Planetary Radio: Space Exploration, Astronomy and Science - Hope for Pluto—Should We Re-Redefine Planets?

Episode Date: March 8, 2017

Planetary geologist Kirby Runyon is lead author of an abstract that proposes a new, geophysical definition of what a planet is.Learn more about your ad choices. Visit megaphone.fm/adchoicesSee omnystudio.com/listener for privacy information.See omnystudio.com/listener for privacy information.

Hope for Pluto, 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. Kirby Runyon is ready to challenge what it means to be a planet. He says our solar system has over 100 objects that qualify. You'll hear his reasoning in a few minutes. Bruce Betts will help me deliver a very late Valentine's Day present direct from the lover's asteroid. Bill Nye has the week off, but Planetary Society digital editor Jason Davis is here to tell us about a company that wants to take passengers to the edge of space, or nearly so.

Jason, I'm going to bet that even for this audience of space geeks that we have for Planetary Radio, a lot of them have not heard about Worldview, but you'll be telling them about them in this blog post, which is coming out just about the time this show becomes available at planetary.org. Give us an overview. Yeah, so they fly under the radar a little bit because it's this novel concept. They take balloons and launch them into the stratosphere. These balloons, mainly right now, are doing scientific research. You can either do remote sensing, so all the stuff you do from satellites, only you're doing it from a balloon, which is a little closer to the ground. And in the future, they want to do humans.

They want to send people up in this pressurized capsule high enough to see the blackness of space, the curvature of Earth, and kind of get that life-changing experience without having to actually launch on a rocket and go into orbit. So they've kind of been getting up to speed the past few years. And then just a couple of weeks ago, they kind of had their grand unveiling, their new facility opened actually here in Tucson, Arizona, where I'm based. Nice. Very convenient for you. There have been a lot of these suborbital startups recently. This one happens to have some really big names connected to it. Yeah. So the founder is Jane Poynter, and she co-founded it with a couple other people. Jane Poynter, for those who don't know,

Biosphere 2 was her main claim to fame. This was back in the 90s when a bunch of people lived inside this giant greenhouse for a couple years to kind of simulate a deep space colony and how you'd have to live off the land by yourself. But some other people that listeners would probably be more familiar with, Alan Stern is a co-founder. Alan Stern, of course, of New Horizons fame. Mark Kelly, the former astronaut and brother of Scott, who recently did the one-year mission. And also another Biosphere crew member, Tabor McCollum, is involved. Just to be clear, these balloons are not really going into space,

right? But they're going pretty high. Yeah, pretty high. So yeah, they call it kind of a near space thing, I think is the technical term. So the stratosphere, it varies depending on where you are on Earth. But I may quote it wrong here without looking at the numbers, but it's somewhere around 30 to 50 kilometers high. And the internationally recognized boundary space doesn't usually start until about 100 kilometers. So not quite space, but in that kind of weird region higher than planes fly, but lower than satellites orbit. And that's where they really think they can kind of capture this untapped market. One thing that they really are promoting, and we'll talk about all this in the article that's coming out, is that they can

do station keeping, which is something that spacecraft can't do very easily, especially spacecraft in low Earth orbit. You know, the International Space Station, it might only fly over one spot on Earth once or twice a day. If you want to stay over the same spot on Earth, you got to go clear out to geostationary orbit. And that's like 35,000 kilometers high. And that's where, you know, some of our communications GPS satellites sit. The advantage of these little balloons that are hanging in one spot is that they're much closer to the ground. And in theory, they could do some really cool stuff taking up payloads and doing imagery. And also, you get the payload back, right? You don't get to bring your satellite back from geostationary orbit.

So it's a really interesting business model. And I was really fortunate to get to go out and check it out. And I hope our listeners will check out the article when it comes out. I hope they will, too. And they'll also find out about the fascinating way humans and payloads are going to be returning from these altitudes after they finish their ride, provided by Worldview, which may be happening before too long. That will, if it's not up now, it will be very soon at planetary.org. That'll be Jason Davis's latest blog post to the website. Jason, thanks for this little preview.

Thanks, Matt. Thanks for having me. Jason Davis, he's the digital editor for the Planetary Society. You can read much more by him at planetary.org. It's not hard to find people who are still upset about the redefinition of what it means to be a planet. I've even seen a protest t-shirt or two. But the International Astronomical Union's decision more than 10 years ago seems to have found some acceptance within the scientific community, especially from astronomers. Many planetary geologists beg to differ. Six of them, led by Ph.D. candidate Kirby Runyon at Johns Hopkins University, will present a very different definition at the upcoming Lunar and Planetary Science Conference.

