Planetary Radio: Space Exploration, Astronomy and Science - The Skies of Super-Earths and Mini-Neptunes

Episode Date: May 1, 2019

There appear to be more mini-Neptunes (also known as Super Earths) across our galaxy than any other type of planet.  Hannah Wakeford wants to learn if some of them support life, and she’s doing this by exploring their skies. Curiosity, the Mars Science Laboratory rover, has reached an exciting and critical part of its mission of discovery. Senior editor Emily Lakdawalla provides an update. The beautiful Pasadena Public Library hosted Bruce Betts and Mat Kaplan for a special afternoon that included recording this week’s What’s Up. You can learn more about this week’s guests and topics at:  http://www.planetary.org/multimedia/planetary-radio/show/2019/0501-2019-hannah-wakeford-mini-neptunes.htmlLearn more about your ad choices. Visit megaphone.fm/adchoicesSee omnystudio.com/listener for privacy information.See omnystudio.com/listener for privacy information.

The Skies of Super-Earths, 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. By Super-Earths, we're not talking about Superman's home planet of Krypton. You may prefer to call them mini-Neptunes, as scientist Hannah Wakeford does in a great Planetary Report article. I'll talk with her about these skies, including their clouds. This week's What's Up segment with Bruce was recorded live at the beautiful Pasadena Public Library. Join us there near the end of the episode. We'll begin by heading to Mars, which has its own wispy clouds. Here's Planetary Society Senior Editor, Emily Lakdawalla.

Welcome back, Emily. It has been a while since we have talked about Curiosity, our Martian friend. How is she doing up there? The rover's doing pretty well, showing some signs of age for sure, but still getting a lot of science done in a place on Mars that they've been trying to get to since they landed. So the scientists are pretty happy, actually. Yeah, happy team. You make that report in your April 25 update, new drill holes despite memory problems. How is the health of the spacecraft? Well, there were some frustrating issues with

the rover's memory a few weeks back. You may recall that close to the beginning of the mission, actually, on Sol 200, the rover had to switch from its main computer, its A-side computer, to its back computer, its B-side computer, because of a memory problem. And things were fine on the B-side computer for a long time until there was a couple of memory issues on the B-side computer that they were having trouble figuring out. So they swapped over to the A-side computer again. And it turns out the A-side computer had some new memory problems. So they're back on B right now.

B's been working well for a while because they've partitioned off a part of the memory that was causing problems. Probably this is all just age-related. The rover's getting science done. There's going to be more souls lost to various little problems like this, but they're still doing well. So at least I have one thing in common with Curiosity, age-related memory problems. Let's talk about the science and sightseeing the rover is doing. You have, as always, some delightful images, including collections of pebbles in what you called or

described as lag deposits. I've seen these many times here on Earth. I should have known there was a name for them. Yeah. So it's an interesting landscape. Curiosity is in this topographic low named Glen Torridon. It's on the opposite side of the Hematite Ridge. Curiosity was aiming for this ridge for a long time, now named Vera Rubin Ridge. They explored the ridge, looked at all the rocks there, had a tough time drilling because who knew that a resistant ridge would also be hard to drill into. And now they're in the valley beyond it, which it seems like the rocks, for reasons they don't yet know, are weathering a little bit more easily and like sediment is blowing away. And what happens is that as the fine sediment gets blown away, then the pebbles that

weathered out of the rocks get kind of concentrated on the top of the surface. And so you have this kind of sandy looking surface that's just covered with pebbles everywhere the eye can see. But the pebbles have different shapes from place to place. In some places, they're remarkably round, which is just cool. So it's been a really interesting place for Curiosity to drive through. It's a great shot. There is one particular pebble which appears to have been, well, like someone started to drill a hole through it. It initially looks just like a green olive, but I've measured the scale and it's only about a millimeter across. It's a little bit more. It's basically the size of a seed bead, if you've ever done any bead work

in your life. And that's the size that it is. It's kind of crazy. Then you've got a shot of some really beautiful outcroppings that Curiosity is traveling among. Have we seen something like these before? Well, broadly, they look pretty similar to a lot of the Murray mudstones that Curiosity has been measuring ever since it arrived at Pahrump Hills, you know, at the very base of Mount Sharp. But they're weathering a little bit differently. They have slightly different looking veins. They may have mud cracks in them that indicated that this was a low stand of the lake. Or those could be features that just appeared when the rock was getting made. So it's all kind of new science right now. There isn't a lot of scientific

interpretation available. I think the thing that's really tough on Curiosity is that these rocks are so old and so many different things have happened to them, it can be a little hard to figure out, did they all start out the same and then they just experienced different groundwater and different geology ever since they formed? Or do they actually reflect different environments when they first formed? And that's a story that the scientists are still trying to figure out. Say something about this little two-image animated GIF that shows Curiosity trying to drill in into some of this surface. And it doesn't exactly go as planned, but it still looks

