. The Court of Appeals courthouse in Pasadena to our fabulous, I'll call it new headquarters that is a really comfortable workspace. So, those are that stuff that's happened.

Mat Kaplan: I'm crossing off my question, ask Bill the top two things he is most proud of.

Bill Nye: Well, what I'm most proud of? No, Mat, what I'm most proud of is hiring Jennifer Vaughn to hire you. So, one day, Mat, I don't know if this was this eight years ago, eight and a half years ago, I said to Jennifer whom I had promoted, I had the power to do that or something. And I said, "Jen, we should hire Mat full time. He's working at the University of Cal State Long Beach and he's working a part." Oh, she's, "Oh yeah, I did that a few weeks ago." No, everybody, just understand, my title is CEO. When I started, I was Executive Director, ED, which we had a focus group. It was agreed that executive director was an old fashioned or British term and we should change my title to CEO, Chief Executive Officer.

Bill Nye: And so what I ended up doing was promoting Jennifer Vaughn to be Chief Operating Officer. And that has changed everything. She is so thoughtful. She has gone back to school, learned all sorts of management things, really trained herself on the software required to manage the budget of a nonprofit like ours and set just really reasonable or concrete or achievable goals. And Jen is all about measurement, metrics, deliverables, and that has just transformed the place. And Certainly have had impressive metrics, impressive deliverables. Well, and you're one of them, Mat. Planetary Radio is going wild. I mean-

Mat Kaplan: We do okay.

Bill Nye: You send us those testimonials from listeners. It is really gratifying, man. That chokes me up. And the eye on the prize is still for me to find out more about the Cosmos and our place within it. I would like to be alive when we find evidence of life on Mars, if it's there to be found and I want the world to embrace the idea that the earth could get hit with an asteroid, a big one, and we don't want that to happen. And it's going to take everybody working together, by everybody, I mean, space agencies, taxpayers and voters around the world to ensure that we're ready if there's an incoming. So, these things are still very much on my mind.

Mat Kaplan: I know that they are on the minds of our members, and probably, everybody else who listens to this show. Of course, they're all members, right?

Bill Nye: If you're not a member out there, if you're not a member, just check us out. There's donate buttons all over the website. Oh, that's another thing. We greatly upgraded the website several times. And most recently, we've really upgraded what is under the skin, as they say in the web design world, the back of our software is so much better than it ever was.

Mat Kaplan: I see. And so nice cosmetic improvements, so upfront as well.

Bill Nye: Yeah. This streamlines things. And it means, you, the donor, you, the supporter get more for your donation. We are much more weirdly more efficient than we were even three years ago because of this latest upgrade. And another thing, when I took over, there were too lose many listeners, may be very familiar with Lou Friedman who's still around, kicking around, designing his amazing orbits to send a solar sail very near the sun and out into deep space. But there was Lu Coffing 00:13:00], different spelling. And Lu Coffing was our accountant, our head of accounting. And I changed her title to Chief Financial Officer, CFO. Lu Coffing said to me, "Bill, what you ought to do is hire Brandon Schultz full time." He works for us part time. He's our IT guy, internet technology, information technology guy.

Mat Kaplan: IT guy, superb. Yeah.

Bill Nye: Oh man. So, everybody's central casting. When you go into Brandon's office he's got a Rubik's cube, sure, he does those without even looking, but he's got the 10 by 10 Rubik's cube and he doesn't just solve it. There's patterns you can work into the Rubik's cube that are not all one code, not monochromatic on each face. And he does that. He, along with Mark Alberta have just done extraordinary things with our internet presence. Then the other thing, Mat, we have really transformed our relationship to donors, our member relationships.

Bill Nye: We hired Rick, and he's just had tremendous experience at the Claremont Colleges here in California. These five colleges that are just famous for the quality of their academics. And that's a result of the money they have to throw at the problem. And so Rick has just really taken it up a notch. And Danielle Gunn, my goodness, she's our head of communications. She has just figured it out, man. She is just so passionate about it.

