Planetary Radio: Space Exploration, Astronomy and Science - Why didn’t Dawn land on dwarf planet Ceres?

Episode Date: October 6, 2021

It started with a question from a listener. The answer comes from Dawn mission chief engineer and mission director Marc Rayman. Marc also tells us about his new job as chief engineer for mission operations and science at NASA’s Jet Propulsion Laboratory, and shares his love of space exploration with Mat. LightSail 2 is still going strong! Program manager Bruce Betts opens this week’s What’s Up segment with a mission status report. Learn more at https://www.planetary.org/planetary-radio/2021-mark-rayman-dawn-ceresSee omnystudio.com/listener for privacy information.

Dawn did not attempt the first landing on a dwarf planet. Mark Raymond will tell us why, this week on Planetary Radio. Welcome. I'm Matt Kaplan of the Planetary Society, with more of the human adventure across our solar system and beyond. I only meant to pass along a simple question from a listener, but conversations with Mark Raymond are just too good to abbreviate. That's why we'll spend a few extra minutes talking with JPL's new Chief Engineer for Mission Operations and Science. More than 27 months

sailing on sunlight, and our LightSail 2 is still up there. We'll get a mission update from LightSail program manager Bruce Betts just before he treats us to a great night sky and much more, including a special extended deadline for the new space trivia contest. Have you seen the newest close-ups of Mercury? The European Space Agency's BepiColombo snapped them on October 1st as it zipped past the planet in a slingshot maneuver. You can read about the mission in this week's edition of The Downlink, the Planetary Society's weekly

newsletter. The spacecraft will finally enter orbit around that hot and cold world in 2025. Stand down, Mars fleet. It's solar conjunction time when Earth is blocked from the red planet by the sun. Don't expect much work to get done till Mars comes out the other side around the 16th. NASA has successfully put the latest Landsat in orbit. Landsat 9 continues a 50-year tradition of Earth observation by this series. Let's see, what else is happening? Oh yeah, Captain Kirk is going into space.

The real Captain Kirk, you know. The original model, William Shatner, will be on board next week when another Blue Origin New Shepard takes flight. Warp factor 0, let's say 0.000000001. New editions of The Downlink every Friday at planetary.org slash downlink. What does the chief engineer for mission operations and science do? I think you'll enjoy Mark Raymond's answer to that question, but first you'll hear him answer a question that came from someone else. Mark has been dropping by Planetary Radio for a

long time, beginning at about the time he became chief engineer and mission director for Dawn, the spacecraft that orbited and revealed both Vesta and Ceres in the main asteroid belt. and revealed both Vesta and Ceres in the main asteroid belt. Mark arrived at JPL in 1986 after working as a postdoctoral researcher with John Hall, co-winner of the 2005 Nobel Prize for Physics. Mark used much of what was learned from the Deep Space One mission to make Dawn the enormous success it became, including reliance on ion engine propulsion. He is the only person to have received both JPL's Exceptional Technical Excellence Award and its Exceptional Leadership Award. Mark Raymond, welcome back to Planetary Radio. I realized just last week we had

to have you on. This began when New York listener Setupong wondered why you left Dawn on orbit instead of attempting to land on Ceres. And I assume that Setupong was probably thinking of, you know, what Rosetta did at Comet 67P, or better yet, look back 20 years to near Shoemaker's little bump down onto asteroid Eros. engineer Shoemaker's little bump down onto asteroid Eros. I wasn't surprised to hear from you soon after we talked about this on the show, but I thought that Setupong and other listeners might like to hear the answer directly from the mission director and chief engineer. So again, welcome. Thank you, Matt. It's always fun to be here. As you know, I'm a regular listener to your show. Thank you. And I always enjoy it. Your shows are informative and fun. So it's always a treat to be here and to discuss Setapong's insightful question of why didn't we do this clever thing? I want to know.

In fact, you've already told me, but we have to share this with everybody. But there's something else that's really eerily serendipitous about this. Tell me the anniversary that you just mentioned before we started recording. You and I are having this discussion on September 27th, which truly by coincidence is the 14th anniversary of the launch of Dawn. So it embarked on its mission from Cape Canaveral on this date in 2007. So that's a nice connection. I'll say, is this perfect or what? Setupong, thank you for setting this in motion. And I assume you were there at the Cape. No, actually I was not. I haven't been

there for the launches of my missions because I'm in mission control at JPL. As soon as the spacecraft separates from the launch vehicle, JPL takes over, and that's where I need to be at launch. All right. Doing your job. That's okay. I don't get to see the cool launch live, but I get to do other cool things, so that's okay. You think? Yeah.