You can read their abstract, which has been gathering a lot of media attention. We'll put a link to it and other coverage on this week's show page at planetary.org. link to it and other coverage on this week's show page at planetary.org. Full disclosure, I've known Kirby for quite a while, as you'll hear in our recent Skype conversation. Kirby, after years of corresponding with you as a listener to the show, it's great fun to finally get you actually as a guest on Planetary Radio. Welcome. Thank you, Matt.

This is a bit of a dream come true for me. I listen every week, and it's great to finally be on the show. Thank you for having me. Yeah, where were you when you first discovered the show? I mean, where were you in your studies? I was a freshman in college in 2004 at Spring Arbor University in Michigan. Amazing, and now soon to be a PhD. Well, I know the Planetary Radio has been entirely responsible for your successes, both academically and professionally. It's played a role. It actually has. I'm really grateful for that and very proud as well. Thank you for whatever small role we played. So Kirby, by your definition, how many planets are there in our solar system? There are at least 110 planets in our solar system.

Okay, that already is going to, those are fighting words for some people, as you know very, very well. Well, I hope it can be a friendly fight. Friendly disagreements occur in science all the time. I've been co-authors on papers with people that we have disagreements about the results, but they're not nasty disagreements. They're just different perspectives. The definition that we that we support is one that is it represents scientific nomenclature that's useful for planetary geologists and other planetary scientists who are closely aligned with the geosciences. If astronomers or people who align themselves with the IAU don't want to use our

definition and want to stick with the IAU definition, that's fine with me. I can't stop them. But I think a lot of people will see the usefulness of our definition, the geophysical definition, and hopefully it receives wide usage. Now, I want to be fair here. Everybody that I have talked to who believes in the newer, the IAU definition that has limited our solar system to eight planets, they're all very friendly, very nice people, and they respect all the planetary geologists out there who have a differing opinion. Most of the real friction seems to come from the public. But before we get into more of the sociological portions of this, let's continue with talking about the definition itself. So among those 110 that you mentioned,

we're talking what? Pluto, Europa, Ceres, Enceladus, Maki Maki, all those other bodies that are way, way out there, right? So read the definition to us as you came up with it in this paper, this abstract that you've created with, by the way, as your second author, a certain Alan Stern, who I talked to this morning. He was thrilled that you were going to be on the show and sends his regards. Well, thank you. I send my regards back to Alan. Alan has been a wonderful mentor. We've had great conversations, and he's definitely been a boost. Working with him has been a boost to my career. So it's been a real pleasure to get to know Alan and to consider

him a colleague. Okay, so give us that definition. Yeah, a planet is a substellar mass body that has never undergone nuclear fusion and that has sufficient self-gravitation to assume a spheroidal shape adequately described by a triaxial ellipsoid regardless of its orbital parameters. Let's break this down. A substellar mass body that has never undergone nuclear fusion. So dwarf stars that have collapsed, no longer fuse, need not apply. Correct. White dwarves, neutron stars, black holes, they're cool, but they're not planets.

Okay. Well, sorry, guys. You have enough to attract attention on your own, no doubt. That's how I put the never undergone nuclear fusion part in there. I love that. That's a great phrase. And that has sufficient self-gravitation to assume a spheroidal shape adequately described, and this is the part that may need some explanation, a triaxial ellipsoid, regardless of its orbital parameters. Now, having enough gravity to pull yourself into a ball, that's been talked about for a long time as part of the definition, right? Yeah, absolutely. And even the IAU uses that for the definition of dwarf planet. My big sticking point is that to them, dwarf planets aren't planets. Now,

the triaxial ellipsoid bit comes from the fact that a body might have enough gravity to pull itself into a ball, but it's probably spinning, could be spinning quickly, and that would tend to flatten it out so that it would have a shorter radius at the north and south pole and a longer radius along the equator. That would be a biaxial ellipsoid. Now, a triaxial ellipsoid would be then if that planet has a moon orbiting it, especially if the two bodies are gravitationally or tidally locked to each other. And that would tend to deform the planet along one direction, but not another direction. So then a diameter going through the equator would be longer than another diameter going through the equator.

