Planetary Radio • Apr 03, 2019

Ice Worlds, A Moon Landing and Blasting an Asteroid

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On This Episode

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Amy Simon

Senior Scientist for Planetary Atmospheres Research for Goddard Space Flight Center

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Jason Davis

Senior Editor for The Planetary Society

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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

When will we return to Uranus and Neptune? Planetary scientist Amy Simon explains why a mission to the so-called ice giants is a high priority as she tells us about these mysterious, blue worlds. Planetary Society Digital Editor Jason Davis takes us through what promises to be a very busy month in space, with the launch of the second Falcon Heavy, a moon landing by Israel’s Beresheet probe, and how Hayabusa2 will blow a hole in asteroid Ryugu, complete with sound effects. Then join us for another round of What’s Up in the Solar System.

Neptune Only Voyager 2 has visited Neptune in 1989. This Voyager portrait is newly reprocessed to show the planet at correct color.Image: NASA / JPL-Caltech / Björn Jónsson

This week's question:

Where in the solar system, but not on Earth, is a feature named Mozart?

To submit your answer:

Complete the contest entry form at or write to us at [email protected] no later than Wednesday, April 10th at 8am Pacific Time. Be sure to include your name and mailing address.

Last week's question:

On what types of bodies have we landed spacecraft that have transmitted (survived) after landing? Hint: Planets are one type.


The answer will be revealed next week.

Question from the March 20th space trivia contest question:

Who was the second youngest person to orbit the Earth?


The second youngest person to fly in space was Valentina Tereshkova when she was just 26.


Transcribed by Planetary Society volunteer Jake Bathman:

[Mat Kaplan]: Lonely Uranus and Neptune and a very busy April 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. Call them ice giants, call them outer planets, call them the blues brothers, or sisters if you prefer. Those big, cold worlds beyond Saturn are still shrouded in clouds of mystery that can only be solved by a visit. Our guest, Planetary Scientist Amy Simon, will provide a tour. As always, we'll visit with Bruce Betts and play Where in the Solar System once again. Planetary Society Digital Editor Jason Davis will get us rolling around the neighborhood. But first, starting with a bang if you'll pardon the expression, Jason and members of the audience. Yeah, nobody can hear you go bang in space, but that's exactly, as we speak, [00:01:00] what's about to happen, right, at asteroid Ryugu?

[Jason Davis]: Yeah. It really gives you a sense of how powerful this explosion that they're about to ignite in deep space is. Hayabusa is about to deploy its SCI experiment, that stands for small carry-on impactor, and it's essentially a little explosive charge—it would fit on your desk it isn't a very big experiment, but packs a lot of power in these this little box of plastic explosives. It's going to shoot a copper plate into Ryugu and create an artificial crater on the surface. And if all goes well while this is going on Hayabusa2 is going to be hiding behind Ryugu because it doesn't want to be anywhere near this explosion when it happens.

[Mat Kaplan]: Are you enough of a Trekkie to know about the roughly 1,000 times over the course of Star Trek that a ship, the Enterprise or somebody else, has hidden on the other side of a planet or asteroid to avoid like they would have been detected by the Klingons?

[Jason Davis]: Yeah, the [00:02:00] one that comes to mind I guess would be like Star Trek 2 when they're the Reliant and the Enterprise are kind of chasing each other around the planet. But yeah, definitely that's that's an old trick.

[Mat Kaplan]: Gene Roddenberry would be so proud. Of course you write this up in a blog post that went up at on April 1st, "What to Expect When Hayabusa2 Blows a Hole in Asteroid Ryugu." By the time a lot of people here this, it will have already happened. But as we speak, it's still what a couple of days away?

[Jason Davis]: Yeah, it should happen, it's April 5th in Japan when it happens, but April 4th here in the US, late in the evening.

[Mat Kaplan]: This makes me think of course of the Deep Impact impactor. Which I think was also made of copper. Why are we doing this? Why do we... do we just like blowing holes in things?

[Jason Davis]: Yeah because it's so awesome. You know who needs a science reason for this? The reason they want to do this is Hayabusa2 is already collected a sample off of the surface and it did that with [00:03:00] actually firing a small bullet into the surface that kind of stirred things back up into the sample collector. But what they want to do is unearth material or I guess unasteroid, if you will. You want to uncover the material underneath the surface that hasn't been exposed to space because we know that over time things tend to weather in space mainly through cosmic rays and things are shifting around. We know this is these asteroids are kind of dynamic and things are shifting ground. So they want to get a look at what's beneath just the very top layer of the surface and that's where the experiment comes in.

[Mat Kaplan]: So what's the idea, then will the spacecraft to maneuver back over to take pictures or perhaps even take another sample?