Bill Nye: And what I guess what I'm proudest of, Mat, is our service to our members. We are improving the product to our members, whether the product is our website, flying our own spacecraft, proving an extraordinary hypothesis that we could tack a solar sails spacecraft fast enough to work in earth orbit for $7 million, not 150 million, which is what it would cost at a space agency. So, we have realized the dream of the founders and I think the expectations of our modern members. And as I like to say, Matt, the best is yet ahead. We are going to provide service to young people, to kids, students and families, to get people excited about space exploration and to really know and appreciate our place in space.

Mat Kaplan: I'm going to mention just one other area. And it's one in which you have played a major role. And that's our enormous success over the last 10 years in carrying on a tradition that goes back to the beginning of the society in Washington, D.C.-

Bill Nye: Exactly.

Mat Kaplan: ... our advocacy and policy efforts. Yeah.

Bill Nye: Three things I like to say we do, Mat, we innovate, there's LightSail, we educate, there's a tremendous website, the long form journalism about planetary science you will find nowhere else. Jason Davis and his guys and girls, and Emily Lakdawalla just does amazing things. Our little niche of gigantic solar systems. And then the other thing we do is advocate. So, we go around the world, but especially to Washington, D.C., to influence space exploration policy, and we've been just extraordinarily effective. It just shows you what you can do when you throw money at the problem.

Bill Nye: By that, I mean, when you hire the right people who have the right personalities to make the right contacts, as the old saying goes, "Washington, D.C. is a small town based on trust and relationships." It's giving people information they need. A Congressman, Congresswoman and their staffs, how money is spent in planetary science, the great value of planetary science, the relative cost of planetary science and planning. NASA gets pulled in all directions for political reasons, but we help the administrator no matter whether she or he is conservative or progressive, we do our best to help the administrator make good decisions about planetary science. And we do that because we have set aside a part of the organization chart, the orange chart for advocacy, innovate, educate, advocate. That's what we're doing.

Mat Kaplan: I am not surprised that you've spent these last few minutes talking to us about our achievements and putting them in terms in large part of the people that we work with, the colleagues, many of whom you and Jennifer hired.

Bill Nye: So, Mat, just everybody, we have a nice headquarters.

Mat Kaplan: We do.

Bill Nye: And thanks to one eccentric donor. We have a very nice coffee machine, but that's not what we have. What The Planetary Society is people, it's our staff that is so valuable. Everybody's so dialed in and so passionate about planetary science, planetary exploration, that we're able to do this, and that's what I'm proudest of.

Mat Kaplan: And I'm glad that you're proud of that. It is utterly true. But I have learned in my many years, working in many organizations that this stuff flows from the top. So, I give you enormous credit, my friend, for getting us to where we are today. And sure you had lots of help, but you put a lot of that help in place and you let it work and you add your own unique brew to making the society what it is today. And I'm just proud to be part of it. And I look forward to the years ahead.

Bill Nye: Well, thank you, Mat. Thank you, indeed. I'm really excited about the future and our staffing opportunities and how we're going to work to include more and more people on the staff and on the board of directors, but especially in our membership. Oh, by the way, the board of directors is something else, everybody. Take a second, look on our website and just look at the credentials.

Mat Kaplan: This is yours, 10th anniversary, you've mentioned everybody else in the world.

Bill Nye: Oh, I did my best, man. So, just everybody know out there, my contract with the society is officially half time. And so there's some times when I feel like I hardly do anything, then other times just really more than full time focus. So, it really is an honor. And you play the hand, you're deal. I went to Cornell. I had one class from Carl Sagan. It changed my life. And now I'm CEO of the organization that he started and I am honored to serve, Mat, honored to serve.

Mat Kaplan: And I'm honored to serve under you. Thank you, Bill. Thank you for everything, and I'm happy anniversary, many more to come that we can celebrate I hope. And many more accomplishments by the society and our members and everybody else you've talked about.

Bill Nye: Thanks a lot, Mat, let's change the worlds.

Mat Kaplan: I was waiting for that. That's Bill Nye. He is the planetary guy, the science guy, the CEO of The Planetary Society for 10 years and counting. We're moments away from a visit with the former Chief Engineer for the Dawn mission. Marc Rayman will tell us what's underneath those brilliant formerly mysterious white spots on dwarf planet Ceres. I hope you'll stick around.

