WEBVTT - What’s Hidden Inside Planets, with Dr. Sabine Stanley 0:00:03.040 --> 0:00:06.800 Welcome to Stuff to Blow Your Mind production of iHeartRadio. 0:00:13.560 --> 0:00:16.239 Hello, and welcome to Stuff to Blow Your Mind. My 0:00:16.360 --> 0:00:19.480 name is Joe McCormick. My regular co host, Robert Lamb 0:00:19.560 --> 0:00:21.880 is out on vacation the day I'm recording this, but 0:00:21.960 --> 0:00:25.360 he will be back again soon. Today we've got an 0:00:25.400 --> 0:00:28.040 interview for you. This is a chat that I had 0:00:28.080 --> 0:00:33.040 with planetary scientist doctor Sabine Stanley about her twenty twenty 0:00:33.080 --> 0:00:37.560 three book called What's Hidden Inside Planets. This is a 0:00:37.600 --> 0:00:41.280 wonderfully interesting book about the science of planet formation and 0:00:41.440 --> 0:00:44.800 about what we know about the insides of planets near 0:00:44.920 --> 0:00:48.440 and far. A quick bit of author bio before we 0:00:48.479 --> 0:00:52.280 get started here. Doctor Sabine Stanley is a distinguished planetary 0:00:52.280 --> 0:00:56.400 scientist and a key contributor to NASA's Mars Insight mission. 0:00:56.640 --> 0:00:59.800 Holding a PhD in Earth and Planetary Sciences from Harvard 0:00:59.880 --> 0:01:03.720 u University, she focuses on the complexities of planetary interiors. 0:01:04.240 --> 0:01:07.280 Currently a faculty member at a top research university, she 0:01:07.360 --> 0:01:11.760 leads innovative studies in her specialized field. Beyond academia, Doctor 0:01:11.800 --> 0:01:15.720 Stanley is a regular speaker at international scientific conferences and 0:01:15.840 --> 0:01:19.560 serves as a consultant for various space missions. Her research 0:01:19.560 --> 0:01:22.720 has been published in leading scientific journals, earning her multiple 0:01:22.720 --> 0:01:26.520 awards for her contributions to planetary science. With a career 0:01:26.520 --> 0:01:30.399 that blends rigorous research and public engagement, Doctor Stanley remains 0:01:30.400 --> 0:01:33.720 a pivotal voice in the scientific community committed to enhancing 0:01:33.840 --> 0:01:37.800 our cosmic understanding. So I guess now let's jump right 0:01:37.880 --> 0:01:45.520 into our conversation, Doctor Sabine Stanley, Welcome to the podcast. 0:01:46.040 --> 0:01:47.119 Thanks so much for having me. 0:01:47.520 --> 0:01:51.680 So I wanted to start off with the idea something 0:01:51.760 --> 0:01:54.280 you bring up in the preface of your book, which 0:01:54.320 --> 0:01:57.280 is that when non scientists look out at space and 0:01:57.320 --> 0:01:59.680 find things to get excited about, one of the things 0:01:59.720 --> 0:02:03.080 I think that really gets people stirring is the idea 0:02:03.120 --> 0:02:06.240 of an exoplanet with liquid water at the surface, or 0:02:06.360 --> 0:02:10.440 a planet with breathable atmosphere breathable to us. And yet 0:02:10.480 --> 0:02:13.600 you say in your preface that quote, arguably a planet's 0:02:13.680 --> 0:02:17.919 interior is more important than the surface in determining a 0:02:17.960 --> 0:02:21.600 world's fitness for life or ability to withstand the pressures 0:02:21.639 --> 0:02:24.360 put on it by its home star. I think this 0:02:24.440 --> 0:02:26.680 might be really surprising to people. Could you explain this? 0:02:27.080 --> 0:02:29.280 Sure, there are actually two parts to this I would 0:02:29.320 --> 0:02:32.840 say the first is deep inside our planet, in the 0:02:32.880 --> 0:02:36.680 iron core, we actually generate the Earth's magnetic field, and 0:02:36.760 --> 0:02:40.000 magnetic fields when they are generating the core, they come 0:02:40.080 --> 0:02:41.520 all the way out to the surface of the planet 0:02:41.560 --> 0:02:44.560 and they basically surround the planet, and our magnetic field 0:02:44.639 --> 0:02:49.359 acts as this amazing shield stopping these high energy solar 0:02:49.360 --> 0:02:52.720 wind particles from hitting us. Now, when you have these 0:02:52.800 --> 0:02:56.160 high energy particles coming from the Sun, if they actually 0:02:56.280 --> 0:02:58.839 blast it into the