fascinating. Yeah, it's really interesting. So Curiosity drilled into this rock at a site called Aberlady. It looks like perfectly flat bedrock. The drilling went really well. It was so easy, in fact, that Curiosity didn't need to use any percussion on its percussive drill. It only needed to use drill rotation in order to just peel right into it. But that may have been, as it turns out, because the rock wasn't very thick. It looks like when Curiosity pulled the drill back up, it lifted the whole rock. So it's not totally clear what it actually drilled into. They did deliver a little bit of the sample to one of the analytical instruments, but they didn't want to put it into the major, like the organics laboratory instrument, SAM. And so they decided to dump that sample out actually

and try again nearby. Nice to be in such good shape that you can actually be a little bit picky about what you want to analyze. Before we go, we got to look up because it's also apparently eclipse time. That's right. Mars has two moons, of course, Phobos and Deimos, and they orbit exactly in the plane of the equator, which means that twice a year, pretty close to when Mars goes through its equinoxes, both of those moons transit the sun quite frequently. And so twice a Mars year, Curiosity looks up to see transits of Phobos and Deimos across the sun. And these are just super cool animations. They're useful for science because scientists use them, use the exact time that the moons cross the disk of the sun to help track very minutely the motions of Phobos and Deimos in their orbits. But it's also, they take them just because they're cool. Yeah. I mean, they really look like the

transits of Venus that we see from here, if you protect your eyes. They really do. What's next for the rover? More traveling around Glen Torridon. The team is pretty much finished. Kind of a first walkabout. They've driven down to the very lowest elevation in the valley.

And they've kind of scoped out the different kinds of rocks. They've identified three main rock types. And now they've drilled in one of them. So the next steps are to start driving back toward the mountain and pick out two more drill sites in the other two rock types before they start climbing again. Wow. All right. That's the report. 75 souls or Martian days all in this April 25 blog post from Emily, our planetary evangelist. And you'll find it at planetary.org. And we will add that more than what you've written here, you've included more of

those official mission updates from members of the Curiosity team, and they also make for great reading. So thanks, Emily. Look forward to talking again soon. Thank you, Matt. She is our senior editor and the editor-in-chief of the Planetary Report that you can read at planetary.org. Another issue coming out before too long. There appear to be more mini-Neptunes across our galaxy than any other class of planet. That's in spite of the fact that our own solar system lacks even one. Might these worlds be hospitable places for life? That's just one of the questions, though a very big one, that Hannah Wakeford wants to answer. Hannah is the Giacone Fellow at the Space Telescope Science Institute in Baltimore,

Maryland. That's where she also develops models of even more exotic skies, those that are above hot planetary giants. Think of Jupiter, but much closer to the sun. But we started with those smaller planets that are much closer in size to our own. Hannah Wakeford, welcome to Planetary Radio. Hello, thank you for having me. Great pleasure to have you on the show and also to have enjoyed your article in the 2019 Spring Equinox issue of the Planetary Report. You called it The Skies of Many Neptunes, Sniffing the Air of Other Worlds to Learn How Planets Are Formed and Evolved. how planets are formed and evolved. This seems to be an ongoing informal series of topics

we're doing on the show, or a topic, and that is studying the atmospheres of other worlds. Obviously something that gives you enormous fascination. Yeah, it's the most fascinating thing that we can do. Since the mid-90s, many thousands of planets outside of our solar system have been discovered. And we want to learn more about them. We don't want to just know that they're there. We want to know what their environments are like. What is the nature of these alien worlds? Let's start at the most

basic level. Which do you prefer, super earths or mini Neptunes, as you put in the title of this piece. I'm a mini Neptune fan. My work really in exoplanets, so planets that orbit stars other than the sun, is kind of rooted in the giant planets, planets that are like Jupiter and Saturn in our solar system, mostly made up of hydrogen and helium. And as you get smaller, you head towards the Neptunes and the Uranuses. And those are kind of the start of the transition into this mini Neptune to super earth regime. So I'm really coming at it from the giant planet end and pushing down towards these small worlds.

So they really are kind of a hybrid or a transition between rocky worlds like our own and the gas giants like Saturn and Jupiter. That's exactly right. These planets occupy that region of space we don't have in our solar system where you have rocky, Earth-sized, Mars, Venus-like worlds, which are dominated by their rocky cores and outer regions, and then a very small atmosphere. And then you've got the giant planets like Uranus and Neptune, which are dominated by this big envelope of hydrogen helium. Most of the worlds that have been discovered outside of our solar system actually occupy this space in between some kind of transition where you go from an earth sized

rocky world to a Neptune-sized gassy world. And we're trying to discover exactly where that transition happens. So it seems like a bit of a downer for our own planet to learn on Earth Day, as we speak, that it's a little bit below average in size, but that's all right. How do we now know that this category of in-between worlds is so prominent across the galaxy? Well, we had the fortune of launching an amazing mission into space called the Kepler Space Telescope. This was launched in 2009 by NASA. What its job was, was to look at a small patch of the sky, study 1,500 different stars, look at them for three years solid and try and determine what planets were orbiting them. And we do that by using something called the transit method, where you look for a planet passing in front of its star, which causes the light of the star to dim a little bit, as that planet causes a shadow. And we see this in our own solar system with the transit of Venus,

and even with the eclipse of the moon, which is just a very, very large transit. So we're looking for these changes in the amount of light, which will indicate the size of the planet that is passing in front of it. And from the amount of light that's being blocked, we work out the size of the planet that is passing in front of it. And from the amount of light that's being blocked, we work out the size of the planet. And Kepler found thousands of these worlds, it was actually more likely 50% more likely that a planet will be in this radius range between the Earth and Neptune than it would be larger than Neptune. And in our solar system, that's really interesting, because we've got four giant be larger than Neptune. And in our solar system, that's really interesting because we've got four giant planets bigger than Neptune and four planets smaller than Neptune.