And so that's where the triaxial ellipsoid bit is to account for the fact that you could get tidal deformation between planets and any satellites orbiting. By this definition, would our own moon, Luna, be a planet? It would be a planet. That's one of the 110 planets in the solar system. Most likely it's got a small iron core. It's got a mantle and a crust. There's active moon quakes that occur. There's landslides, impact cratering, the emplacement of impact crater ejecta. There used to be volcanism on it. Everything that planets do, our moon does or did. And so we just happen to be living on a planet that has another planet orbiting it. And the moon is still the moon. It's still a moon. It's still a satellite,

but it can have the word moon as an adjective to the noun planet. It's a moon planet. A moon planet. Or even you could go, it's a terrestrial moon planet. And only a quarter of a million miles away to another planet by this definition. I kind of like that. It means a lot more of us might make it there someday. Maybe some space tourists with Elon Musk and the Falcon Heavy. Wouldn't that be great? So what's wrong with being called a dwarf planet? I mean, if you apply that term to places like Pluto. There's nothing wrong with it. In fact, I call Pluto a dwarf planet. The difference is that a dwarf planet is still a full-fledged planet. We use

other adjectives besides dwarf to describe other planets in the solar system. Jupiter is a giant planet. Uranus and Neptune are ice giant planets. Earth and Mercury, Mars, they're terrestrial planets. So you can have dwarf planets or icy dwarf planets. It's perfectly fine to put an adjective in front of a noun as long as the noun stays a noun, unlike the IAU definition where a dwarf planet is not a planet, which grammatically just doesn't sit well with me. What about the other portions of the IAU definition? I'm thinking in particular about this ability to, if you're a planet, you've cleared the space around you. Do you have a problem with that? Right. I do a little bit because that tends to exclude like exoplanets that may be in the

process of forming that for all intents and purposes seem to be a planet, but perhaps they're still sitting in a debris disk of asteroids and dust and they haven't gotten around to clearing their orbit yet. So that's one problem I have with that. Other people have defended that part of the IAU definition saying, well, what it really means is that it gravitationally dominates its region of space. Well, okay, if that's what the definition means, why didn't it say that? So, you know, being gravitationally dominant is fine, but then say that in your definition. And also, in terms of talking about a planet's gravity and its effect on other bodies, that's fine if you're concerned about the extrinsic properties of a planet or a body. But as a geologist and for other geoscientists, I'm more concerned about

the intrinsic properties, what a body is on its inside, not what it is on its outside, not who its friends are, but who it is as itself. From a purely intrinsic properties perspective, that's what includes planets orbiting in debris disks or the asteroid belt or moons as planets. Again, an orbital parameter or its gravitational perturbations of something else is an extrinsic parameter. And if you're an astronomer or if that makes sense to you, fine, use that definition for planet. But I think we should be perfectly happy with a parallel definition that more focuses on the intrinsic properties of a planet. You've touched on here what seems to be key to the genesis of this controversy, that it was created, it was actually accepted in, I'm told, the general session of the IAU,

which is not surprisingly dominated not by geologists, planetary geologists, but by astronomers. And that geologists, many planetary geologists, have had a problem with this ever since. Yeah, and if there are astronomers who study planets, and there are, there's planetary astronomers, if this definition works for them, fine. But as a planetary geoscientist, I like having scientific nomenclature that's useful, that gets at the core of what I talk about. And when I'm comparing one body to another, it's helpful for comparative planetology to be able to call lots of things planet. For instance, I study sand dunes on Mars, but my research group also studies sand dunes on the moon planet Titan.

It just gets cumbersome if you have to talk about the planet Mars and then Saturn's moon Titan. If you could just call them both planets, it's much more concise and easier to talk about. But there's other reasons too why having more useful scientific nomenclature is preferable for planetary geoscience. That's planetary geologist and Johns Hopkins PhD candidate Kirby Runyon. We'll talk about the cultural fallout from redefining and re-redefining what a planet is in a minute. This is Planetary Radio. Where did we come from? Are we alone in the cosmos? These are the questions at the core of our existence.

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With your support, we sponsor innovative space technologies, inspire curious minds, and advocate for our future in space. We are the Planetary Society. Join us. Welcome back to Planetary Radio. I'm Matt Kaplan. Planetary geologist Kirby Runyon is lead author of an abstract and conference poster titled A Geophysical Planet Definition.