[Jason Davis]: Yes, so it'll... it'll wait for two weeks for kind of the debris to clear out. There's a chance that a few particles might briefly enter orbit around Ryugu before they either fall back down onto the asteroid or get pushed into space by sunlight, and after this two-week period they'll go back to their home position, come back in, take a [00:04:00] closer look at the surface. They'll decide at that point whether if there are a lot of hazards where they created this crater. If it looks relatively hazard-free in a wide open spot, they'll come down and take another sample. If not, if the way that they created the creator gives them some things they need to worry about when they're coming in for a touchdown, there's actually another spot that might collect from. So we won't know probably for another few weeks what their plan is going to be.

[Mat Kaplan]: Speaking of things to worry about, you have a very graphic demonstration of how different this asteroid looks than what was expected. I mean, you have a slider it's sort of a before and after what they thought Ryugu might be and what it actually is and it is dramatic.

[Jason Davis]: Yeah. Yeah, they really thought it would be a relatively flat surface with a lot of regolith on top, you know, this fine powder like substance kind of like the Apollo astronauts encountered on the moon. And it turns out that's just not the case. These asteroids are very bouldery for lack of a better [00:05:00] term, which you know presented significant challenges when they're planning touchdowns, or when they have to maneuver around some of these boulders to get... some are, you know several meters in diameter. Same things happening right now to OSIRIS-REx as well. They anticipated a pretty flat surface where they could collect a sample and now they're having to search very hard for a place that is a lot more flat and powdery.

[Mat Kaplan]: Yeah, I remember Emily telling us just last week that that's exactly the case, that these two asteroids are surprisingly similar.

[Jason Davis]: And we have such a small sample size at this point, so few spacecraft have visited asteroids and near-earth asteroids. So, you know, they're learning a lot from these missions, the early science results... actually Emily just wrote a blog article about that that posted yesterday that just goes over some of the new science that came out from Ryugu, so they're learning a lot and it's still a little unclear on how would all the processes and situations are they create these asteroid environments.

[Mat Kaplan]: Yeah, that blog post from Emily its [00:06:00] "First Science Results from Hayabusa2 Mission," stuff that she heard at the Lunar and Planetary Science Conference. She talked a little bit about some of these results with us last week. That's also, as Jason said, an April 1 blog posted at Before I let you go Jason, there is another one that you posted on March 28th, and there's been news even since then about Beresheet, the little Israeli lunar lander, which is preparing for its landing, I guess so far so good?

[Jason Davis]: Right now it's on its final Earth orbit. And this orbit actually will intersect with the area around the Moon so when it gets out there on Thursday, same day that by the way that Hayabusa2 is going to do all this cool stuff with the explosives, Beresheet will fire its engines and ease into lunar orbit at that time. And we just heard that they made a final trajectory correction so all that's looking good. Once they get into lunar orbit it'll be about a week before they actually land so a lot to look forward to.

[Mat Kaplan]: Yeah, a lot to look forward [00:07:00] to in April. In fact, I'm going to spring another one on you in a moment, but speaking of Springs you have a video, one of several that have been captured by Beresheet, there's an awful lot going on in this one. Of course, there's no sound in space, but if there was a sound it might sound like this.

[Springy sound plays]

[Jason Davis]: Wow. Yeah, I think it might sound like that.

[Mat Kaplan]: Let people know what we're talking about.

[Jason Davis]: Yeah so there's a video we posted in the Beresheet blog that shows its landing legs being deployed. It happens right after... relatively soon after the spacecraft comes off of the Falcon 9 rocket on launch day. So you can actually see the Falcon 9 upper stage still in the background letting out little puffs from its thrusters. And then in the foreground you see Beresheet the spacecraft deck and all of a sudden one of its legs just pops out and makes that noise just like you'd played. Except it doesn't but I think if you could hear it, it would make it would sound like [00:08:00] that.

[Mat Kaplan]: Maybe if you put your ear right up against the spacecraft bus while it was doing that you might hear something similar. And then in the in the distant background is Beresheet's target, the Moon, it's quite an image.

[Jason Davis]: Yeah, it's really cool that you can see the Moon in that as well. They really got lucky with all the angles on that shot.

[Mat Kaplan]: Alright here's that bonus bit, the launch of a really big rocket if all goes well, right?

[Jason Davis]: The Falcon Heavy is about to go on at second flight as soon as this Sunday, so that will be April 7. So far SpaceX is saying they're still on track, but that can always change. Anyway, the reason that Planetary Society members would be interested is that this is the same rocket that will carry LightSail, not this launch, of course, but the very next Falcon Heavy will have LightSail on board. So we'll be watching this one carefully to make sure everything goes as planned.

[Mat Kaplan]: Great update about a great month, Jason. Thanks very much. I'm sure we'll be talking again soon.

[Jason Davis]: Yeah, thanks Mat.