planet without the magnetic field there, 0:02:58.919 --> 0:03:01.720 they would work to strip off our atmosphere. They would 0:03:01.760 --> 0:03:05.360 bring high radiation levels to the surface. It would essentially 0:03:05.400 --> 0:03:08.200 not be a really great place to live if we 0:03:08.240 --> 0:03:10.600 didn't have our magnetic field. So one really important thing 0:03:10.639 --> 0:03:14.000 when thinking about is that planet going to be really 0:03:14.080 --> 0:03:16.800 good for say, life to form, is does it have 0:03:16.840 --> 0:03:19.639 a magnetic field and that's really created in deep inside 0:03:19.680 --> 0:03:23.600 the planet. The other aspect of this is that most 0:03:23.680 --> 0:03:25.720 of the reasons that we think the surface of Earth 0:03:25.760 --> 0:03:28.720 is so nice and habitable, right the liquid water, that 0:03:28.919 --> 0:03:32.400 breathable air, all of that is related to a kind 0:03:32.440 --> 0:03:36.600 of recycling process that happens inside Earth. Earth's water a 0:03:36.640 --> 0:03:39.360 lot of it came from outgassing a volcano. So there's 0:03:39.400 --> 0:03:43.360 water deep inside the Earth. When you have volcanic flows 0:03:43.680 --> 0:03:46.280 bringing up magma to the surface, there's lots of gas, 0:03:46.320 --> 0:03:49.200 particles and water in that that eventually makes it out 0:03:49.240 --> 0:03:53.040 into the atmosphere. Carbon dioxide is recycled this way. Water 0:03:53.080 --> 0:03:55.760 is recycled this way. So you can't really just focus 0:03:55.800 --> 0:03:57.320 on the surface. You have to ask how does that 0:03:57.400 --> 0:04:00.440 surface interact with what's going on deep inside planet. 0:04:01.400 --> 0:04:04.360 So when people imagine what's going on deep inside the 0:04:04.360 --> 0:04:06.880 planet and the way it affects the surface, probably what 0:04:07.040 --> 0:04:10.080 first comes to the average non scientist's mind would be 0:04:10.080 --> 0:04:13.760 like earthquakes and volcanic eruptions, But actually it's much more 0:04:13.920 --> 0:04:14.680 entangled than that. 0:04:15.320 --> 0:04:18.760 Yeah. Absolutely, But those are also great examples of ways 0:04:18.800 --> 0:04:20.919 that the interior of our planet is really connected to 0:04:20.960 --> 0:04:24.479 how we experience the surface of a planet. Earthquakes, that's 0:04:24.520 --> 0:04:26.920 because the plates on the surface of the Earth are 0:04:26.960 --> 0:04:29.400 moving around and they descend back into the Earth at 0:04:29.480 --> 0:04:34.440 subduction zones and create these frictional spots between plates that 0:04:34.520 --> 0:04:35.839 create these earthquakes. Right. 0:04:35.960 --> 0:04:40.000 Another great example, there's a false fact that I once 0:04:40.080 --> 0:04:42.800 knew that your book corrected me on if you had 0:04:42.839 --> 0:04:46.600 asked me what was the source of Earth's magnetic field 0:04:46.640 --> 0:04:48.960 that you were just talking about. I would have said 0:04:49.000 --> 0:04:52.520 that it was generated by the spinning of the molten 0:04:52.600 --> 0:04:56.520 liquid core around the Earth's solid iron core because of 0:04:56.600 --> 0:04:59.720 the image of spinning, and I guess there's general knowledge 0:04:59.720 --> 0:05:02.719 that sort of dynamo effect, But in the book you 0:05:02.760 --> 0:05:05.640 explained that that isn't exactly correct. That's not exactly what's 0:05:05.680 --> 0:05:08.880 going on. So what does generate the Earth's magnetic field? 0:05:09.600 --> 0:05:12.680 Yeah, you're absolutely right. This is a common misunderstanding out there, 0:05:12.720 --> 0:05:15.520 even some scientists have it. So it turns out in 0:05:15.640 --> 0:05:18.040 order to generate magnetic fields, you do need to have 0:05:18.080 --> 0:05:20.560 a good electrical conductor, and so having a metal like 0:05:20.640 --> 0:05:23.159 iron in this center of the Earth that helps. You 0:05:23.200 --> 0:05:26.240 do need to have it be liquid or fluid ability 0:05:26.279 --> 0:05:29.120 to move around. But the key thing is the motions 0:05:29.240 --> 0:05:32.200 that can create magnetic fields through, like this