The key word there is geophysical. Kirby and his colleagues come at this from a different standpoint than the mostly astronomers who led the International Astronomical Union's there is geophysical. Kirby and his colleagues come at this from a different standpoint than the mostly astronomers who led the International Astronomical Union's 2006 decision that made Pluto and other bodies dwarf planets. If accepted, this alternate view would give our solar system 110 planets and counting. What about the cultural side of this, which you address a little bit? The fact that we all grew up with nine planets,

dropping one of those bothers the people who've always learned that, you know, Pluto was the last in the mnemonic, the P at the end of whatever mnemonic you used. Pizza. Pizza, thank you. But going to 110, well, that's just crazy. Yeah, a lot of people have complained, well, that's too many planets for kids to memorize.

And I said, well, they don't have to memorize them. You know, nobody, well, maybe I would have as a nerdy little kid, but nobody really memorizes the periodic table of elements. There's 92 naturally occurring elements. Instead, what is taught is how the natural system is organized. The fact that the number of protons determines the atomic number, which in turn determines the number of electrons, which is what affects the chemistry of that element. And if you know that underlying logic, you don't need to memorize it. You can look on the periodic chart and get a sense of what that element's chemical properties are just where it is on the chart. For instance,

all the elements in group 1A over on the left side are highly reactive. Don't throw them in water unless you like explosions, which I do. But I can't name what those elements are necessarily in group 1A. The same goes with the organization of our solar system or perhaps other stellar systems with planets in them. Don't memorize 110. Learn how planets form and the fact that heavier elements tend to cluster near the sun or the star in question, things like iron, magnesium, silicon, that form the core and mantles and crusts of these planets. Further away from a star, when solar systems form, you get lighter elements, water, methane, carbon dioxide, carbon monoxide. These lighter elements

then freeze out into ices, and that's what you then have to form planets out that far. So don't memorize all hundreds of planets. Just understand how the solar system is organized and the types of properties that planets in different zones, moving outward from the sun, tend to have. I'm glad you brought up what this might mean in terms of teaching kids about the solar system and our universe. How do you think it would affect education and more broadly, the public view, the popular view of this stuff that, you know, you and I and the audience listening to this love so much? I love planetary exploration. I have since I was a very young child. And I want the public to fall

in love with space. That's what I want. I fell in love with it, and I'm pursuing a PhD as part of that love for the exploration of space. What I have noticed is that for whatever reason, there's a psychological impact attached to the word planet. And I don't understand it, but there seems to be the psychological power to the word planet. Psychological power to the word planet. When you tell a child, a student, someone in the general public, hey, there's up to 110 planets in our own solar system, their mind explodes with the possibilities. Wow, that just opens the mind to realizing how many Europe or whatever to fund NASA and other space agencies around the world. Hey, let's go explore these things. I just saw our colleague Casey Dreyer on Monday in Washington, D.C., and we were doing visits on Capitol Hill talking to Senate and House staffers asking them to please fund NASA and specifically NASA's Planetary Science Division at high levels because, among other things, hey, there's 110 planets. Let's get exploring. You know, kids get sad if Pluto is not a planet. And some of them literally think

that Pluto has physically disappeared from the universe because some people have stopped to call it a planet. We laugh, and it seems silly, of course, but that's the impression some kids get. I don't want anyone to have sad feelings about the solar system. And if a certain definition is making the general public sad and feel bad and have negative feelings about planetary exploration, that's undermining my cause of getting the public excited about space. And it's undermining my cause for a well-funded NASA. I want people to have happy feelings about planets. And I found that this definition tends to make people happier. So not only is it good scientific nomenclature for my own field, it also galvanizes public support. Kirby, your planetary passion is contagious.

Oh, good. And it has been getting a whole lot of attention. You've had enormous media coverage for this. I mean, I think you just told me a few days ago that you'd heard from Wired magazine. Yes, I gave an interview to Wired Magazine on Friday. I've also been on CBC Radio on the show As It Happens. And just yesterday, I was interviewed for a Spanish newspaper in Spain, ABC.es. So I've gotten both international and domestic interest. I'm scheduled to do an interview with the Johns Hopkins University, where I'm a graduate student, Public Affairs next week. I'm thrilled that so many people are interested in this topic and that we have a chance

to galvanize public support behind planetary exploration. What's the reaction you're getting generally? How does it balance out? Generally, it's extremely positive. If I had to put a number on it, I'd say it's 90% positive. I've gotten a few emails from people who either respectfully or disrespectfully disagree with me, but they are in the far minority. So I find that to be very encouraging. So you're going to be putting this up as a poster at the next LPSC, the Lunar and Planetary Science Conference, that our colleague Emily Lakdawalla has such a good time at every year.