[Mat Kaplan]: Jason Davis, Digital Editor for the Planetary Society and our [00:09:00] embedded reporter with LightSail project. So with any luck in the coming months, he'll have much more to say about that Planetary Society project. Amy Simon is just one of the planetary scientists who longed for an up-close and long-lasting examination of Uranus and Neptune, our Solar System's so-called ice giants. More about that term in a few minutes. She uses Earth-based telescopes and the Hubble to peer at these worlds that have only been visited once, when Voyager 2 zoom passed in 1986 and 1989, respectively. Amy has had a hand in many robotic missions including Cassini, OSIRIS-REx, and the upcoming Lucy mission to Jupiter's Trojan asteroids. In 2014, she convened a workshop [00:10:00] on the study of the ice giant planets. Her interest in them hasn't flagged as I learned when she spoke to me from her office at The Goddard Space Flight Center in Maryland where she is the Senior Scientist for Planetary Atmospheres Research. Amy Simon, welcome to Planetary Radio. It's a delight to get you on the show for this conversation and it was all so delightful to read your article in the March Equinox edition of the Planetary Report, the quarterly magazine from the Planetary Society, which is available to everybody right now. It's called "The Realm of the Ice Giants: What exploring these planets teaches us," and we're talking here about Uranus and Neptune, right?

[Amy Simon]: That's right.

[Mat Kaplan]: These are fascinating worlds and they have come up many times in the past on our show. How come they get so little love in the planetary science... at least the mission community?

[Amy Simon]: Yeah those poor cold, blue planets way out there in the solar system. You know, it's kind of interesting because I think even at the beginning of [00:11:00] my career we didn't pay a lot of attention to them because the Voyager 2 flybys had happened, but there was nothing going on out there. So all the hype was on Jupiter with the Galileo Mission and then Saturn with Cassini Mission and its some level, you know, we all had that idea of of Uranus and Neptune frozen in our heads and forgot that of course all these planets are active and interesting planets, and I think just the fact we haven't had a mission out there, it's so hard to get out there, has kind of let us put them on the back burner and forget about them a little bit.

[Mat Kaplan]: They really have been, I mean a lot of people say the same thing about Venus that it had hasn't gotten the attention that it deserves and I'll bet you agree with that, but we've heard from so many people that even though the telescope's based here on Earth and the one in orbit that you're working with—which we'll get to of course, the Hubble Space Telescope—they're doing fantastic work. There's there's nothing like being there, is there?

[Amy Simon]: There really isn't, and there's quite a lot of things we can't do unless we're up close to the planets. There certain measurements we just can't make here on Earth with the atmosphere in the [00:12:00] way or in some cases, you know, measurements we have to physically make in the atmosphere of the planet we want to study. Going there, there's just no substitute.

[Mat Kaplan]: Let's dig in and talk a little bit about what we do know about these worlds, beginning with the one that's our slightly closer neighbor, Uranus. Tell us about this world.

[Amy Simon]: So Uranus is fun. It's strange. It's hard to explain. It's tilted way over on its side and that's probably the thing most people think of when they think of Uranus. And most of us have a view of it is kind of a pale blue ball with nothing going on which isn't true at all actually. So we passed Equinox on Uranus not that long ago, 2007, and since then with the Hubble Space Telescope, with these high-resolution ground-based telescopes, we've been able to watch lots of small storms that pop up now and again in the atmosphere. But also it has actually quite an impressive polar cap, where we see brightness where it's much brighter as the seasons have changed on Uranus. So there's a lot we're learning [00:13:00] even from the ground-based telescopes. But otherwise, you know, we tend to have a view of it is very serene, quiet, not much going on. It doesn't give off much heat. It tends to give this impression of not being very active but there actually is quite a bit going on in that atmosphere.

[Mat Kaplan]: How about around Uranus? What about its moons?

[Amy Simon]: So Uranus has a nice moon system, as all the giant planets do, and they're actually quite interesting as well. They have... they have fun names, are all named for Shakespearean characters, but we have Ariel which seems to have a lot of geological features on it that are indicative of a young surface or maybe activity at some point. There's also Umbriel, which has a crater kind of near its pole that seems to have a ring of ice and we didn't get a very good look at that with Voyager 2, but that's quite intriguing. That's something we'd like to go back and look at much more closely. But it doesn't have any one big moon. So you don't have a Titan or a Triton at Uranus so it has a bunch of smaller moons.

[Mat Kaplan]: Yeah. I think you just gave the reason why my Shakespearean actress younger daughter has made Uranus her... [00:14:00] I believe it's her favorite planet. It's because of those wonderful moon names. Let's go a little bit farther out. Why is it the Neptune, quite a bit farther from the Sun, seems to have more at least visibly going on than its neighbor Uranus?