dynamo action 0:05:32.240 --> 0:05:34.800 that you talked about. Those motions have to be much 0:05:34.839 --> 0:05:38.680 more complex than just spinning around. So it's not just 0:05:38.720 --> 0:05:40.640 that the Earth is spinning and that's causing it. It's 0:05:40.680 --> 0:05:44.719 actually these like helical type flows that occur because of 0:05:44.760 --> 0:05:47.559 the fact that the Earth is trying to cool down, 0:05:47.880 --> 0:05:50.600 so space is cold. The inside of Earth is hot. 0:05:51.040 --> 0:05:53.640 And so just like if you put a pot of 0:05:53.680 --> 0:05:56.279 soup on the stove, the bottom of the pot is hot, 0:05:56.520 --> 0:05:58.200 the top of the pot is cold. You get that 0:05:58.240 --> 0:06:01.680 boiling action that rolling around. Same thing in the core 0:06:01.720 --> 0:06:04.440 of the Earth, you get these churning motions as the 0:06:04.480 --> 0:06:06.960 hot material at the center of the Earth tries to 0:06:07.000 --> 0:06:10.279 make it up and out to cool down the core 0:06:10.440 --> 0:06:12.960 and then the planet. So it's convection, that's what we 0:06:13.000 --> 0:06:16.960 call it. It's convection. That's the motion that's actually creating 0:06:17.240 --> 0:06:18.760 the magnetic field that Earth has. 0:06:19.320 --> 0:06:23.560 So it's this magnetic dynamo that creates the field that 0:06:23.720 --> 0:06:26.480 can in some ways permit and sustain life on Earth. 0:06:27.000 --> 0:06:29.800 To what extent is Earth unique in this regard? What 0:06:29.880 --> 0:06:33.480 do we know about the presence of a possible dynamo 0:06:33.640 --> 0:06:36.200 in other planets or objects in our Solar system? 0:06:36.520 --> 0:06:39.520 Yeah, great question. So lots of the other planets actually 0:06:39.520 --> 0:06:43.640 do have magnetic field. So all the giant planets, Jupiter, Saturn, Uranus, 0:06:43.640 --> 0:06:46.560 and Neptune, they all have these global magnetic fields generated 0:06:46.600 --> 0:06:49.839 by a dynamo deep inside just like Earth. The smallest 0:06:49.839 --> 0:06:52.680 of the planet's mercury also has a dynamo, and this 0:06:52.760 --> 0:06:55.920 was actually quite a surprise when it was discovered. Now, 0:06:56.200 --> 0:06:58.919 for Mars, it doesn't have a dynamo today, so it 0:06:58.920 --> 0:07:01.400 doesn't have this global MAGNETELD, but it did have one 0:07:01.440 --> 0:07:04.800 in the past. So about four billion years ago, the 0:07:04.920 --> 0:07:08.680 rocks on the surface of Mars were magnetized from a 0:07:08.760 --> 0:07:12.320 dynamo that was active at that time. And then there's Venus. 0:07:12.400 --> 0:07:15.360 For Venus, we have no way to tell if it 0:07:15.360 --> 0:07:16.920 ever had a dynamo in the past. It does not 0:07:17.040 --> 0:07:17.960 have one today. 0:07:18.480 --> 0:07:20.280 You bring up Venus, and there's a funny thing you 0:07:20.320 --> 0:07:22.480 mentioned toward the end of the book, which is the 0:07:22.480 --> 0:07:27.120 frustrations that Venus presents planetary scientists, especially the ones who 0:07:27.160 --> 0:07:30.040 want to study the interior of the planet. Why is 0:07:30.120 --> 0:07:32.560 Venus so frustrating? Why is it so hard to study? 0:07:33.040 --> 0:07:35.160 Yeah, Venus is the worst planet in the Solar System. 0:07:35.200 --> 0:07:37.200 I'm just going to put that out there right now. 0:07:38.480 --> 0:07:41.280 Here's the issue, right, it's really hard to study the 0:07:41.320 --> 0:07:43.120 insides of planets. You don't have access to it. You 0:07:43.160 --> 0:07:46.000 can't drill down and study the core of a planet 0:07:46.080 --> 0:07:48.480 that way, so you have to develop all these really 0:07:49.040 --> 0:07:51.320 clever methods to try and figure out what's going on 0:07:51.360 --> 0:07:53.120 deep inside the Earth. A lot of methods that are 0:07:53.200 --> 0:07:55.440 kind of like what doctors use to figure out what's 0:07:55.480 --> 0:07:57.960 going on inside the human body. Right, We do scans 0:07:57.960 --> 0:08:00.480 of things, we use gravity, we use magnetic fields, we 0:08:00.560 --> 0:08:03.200 use seismology. So then you try and use any of 0:08:03.200 --> 0:08:05.960 these techniques on Venus, and they don't work for a 0:08:06.000 --> 0:08:08.200 variety of different reasons. So first of all, let's say 0:08:08.520 --> 0:08:12.840 we wanted to use seismology, right, So the waves that 0:08:12.960 --> 0:08:16.240 pass through a planet when you have an earthquake, for example, 0:08:16.280 --> 0:08:20.400 on Earth, the speed of those waves is completely determined 0:08:20.600 --> 0:08:22.800 by the material properties they are passing through. So we 0:08:22.840 --> 0:08:25.920 actually learn a lot about what the materials are inside 0:08:25.920 --> 0:08:28.280 the Earth by looking at how fast these seismic waves 0:08:28.280 --> 0:08:31.280 travel through it. You want to do this on Venus, Sorry, 0:08:31.320 --> 0:08:34.360 the surface is a horrible temperature, and the atmosphere is 0:08:34.400 --> 0:08:36.520 made of sulphuric acid, and the pressure is ninety two 0:08:37.040 --> 0:08:40.480 atmospheric pressures, so it's just the materials are just going 0:08:40.559 --> 0:08:43.079 to melt and dissolve basically, so no chance to do that. 0:08:43.440 --> 0:08:45.640 Then you try and use a magnetic field, right, Having 0:08:45.640 --> 0:08:48.040 a magnetic field is a great way to learn about 0:08:48.040 --> 0:08:49.840 the interior of a planet. As soon as you know 0:08:49.840 --> 0:08:51.880 a planet has a global magnetic field, you know, it's 0:08:51.880 --> 0:08:56.280 got a liquid molten electrical conductor in its interior, and 0:08:56.320 --> 0:08:58.440 it's got those churning motions. Well, Venus doesn't have that, 0:08:58.480 --> 0:09:01.400 so we can't use that. And you try and say, okay, well, 0:09:01.400 --> 0:09:03.560 why don't we just observe the surface and look at 0:09:03.559 --> 0:09:06.000 the rotation of the surface, for example, while Venus has 0:09:06.040 --> 0:09:08.880 this horribly opaque atmosphere that you can't actually look through 0:09:09.160 --> 0:09:11.760 and try to do that. And then one of my 0:09:11.800 --> 0:09:14.160 favorite things about Venus is that when you look at 0:09:14.200 --> 0:09:16.040 all the planets, all the planets, you know we talk 0:09:16.080 --> 0:09:18.560 about planets being spheres, they're not spheres. They're actually kind 0:09:18.600 --> 0:09:21.640 of bulgy oblate spheroids, we call them. So they're fatter 0:09:21.760 --> 0:09:24.640 across the equator than they are at the poles, and 0:09:24.640 --> 0:09:27.600 that bulging of the equator is because of the fact 0:09:27.600 --> 0:09:32.000 that the planet's spin. Now we can use that information 0:09:32.160 --> 0:09:35.880 how bulgey a planet is to actually tell what material 0:09:35.960 --> 0:09:38.720 is inside it, how dense it is inside it. And 0:09:38.760 --> 0:09:40.120 you go and try and do this at Venus, and 0:09:40.200 --> 0:09:43.600 Venus is rotating so slowly that it basically has no bulge. 0:09:43.640 --> 0:09:46.120 So we can't use that either. Basically, Venus is just 0:09:46.240 --> 0:09:49.000 very frustrating doesn't want us to know anything about its interior. 0:09:51.280 --> 0:09:54.880 So there's a great section in the chapter Gazing Outward 0:09:54.960 --> 0:09:57.880 where in this chapter you're talking about the formation of 0:09:58.280 --> 0:10:01.960 our Solar System from the orig original molecular cloud that 0:10:02.040 --> 0:10:03.880 came together to make the Sun and the planets the 0:10:03.880 --> 0:10:10.559 protoplanetary disc. And you talk about how the interesting ways 0:10:10.600 --> 0:10:14.640 the connections between the features of that initial cloud and 0:10:14.880 --> 0:10:18.400 features of the current Solar System and even everyday life 0:10:18.440 --> 0:10:21.320 on Earth. So, for example, the elemental composition of that 0:10:21.440 --> 0:10:24.360 vast cloud determines the elements that make our Solar System, 0:10:24.640 --> 0:10:27.760 but also more interesting and subtle things like how the 0:10:27.800 --> 0:10:31.960 slight initial rotation of that cloud governs so much about 0:10:32.000 --> 0:10:34.280 our world. Could you talk about some of these connections 0:10:34.280 --> 0:10:37.120 between the properties of the cloud and the way the 0:10:37.120 --> 0:10:38.319 Solar System is now? 0:10:39.040 --> 0:10:43.960 Yeah? Absolutely, So. I remember once sitting there and just thinking, 0:10:44.280 --> 0:10:47.000 you know, okay, yeah, we know that the planet's orbit 0:10:47.320 --> 0:10:50.720 around the Sun, we know that the planets are spinning. 