Bill Nye: Greetings once again, Planetary Radio listeners, Bill Nye, the planetary guy here, CEO of The Planetary Society. You and I know better than to ask if another world shattering asteroid will come our way. The only question is when? Here at The Planetary Society, we're committed to protecting the planet. You can be a defender of earth. We need you on our planetary defense team. It's the only large scale natural disaster we can prevent. Donate today at to power our crucial work with your gift. That's Thank you for helping us save the world.

Mat Kaplan: Welcome back. Marc Rayman wasn't just Chief Engineer for the Dawn mission, he also served as mission director and project manager for the ion power spacecraft that first visited Vesta and then departed for Ceres, the second largest and largest objects in our solar system is asteroid belt, out there between Mars and Jupiter. The Dawn spacecraft finished its work nearly two years ago, but we got proof that it is still delivering exciting science last month. Marc also continues to deliver at the Jet Propulsion Lab. He was promoted to Chief Engineer for Mission Operations and Science. Add this latest honor to the many awards he has received across his career, including the Collier Trophy, the highest us honor for achievement in space or aviation. It's on permanent display at the National Air and Space Museum in Washington, D.C.. Marc it is always a pleasure to welcome you back to Planetary Radio. Thanks for returning and congratulations on the new job at JPL.

Marc Rayman: Thanks, Mat. And it's always a pleasure to be here with you. I love your show and I'm always happy to talk with you.

Mat Kaplan: Well, you are one of our most frequently recurring guests, I'm happy to say. And so this won't be the last time. When did you make this transition from a leader of the Dawn mission to Chief Engineer for Mission Operations and Science?

Marc Rayman: Well, Dawn ended late in 2018, so it was early 2019 that I took this new position at JPL, and it's a lot of fun.

Mat Kaplan: I bet it is. I know at least one other chief engineer there and he has a good time too. So, I'm sure you are as well before we talk about Dawn a little bit, tell me more about this position. I mean, obviously, it carries a lot of authority, but what does it really mean? Are you a go between still between the scientists and the engineers who put together and design and operate these spacecraft?

Marc Rayman: Well, that's something I've always done, but for me, the fun thing about this new position is that I get to be involved in many different projects. I'll tell you, to me, there's nothing cooler than being responsible for one of JPL's many, many exciting missions, but as much as I love that I've been a space enthusiast my whole life. And in fact, my only real disappointment about my career is that it has interfered with my lifelong hobby of learning about space exploration. And so now, instead of being in charge of one mission, I get to be involved in many. I've accumulated a fair amount of worthwhile experience at JPL. And so, I can pass some of that along to people who are focused on their individual missions. So, it's a lot of fun.

Mat Kaplan: Sounds pretty fun and pretty thrilling to me actually. Let's turn to Dawn. I figured we'd spend a few minutes re-Introducing the mission to listeners, but you've saved me that trouble because you shared with me this terrific video produced by JPL that also features your colleague, Carol Raymond, who of course became principal investigator for the Dawn mission. But it opens with you, and I think we'll just play the audio. And then I will explain to people why they hear an interesting sound effect in the beginning of the video. So, here it is.

Marc Rayman: Did you know that cereal comes from the word Ceres, the Roman goddess of agriculture and grain? We may not know that there's a distance solar system world Ceres. It was discovered 200 years ago, and it's had a sort of identity crisis, used to be known as a planet and then an asteroid, and now it's worth planet. Well, whatever you call it, Dawn with the xenon ion propulsion system is about to call it home.

Carol Raymond: Dawn is truly an historic mission, it's the first mission to orbit a main belt asteroid. And it's the first mission to orbit two interplanetary bodies, to fossils from the very beginning of our solar system. And thus it's telling us part of the story of our own beginnings.

Marc Rayman: Dawn orbited Vesta and spent 14 months exploring that alien world. We saw a crater there 300 miles in diameter. And in the center of that crater, there's a mountain that's two and a half times the height of Mount Everest.

Carol Raymond: It's very young. It formed very hot, but we also found that there was water on Vesta and that water had to come from somewhere else.

Marc Rayman: And now we're on the verge of exploring an even larger alien world, Ceres. Thanks to Dawn's unique ion propulsion system. It has a different way of going into orbit around Ceres from what we're used to. It will slowly creep up on Ceres and gently use its high on propulsion system to gracefully slip into orbit. Dawn is going to be revealing to us this mysterious world, that for more than two centuries, it's just been a faint smudge of light amidst the stars. We're now getting pictures that are better than the best we'd ever had before.