[Amy Simon]: Yeah Neptune is intriguing in its own way. So even with the Voyager 2 fly by we had the Great Dark Spot, so there's a raging storm and when we looked a few years later with the Hubble Space Telescope, it was gone, which surprised us too because we were used to the Great Red Spot on Jupiter which kind of sticks around. But we also see a lot of cloud activity. We see I think a little deeper into the atmosphere. We're not seeing quite as much of the overlying haze. So we see a little deeper maybe we can see a little more structure that way, but also it has a lot more internal heat. So it's giving off more heat than it's receiving from the Sun, unlike Uranus, so that perhaps drives a little bit more of convective storm activity like we have here on Earth, but honestly, we don't know why they're so different and why they can have such [00:15:00] high speed winds when they're so far from the Sun. So there's a lot about these planets that really ties that interior structure that we can't see from the outside.

[Mat Kaplan]: And is that greater amount of heat coming from its interior, that difference from somewhat more serene Uranus, is that one of these mysteries you're talking about?

[Amy Simon]: It absolutely is. Now this difference in heat flow that we're talking about is based entirely on one measurement from Voyager 2. So there's possibility maybe that measurement had something not correct in it or there's something we missed. There's possibility it changes with the seasons. Also, whatever tilted Uranus over on its side, maybe a great collision, may have been responsible for changing that interior structure and getting rid of a lot of excess heat. So there's quite a lot of theories on why they're so different from each other. But honestly until we can get there and make more measurements and actually get a bit more of a handle on their interior structure we won't know.

[Mat Kaplan]: You just mentioned the other factor about this planet that I was about to bring up which is that it's so out of step. I mean, it's it [00:16:00] really is leaning on its side compared to the other planets that are rotating basically along the plane of the solar system.

[Amy Simon]: Yeah, you know between the two of them they kind of cover the extremes of what we'd expect in planets out there. We have one that's tilted more or less about the same as the Earth, one that's way over on its side. One that has lots of internal heat, one that doesn't. One similarity they have is they both have complicated magnetic fields that are not centered in the absolute core of the planet, but probably being formed somewhere around the edge of that core. Really strange planets that we need to learn more about if we want to understand extrasolar planets, too, which a lot of them are about this size.

[Mat Kaplan]: If we got up close to Neptune, would we with the naked eye be able to see it's ring?

[Amy Simon]: Ah, that's a tricky one. So they have somewhat different ring systems as well. These are not big expansive rings like Saturn. But in Uranus' case they're kind of tenuous and circling the whole planet and [00:17:00] Neptune's case the rather clumpy. So you see little arclets of rings. And so if you were behind the planet looking back towards the Sun you might see them but they're pretty hard... pretty faint to see. They tend to glow better in the infrared than in the visible.

[Mat Kaplan]: Let's not ignore the moons of Neptune. There's some interesting things going on there as well, right?

[Amy Simon]: Yes. Actually Neptune's moons are interesting in that it seems like they may have been captured rather than forming in place. And in particular Triton is quite interesting. It's a bigger moon and we didn't get a good view of the whole surface, but it's got weird cantaloupe skin looking terrain and then possibly even nitrogen ice geysers near its south pole. And so we think it might be very similar to a Kuiper Belt object or Pluto type object. So that's why we'd like to see the other side of, especially see what's going on all sides, of Triton.

[Mat Kaplan]: Is there a chance that any of these moons are, like we are beginning to find among so many moons, that maybe the they're hiding liquid water?

[Amy Simon]: Absolutely. We know there's a lot of ice in the outer solar [00:18:00] system and if they had enough tidal stressing or some other thing going on where they could retain a little heat, they could have liquid water deeper down. We're not so sure about that, but when we look at Uranus' moons, at Mab in particular, it's embedded in a very tenuous ring and we might wonder if it's similar to Enceladus at Saturn where perhaps it's causing some of the ring, but we just don't have enough information to make that connection yet.

[Mat Kaplan]: I think you've demonstrated this is not a case of if you've seen one you've seen them all, and I think of all the other worlds—thousands of them now—that we're discovering across our section of the galaxy with all the Kepler discoveries and think I just heard the other day that now we've got something like 4,000 confirmed exoplanets. I think I heard that over the weekend. A lot of these are what might be called ice giants.

[Amy Simon]: Yeah, I think most of the ones we found so far are quite a bit closer to their parent stars. They're not going to be as cold as our Uranus and Neptune, but they're in that same size, that same [00:19:00] mass class, and the fact that we're trying to understand an exoplanet when we're only seeing it basically as a wiggle on a light curve or maybe a single point, it's hard to piece together what that planet is like. And when we look at our own solar system, we essentially have resolved exoplanets. And so to have two planets that are so similar to all those exoplanets, but we know so little about, you know, just begs for us to go back and learn more about them.

[Mat Kaplan]: Having these worlds so close to us, the others are... we're not going to be visiting them anytime soon, any of these exoplanets, we have the opportunity to learn from Uranus and Neptune and extrapolate that to worlds across the galaxy and perhaps across the universe.

[Amy Simon]: That's the key is understanding the diversity in our own solar system so that we can kind of put boundaries as we try to look at these other exoplanet systems.