And what we're finding is that 50% of the worlds that are out there that we've discovered so far near to our star, near region of our galaxy, are in this region between those two. And that's something we never thought we would find. As you might imagine, and as I'm sure it is on your own podcast, the Exoplanet podcast, the Kepler spacecraft comes up a lot on this program because it has made such terrific discoveries. There is that other way of discovering exoplanets, the Doppler method, but are we still discovering exoplanets, the Doppler method, but are we still discovering exoplanets

using that other technique? Yes, the Doppler method is fundamental in our discovery of exoplanets. It looks for slightly different types of exoplanets, but actually where it's incredibly important for these worlds that we're talking about is we have to use this Doppler method to measure the mass of the planets. With the transit method, we get the radius, we get the relative size of that planet relative to the size of its star. So the amount of light blocked out is the relative size of the planet to the star. The Doppler method is needed to actually put a mass to that planet, to understand the actual density of the world is a combination of the radius and the mass. So if we don't use the Doppler method,

we can't actually work out just the basic nature of these planets. One of the great illustrations in your Planetary Report article is this graph that shows the distribution of all these different worlds, including the ones in our own solar neighborhood, where you plot diameter against planetary mass. There are some surprises here in what we've discovered. Yeah, there's always some surprises. It's the beauty of studying our universe. Nature's imagination is vast and we're learning just how to match it. What we're seeing, if you look at this figure, is you're seeing this trend. As you increase your radius, you increase your mass. And then at some point, your radius doesn't increase anymore, but your mass can keep increasing. And that's in that Jupiter-Saturn range. So as you get to the size of the radius of Jupiter, which is 11 times the size of our Earth, you can increase the mass hundreds and hundreds of times and the size of that planet will stay relatively the same.

So we're seeing these different types of planets and different densities of planets as well. planets and different densities of planets as well. We're finding planets roughly the size of Neptune, but way as much as Jupiter. Now, Neptune is 17 times the mass of the Earth and Jupiter is 300 times the mass of the Earth. So there's a huge difference in the densities you would have there. And in fact, if you look across the exoplanet population, we're finding planets with densities of styrofoam up to solid lead. There is a huge diversity of worlds out there that we're just trying to understand and explore a little bit more. these worlds in a moment or two, but I have to bring up that I had no idea that the transit technique for detection of exoplanets was first suggested so long ago. Talk about the first person to come up with this concept. One of my favorite things to do is talk about the history of exoplanet discoveries. It's not a new thought and the thought of planets outside of our solar system has been around since 450 bc with the epicurean philosophy the ancient greece but it wasn't until

the 1600s where after the dark ages in in medieval europe when christiana huygens who is a dutch astronomer postulated that we would be able to observe planets as they pass in front of the star and block out that light. Now, the reason he came up with this is because he was studying the moons of Jupiter. And he observed that the moons of Jupiter as they pass in front of Jupiter block out a small amount of Jupiter's light. Now, if you translate that out to the stars, you should be able to find planets, as we do now. However, back in the 1650s, when he came up with this idea, they had absolutely no idea how far away the stars were. They had no way of being able to

measure the distance to other stars, and therefore how difficult this method is. What we're doing when we're looking at these planets pass in front of their star is looking for a change by 1%. 1% of the light is blocked out. That's roughly the equivalent of a small fly or mosquito passing in front of a street lamp that is a mile away. mile away. It's a really small change in amount of light that we're measuring. And if you don't know the distance to the star, you don't know the size of the star. And if you don't know the size of the star or that street lamp, you don't know the size of the thing blocking out the light. So while it was postulated in the 1600s, it wasn't until the mid-90s, 300 years later, that something happened. Now, of course, with Kepler and with some ground-based observations as well, we have learned, as we love to say on this program and across the Planetary Society, that we now are fairly certain, right, that there are more

planets in our galaxy than there are stars. Yes, that's absolutely right. There is almost certainly more planets than there are stars. And just think about that for a second. How many billions and trillions of stars and galaxies there are in our universe? And then think about how many planets there would then have to be. It's a truly staggering and very difficult number concept to kind of really put something to. Staggering, and yet I find it kind of comforting to know that we have all that company. And of course, you are, in the work that you do, part of this grand goal of finding life elsewhere across that vast universe and even just our vast galaxy. And to do that, it seems to make very good sense to be learning about the air, the atmospheres of these different

worlds, which is really where your focus is, right? Exactly. If we want to try and understand more about these planets, we have to look at their atmospheres. We have to look and understand what their atmospheres are made of, how they're circulating around, what is their weather like? Weather is simply defined as the presence of atmosphere, how it changes in time and space. We need to try and understand just the fundamentals of what is making up that atmosphere so that we can move on and try and understand how it changes in time and space around the planet, make them 3D objects rather than 1D objects that are on the sky. So it's a really fundamental concept that we have to really understand the planets deeper than just their size and their mass to understand their potential for this life.