Carol Raymond: The bright spot has been seen in the approach images is very interesting because it's in the same region where the Herschel Space Observatory detected water vapor emission from Ceres' surface. It's possible that objects like Ceres brought water to the earth. It has a rocky corer and an ice mantle. And in the past, had an ocean like Europa and Enceladus.

Marc Rayman: Dawn carries a suite of sophisticated instruments that will allow us to determine not only what Ceres looks like, but what it's made of and what its interior structure is. So, we're going to learn about the geology and the chemistry. What minerals are on Ceres, all about the nature of this world. And it's like a time capsule from the dawn of the solar system.

Mat Kaplan: That was Marc Rayman and his colleague, Carol Raymond in there in that little video describing very, very well the Dawn mission. But this is radio or a podcast, audio podcast, so they missed out on one of the greatest little visual jokes I've ever seen in a video like this. And it's because you are sitting at a table with a bowl in front of you at the beginning of the show. Marc, tell people what you're doing.

Marc Rayman: I'm having breakfast. You could call it breakfast at dawn, a pouring my Ceresos cereal, enjoying breakfast and enjoying talking with my breakfast companions about this exotic alien world.

Mat Kaplan: And there actually is a connection right between cereal and Ceres.

Marc Rayman: There is a connection because Ceres and serial are atom logically derived from the same word. And it's just a fun way to help people remember the name of the first dwarf planet that was ever discovered.

Mat Kaplan: Kudos to your colleagues at JPL who made that cereal box for you because it's perfect. It looks like it could be on the shelf at a supermarket and maybe it should be too. I don't know if I'd want to eat the little gray spheres that you pour out of it, but they are appropriate.

Marc Rayman: Yeah. Well, whether Ceres ores tastes good or not it's a separate question. I can tell you that that cereal box is on a shelf somewhere. It's not at a grocery store, it's in the office at JPL, which unfortunately, I haven't seen in six months, but I have no doubt that the cereal inside won't taste any worse when I get back to my office than it did when I was last there.

Mat Kaplan: I'm sure it's loaded with nutrient packed minerals just like Ceres is.

Marc Rayman: Absolutely.

Mat Kaplan: Yeah, you and me both, it's fair, I sure miss my office, I look forward to going back when we're all vaccinated. And by the way, this video, we will put up a link to it on this week's show page. You can get that from, and you'll find other relevant resources to this week's episode. Here's why I got a hold of you, again, Marc, it's because of a press release that came out from JPL and NASA just a few weeks ago, "Mystery solved, bright areas on Ceres come from salty water below." And of course we are talking about those bright spots, which mystified many and fascinated all who saw them. I guess now, we seem to understand what they are. Would you tell us what's going on here?

Marc Rayman: Yeah, I think this is really exciting. And before I tell you what we learned, let me tell you how we learned it. When Dawn was orbiting Ceres, so Dawn got to Ceres in 2015, our prime mission there lasted a year and a half or so when we mapped the body and took a tremendous number of measurements and accumulated a vast wealth of data. But clearly these bright areas that you mentioned were the most intriguing. And so in Dawn's second extended mission that is after the prime mission had ended, NASA approved our continuing our exploration of Ceres. We focused on that bright region and maneuvered Dawn to an orbit that once every 27 hours, dip down to just a little more than 20 miles above the ground. So, only about three times higher than you are when you fly cross country on a commercial aircraft.

Marc Rayman: This was an extremely challenging, but incredibly part of the mission because we got a fantastic view of this area. The crater that we're focused on here is called Occator, it's 57 miles across. We know that it was formed about 20 or 22 million years ago, something like that. But these bright areas in the interior of the crater are younger than that, significantly younger. We now understand that what happened is when the impact form the crater, it melted some of the material there. So, I should take a step back and remind people that Ceres has a substantial inventory of water. Most of it frozen, as well as salt and rock. So, the impact melted that material and made what's called a melt chamber underground. And some of that material came up to the surface and when it froze, and the water dissipated with this bright, reflective material left on the ground, salt flats, in some sense. But the impact also, created fractures underground that connected with a deeper reservoir of liquid that is perhaps 25 miles down. A large reservoir of this brine that has salt and rich water.