How do you think it will be received there? I think it will be generally positive. We made a strategic decision to put this as a poster specifically in the education and public outreach section of the poster session. I want teachers and curriculum developers and textbook writers to jump on board with this definition and get the kids while they're young. Get them excited about planetary exploration because there's at least 110 planets in our solar system, plus all the

interesting asteroids and comets out there. A teacher can explicitly say the definition, but memorizing definitions is kind of useless in my opinion. It's got limited utility. It's when the student's understanding is such that they would be able to come up with a definition on their own. That means that the student has really understood the concept. In addition to introducing the definition, you can also use it easily in context. For instance, in our LPSC abstract, a teacher could introduce a new moon to their students with phrases such as, in the 2020s, NASA will send a spacecraft to study the planet Europa, which orbits around the planet Jupiter as one of its

many moons. And so that's just an implicit usage of the definition where you don't even think about the definition, but you still end up using it. I'm expecting the most pushback to come from people who don't think that moon planets should be planets. Although even in those cases, it's usually a friendly disagreement. Kirby, how far are you from adding PhD to your title? disagreement. Kirby, how far are you from adding PhD to your title? Hopefully just a couple more months. I'm slated to defend my PhD dissertation on April 26th. Not bad. Sand dunes, we've talked about those on this show. Why do you find them so fascinating? Well, a couple of reasons. They're the most active process on Mars today. The current geologic epic that we're at today is called the Amazonian epic, and it reaches back to the last couple billion years.

And windblown sand, what we call eolian processes and eolian geology, is the most active process on Mars today. So if you like things that move, and our brains are somehow evolved to like things that move, sand dunes are your thing. You know, also as a kid growing up in Michigan, we used to go to Lake Michigan, which has beautiful sand dunes. And you used to run up and down those sand dunes. I never thought I'd be studying them professionally. But it also gets me a chance to use the HiRISE camera on Mars Reconnaissance Orbiter, the high resolution imaging science experiment, which is basically a spy satellite around Mars, as many of your listeners know.

And in terms of declassified orbital data for Earth, nothing is better. The declassified orbital imagery of Earth is less. It's around one to five meters per pixel. And we've got 25 centimeters per pixel at Mars. So it's pretty stinking good at Mars. And studying Sandians gives me a chance to take a lot of pictures with HiRISE. I'm a collaborator on that instrument, so I get to go to HiRISE team meetings, which is great. And it's just a chance to enjoy the

beauty of Mars from a scientific perspective. You know, even on her sabbatical, our Emily Lakdawalla could not resist sharing with us some images just in the last day or two that actually show enormous movement of the sand on Mars and covering up the tracks, in fact, of Curiosity. It really is a dynamic place still, isn't it? Sure is. And any astronauts that will hopefully get there soon will hopefully have their footprints covered up real quick by blowing sand. Kirby, you're leaving your footprints around the solar system, it seems, with this paper. Have a great time at LPSC, and congratulations on renewing the debate over what is a planet.

It's my pleasure, Matt, and thank you so much for somewhat paraphrased, that Kirby provided when I asked him for it. Kirby's a graduating Johns Hopkins University Ph.D. candidate in planetary geology and a science affiliate on the New Horizons mission to Pluto and beyond. More than that, he's a lifelong space fan, longtime Planetary Society member and planetary radio listener, although he's never won a planetary radio t-shirt size medium, the only prize he's ever wanted from the trivia contest. And as you can tell, he's passionate about helping non-scientists fall in love with space exploration. And judging from his activities in Congress this week, helping them to understand why this is important and why NASA deserves more funding. Kirby, I think we can afford to send you that t-shirt. That'd be great.

Yes. Finally. Thanks so much for joining us on the show. Thank you. That's Kirby Runyon. And now we're going to talk to Bruce Betts for this week's edition of What's Up. On the Skype line is Bruce Betts, the Director of Science and Technology for the Planetary Society, here to tell us more about the night sky and give some stuff away to the winner of the space trivia contest. Welcome again. You love giving stuff away, don't you? I give it all away. I'm giving it away. Want me to give you some information? Yeah, would you? How was that segue? Sure, we've got in the sky, of course, Venus still just dominating the

evening west. Mars still getting farther apart from Venus, but much dimmer and reddish to its left. We got Jupiter coming up around 9 or 10 p.m. over in the east, looking also super bright. There will be a lovely pairing on the 14th when the moon is hanging out very close to bright Jupiter. And then Saturn up in the pre-dawn east. We move on to this week in space history. It was 2006, 11 years ago the Mars Reconnaissance Orbiter arrived at Mars. Still working. Still doing