With the transiting technique, if the planets passing in front of their star typically only reduce that star's light, the number of photons reaching us by 1%, the reduction of that light or the filtering of that light by that planet's atmosphere must be yet again a tiny percentage of what you started with. For a large gassy world like Jupiter, we would be measuring roughly 1% on top of that 1%. Wow. I like to joke that we're measuring a point source on a point source on a point source. I love that. That's great. Because it makes it sound just as ridiculous as it is. And it really highlights how difficult this measurement that we're making is for all of these worlds. And we've got roughly,

I would say right now, about 300 planets, give or take, out of the roughly 4,000 in total that have been discovered, that we can actually measure their atmospheres. So it's quite a small number of these worlds in total that we're able to make this really difficult measurement for. But we're getting better. And we're learning as we go along. And that's really the process that's been happening over the last decade. So that's really been the thing that the community, the characterization community that I work in is building up, just an understanding of the techniques we're using and getting better and better and pushing the number of planets that we can study to larger numbers. And a promise of much greater improvement, but we'll get to that later in the conversation as

well. With what we have been able to do so far, here is much too broad a question. What are we finding in the air of these worlds? What we're finding is that there's a huge diversity out there. If you look at all of the planets in our solar system, every single one of them is unique. It's got its own little differences, little nuances. We're finding that in these worlds that we're discovering as well. But one of the fundamental things that we're currently looking for in these atmospheres is signatures of water vapor in their atmospheres. Now, water vapor is not in any way related to biosignatures or evidence for life. It is a fundamental molecule in the universe. In fact, it's the third most abundant

molecule in the entire universe. You can find it absolutely everywhere. And we're really looking in these atmospheres to try and see this water vapor, because that will tell us a little bit about the temperature of the atmospheres, the dynamics of the atmospheres, and the just bulk extent of those atmospheres, so how much atmosphere there is. And that's really important as just a first principle for looking at these worlds. What we're also looking for is evidence of different atomic species and carbon-based species, but that's a little bit harder for us because we need the wavelength coverage. We need to be looking in lots of different colours, build up a spectrum of that atmosphere because each different molecule has its own unique fingerprint. And we're looking for those individual fingerprints.

So at the moment, we're really focusing in on these signatures of water vapor. What about organics like methane, which is causing so much curiosity and no pun intended about Mars, the perhaps most likely representative in our own solar system for finding life other than what we know exists on our own world. Are you talking about organics like methane as this search goes on? We certainly are talking about organics like methane. In fact, the search for methane has been there since the first transiting exoplanet was discovered in 2000. But thus far, it's remained incredibly elusive. Where we thought we should be seeing signatures of methane, we haven't seen them. This is likely due to the way that heat is distributed around these planets. The way that the heat is distributed will change the chemical makeup of the part of the atmosphere

that we're looking at. So we're starting to try and understand that. And to look for methane, you need to be looking at that cold world. Now, I will define my temperature structure here. Now, I will define my temperature structure here. Some of the worlds that we're looking at are in excess of 1,000 Kelvin. These planets are often anywhere between 1,000 and 2,500 or maybe 3,000 Kelvin. This is the equivalent of sitting under a rocket when it's taking off. It's just hot enough to melt lead. It's really hard to imagine. It's really difficult

to think of a planet existing in those temperature regimes. Or of life existing in those. Or of life, yeah. None of the planets that we've looked at so far, there's a handful that we're not so sure they have the potential to harbor life. But the ones that we've really been able to study in detail, they're not any nice place that you would want to go on your travels. They're pretty hellish, hot, giant, gassy worlds. And that's really where we're at in terms of the ability to characterize things right now. And we're really pushing it towards these more terrestrial worlds, such as the Trappist-1 planets that you can see in the article in that diagram. These smaller worlds

just are much, much more difficult. And they sit around stars that are very different from our own star. And that's because of the relative size of the planet to the star is really the fundamental measurement that we're making. So the smaller the star, the smaller the planets that we can see and measure. So we're talking about very different environments from our own and trying to understand the fundamentals of these worlds. The organics that we're talking about really exist at colder temperatures. They exist at temperatures below this 1000 Kelvin limit or in equilibrium. If we think about how all of the chemicals balance out if they're all balanced in equilibrium it should exist below this 1000 kelvin temperature bar but we're looking at planets now in this

temperature range in this colder temperature range where we should see it and the atmosphere should be big enough that we can measure that but we haven't found it yet and this is really baffling us right now with what we're doing. But in the future, with new technologies that are coming online very, very soon, we should be able to solve this mystery. sadly, has none of these mini-Neptunes for us to study. Is our own solar system proving in other ways to be a good model for what we find elsewhere? The answer in your article was kind of surprising. Our solar system is a little tricky. It doesn't currently match much of what we're seeing out there. Now, I want to make it very clear that what we're seeing out there is biased towards the technologies that we're able to use to measure it. And right now, we aren't able to measure a solar system like our own. It's incredibly difficult for us with the technology we currently have.