[Mat Kaplan]: Before we go any further, I want to talk about this term ice giants and it doesn't bother me but it does bother a guy who's one of my favorite people [00:20:00] on this planet, the science educator, Jeff Bennett, who wrote me a very thoughtful note about how he talks with kids and when people mention the ice giants, Uranus and Neptune, kids tend to think of these is as, "oh, it's a ball of ice. It's just blue ice." Does that term bother you at all or does it seem to describe these properly? Or does does it ever give you any any concern?

[Amy Simon]: Well, you know, that's interesting. Actually when the term first got coined I really didn't like it either for that exact reason. These are not solid objects. But you know, I think gas giant is also a bit of a misnomer for all of our giant planets as well. So I prefer just giant planet if I have to. But I think they are a distinctly different class from Jupiter and Saturn and that's kind of what started this in the first place. When we talk to kids or anyone about Jupiter and Saturn we said are primarily made up of hydrogen and helium, and the difference with the ice giants is they have a much bigger amount of water and presumably ices. So there's a lot of ionic [00:21:00] water and it's much colder so a lot of things freeze out. But in both cases you're talking about extended thick dense atmospheres, and sp probably would be better to call them both fluid planets, but you know, that doesn't roll very well either. So, I tend to personally think of them as gaseous but slushier. And again, it's not like you're really literally walking through slush on one of these planets, but they do have a higher content of water and it's not just hydrogen, and that's kind of why we gave them these distinct classes.

[Mat Kaplan]: And I get the feeling that ice giant is so well-established now, we're not going to be changing it. So we'll just have to be careful how we explain these in the future. What role might these worlds play in helping us understand how our solar system came to look the way it does?

[Amy Simon]: It's interesting to look at the evolution of how we think the solar system formed. Early models, everything pretty much formed in place. We had this big cloud of gas and maybe some rock as the Sun was forming and every planet just condensed in its own little orbit. But then we had to explain all [00:22:00] these things that didn't fit in that model including the fact that Uranus was over on its side and where our giant planets were and so the model started to get fancier and fancier. And then when we looked at extrasolar planet systems where suddenly we had these giant planets very close to their parent stars, our current model started to fall apart again. Why didn't that happen here? Why didn't Jupiter just keep migrating in and sweep up all of the terrestrial planets? I think what we need to do is understand when and where each one of the giant planets formed because they all influence the other and we think now that having a Saturn, having a Uranus, having a Neptune, kept Jupiter from migrating in that far. And so without having the bunch of them we wouldn't be here today. And so part of this key is understanding exactly when and where they were as they were forming and whether they moved around.

[Mat Kaplan]: So we owe these big outer planets a big debt of gratitude. There are people who believe that Uranus and Neptune formed much closer to the sun, right?

[Amy Simon]: That's right. So some [00:23:00] models have them out farther, some have them closer, and in most cases they do migrate around before they hit their final positions.

[Mat Kaplan]: Let's talk about how a mission to these worlds, at least one of the two of them and my guess is you prefer to visit both...

[Amy Simon]: Of course.

[Mat Kaplan]: this might help us. We have a new generation of Earth-based telescopes about to come online. We talk about them on this show all the time. They're going to give us much better images around the solar system as well as around the universe and then of course, fingers crossed, the James Webb Space Telescope while it seems to have receded again a little bit we're all hoping that it's going to be in place soon. And I know they're going to do planetary observations with it. You already said it just doesn't compare. I mean it's valuable data, but it doesn't compare to being able to send a mission out there, and these few data points that we have from Voyager 2, they just don't match up to what we would do if, let's say, we could send an orbiter to [00:24:00] one of these worlds and then have it move on someplace else which I guess might be the ultimate dream.

[Amy Simon]: Yeah, absolutely. I think there's several key measurements that you just can't make here on Earth for a few reasons. So the first is thinking about looking at these outer planets from Earth. We don't ever see the backside of them, the unilluminated side, and that's key for getting those thermal measurements for understanding how much heat they're giving off. So that's number one. Number two is that we'd like to get in there and really explore their magnetic fields, understand where they are centered, whether their varying around and you can only do that if you're in orbit. And by the same token gravity measurements. Gravity tells us quite a lot about its interior structure, how big a core is, whether it has layers, and so on. To do that, you have to get actually very close, do very close passes, similar to what Juno is doing it Jupiter. But then lastly, you know, you really want to be able to taste that atmosphere, and that's key for a number of reasons. And the first is that when we're trying to understand when and where these planets formed, how old they are, we need [00:25:00] to measure the noble gases. And the noble gases are one of those few things that have no spectral signature whatsoever because they're so stable. And so the only way to do it is to literally measure them directly. And so a key to either of these missions, so either planet would be having an atmospheric probe that can get those noble gases. And then the other thing that can potentially do is measure how things vary as you're descending down into the atmosphere, how the winds vary, how the temperature varies, and how the composition varies. And so those are things you just can't do when you're sitting back remote no matter how good your telescope is. So those are the sorts of things we'd like to measure in a mission to one of those planets.