Marc Rayman: That could be hundreds of miles wide. Then through those cracks, the water subsequently made its way up to the ground and has continued to replenish what was left from after the impact. So, we know that this melt chamber that was formed would have frozen long ago, millions of years ago. It would have taken millions of years to freeze, but still would have frozen long before the present. But the material that we see on the ground could only persist on the ground in Ceres for a matter of maybe tens or maybe a few 100 years. We see it now, which means it has continuously been, not necessarily continuously, but it has repeatedly been refreshed. I think that is really, really cool. We know now, that indeed there is subsurface liquid and it has this path up to the surface.

Mat Kaplan: Absolutely, fascinating. How is this possible? We know that the liquid water ocean under the surface of Europa is kept warm and liquid by the tidal stress from Jupiter. We talk about that a lot, but Ceres, it has no giant nearby worlds to keep its innards from freezing.

Marc Rayman: Right.

Mat Kaplan: How's this happening.

Marc Rayman: Yeah, that's one of the things so cool about this. Ceres is the largest body that isn't a planet or moon on which we now know there's liquid. And as you observed on places like Europa and Enceladus, of course, one of the moons of Saturn, the gravitational interaction with the planet and the other moons flexes the body stretches and squeezes it, and that imparts energy to it to keep the liquid from freezing. Ceres doesn't have that because it's a dwarf planet, it's orbiting the sun and it's doing so basically by itself from the standpoint of gravitational heating. So, the heat is what's left over from the radioactive materials that it incorporated when it formed. And the chemical composition of Ceres is such that it's able to retain that heat, that is, as the materials have decayed, the radioactive elements have decayed over the lifetime of the solar system, the heat has not been able to leak out from inside Ceres and escape out into space.

Marc Rayman: Or not all of the heat has been able to. So, it has retained much of that heat and the salts, particularly as people who live in parts of the country that get a lot of ice and snow know, the salts lower the freezing temperature of the water. That's why they salt roads to help melt that ice. Well, on Ceres, it works as an antifreeze there as well. And so even though it can be below what people normally think of as the freezing temperature of water, 32 degrees Fahrenheit, it can stay liquid. And so this combination of the materials that are able to help retain the heat and the ones that keep the freezing temperature low, have allowed Ceres to retain this liquid for the lifetime of the solar system. Pretty cool, huh?

Mat Kaplan: Absolutely, utterly fascinating.

Marc Rayman: It is.

Mat Kaplan: And the coolest, well, and not as cool as it might be otherwise, I guess. But how did you in the Dawn team figure out that there is this much bigger, I'll call it a sea, deeper below the surface of this dwarf planet?

Marc Rayman: Well, it's a combination of many different measurements, but a key one is measuring the gravity of Ceres. Of course, the gravity doesn't mean just what its overall mass is and thus how strongly it pulls on the spacecraft, but rather the variations as the spacecraft changes its location. So, when there are underground regions of higher density, they pull more strongly on the spacecraft and underground of lower density pull less strongly. And so with the exquisitely accurate sensitive measurements of the spacecraft's motion, when it gets down very close to the surface, scientists are able to determine the distribution of material underground.

Marc Rayman: So, combination of the gravity measurements, mathematical models that describe the movement of heat inside Ceres, based on the chemistry measurements of things like the ratio between the depth of a crater and its diameter, that tells you about the mechanical properties of the ground and how it both responds to an impact and how it changes the shape over time and studies of the mineralogy. That is, what are the rocks and minerals there, all these different sources of information and methods of analyzing the data have combined to show that there's this large region that just happened to be located near where this impact occurred, that then these fractures were able to tap into.

Mat Kaplan: I never ceased to be amazed when I hear these stories about what we can learn about the deep unseen interior of a body by orbiting something above it. I mean, when you talk about exquisite measurements of those Doppler shifts in the radio signal, it makes me proud to think that we're capable of doing this kind of science.