If we were sitting on another alien planet and looking at our solar system, we would perhaps see Jupiter and that's it. solar system, we would perhaps see Jupiter and that's it. So it's very difficult to say fundamentally whether we are alone, unique, but from the evidence that we have thus far, there's nothing like our solar system that we're looking at and investigating right now. And one of the things that I've been learning throughout my career is just how nuanced all of our understanding of planet formation is. And it's all been focused on trying to recreate our solar system. And what we're finding is planets that are nothing like those in our solar system.

We're finding these Jupiter size worlds sitting right next to their star, these things called hot Jupiters, which are 20 times closer to their stars than we are to the sun, these things called hot Jupiters, which are 20 times closer to their stars than we are to the sun, but they're the size of Jupiter. None of these formation models that can create the solar system can create those worlds. None of the solar system models are creating these super earth mini Neptune sized worlds because they've got these little tuning forks which allow them to create our solar system and we need to really broaden that again we need to go back to basics

and really pick them apart and go okay what if we break it down in just two fundamentals take all of these little things that we've learned about our solar system about the fact that jupiter formed and moved in and moved out again which helped create mars and the size that Mars is now, how can we use all of those little things, turn them off and see if we can create the diversity of worlds that we're seeing out there? And that to me is truly fascinating, trying to link the things that we're measuring to our understanding of the formation of worlds. And that, unfortunately, is even more difficult than measuring the atmospheres. I can sense how anxious the audience is for us to get on to those new technologies that are around the corner. But before we do that, you've already mentioned TRAPPIST-1. That system of worlds gets such good press. But you have some other favorite worlds,

I think. Could you help us explore some of these? Yeah, I'll take you up in the size range. So Trappist-1's worlds are roughly the size of the Earth, roughly the same density as the Earth. So they're rocky, what we would call terrestrial-like worlds. As we move up in the mass range, we're heading towards the Neptune-sized worlds. And there's this one world which is really, really fascinating. It's called GJ3470b. So we call it 3470b. And I like this one because it is a mini-Neptune. So it's got a gassy envelope of hydrogen helium around it but what we've done is we've used the hubble space telescope to measure it in the uv and in the uv what we're what we have measured is that the atmosphere is

being stripped from this planet it is being ripped away from this planet's atmosphere and it's lost a huge amount of its hydrogen helium envelope since it was born so it possibly started out bigger than Neptune but it's so close to its star that the star has ripped that atmosphere away and this leads me to another type of world right on that super earth mini Neptune boundary. It's called GJ 1214b. And I talk a lot about this in the article. GJ 1214b has been studied the most out of all of these super earths with the Hubble Space Telescope and from the ground and from many, many famous ground-based telescopes like the VLT in Chile. This world appears to be completely shrouded in a thick, dense cloud. Now, because of its temperature, roughly 900 Kelvin or so, this cloud has to be made of salt-based materials, so potassium chloride or zinc sulfide or sodium sulfides so it's made the

clouds in this atmosphere are made of very alien material that we have as rocks here on earth so think of rock salt and then turn that into a liquid cloud droplets in the atmosphere but it's completely shrouding this planet's atmosphere and we're really baffled by that and it was the first evidence that we had of this just completely shrouded planet and that's been really a focus of a lot of people's attention on this super earth mini neptune regime for this gj 1214 and it's all in this mass boundary where we have evidence that the star that they're orbiting has a huge impact on that planet's environment. As you mentioned, GJ 1214b in the article, you say that, well, it could be a rocky core with a hydrogen helium atmosphere, hundreds of kilometers deep. I'm reading directly or much more intriguing.

It could be a world covered in a deep ocean and atmosphere of steam. Are you talking about an ocean of water there, it sounds like? We are talking about an ocean of water there. And what we're really talking about for these, what we would call water worlds, is in fact, very, very deep oceans that at deep pressures would be forming these massive, massive shells of high pressure ice. Now, high pressure ice is actually ice that would have to form globally around that planet, like almost like an ice mantle. But it would be hot ice because it would be under pressure. So it's a really weird regime in terms of chemistry, in terms of physics. And if you look at the phase diagram of water,

there's many different and very interesting portions of water's phase diagram where ice, water, liquid, gas can exist in different combinations at different pressures and temperatures. can exist in different combinations at different pressures and temperatures. So these ocean worlds can be anything from a nice rocky world with a crust on top of it and then covered in a global ocean. So imagine you took away all of our continents and just had an ocean around the Earth. It could be anything from that to something like more Enceladus, anything from that to something like more Enceladus, which is a global ice ball where the surface is completely ice, but underneath we think that there's a liquid global ocean with liquid

water at pressures of roughly 80 times that standing here on the earth. So the ocean world definition is so vast and we're just starting to explore it. We're starting to explore it in detail in our own solar system, trying to understand the difference between an Earth-like world where we've got liquid water pooling on the surface to a ice world where we expect there to be a liquid ocean underneath the ice surface. And for exoplanets, we can expand that even further by putting these types of worlds much closer to their star in a more energetic environment in terms of the radiation they receive. And we might then expect not only ice and water, but also an atmosphere just completely composed of water vapor, steam. So water, its existence is one of the most important things in our universe. And as I said before, it is the third most abundant molecule in our universe. Exploring the places it exists and how it exists in these different environments is really