Okay. Yeah, you think? Yeah. Okay, so why didn't you just sidle up to Ceres the way we saw near Shoemaker do in an unplanned rendezvous with that asteroid 20 years ago? Well, the first thing I could say is, why didn't anybody think of this when Dawn was at Ceres? I mean, set upon, why didn't you send

this suggestion to us? Maybe we never thought of it. In fact, of course we did. There are two parts to the answer, but part of it is contained in your description of Ceres. Yes, in some sense, it's an asteroid, but it's a dwarf planet. That's an important distinction. I think when people think of asteroids, they think of these small bodies like Eros, Ryugu, Itokawa, Bennu, Cheryamov-Gerasimenko. I'm not saying that size is a measure of importance or interest, but still it's an important physical parameter. And Ceres is not at all like those. You know, there are millions, literally millions of objects in the main asteroid belt. 35% of the total mass is in dwarf planet Ceres. I love that statistic. That's just fantastic.

Random space fact, as Bruce would say. That's right. But this one wasn't random. It was, well, what would you call it? A CCSF, carefully chosen space fact, maybe. I like that. Okay. Ceres is subject to planetary protection, which is a set of standards that NASA subscribes to designed to ensure the integrity of extraterrestrial bodies, including this alien world was once covered with an ocean of liquid water.

And we know from Dawn's exploration that it still harbors a vast inventory of water. Most of it is ice, but there's some liquid still underground. It has a supply of heat. still underground. It has a supply of heat. Dawn discovered organic materials and a rich inventory of other chemicals. With all these ingredients, Ceres could have undergone some of the chemistry related to the development of life, and we don't want to contaminate that pristine environment with Dawn's terrestrial materials. Much like we saw Cassini end up crashing into Saturn instead of taking the chance that it would run into Titan or Europa or whatever. Sorry, not Europa, Enceladus. And we knew what you meant.

Yeah, thank you. But you're absolutely right. So the requirement, our requirement was to ensure that Dawn would be in an orbit for at least 20 years and preferably longer, would not change enough that Dawn would actually crash into Ceres even after the mission was over. Two decades is long enough. There's a common misconception here that I hear often that the 20 years was so that the space environment would sterilize any follow-up mission. That is to allow enough time to conduct possible future biological exploration of this dwarf planet. And so two decades is long enough that we could mount a mission to build on Dawn's discoveries, and we wouldn't want it to be misled by microorganisms or non-biological organic chemicals that might have been deposited there by our spacecraft. Okay, that's one good reason. What's the other one?

Well, the other one is Dawn was not physically capable of accomplishing a controlled landing. was not physically capable of accomplishing a controlled landing. Once again, Ceres is not just one of these chunks of rock. It's a big place and its gravity is significant. Now, when missions like the ones you and I have mentioned, which I should say are incredibly cool missions. You know, you and I, and essentially everybody listening, we're all enthusiastic space buffs. These other missions, which are super neat, which accomplished their landings or their contact with these bodies, did so because the gravity, the gravitational attraction was exceedingly low. It's much more like, that is for those missions, it's much more like when two spacecraft rendezvous in orbit.

Yeah. You think of a spacecraft flying up to the space station. The gravitational attraction is almost entirely negligible. Not quite, but very close. So you just fly up next to the body and go from there. A series gravity was much too great for that. For reference, if Dawn had gone to a very low altitude orbit, even lower than we did, its orbital velocity would have been 800 miles per hour.

Well, you can't just gently drop out of orbit like that. And even if we could have, you need a rocket engine to slow your descent, right, to make a controlled landing. Well, Dawn had its famously efficient ion propulsion system, uniquely efficient, actually, without which this mission would have been not just difficult, but truly impossible, would have been impossible with any other propulsion system. But as I think another one of your listeners wrote in, the thrust from the ion engine is comparable to what you would feel if you hold a single sheet of paper in your hand. One way to think of this is, imagine you had a balance, a scale, where on one side you have the piece of paper. On the other side, you have Dawn's weight