Marc Rayman: Yeah. I agree with that. I mean, it sort of makes you proud to be a human being and part of humankind's collective effort to understand the Cosmos. And it's no one person and it's not even any one team because it's the collective progress of science that allows this to happen. And I think that's deeply profound and incredibly exciting. And I think we're all lucky to be not only part of a species that can do that, but part of a culture that does do that

Mat Kaplan: Well said. We stand on the shoulders of giants and then folks like you become the giants for others to stand on. I got to bring up one of the thing that was in this press release, partly just because they have such a cool name and they have a relationship to earth, and those are these features that you found on Ceres that resembles something very similar on our own planet. You know what I'm talking about, right?

Marc Rayman: I do. You're talking about pingos, and yes, they do have a neat name. P-I-N-G-O, pingo. It's a Hill, shape of sort of a dome that forms in permafrost here on earth from the pressure of groundwater that freezes and pushes up the frozen material in the ground. Pingos have been observed on Mars as well. And now, on dwarf planet Ceres.

Mat Kaplan: And for the same reason, right?

Marc Rayman: That's right, because of the pressurized frozen groundwater.

Mat Kaplan: I said up front that Dawn is ... Well, obviously, the mission ended nearly two years ago now, but it's going to remain at Ceres forever, but not on Ceres. I mean, why is it still orbiting? Why didn't you let it impact?

Marc Rayman: Yeah. Well, the reason is because Ceres is of astrobiological importance. We've talked about the water, Dawn discovered a tremendous amount of organic materials on Ceres. These are chemicals that we know are important for life and Dawn discovered many other chemicals besides organics that are also of interest for life, or at least the chemistry that leads to life. We just discussed a few moments ago, it still has this internal heat. So, there's a rich combination of the ingredients that are of interest for astrobiology. We didn't want to take a chance and contaminating that pristine environment with the terrestrial chemicals that we call Dawn.

Marc Rayman: So, the plan at the end of the mission, which we did execute was to leave the spacecraft in an orbit that would not allow it to impact for decades at least. And that would allow humankind, if it made the decision, to do so to conduct a followup expedition, that wouldn't be misled by what it found on the ground, but the possibility that it was the materials brought there by Dawn. This final orbit that we put it in that dips down to 22 miles, then coasts up to 2,500 miles and then plunges back down to 22 miles and it completes each loop every 27 hours that we purposely designed that carefully so that it would not crash even in decades.

Mat Kaplan: Planetary protection, something else we talk about pretty regularly on this show. And there's a good explanation for why it's so important. We talk with other folks who were key contributors to mission's past. I mean, Linda Spilker still comes on regularly to tell us about science that is still flowing from the Cassini mission at Saturn. Are you still talking with other partners in the Dawn mission from around world?

Marc Rayman: I am. Now, I should say that my current responsibilities don't allow me a lot of time to devote any more to Dawn's legacy, but I do still talk to them. And I know that there are people working on further exciting questions that can be addressed with the vast treasure trove of data that Dawn collected. And I'm confident that scientists will continue to gain fascinating new insights for many, many years to come.

Mat Kaplan: I look forward to those. Marc before I let you go, I want to bring up that hobby of yours that you said your job keeps you from. I'm going to put up a link to that terrific video we did when you gave me a tour of your home, not far from JPL.

Marc Rayman: Yeah, that was a lot of fun. I particularly like our shared laugh, right at the beginning. You got it off to a good start and you did a nice job with that video, Mat.

Mat Kaplan: Thank you. We'll just tease the audience with that. But the video will be on the show page, once again, for this episode of Planetary Radio. It was a lot of fun. How has that great space library of yours? Still growing?

Marc Rayman: It is, and it's my expression of my lifelong fascination with space. I just love it. And that's of course, one of the reasons I love Planetary Radio.

Mat Kaplan: Oh, thank you, Marc. Well, more power to you, Marc. And thank you for joining us here and for sharing all of this and for the great work you continue to do on behalf of those who believe so strongly in the science that is being conducted around our solar system and beyond it as well.

Marc Rayman: That's very nice of you to say, thank you. It is truly my pleasure. I recognize, I'm extremely lucky, I really get to do something that I've wanted to do my whole life. So, it's truly a delight to be able to share it with you and the listeners, because I know as I told you once before, these are my people, we're all same, we share the same fascination with the Cosmos. So, it's really fun to be able to talk with you about it.