important. So amazing. As you talk about this diversity that we discover everywhere we look, that even water itself seems to display incredible diversity. I'm sorry that Kurt Vonnegut is not around to hear about this and that there actually may be real world corollaries for the ice nine as he put in one of his books, not something you'd want to come in contact with or bring home by the way. Let's get on to new tech, new technologies, the stuff that you and so many other astronomers are so looking forward to. You work a lot with the Hubble. We all know that it's follow on, uh, sad to say delayed once again, not long ago, the James Webb space telescope is still going to be

making its way out there. And with any luck, knock on my desk, unfolding properly and revealing far more of what we can learn about exoplanets. It's an infrared telescope, we know. And how much of that is key to what you hope to get from the JWST? The James Webb Space Telescope set to launch in spring of 2021 is going to open up our eyes. It's going to take the blinders off. We will be looking at wavelengths in the infrared, like you said, and that's going to allow us to see the fingerprints of carbon-based species. It's going to allow us to detect methane, if it's there, in multiple different bands, in multiple different parts of the planet's spectrum. And that's really important for the confirmation of these molecules. We're going to be able to measure carbon dioxide,

carbon monoxide in these atmospheres. For the smaller terrestrial worlds, if we look at Venus as an example, carbon dioxide has a really nice spike. It's got a signature that we can measure for a Venus-like world. And we should be able to see that for just maybe less than a handful of some of the best planets we can point that telescope at. So the carbon dioxide is hugely important for these giant planets as well. Take this back to planet formation. Planet formation, we want to understand how planets form, how they evolve over time and end up the way they are and the way that we see our solar system today.

The ratio between the water and the amount of carbon monoxide and carbon dioxide tells us a huge amount about potentially where that planet formed in its disk and how it evolved over time. And that's something that we're really interested to find out. And we can't do that without the James Webb Space Telescope. So I understand your enthusiasm for the Webb, but we have all these, this whole new class of ground-based telescopes also about to start coming online in the next few years. What role will they play? And are they, because they're ground-based, are they going to be less useful than a space-based telescope? The difference between a ground-based telescope and a space-based telescope is the Earth's

atmosphere. From the ground, we is the Earth's atmosphere. From the ground, we have the Earth's atmosphere in the way, and it's made up of many different molecules which absorb light in the same way that we're measuring the absorption of light in alien worlds. So the Earth's atmosphere has a lot of water vapor in it. That's what all of our clouds are made of as well. And that blocks light, that absorbs light in these infrared wavelengths. So in fact, it's much harder for us to make these measurements from the ground, especially of water, because we would be measuring the water in our Earth's atmosphere. I always like to make the analogy that it's looking for a small fluffy kitten for a sea of cats. And you can't find it unless it squeaks um but we don't have that so it's much

harder from the ground at these particular wavelengths but what you can do from the ground which is beautiful is build 30 meter telescopes and by the end of the 2020s we should have multiple 30 meter telescopes on the ground now the biggest one that will be in space when James Webb is open and ready to take its science data was 6.5 meters. So that is a vast difference in the amount of collecting area for our photon bucket and all we want to do is count those photons. So from the ground you have access to all of these beautiful optical wavelengths, the wavelengths that we can see with our eyes, and a number of gaps in the near infrared. Those are really, really important for understanding and detecting planets.

One of the things I'm really excited about with these very, very large ground-based telescopes is the direct imaging method. Now, the direct imaging method is looking at a planet directly. So it's taking a star, you block out the light from that star, and you have to be able to then see the light coming directly from the planet orbiting that star. And this method is really very difficult to do. It involves very complex instruments, and we're trying to put those in space. The James Webb Space Telescope will have a coronagraph on board. But from the ground, we can use these incredibly complex instruments, and we can customize them for different situations. And I'm really hoping and I'm really looking forward to getting way more

information about these directly imaged worlds, where we can get a spectrum directly from the planet rather than what we're currently doing which is inferring indirectly different things about that planetary atmosphere so there's a big combination and they all really work together to give us this full picture which really puts our solar system in context which is something that we're just trying to understand it's the fundamental question that human beings have had is, how did we get here? Why are we here? And we're just really trying to use everything that's out there, this beautiful array of hundreds of thousands of planets that are out there, to look back at ourselves and understand it a little bit more. We live in the most amazing times. I've mentioned before on this program,

and I'm considerably older than you are, I suspect, reading books as a kid, at least one book that said, we will probably never have a telescope powerful enough to reveal any star other than our own as more than a point of light. Well, we've certainly made a great deal of progress. Do you feel fortunate to be doing this work at this time in our human evolution?