in the Ceres gravitational field. That weight would have been about the equivalent of about 50 pounds on Earth. Well, the weight of a single sheet of paper is not going to be very effective against a 50-pound weight. On Earth, of course, Dawn would have weighed much more, but it wasn't at Earth, so that doesn't matter. It have been 50 pounds in Ceres gravitational field. So the ion propulsion system, which propelled Dawn from Earth past Mars into orbit around Vesta, allowed us to maneuver in orbit extensively at Vesta, break out of orbit, fly for another two and a half years to get to dwarf planet Ceres, go into orbit around Ceres, fly to 10 different orbits at Ceres go into orbit around Ceres, fly to 10 different orbits at Ceres, that ion propulsion system would have been totally ineffective in controlling the spacecraft's

descent to that intriguing alien surface. And so it would not have been physically possible. But if not for those two reasons, sure, it would have been fun. have been physically possible. But if not for those two reasons, sure, it would have been fun. And all of this, of course, goes along with the enormous success of this little spacecraft. Don't you like to call it the first true interplanetary craft? Because it is still the only one to ever orbit two different bodies. because it is still the only one to ever orbit two different bodies. Right.

It's just as a detail, it's the only spacecraft ever to orbit two extraterrestrial destinations. Gotcha. Once again, for all of us who are space enthusiasts, spacecraft have orbited two solar system bodies many times. Orbit the Earth and then the Sun or the Earth and then the Moon. Even Mariner 9 and then many others after it orbited the Sun and then Mars. But the Sun, while it's an extraterrestrial body, wasn't an extraterrestrial destination. Dawn is the only one that had the capability to go to a distant body, go into orbit around it, maneuver extensively, break out of orbit, and then go to another body and do that. Maybe that's more than you care about, but I think

among space enthusiasts, these details are fun. They're not just fun. They're impressive as all get out. It's also, of course, along the way after visiting those destinations, Vesta, and then Ceres, the body that we've been talking about, doing tremendous science and returning all of those great images. And a wealth of other data. But if I could just add, as long as we've mentioned Vesta, Vesta is the second most massive object in the main asteroid belt. Vesta and Ceres combined contain about 45% of the total mass in the main asteroid belt. So Dawn single-handedly explored a tremendous fraction of the mass, although of course there's a great deal of diversity and other ways to characterize the nature of the asteroid belt other than just mass.

But it's a fun bit of trivia. It's another carefully chosen space fact. What did you say? CCSF. It's also an interesting way, again, to think about how very massive Ceres is, even compared to number two, to Vesta. Because you said Ceres on its own was 35%. Right.

And Vesta only adds another 10% of all the mass of all that, those rocks out there. Right, and everything else is smaller and lower mass. But you're right. I mean, we've discussed this before. When Ceres was discovered and subsequently Vesta in 1801 and then 1807, they, along with two other bodies in the main asteroid belt, were described as planets. And there were only four of them known until the middle of the 19th century. And then as science and technology advanced, more and more bodies

started to be discovered in that part of the solar system. And eventually they were no longer called planets. But, you know, you and I and most of the people who are listening grew up during a narrow window in human history when the planetary status of Vesta and Ceres had been forgotten, but Pluto still had planetary status. Now we're in a time where Pluto and Ceres and other bodies are collectively described as dwarf planets. And when the categorization or the category of dwarf planets was defined, Ceres was the first body to have been discovered that fit that category because it was discovered 129 years before Pluto.

Dare I ask, dare I drag you into the great debate, the great planetary definition debate, which... Matt, you can ask me anything. Yeah, you can choose whether to answer or not. Seriously, seriously, do you believe that we need to go back to the old classification that would make Pluto a planet, but along with it, bodies like Ceres? All right, I will answer the specific question you asked, and then we can ramble from there. Do we need to? No, not at all. We don't need to because it's a matter of vocabulary. We could make intelligent

choices of what the vocabulary, the terminology should be. There's no need to. The universe is the way it is. We choose our terminology, sometimes well, sometimes not as well, and sometimes we don't choose it. Sometimes we allow it to evolve. The way I think of this is the following. First of all, in 2006, when many people thought, oh my gosh, this is so awful. Pluto got demoted. Earth is an interplanetary bully. How could we be so inconsiderate? Poor Pluto's feelings. This was just terrible. The way I think of it is this was a wonderful missed educational opportunity to help people understand, again, that it doesn't matter how you want the universe to be. It is the way it is. And our job as scientists, engineers, explorers,

and communicators is to understand what that reality is and to find clear ways to communicate it. The underlying motivation for the debate about whether to call Pluto and hence these other bodies like Ceres, a planet or a dwarf planet was because scientific knowledge had advanced, right? When Pluto was discovered now 91 years ago, it was discovered in 1930, this debate was in 2006, when it was discovered, it was the only body known in an orbit like the one it was in. But now we know of many, many, many bodies there. Let's not decide on the basis of Pluto's feelings, nor I think on the basis of the feelings of people who grew up during that time in human history, but rather let's talk about it in terms of what is the modern scientific understanding of the nature of our solar system and others. And that's my answer.