0:10:50.760 --> 0:10:53.760 Why is everything spinning all right? Why don't doesn't anything 0:10:53.840 --> 0:10:56.280 just stay still? And the answer has to do with 0:10:56.320 --> 0:11:00.439 this great concept in physics called angular momentum conservation. So basically, 0:11:00.480 --> 0:11:02.920 you can't just change the spin of something without putting 0:11:02.960 --> 0:11:05.520 a lot of torque on it, like forcing it. Right. 0:11:05.880 --> 0:11:07.680 And so then you put something out in the middle 0:11:08.000 --> 0:11:11.280 of nowhere, a molecular cloud, right, and you don't have 0:11:11.360 --> 0:11:14.000 anything really torquing it or anything, and you ask, well, 0:11:14.000 --> 0:11:15.679 how much spin is it going to have? And it's 0:11:15.720 --> 0:11:18.880 going to have some random amount, right, like nothing's perfectly 0:11:18.960 --> 0:11:21.720 isolated and still, so you take all those particles in 0:11:21.720 --> 0:11:24.320 the molecular cloud and you add up all their spins, 0:11:24.360 --> 0:11:25.800 and a lot of them will cancel out. Someone will 0:11:25.840 --> 0:11:28.199 be spinning in one direction, other particles will be spinning 0:11:28.200 --> 0:11:30.720 in the other direction. And you add it all up 0:11:30.760 --> 0:11:33.400 and it almost all cancels out except for a little bit. 0:11:34.160 --> 0:11:36.920 And that little bit in a molecular cloud. Here's the 0:11:36.960 --> 0:11:40.520 amazing thing. Once gravity gets hold of that molecular cloud, 0:11:40.600 --> 0:11:44.520 it starts gravitationally collapsing to eventually form our solar system. 0:11:44.880 --> 0:11:48.119 That amount of spinning just increases and increases and increases 0:11:48.240 --> 0:11:50.640 as the cloud gets smaller and smaller and smaller. And 0:11:50.720 --> 0:11:54.920 you have a total understanding. People have a total understanding 0:11:54.920 --> 0:11:57.480 of this effect. If you've ever watched, for example, figure 0:11:57.480 --> 0:12:00.320 skaters who are about to do a jump with a 0:12:00.320 --> 0:12:02.240 spin it and they pull their arms in. As soon 0:12:02.240 --> 0:12:05.280 as you make something more compact, it spins faster, even 0:12:05.320 --> 0:12:07.320 though you don't do anything to it. And the same 0:12:07.320 --> 0:12:10.320 thing happened to the molecular cloud. As it became smaller 0:12:10.360 --> 0:12:12.640 and smaller and smaller, it spin faster and faster and faster. 0:12:12.679 --> 0:12:15.280 And that's what led to all the spinning we have 0:12:15.800 --> 0:12:18.120 in the Solar System now. And this is true not 0:12:18.200 --> 0:12:20.320 just of our Solar System. We can look out and 0:12:20.360 --> 0:12:23.400 see other Solar systems forming. We can see other planets 0:12:23.440 --> 0:12:26.240 around other stars. They're all spinning too. It's all the 0:12:26.440 --> 0:12:29.080 kind of we share that among all the planets. 0:12:29.520 --> 0:12:33.880 We call the roughly spherical objects that orbit stars planets, 0:12:33.920 --> 0:12:37.120 and we call the objects that orbit planets moons. But 0:12:37.520 --> 0:12:41.480 are there any other material differences between a planet and 0:12:41.520 --> 0:12:43.360 the moon? Are there even any trends? 0:12:44.400 --> 0:12:47.680 Yeah, it's a great question. So moons can be complicated. 