Mat Kaplan: And I feel some of that luck as well, just for the opportunity to talk with folks like you. Thanks again, Marc.

Marc Rayman: You're welcome. Thank you, Mat.

Mat Kaplan: That's Marc Rayman. He is now Chief Engineer for Mission Operations and Science at the Galactic Capital of robotic exploration of our solar system and beyond the Jet Propulsion Lab near Pasadena, California. And of course he previously served, well, many jobs, but for the Dawn mission was Chief Engineer, Mission Director and Project Manager. We'll be right back with this week's What's Up? And Bruce Betts. Time for What's Up on Planetary Radio. We are joined by the Chief Scientist of The Planetary Society, that's Bruce Betts of course, who's here to tell us about the night sky and resolve a question about the gods. Welcome.

Bruce Betts: Yes. Using my expertise in such things.

Mat Kaplan: Who's better qualified, frankly? You're the chief scientist.

Bruce Betts: Scientist.

Mat Kaplan: World's foremost authority, I think.

Bruce Betts: Yeah, it's on Greek and Roman mythology. That is-

Mat Kaplan: No, on everything.

Bruce Betts: Finally, you acknowledged it. You know what I can tell you about? A lot of things, but I'm going to tell you about the night sky and I'm going to emphasize once again, all the glorious, bright planets that are named after Greek and Roman gods, we've got in the evening sky in the South, Jupiter looking super bright, Saturn looking yellowish to its left, and then coming up now in the early evening in the East, is Mars getting really brighter than the brightest star in the sky looking reddish. Moving towards, its closest approach on October 6th.

Bruce Betts: And then in the pre-dawn sky still got Venus just dominating over there, and this looking super bright, the moon will hang out with Venus on September 14th. We move on to this week in space history. It was 1975, that Viking 2 was launched off towards Mars, and my yearly bow to you, Mat, and your interests, 1965, 55 years ago, danger, Mat Kaplan, danger. Last in space premiere.

Mat Kaplan: There must be episodes on YouTube. Even at its worst, I bet it was better than the movie version that came out with William Hurt, which was just God awful. Speaking of God, Maybe I should say God's awful.

Bruce Betts: You can find more of Mat's movie reviews. Okay, let's move on to non space fact.

Mat Kaplan: I remember all those themes.

Bruce Betts: Sorry. I don't have a Lawson space, random space fact for you. Speaking of Bill Nye, CEO of The Planetary Society, the mother of Bill Nye was a code breaker in World War II. His father spent four years in Japanese prison camp where he learned to tell time using shadows, spring his interest, and later Bill's interest in sundials. Bill helped create the Mars exploration Rover's camera calibration targets to also be sundials or Mars dials, which were used by students in The Planetary Society's, Red Rover goes to Mars during those missions. Speaking of exciting, let's go on to this apparently controversial Trivia Contest question where I said, assuming a combined Greek and Roman Pantheon mythology within this mythology, which planet is named after the earliest or oldest god? How would you like to handle this, Mat?

Mat Kaplan: Well, let me just read this first one from Bjorn Ghetto, regular listener, because it gives you an idea of just how ridiculously complex this is. Bjorn says, "So the oldest DAD in the solar system is in Roman, Tara or Talos or Gaia in Greek mother earth. She was the mother of Uranus." And then he adds, sorry. Some of what follows is pure nitpicking, "Uranus together with Rhea was the father of the Titans of which one was Saturnas Cronus." So, if we are picky, we still haven't come to the gods yet. The oldest of Saturnas' children where the gods start to have a planet is Pluto. "Oh, sorry, that's no longer a planet," he says. So, the prize could be argued to go to Jupiter. Saturnas' youngest son. Phew, a lot of this comes down to Titans versus gods. And then whatever the folks who came before the Titans were.

Bruce Betts: My source, which is unimpeachable is Wikipedia.

Mat Kaplan: A lot to take, God.

Bruce Betts: Wikipedia, those things are all called gods, including Uranus. Uranus, which is a very complicated Latinized version of a Greek god equivalent to the Roman Kayla. So yes, we're in a mess of mythology and I sort of regret it, but I thought it was interesting to me because Uranus, which is the answer I was looking for given the combined mythology, Uranus was the father as was mentioned, Uranus is the father of Saturn. Saturn was the father of Jupiter and Neptune. So, it's kind of a whole giant planet family tree. And they were all so loving within their families.