Thank you. Thank you. Good answer. We will provide equal time to the other side, as we have often done on this show. Although I'm not sure, frankly, what the other side is, because I wasn't saying whether all of those bodies should be called planets or they should be called dwarf planets or something else? I think that your point that merely labeling them or relabeling Pluto as a dwarf planet didn't suddenly turn it into a munchkin. It didn't lose any stature. In fact, we now know from wonderful missions like New Horizons and Dawn that these minor worlds, these dwarf planets are as fascinating as pretty much any place else we might want to go in the solar system. Right. And we should be careful about ascribing different kinds of significance to the name.

It should have a good name, but your listeners won't be able to appreciate this. But look, this is a glass of water. And it's half full. That's how I see it. It is. Well, or it's twice as big as it needs to be. But the point is, it's just a name to the noun. There's a lot more to the body than the noun and the adjective that goes with it. Sorry. As long as we're going this long, Mark, you have a different job now at JPL, the Jet Propulsion Lab,

Chief Engineer for Mission Operations and Science, as I said up front. What does the Chief Engineer for Mission Operations and Science do? Mostly, I just get to keep having fun getting involved in missions that are in operations, missions that are preparing for operations, missions that are, of course, doing science. And JPL has so many exciting missions that it's, for me, just more of my life as a kid in a candy shop. Well, that's good.

I'm glad you're having fun, and that's a great overview. But I mean, I assume this is allowing you to use your experience. You've been at this a long time to benefit people who are working on new missions that are constantly in development at JPL. Right. New missions and not so new missions that are constantly in development at JPL. Right. New missions and not so new missions. I've spent a very enjoyable and significant amount of time recently working with the Voyager team. Because it, as you know, is in operations.

And so it's, as you said, I have a fair amount of experience. Much of the experience is mostly things like me saying, oh, this is so cool, but I do have some other experience as well. And so where missions might benefit from some of that experience, then I work with them either, some of that experience, then I work with them either, again, while they're in operations or preparing for operations. Because we want missions to have the best chance of success because all missions are challenging. But for ones that have some additional challenges, it's a great opportunity for me to get involved. And if you care, it's fine if you don't. To me, the coolest thing is getting to work on the missions. But I've done that for a long time. And as you well know, I have very broad interests. You and I have discussed them right

here in my space room at home together. And when I work on a project, I put all of my cognitive and emotional energy into that project. And that's great. It's wonderfully rewarding. And some of my, in fact, my most gratifying professional experiences have been on projects. Gratifying professional experiences have been on projects. I even talked about that in my TED Talk. But at the same time, I feel like I miss out on the rest of the universe. And my biggest disappointment about my JPL career is that it interferes with my hobby of learning about and studying space exploration. So now that JPL has kindly created this position for me because I didn't want to work on another project, so I get to be involved

with more projects. Probably more than you care about, but that's how it came about. A lot of other questions and comments come to mind, including the fact that another old friend of Planetary Radio, Linda Spilker, was back on the show not long ago. And she is delighted. I mean, she's still Cassini Project scientist, but she is now back on the Voyager mission, deputy project scientist for those two spacecraft, which are likely for a very long time to be the farthest out there emissaries of humanity. Have the two of you crossed paths since you're working with Voyager folks? We have, and it's been a delight. I'm as big a fan of Linda as you are, and it's been lovely to see her join the project.

Looking forward to continuing to work with her. I'm glad you mentioned that TED Talk again, because we talked about it last week. I mentioned it, and it didn't show up on the website, which I apologize for. But this time, for sure, as Bill Winkle used to say, this time for sure. And I think it's called, if it's not impossible, it's not worth doing. Right. That, of course, I mean, let's be realistic. That's sort of a grabber. Yeah. But maybe now that you've mentioned it, enough people will be grabbed that they'll listen to it. You can find it at tinyurl.com slash T-E-D-M-A-R-C or at the Planetary Radio webpage. Yeah, on this week's episode page at planetary.org slash radio.

week's episode page at planetary.org slash radio. I'll just mention one more thing because you pointed out to me not too many days ago that that wonderful tour you provided some years ago of your home, which is a bit of a space memorabilia museum and library as well, that that video had somehow become private. It is available again. We'll put that link up as well, that that video had somehow become private. It is available again. We'll put that link up as well so that people can see that amazing collection you have, which I'm guessing has grown since I was last there. It has, but let's be clear, you made the video and you made the video fun. Oh, good. I'm glad.