0:12:47.720 --> 0:12:50.040 So in reality, if you're someone like me who's interested 0:12:50.080 --> 0:12:53.079 in the interior of planets, you're just as happy to 0:12:53.120 --> 0:12:56.240 consider moon's planets. Right, Moons for their they're made of 0:12:56.360 --> 0:12:59.160 similar stuff. They have the same laws of physics that 0:12:59.200 --> 0:13:02.800 govern their interior. We have moons that have magnetic fields. Ganymede, 0:13:02.800 --> 0:13:04.840 which is a moon of Jupiter, actually has a magnetic 0:13:04.880 --> 0:13:07.640 field generated in its core. So we study the same 0:13:07.679 --> 0:13:12.120 processes on these bodies. Where moons can be a little 0:13:12.120 --> 0:13:16.720 bit different than planets, there's a lot bigger possibility of 0:13:16.760 --> 0:13:19.040 where they came from compared to where they ended up. 0:13:19.320 --> 0:13:24.240 So for example, the rocky planets in the Inner Solar System, Mercury, Venus, Earth, Mars, 0:13:24.640 --> 0:13:27.800 they all pretty much formed close to where they are now. 0:13:28.480 --> 0:13:31.800 Some moons actually come from very far away and then 0:13:31.840 --> 0:13:34.120 get trapped in the gravitational field of a planet and 0:13:34.160 --> 0:13:36.160 then become a moon there. And that happens a lot, 0:13:36.160 --> 0:13:38.600 for example in the Outer Solar System. So if you 0:13:38.679 --> 0:13:41.480 look at Jupiter or Neptune or any of these planets, 0:13:41.480 --> 0:13:43.600 some of their moons are on these really weird orbits. 0:13:43.640 --> 0:13:46.600 They're like orbiting in the opposite direction as the planet 0:13:46.679 --> 0:13:49.480 is spinning. They're not around the equator at all. And 0:13:49.559 --> 0:13:52.800 those moons we think are actually captured basically comets. They're 0:13:53.080 --> 0:13:56.320 captured comets or asteroids that were doing their own thing 0:13:56.679 --> 0:13:59.640 got gravitationally kicked into the Solar System a little bit 0:13:59.679 --> 0:14:02.600 close in and then got trapped around a planet. So 0:14:02.640 --> 0:14:06.000 you can actually find some bodies orbiting these planets that 0:14:06.000 --> 0:14:08.800 were probably formed much further away, and so in that sense, 0:14:08.840 --> 0:14:20.960 that's a little bit different than what you see with planets. 0:14:21.320 --> 0:14:24.520 One of the most shocking facts that you discussed in 0:14:24.560 --> 0:14:28.880 the book concerns the formation of the Earth's moon. Now, 0:14:29.000 --> 0:14:31.600 I know the leading theory on the formation of the 0:14:31.600 --> 0:14:37.240 Earth's moon is the giant impact idea, but specifically, the 0:14:37.320 --> 0:14:41.040 thing that you introduced to me was how rapidly the 0:14:41.080 --> 0:14:44.640 Earth's moon was probably formed according to the leading theory 0:14:44.640 --> 0:14:46.320 of its origin. Could you explain this. 0:14:46.640 --> 0:14:50.120 Yeah, this blows my mind. By the way, so we're 0:14:50.280 --> 0:14:52.400 somewhat I think people have heard of this theory that 0:14:52.520 --> 0:14:57.480 something about the size of Mars, usually called they crashed 0:14:57.520 --> 0:15:00.120 into Earth, had this kind of glancing impact into pro 0:15:00.160 --> 0:15:02.480 to Earth Earth. This was like four point five billion 0:15:02.560 --> 0:15:07.200 years ago, and that crash caused some of that body 0:15:07.240 --> 0:15:10.720 and some of the Earth to get kind of blasted 0:15:10.720 --> 0:15:14.160 off the surface of the planet and small chunks were 0:15:14.160 --> 0:15:16.240 put into orbit. And then you ask the question, Okay, 0:15:16.320 --> 0:15:19.040 so now you have this disk of material surrounding the Earth. 0:15:19.400 --> 0:15:21.360 How long did it take for that disk of material 0:15:21.440 --> 0:15:24.680 to become the Moon a single object? Now, that disk 0:15:24.720 --> 0:15:27.000 of material followed the same laws of physics as the 0:15:27.040 --> 0:15:31.000 planet's forming out of the disc. Initially on gravity caused collisions. 