awesome stuff. Yeah, still taking spy photographs of the surface with HiRISE. We move on to Random Space Fact. Random Space Fact. Let's go back to the lunar modules of the Apollo program and they consisted of two parts the descent stage and then the ascent stage that would take the astronauts off the moon

there is only one intact lunar module ascent stage at least we assume it's intact. We don't actually know where it is. And that is from Apollo 10. The Snoopy ascent stage was sent off into a heliocentric orbit around the sun. All the other ascent stages were either left in orbit, crashed into the surface. And if they were left in orbit, they've crashed into the surface. Or burned up in the Earth's atmosphere. So there you go. Hang on, Snoopy. Hang on.

Yeah, we'll find you someday, Snoopy. Don't worry. The contest. We played Where in the Solar System? Where in the solar system would you find a crater named Valentine after St. Valentine? How'd we do, Matt? Nice response, though. I think this probably was a tough one. A lot of people talked about how difficult it was to find this answer. Among them, Earl Green in Alma, Arkansas. He said, tricky one to find. He finally gave up and searched the U.S. Geological Survey Planetary Nomenclature Database.

I didn't know such a thing existed. The Planetary Gazette-er. Oh, really? Is that what it's called? Yeah. I love it. Most people came up with this answer, one of them being Jordan Tickton in Westlake Village, California, not far from our headquarters in Pasadena. He said that the Valentine Crater is a feature on the asteroid Eros, approved by the IAU in 2003 as an officially accepted name, an important element of this. Is that what you were looking for? Yes, that is indeed correct. Eros visited by the Shoemaker-Near spacecraft. As we talked about in a very fun random space fact video that I had fun shooting

with Bob Picardo, that the theming for the craters on Eros is characters of love. And so we have Valentine and Casanova, famous lovers of history. Which was also pointed out by a number of people. We got a surprising number of entries from folks. They included Norman Kassoon, Kevin Kimball, Howard Medlock, Tracy Jones, who talked about Mars and even sent pictures of a crater on Mars that sure looks like a Valentine heart, but it is not official, right? That is correct. According to USGS Planetary Gazette, the only official Valentine in the solar system in terms of a crater is on Eros. So you can look like Valentine's Heart, but you don't get the crater name being officially Valentine. Here is our official entry from the poet laureate of Planetary Radio, Dave Fairchild in Kansas.

The asteroid Eros is NSFW. Don't worry, though, this is not going to trouble you. All of its craters are lover-designed, and that includes one named for St. Valentine, but also for Cupid, Lolita, and Psyche. Don Juan is there, as is old Don Quixote. Suave Casanova. But don't be embarrassed.

There isn't, as yet, a Last Tango in Paris. And for Mark Little, gee, all those creators named after famous lovers. Odd that there's no Bruce. You know, they wanted to do that. I said, no, no. Too modest. All right. It is Jordan, as I said, who's our winner this week.

So he's going to get a Planetary Radio t-shirt. He's going to get a 200-point itelescope.net astronomy account, that worldwide nonprofit network of telescopes, and a Planetary Society rubber asteroid, which is also the package for the winner of this new contest that Bruce is about to get set up for us. This one should be easier to find. How big is the primary mirror? What is the diameter of the primary mirror on the great observatory, the Spitzer Space

Telescope, Infrared Space Telescope? How big is the primary mirror? Go to planetary.org slash radio contest. Yeah, Spitzer has been talked about just recently on this show. It sure has. Yeah. You've got this time until the 15th. That'll be March 15, Wednesday at 8 a.m. Pacific time

to get us your answer. We're done. All right, everybody, go out there, look up at the night sky, and think about traffic lights. And, Matt, may your traffic lights We're done. All right, everybody go out there, look up at the night sky and think about traffic lights. And Matt, may your traffic lights always be green. Thank you and good night. That's the nicest thing anyone has ever said to me. That's Bruce Betts, not Joe Friday, Bruce Betts, the Director of Science and Technology for the Planetary Society, who joins us here every week for What's Up. Planetary Radio is produced by the Planetary Society in Pasadena, California,

and is made possible by its highly defined members. Danielle Gunn is our associate producer. Josh Doyle composed our theme, which was arranged and performed by Peter Schlosser. I'm Matt Kaplan. Clear skies.