Well, I try only to talk to fun people because that makes it a lot easier for it to come off that way. So thanks, Mark, for being a fun person to talk to for a long time, fun and informative. And if we get a nice statement of gratitude from Set Upon, I will pass that along as well. Good. Well, as always, it's a pleasure to talk with you and with your listeners, and I will listen to this show as I do all of them. That's Mark Raymond, solar system explorer, scientist, engineer. His title now at JPL, NASA JPL, is chief engineer for mission operations and science. I'll be right back with Bruce, who is standing by with his LightSail report and much more. Hi again, everyone. It's Bruce.

Many of you know that I'm the program manager for the Planetary Society's LightSail program. LightSail 2 made history with its launch and deployment in 2019, and it's still sailing. It will soon be featured in the Smithsonian's new Futures exhibition. Your support made this happen. LightSail still has much to teach us. Will you help us sail on into our extended mission? Your gift will sustain daily operations and help us inform future solar sailing missions like NASA's NEA Scout. When you give today, your contribution will be matched up to $25,000 by a generous society member. Plus, when you give $100 or more,

we will send you the official LightSail 2 extended mission patch to wear with pride. Make your contribution to science and history at planetary.org slash S-A-I-L-O-N. That's planetary.org slash sail on. Thanks. Time for What's Up on Planetary Radio. Here's the chief scientist of the Planetary Society. He is also the program manager for LightSail, LightSail 2 that is still

orbiting above us right now. Welcome. How is that great bird doing? The great bird's doing very well in general. LightSail 2 still orbiting, flying two and a third years into the mission, something like that. We have things that go well and things that don't go as well. We had a power outage that shut down our ground systems and caused a little software hiccup. So we're still recovering from that, but we're getting data again from the spacecraft. Spacecraft is fine and healthy and happy. I was just reading, because I'm going to be talking to people in charge of the Lucy mission next week on next week's show. And they've put a plaque on the spacecraft because it's going to be orbiting for possibly tens of thousands of years. Maybe we should have done that with LightSail. It just seems to keep going. Well, we do have a mini DVD on there. That's true.

It has all the members' names and people who signed up and selfies from space and all sorts of good stuff. But yes, it is. LightSail 2 is the spacecraft that keeps going and keeps staying up. Now we're starting to see some degradation of the sail over time from the space. And now we're back in the drag pulling us down. But we keep fighting it with sailing and keep learning. Sail on. And tell us about the night sky. All right.

Well, besides light sail, which usually is not very bright, the evening sky is really cool, Matt. Have you been checking it out? Yeah, now and then. Been too cloudy and rainy and even thundery down here the last few days, but it's been beautiful nevertheless. Yeah, we had weird thunderstorms last night, but that's not important. What is important is when you don't have clouds. Venus, super bright over in the west after sunset. It's that really bright star-like object. And then over in the east, rotate yourself towards the east, and you'll see another really bright star-like object.

That's Jupiter. And to Jupiter's right is yellowish Saturn. We have the moon wanting to come and play. The crescent moon hanging out with Venus on the 9th, looking lovely. Red Antares. The Antares, the reddish star in Scorpius, lining up with Venus and the 9th, looking lovely. Red Antares, the Antares, the reddish star in Scorpius, lining up with Venus and the Moon on the 9th, but then lining up in general with Venus

and hanging out near it for the next week or two. And the Moon then gets up to hang out with Jupiter and Saturn around the 14th. So much to see. That's wonderful. Thank you. It's good stuff. Some interesting things as well in this week in space history. 1959, Luna 3 became the first spacecraft to take pictures and return them. Pictures of the far side of the moon.

Our first mediocre views, but the first views ever of the far side of the moon. Quite a milestone. When you think how long humans have been looking up at that single side of the moon, that one hemisphere, and it took that long. You know, nice work the Soviets did way back then. Indeed. And they also did in 1964 with Voskhod 1, which I'll come back to in just a moment. Voskhod 1's mission was this week in 1964, which leads us to random space fact. Спасибо.