I am insanely fortunate, not just to be in the time period where we have the discovery of these planets, but the time when I started working on these was the time when it all just started picking up and we started getting a better understanding. We started pointing the Hubble Space Telescope at these worlds I started right at the point when we were really getting that data from these space-based missions and I am incredibly lucky to be working in that time period the way that this science works is the right people at the right time doing the right things but it's really just that timing that timing is

so vital in really pushing just the frontiers of instrumentation we need these amazing engineers just insane leaks in technology that have happened to make the james webb space telescope work and functional is amazing when you think about it and i was lucky enough to be working at the place they were building it. So I got to see it be built and evolve and change every time I went back to look at it. And now I'm working on trying to understand how we can use those instruments. And it's incredibly lucky and it's all about timing. Thrilling indeed. Before we go, there's another statement in your article that i'd never really never thought about although it may on in hindsight seem obvious you say that every planet we've ever

found that has an atmosphere also has clouds i'm thinking that even includes mars which has so little air to begin with and i know that another part of your work has involved the study of clouds understanding them on those bigger worlds, the gas giants. With apologies to Joni Mitchell, are we getting to know clouds at all? We are, and I love clouds. I'm British, as most of you can hear from my accent. I grew up with clouds shrouding. I love them.

They're fascinating because they really define the dynamics of a planetary atmosphere. They define the temperature and the way the air is moving and the weather and in these alien worlds we're truly finding exotic alien clouds some of the clouds that we're finding and some of the ones that we think are most abundant in these hot Jupiter atmospheres are made of glass liquid glass clouds. This is because magnesium silicates, which is essentially the sand you find on the beach, is just broken down rock here on the Earth.

In the atmospheres of these planets where it's heated up so much and it's under very low pressures, it's a vapor that can then condense into a liquid, liquid glass droplets forming a cloud in an atmosphere. It's just something that, it's a work of science fiction. But it's not, it's science fact, and it's out there. And it's, I'm a massive science fiction fan. I grew up on science fiction.

And this is just, being the person to work on these and trying to understand these exotic species is really a privilege. I work on another planet, which is one of my favorites, called WASP-12b. It's got a temperature over 2000 Kelvin. We know from the measurements that it's got clouds in its atmosphere. It's cloudy. There's something in the atmosphere scattering light. But at that temperature, the only material that can exist in a liquid form to scatter the light in that way is something called corundum. And corundum is an aluminium oxide.

And for geologists in the audience know that this is the basis of rubies and sapphires. Every time I walk around Natural History Museum, I go into the Hall of Gems, because it's a gorgeous place to go. And I go, I want to melt that and that and that and that and put it in the atmosphere and see what happens. Because that's what we're seeing. That's what we're measuring, these exoplanets. It's something we can't do here on Earth. So we're just using them as little laboratories to try and test out the fundamentals of geology. Almost literally jewels strewn across our skies. I think you've answered this last question just with the enthusiasm that you've expressed, but I don't

think anybody ever told you, hey, Hannah, great science, but you've got to start a podcast and do public appearances if you want to keep your job. You got to be pretty busy doing just science. Why take on these added tasks? Because what's the point in learning all this stuff if we can't tell everybody? This isn't for me. This isn't something that should be limited to myself. These are fascinating things and they excite me and drive me to do the science that I do. And I know as a kid, I wanted to know all of this stuff. I wanted to know everything. So why not tell everybody? And if you can't explain the work that you're doing to any audience then you don't truly understand it so it's also really I think for scientists

even if you don't have the confidence or you don't want to go talk to audiences practice the language that you might use in front of them because that will help you really understand the problem and I think that that's something that's missed out a little bit more and not appreciated as much but I think it's it's the stuff that I'm most proud of. And with very good reason. Hannah, thank you so much. It has been lovely talking with you. I look forward to the discoveries that will be made with these new instruments and even with the ones we have now as you and others continue to use them to reveal the true nature of worlds across our galaxy. So do I. Thank you. This has been a fun conversation.

I couldn't agree more. Hannah Wakeford, she is the Giacone Fellow at the Space Telescope Science Institute in Baltimore, Maryland, where she focuses on characterizing the atmospheres of exoplanets. And, as you've heard, she also develops models of exotic cloud species for hot giant planets, like places like Jupiter, although hotter. You can check out her website. It's stellarplanet.org. You might also want to check out her podcast, Exocast. She's a co-host of that and used to do the Science Hour on Expression FM.

And there's one more thing I got to mention here, Hannah, that you primarily work at the STSI with the Space Telescope Advanced Research Group for the Atmospheres of Transiting Exoplanets. And that acronym is? Stargate. I love it. Hey, I told you I was a science fiction fan. And now, you're in good company. Thanks again, Hannah. Thank you.

From the Pasadena Public Library, this is a live version of What's Up with Bruce Betts here on the stage. Welcome, everybody. Thanks for joining us. Welcome everybody, thanks for joining us. We've just been up here talking with Bruce about his great book, Astronomy for Kids, and we thought, well why not? We have this great group of families and others here, and we ought to do What's Up. So welcome Bruce.

Thank you Matt, it's great to be here and really grateful to have such a great audience. Now you just showed the people here at the auditorium here at the library what's up in the night sky from here in Pasadena. You're going to have to do this without any pictures though this time. Okay close your eyes and imagine, well unless you're driving in which case do not close your eyes. We've got in the evening sky Mars is getting lower and lower in the west, looking reddish and fairly dim right now. There will be a beautiful conjunction, two things hanging out next to each other in the sky, when Mars hangs out near the crescent moon in the evening west on May 7th.