[Mat Kaplan]: So you would want to do what Galileo and Cassini both did, pretty successfully, and send those probes down and taste those atmospheres.

[Amy Simon]: Absolutely.

[Mat Kaplan]: You know we seem to be talking about planetary atmospheres a lot on this show lately, which must please you because that's what you do for a living?

[Amy Simon]: It is, I've been studying all four of the giant planet atmospheres now for quite a long time. [00:26:00]

[Mat Kaplan]: How do you make use of the Hubble Space Telescope to to conduct this work? I mean, I know that you lead something called the Hubble Space Telescope Outer Planet Atmospheres Legacy Program. Why Legacy?

[Amy Simon]: Legacy because Hubble's been around for quite a long time. And as we started to piece together observations over the years, primarily actually of Jupiter, we always had big gaps in our data set and then when we look to Saturn or Uranus or Neptune, we have very little data at all. So one of the things we propose to do was a Legacy of Hubble, study these planets on a yearly basis. Almost turning Hubble into a weather satellite and getting this frequent look at each of those planets, looking at the clouds, how the storms are changing, the colors, the winds, to build up a timeline of how these planets vary over time because they all have unique seasons and it was something we just couldn't do up until now. And so a primary goal of OPAL was absolutely just monitoring those planets [00:27:00] every single year.

[Mat Kaplan]: So this is exactly what Linda Spilker used to tell us about why it was so valuable that Cassini was active at Saturn for so long, because you got to see a substantial portion of the Saturnian year, just like this, right, for these even farther away worlds?

[Amy Simon]: Exactly. And as a matter of fact with OPAL we chose not to start observing Saturn until Cassini ended because Cassini already was fulfilling that Legacy, but now we can tie it all the way back to Voyager. Look at Saturn over, you know, multiple seasons and you know include Hubble in there and it's been just a fabulous tool for understanding weather on these planets.

[Mat Kaplan]: What about the new generation of telescopes? Are you looking forward to these which with as much anticipation as a lot of people we talked to?

[Amy Simon]: Oh, definitely. I mean for one thing some of them now are getting the Adaptive Optics to the point they work in the visible and that's going to be key for getting these high-resolution observations that we can only do with Hubble. It's still not going to surpass Hubble and that we can't look in the ultraviolet because the atmosphere blocks that [00:28:00] but I think these telescopes are just going to be fabulous for letting us monitor events we don't expect, you know, when an amateur reports that they've seen a fireball on Jupiter or Saturn, right now it takes a lot of lead time to turn around and use Hubble or something like that. So having a telescope on the ground that actually has a resolution to go back and investigate, it's just going to be so vital to understanding how things change.

[Mat Kaplan]: Are you and other outer planet specialist going to be fighting for time on the James Webb Space Telescope?

[Amy Simon]: Of course we are, but it's a friendly fight.

[Mat Kaplan]: Of course. What's the outlook for a mission to this this far away portion of the of the solar system. I know you worked on at least one mission concept. Is there anything currently in the works?

[Amy Simon]: Sure. So our last planetary decadal survey which is where scientists basically sit down and lay out the science priorities for the next 10 years. The next big flagship after Mars sample return and Europa is to an ice giant. But to do that still [00:29:00] requires getting a new start, getting the finances to do this. And so in the meantime we've continued to do the studies. What could you do with a flyby mission? What can you do with an orbiter mission? Should it be Uranus? Should it be Neptune? Can we do both? You know, these are all key questions the community has and I think there's a lot of interest right now, a lot of people are starting to seriously study what we should be doing. It's just going to depend on timing. But you know, we'd like to get that launched in the late 2020s, so we could potentially take advantage of a Jupiter gravity assist. Either way, you know, we can get out there with the technology we have now.

[Mat Kaplan]: Is this going to take a big flagship mission like Cassini or Voyager for that matter, or is it envisioned that it might be done at one of the lower levels, a Discovery or New Frontiers mission?

[Amy Simon]: You know, we've looked into those options. They're challenging, certainly and in my own perspective just speaking for my science, we want to have... if we're going to get out there, we want to make sure we can put everything on there [00:30:00] that we need to do it right, and that becomes the challenge under a smaller cost cap. But you know, there's a lot of smart people out there, a lot of innovative ideas, so we're looking into different ways to do it that combine a lot of science objectives and can get us out there in you know a reasonable time. So I'm not giving up hope, but you know, we'll see.

[Mat Kaplan]: Let's say we get something launched by the late 2020s as you said, still long time to wait, and we get that Jupiter gravity assist, when are we looking at the arrival at well, we'll say Uranus since I assume that would be the first stop?

