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The Mysteries Under Our Feet (With Dr. Sabine Stanley)

Dean explores the hidden wonders inside planets and across the solar system with guest Dr. Sabine Stanley, a planetary physicist and author of "What's Hidden Inside Planets." New episodes release every other Friday!

Additional resources referenced in this episode:

John Hopkins University
Dr. Sabine Stanley
Sabine’s research involves understanding planetary interior processes and evolution. She focuses on planetary magnetic fields, dynamo theory, interior structure models and other geophysical methods to learn about the deep interiors of planets. Her work includes projects on many solar system bodies (Mercury, Moon, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, asteroids and planetesimals) as well as extrasolar planets. She uses a combination of numerical simulations, theory and comparison to observations from various missions to explore her science questions. More about Dr. Sabine Stanley.
Morton K. Blaustein Department of Earth & Planetary Sciences, John Hopkins University


Looking Up is transcribed using a combination of AI speech recognition and human editors. It may contain errors. Please check the corresponding audio before quoting in print.

Dean Regas: The Earth is full of breathtaking natural wonders: volcanoes, geysers, canyons, oceans, forests. And since we're on the surface—the crust of the planet—it's easy to forget all the wonders hidden inside of the Earth. So today, we're going to uncover the magic inside our planet and planets across the solar system.


From the studios of Cincinnati Public Radio, I'm your host, Dean Regas, and this is "Looking Up," the show that takes you deep into the cosmos or just to the telescope in your backyard to learn more about what makes this amazing universe of ours so great.


Our guest this week is Dr. Sabine Stanley, professor at Johns Hopkins University, author of the new book, "What's Hidden Inside Planets." Now, our guest today will be taking us on a tour of planets far, far away, but I thought it might be a good idea to get a refresher on what's going on with this planet right here, right now.


So, here's where I'm going to jump out of my comfort zone, and I'm going to put a disclaimer out there right now. I am an astronomer. I am not a geologist. And I almost said geologer. Well, I'm not a geologist, obviously, but I will like to put in that I thought I should be a geologist at some point. It was my backup to my backup to my backup plan because living here in Cincinnati, Cincinnati is one of the geology hotbeds. And I was really excited about all the fossils that were all around and the creeks and the cuts in the hills and all that kind of stuff. I thought I could be a geologist, sure.


So, at the very center of our Earth, there is this thing: the inner core. It's like a solid metal ball, mostly made of iron and nickel. And it actually rotates. It spins incredibly fast there at the very center.


Educational Video: Let me cut this peach in half. This will be our Earth. The pit is like the core of the Earth. The Earth's core is about half of its diameter.


Dean Regas: And then outside of that is the outer core, which is also made of iron and nickel. And it's more resembling of a liquid than anything. And this is the section that generates the Earth's magnetic field. This is the thing that kind of protects us from excessive solar radiation and things like that. So really, really important.


Educational Video: The part of the peach that you eat is called the Earth's mantle.


Dean Regas: Which is mostly made of iron, magnesium and silicon. It also kind of moves around as well as it's under there. So, we kind of think of the Earth as this solid thing. But there's all these different layers to it.


Educational Video: What's the outside called?

It's called the crust. Just like the crust of bread.

Very good.


Dean Regas: And then, of course, there's the part we know the most about because that's what we live on is, the crust. And it's very thin compared to all the other layers, but we've never really drilled past that.


Educational Video: Wait, Dr. D. You lost me. How do we know how big the core is and what it's made of if we've never been there?

Well, it's just a guess. You're kidding.


Dean Regas: Well, now let's get in a real expert to the field here. We're going to be talking with Dr. Sabine Stanley, Professor at Johns Hopkins University and the author of this really, really cool book about the solar system. What's hidden inside planets?


Well, Sabine, thanks so much for joining me today.


Dr. Sabine Stanley: Very happy to be here.

Thanks for having me.


Dean Regas: First question is what is a planetary physicist? And what kind of drew you into that line of research?


Dr. Sabine Stanley: Oh my gosh, what a great question. So, a planetary physicist is essentially someone who uses the tools of physics in order to study planets. I did my undergraduate degree in physics and astronomy and was very fortunate to have some great mentors that were working in the space of Earth and planets and kept giving me these really cool examples. Hey, you know, you could apply that type of physics to Earth and the planets. And that really got me interested in this and eventually decided to pursue it as a research career.


Dean Regas: So why is it important to you to know what's happening inside planets?


Dr. Sabine Stanley: So, at some point you think, well, it's happening inside the planets, it doesn't affect me, but that's actually the furthest thing from the truth. Here on Earth, if we think about our experiences on the surface of Earth and what makes it a lovely place to be, and also sometimes not so lovely place to be, all of those things are related to the interior of the planet. The air we breathe comes from outgassing of the interior of the Earth through, for example, volcanic eruptions. So, the fact that we have a habitable atmosphere is because we have stuff coming from the deep interior, the oceans we have, water comes from the interior of the Earth. And then some of our biggest hazards, things like volcanoes and earthquakes, they're all a surface manifestation of something that's happening very deep inside the planet.