In the pre-dawn, it's a planet party. We've got Venus looking super bright low down in the east, and then you go to its upper right, kind of in the southeast, and you will see Saturn looking yellowish. Farther to the right, actually rising in the east around 11 p.m. now, is super bright Jupiter. It's going to be tough to catch Mercury. Mercury's pretty much gone underneath Venus, so sorry. But what you can catch is a meteor shower. The Eta Aquarids meteor shower, which we mentioned last week, is better in the southern hemisphere, up to 60 meteors per hour there, but up to 30 meteors per hour in the northern hemisphere. And that will peak on the night of May 6th and 7th. And there's a thin crescent moon that sets early in the evening, so it'll be a nice dark sky and a good opportunity to check out some meteors. I love that slide you showed the people here at the library earlier that showed everything in that wonderful line.

Yeah, no, it's spectacular, the whole planet lineup. I hope people have been getting up to see it. What else have you got for us? All right, this week in space history, it was this week in 1961 that Alan Shepard became the first American in space on a suborbital flight. Up and back. Up and back, but that counts. Yeah, yeah, he made it. And now we're going to move on to the next segment, and here I could use your help.

So I'm going to count to three, and when I do, I want you all to say, random space fact. You ready? One, two, three. Random space fact. Nicely done. That was very nicely done. So Saturn's rings are really, really thin compared to their width, really thin. In fact, Matt, if Saturn's rings were the thickness of a pizza, that pizza would have to be as big as Belgium.

The country's Belgium. I can eat that. Yeah, I believe you could. So really, really thin compared to how wide the rings are. Very cool. All right, we're going to to how wide the rings are. Very cool. All right, we're going to move on to the trivia contest. And tell me about the trivia contest. Well, normally we would have, we'd be giving the answer and announcing the winner of a trivia contest right now.

Contest that we do for the listeners to the radio show and the podcast. But for reasons I won't go into, we didn't have a contest two weeks ago. So we have no winner today. But we will have one again beginning next week. And in a moment, Bruce will have a new question for people listening to the radio show. So when he asks that question, don't shout out the answer because that'll be for the folks at home. But we can go to our contest for the people here. Let's do that. So I'm going to ask a question. I want you to raise your hand if you know the answer. What is the largest planet in our solar system? And somebody's going to come over with a microphone.

He's got it right there. Why don't we go to this young woman right here. Angelina. And what is that largest planet? Jupiter. That is correct. Jupiter. All right.

Angelina. Here is your rubber asteroid. Fortunately, it's rubber because Bruce is a much better – has a much better arm than I do. Oh, good. I made it okay. She just got a rubber asteroid. Okay. What's another one for our audience? Let's see how much you're paying attention. What star is called the Dog Star? What's the name of the star? Brightest star in the sky, not a planet. How about this young lady right over here? Wait for the microphone.

And what is your name? Alexia. And what's that big star's name? Sirius. Yeah, Sirius, that is right. Good job. Yes, give her a hand. I got one.

You want to do it? Thank you, everybody. You guys, you know your stuff. That was really fun. Now we're ready for the contest for the people at home. Remember, don't shout out the answer. But you can enter if you go home. Listen to Planetary Radio

and go to the contest page that Bruce is going to tell you about. We talked about the Eta Aquarius meteor shower. What comet's debris is responsible for the Eta Aquariids meteor shower? Go to planetary.org slash radiocontest to enter. And you have until May 8th. That'll be May 8th.

It's a Wednesday at 8 a.m. Pacific time to enter the contest. And you will win, if you are chosen by random.org and you have the right answer, you'll win yourself a Planetary Society rubber asteroid and a 200-point itelescope.net account. iTelescope is a network of telescopes. They are all over planet Earth. Anybody can use them online. All you need is a network of telescopes. They are all over planet Earth. Anybody can use them online. All you need is a computer or a device like this. You can actually work with any of those telescopes and take pictures of some of the things that Bruce was talking about earlier today as he told you about the night sky and as you can learn about in Bruce's book, Astronomy for Kids. Now all you have to do is enter the contest, and you might be the one who wins this time. All right, I think we're done.

All right, everybody, go out there, look up at the night sky, and think about your local library. Thank you, and good night. That is Dr. Bruce Fetz, the chief scientist for the Planetary Society, who joins us every week here for What's Up. What's Up. Society, who joins us every week here for What's Up.

Join Bill Nye and me at Science Museum Oklahoma on the afternoon of May 8 for Planetary Radio Live and more. Then consider attending this year's Great Humans to Mars Summit in Washington, D.C. I'll once again host the H2M webcast and moderate a panel or two. An amazing list of space geeks will participate, including NASA Administrator Jim Bridenstine and a guy named Buzz Aldrin. We've got the links you need

on the show page at planetary.org slash radio. Planetary Radio is produced by the Planetary Society in Pasadena, California and is made possible by its members who love clouds and clear skies. Mary Liz Bender is our associate producer. Josh Doyle composed our theme, which was arranged and performed by Peter Schlosser.

I'm Matt Kaplan and Astro.