[Amy Simon]: Right, certainly depends on your launch vehicle. So essentially how much you know lift you can get from the Earth. Depending on that, you can get there in six to ten years, all the way to 14 years. You know, it just it just depends on a few factors, but you know, I would say on average 8 to 10 years.

[Mat Kaplan]: Wow. Well, you've shown once again that anybody who wants to study this part of the solar system is playing the long game. You've been at this for quite a while, haven't you? [00:31:00]

[Amy Simon]: I have, I've been studying plans for about 25 years now.

[Mat Kaplan]: Tell me about the work that you do at Goddard. I mean, you're a planetary scientist there. Is it entirely focused on on these outer worlds?

[Amy Simon]: Mine is not, I've been very lucky in part because of studying the outer planets I've gotten to now study inner planets and small bodies that was in part because of the New Horizons flyby of Jupiter. I became involved with that team helping out with some of the Jupiter observations and as I did that the instrument scientist I was working with asked if I'd like to be involved in his next project which turned out to be an instrument on OSIRIS-REx. So I kind of go all over the solar system at this point.

[Mat Kaplan]: And you've got something on Lucy which we will be talking about on this program again, very soon, this mission to the so-called Trojan asteroids at Jupiter?

[Amy Simon]: That's right. We have a another instrument very similar to the one on New Horizons that will be going out to the Trojans.

[Mat Kaplan]: Amy I'm sure [00:32:00] even though you've been at this now for a lot of years that you hope to stay in this business for a lot longer so that with any luck you and the rest of us can see one of these dedicated missions that will take us out to the ice giants, pardon the expression, and help us solve some of the mysteries that you've just talked about.

[Amy Simon]: You, I think as scientists were so lucky particularly when we're involved in these missions we get to see new and exciting things all the time. And you know, it does keep you coming to work. Absolutely.

[Mat Kaplan]: Best of luck with all of this, Amy. We stand behind you at the Planetary Society. We also thank you for this delightful article, "The Realm of the Ice Giants: What exploring these planets teaches us." It's in the current issue of the Planetary Report the March Equinox issue and you can read it now because we have the entire magazine online at It's a great way to check out this award-winning magazine edited by my colleague [00:33:00] Emily Lakdawalla, our Planetary Evangelist. Thanks very much for spending a few minutes with us on Planetary Radio and best of continued success.

[Amy Simon]: Thank you.

[Mat Kaplan]: That's Amy Simon. She is the Senior Scientist for Planetary Atmospheres Research at the NASA Goddard Space Flight Center. As you heard she is also the leader of the Hubble Space Telescope Outer Planet Atmospheres Legacy program in addition to being involved with other work all over our solar system and interested in what's happening beyond our solar system. Time for What's Up on Planetary Radio. We have the Chief Scientist of the Planetary Society back to tell us about the night sky and give us a random space fact and and other good stuff. Welcome.

[Bruce Betts]: Thank you.

[Mat Kaplan]: Did I mention that you're Bruce Betts? I'm not sure if you knew that.

[Bruce Betts]: Who?

[Mat Kaplan]: Tell us about the night sky.

[Bruce Betts]: It's still a planet party, particularly in the pre-dawn. We've got lined up from the upper right to [00:34:00] lower left in the East we've got super... well very bright Jupiter and then yellowish Saturn and then down by the horizon super bright Venus, but you're going to need to clear view to the horizon in the East. But if you can get, you can also look for Mercury which is snuggling with Venus over the next two to three weeks. It will be much dimmer but hanging out to Venus' left although its position will be changing. In the evening sky, we've also still got Mars. Although it's looking dim and reddish, but it's near Aldebaran brighter reddish star in near the Pleiades, and on April 8th it will be hanging out with the Crescent Moon. So look for the Crescent Moon and Mars and Aldebaran forming a lovely triangle with Pleiades off to the right. That's all in the evening West, medium low in the evening west, southwest.

[Mat Kaplan]: That's a very romantic report. Lovely triangles, snuggling planets. [00:35:00]

[Bruce Betts]: Yes, it's just loves in the space. All right, we move on to This Week in Space History. Speaking of love, we love that Mars Odyssey is still working even though it launched this week in 2001. The Orbiter still working on Mars.

[Mat Kaplan]: That's quite a testament to... I mean there are several around the solar system and even outside the solar system now, but that's quite a testament to engineering.

[Bruce Betts]: It is indeed. All right, we move on to Random Space Fact. So a lot of wavelengths of light, as you may be aware, are totally kept from reaching the Earth's surface by the atmosphere, which is a good news particularly at the high energy wavelengths. Earth telescopes have to use atmospheric transmission windows. For example, looking visible, some of the infrared, most radio wavelengths, but one needs to use space telescopes for gamma ray, x-ray, most of the ultraviolet, and some infrared wavelengths.

[Mat Kaplan]: Gee, what a shame it would be so [00:36:00] much better if our atmosphere allowed x-rays and gamma rays to pass right through.