Dean Regas: And, and we're kind of biased towards rocky planets here, living on Earth, but do you do other things with like the gas giants and things that aren't quite as solid as the Earth?


Dr. Sabine Stanley: Yeah, absolutely. It's really quite fascinating to think about what goes on inside a giant planet like Jupiter. So, you've got something that's about over 300 times as massive as Earth. It's mostly made up of hydrogen with about 25 percent helium and a smattering of other elements. So very different in composition than the Earth. So, what would happen on the inside of that planet? On Earth, when we talk about hydrogen and helium, we think of them as being these kind of gases. in the atmosphere, but in Jupiter, if you go deep enough, the pressure gets so high, and the temperatures get so high that the hydrogen can actually become a metal. So, we have metallic hydrogen in the interior of Jupiter, and that's actually where Jupiter generates its magnetic field because metallic hydrogen is a great electrical conductor. So, the magnetic field of the planet is generated in hydrogen, which is just something that you would never expect. here on Earth.


Dean Regas: So, you're not exactly bringing back large samples from these solar system bodies, but you can learn a lot just from observations, right?


Dr. Sabine Stanley: Absolutely. So, we actually are starting to get more and more samples from other solar system bodies. So that's exciting. So, for example, the OSIRIS REx mission just brought us back some lovely samples of an asteroid, but most of the data that we get from other planets comes by taking data from a spacecraft that's surrounding that planet. And they use methods kind of similar to what a doctor might use to figure out what's wrong with you when you go to the hospital, right? It's unlikely that they're going to start by drilling a


hole in you to figure out what's wrong with you. They're going to start by using all sorts of sensing methods to figure out what's wrong with you. And we do the same for the earth. We use waves that travel through the earth from earthquakes to study what the structure of the planet is. We use magnetics. So magnetic fields that emanate from the deep interior of the planet and we can observe outside of them. We can use and even the gravity field we can use our gravity field as we move around a planet to figure out What is the mass and what is the composition of the planet below it.


Dean Regas: Given your expertise, your experience, what would you consider the ultimate cosmic road trip? You know, like what objects or phenomenon would be like must see attractions as you travel around?


Dr. Sabine Stanley: Oh gosh, I've got two for me. one of them I think is Saturn. Saturn is just this beautiful planet. One of the amazing things about Saturn's rings is that they have waves in them. And the waves in the rings are coming from These motions that are occurring very deep inside Saturn. So, we almost have this like, telegraph system that can tell us what's going on in the deep interior of Saturn just by studying the rings. The other place that we need to go back to are the ice giants in our solar system. So, this is Uranus and Neptune. These planets, they're about almost 15 times as massive as earth. They're mostly made of water and other ices like methane and ammonia. And they're just really cool places when you start thinking about what happens when you take water and you extremely squeeze it to really high pressures. What happens when you take carbon dioxide and do the same thing? And we're finding that you take those materials, you squeeze them, you put them under really high temperature and pressure. And you can actually make things like diamond icebergs that float on a diamond sea very deep in the interior of Neptune. So that's where I want to go.


Dean Regas: What's the most bizarre or unexpected fact that you found from the, like the interiors of planets?


Dr. Sabine Stanley: Yeah, I think the most unexpected fact, and it's one that I'm still trying to understand. When the Voyager 2 spacecraft flew by our ice giants back in the 1980s, it found that their magnetic fields are not like the magnetic fields of the other planets in the solar system. So, Earth, for example, our magnetic field looks like a giant bar magnet. It's got a north pole and a south pole. You go to Jupiter, you go to Saturn, you go to Mercury, they're all like this. Then you get out to Uranus and Neptune, and suddenly the magnetic fields are completely different. They have many poles. So, there are North and South poles all over the place. And so, the geometry of the field is very different. And so, we really want to understand why, why is Uranus and Neptune's magnetic fields so different from the other planets? Could Earth's magnetic field one day become like that?


Dean Regas: Well, since you bring up the Earth, there's been all this talk about the pole flip, that it is imminent. Is that something that you get into also in your research? And what can you tell us about the imminence of it, or lack of, and any implications?


Dr. Sabine Stanley: So, on average, the Earth's magnetic field flips its poles, so the North Pole becomes the South Pole in terms of magnetism about once every half a million years. And that's been doing that for the past at least three billion years. But it's not periodic. So, it doesn't happen every half million years. Instead, it randomly happens. So, we can never actually predict when the next one's going to happen. The last reversal we've had on Earth was about 750,000 years ago. So, in some ways we're kind of overdue for a reversal. But that doesn't mean that one's going to happen tomorrow. The other intriguing piece of, evidence that comes into this story is we think that the beginning of a reversal might actually happen by having the strength of the magnetic field get weaker. And we kind of see that happening right now. What we don't know is whether what we're seeing is just like a little dip that will go back to its regular strength, or if this really is the beginning of a decline in the field strength that will then lead to a reversal.