Mat Kaplan: Oh man, were they? This from Darren Richie, one of the many people who said, "Well, he was going to go with Gaia or Tara, Earth as the grand mother of us all." But then of course, those are not what we call Earth anymore, at least not for our purposes. Here's how much worse it gets. Uranus was in turn the son and the husband, you of Gaia Tara, the primordial earth mother. So of earth counts she's the winner and looking great for her age, but then he said otherwise, Uranus." So, he kind of covered his bets there. Here is a portion of a poem, a fragment of a poem from Jean Lewin in Washington, along these lines, we don't have time to read the whole thing, "Known to us is Tara Gaia in Greek, then mother Earth is the answer you seek. But that requires us all to construe." Is this something that Bruce would do?

Mat Kaplan: So, not to assume and to avoid debility Uranus is what my choice will be. So, he's with you. And so was Paul Hoover, and Paul Hoover is our winner. Paul Hoover in my old hometown of Long Beach, California, who indeed said Uranus. And also he thought it was fair. He did father Jupiter, then tried to eat him, but I guess that didn't work out so well. And he thanks for sticking with all of this. He loves to listen to the show. Paul, congratulations, you're getting a copy of the end of everything, astrophysically speaking by Katie Mac our guest of a couple of weeks ago. And boy, were there a lot of people who enjoyed that conversation and hopefully you're also going to enjoy the book.

Bruce Betts: Yeah, it was throwing earth out because we call it earth, not Tara or Gaia officially as a planet name. One thing I should have done, however, was to specify that English was the language I was working with because otherwise it just gets even more complicated. So, sorry for all the confusion, everyone. But well, it's confusing because it's mythology.

Mat Kaplan: I think I speak on behalf of almost all listeners in forgiving you this because it was still fun. It sure generated a lot of conversation.

Bruce Betts: Oh, good.

Mat Kaplan: Todd [Yampoll 00:53:17] in Arizona, I post this question to my 12 year old who knows a lot more about mythology than I do after amusing for a moment about whether earth equals Gaia and deciding not, she chose Uranus. So, good on your daughter, Todd. Sean Kane in New York who but ring Saturn, the richest of all the spheres could be eldest godfather of all his peers. And I read that little DAD from Sean, partly because he says, "Love the show." He's a history PhD student studying first context situations in the last age of exploration. Is that cool or what?

Bruce Betts: That's quite cool, much more tangible than mythology.

Mat Kaplan: Finally, this firm [Ayrton Uzek 00:54:01] in Arizona. I'm going to say Saturn, but how can you be sure unless you see their birth certificates.

Bruce Betts: I was starting to even think of that.

Mat Kaplan: Thank you everybody. This was fun. We're ready to go on.

Bruce Betts: Back to the CEO of The Planetary Society, Bill Nye, he holds three patents. One of them relates to shoes. What kind of shoes? Go to

Mat Kaplan: Wow, I only know about one of his patents and it relates to baseball, but shoes that's new for me. Oh, I guess I can enter the contest. As long as I do that by Wednesday, September 16th at 8:00 AM Pacific time, and I might just win myself. Are you ready, Bruce? We haven't done this in a while.

Bruce Betts: I'm ready?

Mat Kaplan: How about a planetary society kick asteroid, rubber asteroid.

Bruce Betts: Nice. Bringing back the rubber astroid.

Mat Kaplan: Thank you. Roll those R's. All right, we're done. No, rolling them under water.

Bruce Betts: All right, everybody, go out there, look up the night sky and think about what this show would sound like underwater. Thank you, and good night.

Mat Kaplan: Do I get to wear my snorkel? He's Bruce Betts, he is the Chief Scientist of The Planetary Society who joins us every week here for R ... I can't do it. That's terrible. Planetary Radio is produced by The Planetary Society in Pasadena, California and is made possible by its proud members. Mark Hilverda, our associate producer, Josh Doyle composed our theme, which is arranged and performed by Peter Schlosser. Ad astra.