[Bruce Betts]: Really work on my tan.

[Mat Kaplan]: Yeah.

[Bruce Betts]: Yeah no. It's a really very good thing but it makes astronomy in those wavelengths challenging. We move on to the trivia contest, where I asked you, who is the second youngest person to orbit the Earth? How do we do, Mat?

[Mat Kaplan]: This was a real challenge for a lot of people because apparently, as we heard from a lot of people, there's just no really good database online that well, it has the age of the astronauts when they first flew and so a lot of people had to do cross-checking so it did hold down the number of entries somewhat. So more power to those of you who did get through. No power at all to those who said Sally Ride, because she wasn't even close.

[Bruce Betts]: She was the youngest American that's where they would have gotten led astray.

[Mat Kaplan]: Here's the actual answer to what Bruce asked and we will put it in the form of a poem, thanks to our Poet Laureate Dave [00:37:00] Fairchild, the second youngest person that has ever flown in space was Valentina Tereshkova of the human race. She's also the first woman and the first civilian, too, no wonder that her name is on a crater on the Moon. Wait a minute. That doesn't really rhyme. Yeah. That's alright. We'll give you that Dave. But it's true, she does have its like a thirty one kilometer crater on the far side of the Moon is the one named Tereshkova.

[Bruce Betts]: That is correct.

[Mat Kaplan]: Congratulations go then to, get this, Torsten Zimmer.

[Bruce Betts]: Hey, regular entrant.

[Mat Kaplan]: He entertains us regularly with very funny entries pretty much every week. But he has not won, as far as I can tell, in three and a half years since October of 2015.

[Bruce Betts]: Way to be persistent.

[Mat Kaplan]: Yeah, really. He indeed says Valentina Vladimirova Tereshkova who was 26 at the time of her flight. [00:38:00] He adds or so I hope because I found it surprisingly difficult to find a list of astronauts including their age at the time. He's assuming that Wesley Crusher was not sent into space by that point.

[Bruce Betts]: I think that's a valid assumption.

[Mat Kaplan]: She was actually I figured it out 26 years and 3 months old. Norman Casoon in the UK and Ola Francine in Sweden both mentioned Boris Yogorov, Yegorov, but he was a little bit behind. 26 years and 11 months. So maybe he was number three, although I didn't actually check that out. So Valentina who is still around by the way, and apparently a member of the Russian Duma the Parliament, Congress in Russia.

[Bruce Betts]: Yes, and she married another Cosmonaut and they had a child the first child produced by two people who'd gone to space. I think we've covered that in a previous random space fact or trivia, but it's kind of an interesting tidbit.

[Mat Kaplan]: Did we mention that she's not a lizard person or anything like that? [00:39:00] She's a perfectly healthy woman.

[Bruce Betts]: No, I don't think we mentioned that but now we have.

[Mat Kaplan]: This came from Carl Gendler in Santa Clara, California. He says, oh man, I'm 26. You're telling me I could have gone to space already? I must have squandered my youth. Not entirely Carl you are listening to Planetary Radio.

[Bruce Betts]: Oh good point.

[Mat Kaplan]: Anyway, we are going to send Torsten our usual prize package, at least the one that is current, of a Planetary Society kick asteroid rubber asteroid and a 200 point account for that worldwide network of telescopes that you can use remotely anywhere on the planet.

[Bruce Betts]: All right, it is time. Once again, I know you love it to play. Where in the Solar System?

[Mat Kaplan]: Indeed.

[Bruce Betts]: So to be explicitly clear: [00:40:00] other than on Earth. Where in the Solar System is there a feature named Mozart? Go to

[Mat Kaplan]: A feature named Mozart not on Earth, implying that there is one on Earth, which I will now have to look up. You heard him. You heard the man, you have until the 10th, that it be Wednesday, April 10, 2019, at 8 a.m. Pacific time to get us the answer. We will award somebody a 200 point account and a kick asteroid rubber asteroid.

[Bruce Betts]: All right, everybody go out there look up at the night sky and think about since there're insects name bees, should there be insects name C's and D's? E's? Thank you and good night.

[Mat Kaplan]: Well, there's candy name sees. Anyway, he's Bruce Betts. He's the Chief Scientist of the Planetary Society who joins us every week here for What's Up? HardwareCon arrives in California's [00:41:00] Silicon Valley April 17 and 18. I'll be there to moderate a great panel called Opportunities to Innovate in the New Frontier of Space Tech. Be sure to say hi if you attend. We've got a discount link on this week's show page at Planetary Radio is produced by the Planetary Society in Pasadena, California and is made possible by its planet-passionate members. MaryLiz Bender is our Associate Producer. Josh Doyle composed our theme which was arranged and performed by Pieter Schlosser. I'm Mat Kaplan. Thanks for those ratings and reviews. Ad Astra.