Dean Regas: Well, in my field, I get all sorts of doomsday predictions, and, so, can you make me feel better that a pole flip won't be bad?


Dr. Sabine Stanley: So, a pole flip, we think, takes about 100 to 1,000 years, so the good news is we'll have time to prepare for it. What we could expect during a pole flip, for example, is that because the magnetic field We'd have less of a protection from the electromagnetic radiation coming from the sun and from cosmic rays. That could do things like damage spacecraft that are in orbit around the Earth. So we have a lot of satellites that do everything from GPS and telling us where we are on the surface and helping us land planes and plant crops to navigation to communications. So all of our satellites would be in much more danger, if a pole flip were to happen, but we'd have time hopefully to develop and prepare for that technology shift. We would have to make also the power grid on the surface of the earth, right? Our power grid does not like spikes. In electromagnetic fields, and when you have a reversal because the field gets weaker, we are more prone to these intense solar storms that might come off of the sun, creating a geomagnetic storm, and those could, for example, knock out power.


Dean Regas: Well, I know we've been talking a lot about planets, but you can't forget moons because moons are these worlds in their own. And so, what do you think about some of the crazy moons that are out there? There's some that kind of appeal to you.


Dr. Sabine Stanley: Oh, yeah, absolutely so the moons are the cool place to be because in the outer solar system Although the planets out there don't really have solid surfaces, the moons do, right? And then you get out to Jupiter's moons and Saturn's moons, and a lot of them have kind of the building blocks of life that we think of here on Earth, so they're very water rich. They have energy sources. And so, you start asking the question, huh? Could there be life on these moons, in the outer solar system surrounding Jupiter and Saturn, for example? My favorite moon is Titan, which is a moon of Saturn. It's an incredible place because it has a nitrogen-rich atmosphere, just like the Earth does. So, in some ways, its atmosphere is the most similar to Earth's of all the planets in the solar system. The atmosphere is thick, like the Earth's, so the pressure at the surface of Titan is about one and a half times atmospheric pressure here on Earth. So, we're used to that, but the gravity on Titan, because Titan's such a small moon, the gravity on Titan's really low.

And so, it's a really cool place to think about, but it also seems to have a lot of the ingredients for life. It has liquids running on the surface. Now, they aren't liquid water. Right here on Earth, we're used to having rivers, seas, and oceans of water. On Titan, they're made of hydrocarbons, things like methane and ethane.


but underneath the surface is a global water ocean. So, we know that water is there, and we know there are energy sources at Titan that could help fuel potential life. So, we're really interested in figuring out what's going on with Titan. And that's why the Dragonfly mission by NASA is scheduled to go to Titan and do some really cool science there.


Dean Regas: Wow, you really kind of talked me into Titan. I'm always an Enceladus fan; that's my moon of choice. But boy, maybe I shouldn't reconsider Titan. Sounds pretty cool. If I bring some cardboard with me to start flapping with your new book, you know, what's hidden inside planets. Can you tell us a little bit about that?


Dr. Sabine Stanley: Yeah. So, this book, I'm hoping that when people read it, the next time they look down at their feet, they're going to ask the question, "Hmm, there's some really cool stuff. What's that really cool stuff happening like 2000 miles below my feet? Like it's not nothing. There's some amazing things going on down there. So not only staring at the stars but staring down below your feet is also important.


Dean Regas: Well, this has been so fun talking with you today. Thanks so much for joining us. This has been great.


Dr. Sabine Stanley: Thanks so much. My pleasure.


Dean Regas: So, I know our show is called "Looking Up," and we've been doing a little looking down here and talking to Dr. Stanley got me thinking about my own geological experiences. So, I got to explore a little bit of the Earth's crust. Recently I was in New Mexico and went to Carlsbad Caverns National Park, and this thing was unbelievable! Carlsbad Caverns was, I mean, I'm still baffled as to how good it was. Like I'm walking down this trail into the earth, this giant hole basically that you're circling down on this walkway. Each twist and turn around the cavern, you see these formations, these unbelievable, you know, stalagmites, stalactites made me think, maybe I could be a geologist again someday. And then at the end of it, I thought, "Oh man, this is going to be great. I'm going to be like exploring caves. Like, yeah, I'm going to be a totally cave explorer." Forget that. Forget the stars. I'm going on the caves. And then it occurred to me, the lights were on, and I was walking down a nice little rated slope, and then thinking about when the lights go out and how dark it would be in there. I'm going to stick to the stars, if that's all right with everybody.


Well, thanks for joining us today and looking up with Dean. Regas is a production of Cincinnati Public Radio. Ella Rowen is our show producer and actual rock star, Marshall Verbsky assists with technical support and geological surveying. I guess we're surveying for a new place, aren't we? Anyway, our theme song is "Possible Light" by Ziv Moran. I'm Dean Regas and keep looking up!