0:15:31.000 --> 0:15:33.720 Some of those collisions caused things to clump together. Eventually, 0:15:33.880 --> 0:15:36.440 the Moon grew and grew and grew, and estimates suggest 0:15:36.480 --> 0:15:39.280 it took forty years for this to happen. Now, when 0:15:39.280 --> 0:15:42.520 you're talking about things in astronomy and in Earth science, 0:15:43.000 --> 0:15:45.960 you're working on millions of years, billions of years. Those 0:15:45.960 --> 0:15:48.360 are the types of lengths of time we're used to. 0:15:48.800 --> 0:15:51.520 So talking about a process that takes forty years is 0:15:51.600 --> 0:15:54.120 just shocking. And so I always have this image in 0:15:54.120 --> 0:15:56.560 my head, and this is obviously impossible because it was 0:15:56.560 --> 0:15:58.240 four point five billion years ago, But I have this 0:15:58.280 --> 0:16:01.440 image in my head of like some parents sitting down 0:16:01.480 --> 0:16:04.240 with their kids and the parents going, you know, when 0:16:04.280 --> 0:16:06.320 I was your age, there was no moon in the 0:16:06.360 --> 0:16:08.840 sky kind of thing, right like that. It's on a 0:16:09.080 --> 0:16:12.480 human generational timescale that this changed. 0:16:13.040 --> 0:16:16.400 That's truly unbelievable. And you actually mentioned several other things 0:16:16.440 --> 0:16:19.200 about the Moon that I didn't quite know about and 0:16:19.280 --> 0:16:22.480 were so interesting one is that it's a parent magnitude 0:16:22.560 --> 0:16:25.960 from the Earth was larger initially, I guess because it 0:16:26.000 --> 0:16:28.640 was closer. But you also mentioned something called a fossil 0:16:28.920 --> 0:16:31.520 bulge in the moon. Could you explain these? 0:16:31.920 --> 0:16:34.280 So when the Moon formed, it was much closer to 0:16:34.320 --> 0:16:38.160 the Earth, and since then it's been slowly receding away 0:16:38.200 --> 0:16:41.440 from the Earth. And we can even measure this change 0:16:41.480 --> 0:16:43.840 in distance of the Moon to the Earth. And that's 0:16:43.880 --> 0:16:47.680 happening because of really interesting gravitational interaction between the Moon 0:16:48.200 --> 0:16:50.520 and the Earth. And it's the same reason, for example, 0:16:50.560 --> 0:16:54.440 that the Moon only shows us one face, so tidal interactions, 0:16:54.480 --> 0:16:57.440 the fact that you know, the Earth's not a perfect sphere, 0:16:57.480 --> 0:16:59.360 the Moon's not a perfect sphere, and they tug on 0:16:59.400 --> 0:17:02.000 each other when are not kind of facing the right way. 0:17:02.760 --> 0:17:07.000 That has caused the Moon to start moving further away. 0:17:07.040 --> 0:17:09.520 It's also caused the Earth to start slowing down its 0:17:09.640 --> 0:17:12.480 rotation a little bit, and so over time, the Moon's 0:17:12.560 --> 0:17:14.320 moving further away and it's going to make it smaller 0:17:14.359 --> 0:17:17.040 and smaller and smaller. And one reason we know all 0:17:17.080 --> 0:17:22.040 of this is that the moon, if you look at 0:17:22.040 --> 0:17:24.080 how bulgy it is, Like I talked about how spinning 0:17:24.119 --> 0:17:27.440 objects have this bulge on them. The Moon is too 0:17:27.520 --> 0:17:30.399 bulgy for how fast it's spinning right now, and the 0:17:30.440 --> 0:17:32.239 only way to explain that is it must have been 0:17:32.280 --> 0:17:35.119 spinning faster in the past. And the only way for 0:17:35.200 --> 0:17:37.159 it to have been spinning faster in the past is 0:17:37.160 --> 0:17:39.439 if it was much closer to the Earth, because we 0:17:39.560 --> 0:17:42.080 know it's locked. It's day is locked to the Earth's 0:17:42.680 --> 0:17:45.200 you know, it's always facing the Earth the same side, 0:17:45.359 --> 0:17:49.000 so it had to have a much faster spin in 0:17:49.080 --> 0:17:50.920 order to get that bulge that it had. 0:17:51.359 --> 0:17:55.639 With exoplanets, we often hear about the habitable zone of 0:17:55.680 --> 0:17:58.600 a star, the area of the distance out from a 0:17:58.640 --> 0:18:01.880 star that we believe there could be the conditions possible 0:18:01.920 --> 0:18:05.440 for life to arise. But an interesting fact you mentioned 0:18:05.600 --> 0:18:09.040 is that if a faraway exoplanet astronomer we're looking at 0:18:09.119 --> 0:18:12.639 our Solar system, they would see not one but three 0:18:12.840 --> 0:18:16.760 planets within our habitable zone, Earth, Venus, and Mars. But 0:18:17.080 --> 0:18:19.080 neither of the other two planets, Mars or Venus are 0:18:19.240 --> 0:18:23.520 especially hospitable now, and Venus is really inhospitable. So what 0:18:23.760 --> 0:18:27.760 does that tell us about looking for exoplanets that could 0:18:27.800 --> 0:18:29.440 sustain life elsewhere? 