Пожалуйста. Voskhod 1 in 1964 was the first space mission with more than one person aboard. Hooray. There were three, rather than the two it was originally designed for, apparently due to political pressure. So they also had the distinction of becoming the first to fly without spacesuits because there wasn't room for them. Oh, gosh. I don't even want to think about this. I mean, all I have to do is look at how they cram three people into a Soyuz now and think, what, it was even tighter than that?

Oh, my. Yeah, there's just a lot of intriguing things with Asgad I that we will come back to even more in just a few moments. But first, let's go to the previous trivia question. I asked you the somewhat challenging question, what currently functioning Mars orbiter has the longest orbital period? How do we do, Matt? You know what was surprising this time is how many people got it wrong, at least by the determination that I believe you made. I would say half of the entries said Mars Express or the Emirates Mars Mission Hope, even some that went to like MAVEN and things like that, which I guess has a fairly eccentric orbit.

Here's the answer we got from Martin Hajoski's mom, the Mars Orbiter Mission from India, also known as Mangalayan, with an orbital period of 72 hours, 51 minutes, and 51 seconds. That is correct. It is significantly longer than everyone else, although the Hope mission is also in the really long category of 55 hours. But everyone else is pretty much under, say, eight hours. I would say Hope definitely came in second, and a lot of people did note that also long orbital period. But yeah, couldn't touch mom. Congratulations, Martin. And it has been, I know how that sounds. Wait, there's more. It has been almost four and a half years since Martin,

who regularly enters the competition, has won the contest by my records. So again, congratulations. And we are going to send you, Martin A Planetary Society Kick asteroid, rubber Asteroid, we're going to send it to Texas Why not? That's where he lives Put this This is cute, he says You know, heads much farther away from Mars

Each time around, allowing it In a sense, to watch over The other seven functioning Martian orbiters, exactly what you might expect mom to do. I never thought of it that way. Yeah. Yeah. That makes sense. Yeah. Similar response from Kent Murley in Washington. Like my mom, she swoops in every 72 hours for close inspection.

And while slowly stepping back out claims not to be judgmental. Finally, we'll just do one poem this week. It's a fairly long one from Gene Lewin in Washington. You need to know up front that SHAR, S-H-A-R, that's the Sriharikota Range in India, and it's where the MOM mission was launched by the Indian Space Research Organization. Here's the poem.

To Barsoom from the Bengal Bay, Mangalayan left from Shar, achieving orbit on its first attempt, the ISRO has set the bar. This mission plan for just six months continues to this day, traveling round the Crimson Orb. MOM still has things to say. Its orbit takes about three days, well, three and a skosh more, around the fourth rock from the sun named for the god of war.

Impressive. Yeah, nice work, Gene. Thank you very much. We are ready to move on, and this is going to be something special in more than one way. From my side of special, here's your question.

What major political event in the USSR happened during the only 24-hour long Voskhod-1 mission? Major political event in the Soviet Union occurred during Voskhod-1 mission while it was in space.

Go to planetary.org slash radio contest. You said this was in 1964? Yes, 1964. All right, everybody. Here's the other special thing about this contest. You have no excuses because I'm going to be going on vacation, and therefore we have to- What?

Yes, I've earned it. All right. We have to mess with the contest somewhat. So you're going to have not one, not two, but three weeks to respond to this one. You have until Wednesday, October 27, at 8 a.m. Pacific time to get us the answer to this one and win yourself, what else? A beautiful, safe and sane rubber asteroid. Excellent. We'll have a lovely vacation, Matt, when that happens. Thank you. I'm really looking forward to it.

It's been a long time since I've been away for, this will be just short of two weeks, and there's a lot of stuff to get ready before then, but boy, is it going to be fun. All right, make sure you let me know what I need to pack. Wait a minute. Hey, honey. Oh, no, I'll tell her later. It's okay. She'll be so happy. Say goodnight, Bruce. All right, everybody, go out there, look up at the night sky, and think about what you'd pack if you went on vacation with Matt Kaplan.

Thank you, and goodnight. Hey, honey, put a couple of extra cans of coffee in there. Anyway, he's Bruce Betts, the chief scientist for the Planetary Society, who joins us every week here for What's Up. Cans? Planetary Radio is produced by the Planetary Society in Pasadena, California, and is made possible by its members, who don't mind revolving around any world. Take a spin with them at planetary.org slash join.

Mark Hilverda and Jason Davis are our associate producers. Josh Doyle composed our theme, which is arranged and performed by Peter Schlosser at Astro.