0:18:29.880 --> 0:18:31.520 I think it tells us that we have to be 0:18:32.560 --> 0:18:36.200 a little more subtle in how we figure out whether 0:18:36.400 --> 0:18:38.800 a planet is a good candidate for some of that 0:18:38.880 --> 0:18:42.520 might have life or not. Right, totally, get why we 0:18:42.560 --> 0:18:45.240 are using these criteria right now. Right, what's the distance 0:18:45.280 --> 0:18:49.119 from a planet star at which the temperatures are just 0:18:49.200 --> 0:18:51.360 right so that water could be liquid on the surface 0:18:51.400 --> 0:18:53.520 if there was water there. That's kind of the condition 0:18:53.560 --> 0:18:58.200 we're using now. But as mentioned, planets are complicated, and 0:18:58.440 --> 0:19:01.239 you could have a planet that comple letly changes its 0:19:01.280 --> 0:19:04.520 surface temperature through a greenhouse, a runaway greenhouse effect. That's 0:19:04.560 --> 0:19:07.560 what happened on Venus. Right, Venus is getting not that 0:19:07.680 --> 0:19:10.520 much more heat from the Sun as we are, but 0:19:10.760 --> 0:19:13.600 it happened to go through this climate process, this runaway 0:19:13.600 --> 0:19:16.040 greenhouse that made the temperture on the surface incredibly hot 0:19:16.080 --> 0:19:19.199 and not able to sustain any water. The water all 0:19:19.240 --> 0:19:22.159 evaporated off of Venus. So we have to be a 0:19:22.200 --> 0:19:24.639 little bit more careful. We need to understand the dynamics 0:19:24.640 --> 0:19:27.640 of what's going on inside the bodies and outside, because 0:19:27.640 --> 0:19:30.960 that's what creates the atmospheres. Another great example of this, 0:19:31.040 --> 0:19:33.240 I think we also need to kind of broaden the 0:19:33.320 --> 0:19:36.960 search for habitable worlds, let's say, because if you look 0:19:37.000 --> 0:19:39.600 in our Solar system, aside from Earth, the next best 0:19:39.640 --> 0:19:42.760 place to possibly look for where life might form are 0:19:42.800 --> 0:19:45.920 actually in the water oceans of some of the moons 0:19:45.920 --> 0:19:48.680 in the outer Solar System. Now, these oceans are buried 0:19:48.960 --> 0:19:52.480 like miles beneath the surface, but they're liquid water, they 0:19:52.480 --> 0:19:57.520 have energy sources, they have complex carbon molecules, all the 0:19:57.600 --> 0:19:59.879 kind of ingredients that we think might be important for life. 0:20:00.040 --> 0:20:03.280 So I think we need to think more carefully about 0:20:03.280 --> 0:20:06.480 what the conditions are for life on exoplanets out there, 0:20:07.440 --> 0:20:10.119 and we might end up finding life in places we 0:20:10.160 --> 0:20:10.920 didn't expect. 0:20:11.720 --> 0:20:15.240 So when trying to understand what's inside planets, we've talked 0:20:15.240 --> 0:20:20.280 about using detection methods for like magnetic fields and seismic 0:20:20.320 --> 0:20:23.720 research and things like that. But what can isolated pieces 0:20:23.760 --> 0:20:28.160 of physical evidence like meteorites and diamonds tell us about 0:20:28.240 --> 0:20:30.440 how planets are formed and what's inside them. 0:20:30.920 --> 0:20:32.920 Yeah, this is one of my favorite things in the world. 0:20:32.960 --> 0:20:35.320 So I'm going to start with the diamonds thing. We 0:20:35.440 --> 0:20:37.760 really would like to actually have samples from deep inside 0:20:37.760 --> 0:20:39.199 the Earth, because that would be the best way to 0:20:39.200 --> 0:20:42.439 study it. It's impossible to do this, we can't drill 0:20:42.600 --> 0:20:45.199 deeper than about eight miles or something like that, right, 0:20:45.280 --> 0:20:49.080 and the earth goes down about almost three thousand miles, right, 0:20:49.160 --> 0:20:52.960 So this is just not possible, luckily for us. Sometimes 0:20:52.960 --> 0:20:55.400 the Earth brings samples from the deep up to the surface, 0:20:55.520 --> 0:20:57.720 and one thing it does is it brings up diamonds. 0:20:57.920 --> 0:21:00.639 Lots of people know about diamonds because they're important in 0:21:00.840 --> 0:21:03.719