Where did the Earth's atmosphere come from?

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Speaker 1: Hey, Daniel, did you see that amazing volcano that erupted in Iceland? Is that the one in oh Nice? Is that how you say it in Icelandic? I don't actually speak Icelandic, though I do speak some Danish. Icelandic is more like old Norse. But Iceland, the country is super awesome and filled with volcanoes. Yeah, and there's one right now. It's spewing hot lava like as we speak. Yeah, it's like the Earth is breathing out more like burping or vomiting. The Earth got indigestion, I think I wonder how you say indigestion in Icelandic. It's just a volcano. I am more handmade cartoonists and the creator of PhD comics. Hi, I'm Daniel. I'm a particle physicist, and I'm substantially less gassy than the island of Iceland. Are you less gassy than the average physicists? No comment? Are you all full of I'm more full of hot area exactly. But welcome to our podcast. Daniel and Jorge Explained the Universe, a production of I Heart Radio in which we blow your mind into tiny, little hot pieces of gas by talking about all the crazy stuff that exists in our universe. We go way way back to the very beginning of the universe. Talk about how all that happened, how it led to this crazy, beautiful structure that we see today, and what progress we've made in unraveling that structure and understanding the fundamental nature of matter and space and time, and of course what the open questions are still. Yeah, we are here burping out amazing facts about the universe and expelling them out into the atmosphere for all of YouTube. Breathe in to your brains and absorb them and hopefully get nursed with some amazing pruce about the universe. That's right. We want these hot truth to roll over you like lava floating out a volcano. But you know, we're hoping not to burn you too much. Things are getting kind of hot, Dannie, I love it. I love it, and I love it, and who doesn't love lava. But yeah, it's a pretty big universe, and we are just this small, tiny little planet floating in the middle of mostly emptiness, careening through the space, ready to be hit by an asteroid perhaps. And this planet has a long and illustrious history. It hasn't looked the way it currently does for most of its life. We don't think of the Solar System and the galaxy is changing very much. They seems sort of static. But on a cosmological time scale, things are crazy, things are chaotic, things are changing all the time. Yeah, it's easy to think when you look out into the universe and to the stars that things are always the way they are right now. But no, actually, the universe is very dynamic, and it's changing, and it's constantly evolving, which tells us something important about what is gonna be like. If we want to know what the future Earth is going to be like and whether he means can still live on it, we better dig into its past and understand how it got to be such a warm and wonderful, cozy place to live. Yeah, what are we gonna be burping in a hundred million years perhaps or having indigestion with Yeah, So the Earth has an amazing history, and so one part of the Earth that's very important to us is its atmosphere. I count on it every day breathing. It fills me with life every single moment. Really, when you think about it, No, absolutely, we rely on it every single day. Well, we couldn't live without it. It feeds not just us, of course, but all the things that we eat drink. The atmosphere. It's a very complex and elaborate system of pumping gases out of plants and into plants and out of the ocean into the ocean. It's an amazing and complicated system, and it's incredible that it works at all, frankly, and then it's even at all stable. Thank goodness, we haven't because without an atmosphere, we wouldn't be here. We wouldn't just be out of breath and choke to death, but we would also be a pretty toasted thanks to all of the radiation coming from space. That's right, themospheres here. He keeps us warm and acts like a blanket and also acts like a shield protecting us from so many rocks and particles and all sorts of stuff coming from space. So it's a pretty important part of life here on Earth today and hopefully it'll stick around for another billion years or so. Yeah, and we should appreciate it because it wasn't always here on Earth. The Earth didn't always have an atmosphere. There was time and the history of Earth that we were basically naked right out in space nothing to drape over us. That's right. If you build a time machine and you want to see the early Earth, don't neglect to bring your space suit, because if you go back to three four billion years into Earth's history, you're not gonna be able to breathe whatever was on the Earth, if there even was anything. Yeah, and so a big question would be how did it get this way? How is it that we have this beautiful and fresh well depending on where you live, fresh air for us to take in and enjoy and live with. It's a fascinating story that dates way back to the very beginning of the Solar System and involves lots of dramatic pauses like volcanoes and the years and all sorts of other crazy stuff. So today on the podcast, we'll be asking the question where did the Earth get its atmosphere? Yeah? Where did it get its airs? Daniel? It's ambiance, that's right. And it's a very very fine place to hang out. It's very airy, it's very blue and transparent. I love what you've done with the place, really, Dole are burping apparently, I'm guessing maybe does that count as interior design if you're designing an entire planet or is it the still exterior design. I guess it depends. Are you like an alien shopping for planets? Are you like an earthling looking around? I'm imagining the aliens come, they take over the Earth, and they don't really like what we've done with the place, and they want to fix it up a little bit. So they hire some like massive geoengineering firm to do the equivalent of interior design, but for the whole planet. I wonder if that would be like a future career, like, hey, mom, I want to be a geo designer or a geodecorator. That's right, Mars has been using that same shade of red for like a billion years. It's time to pick a fresh color. How about cyan or a nice mango glaba. You need always three words in every name for a shade of paint, you know, wild Mountain, raspberry or something right that, so you can sell more of them, to be honest, because maybe you just sell red and blue, you're out of business. Well, if you're covering a whole planet, I think you're gonna sell a lot of gallons of paint. So yeah, So the Earth didn't always have the atmosphere that we're breathing right now. It used to be a pretty inhospitable place, right, that's right. It used to be a place where humans or animals could not survive because I guess initially, you know, we formed around a brand new Sun and we were just a bunch of rocks and gas kind of gathered together by gravity. Right. Yeah, everything in the whole Solar system, of course, came from the same big cloud of gas and dust to form the Sun and the planets and everything. But the story is a little bit more complicated. Yeah, So we were wondering, as usual, how many people out there know the story of our atmosphere and now how we got to have the air that we have. So, as usual, Daniel went out there into the wilds of the internet to ask people where did Earth get its atmosphere? And so, as usual, if you'd like to participate by answering funny questions with no preparation, please write to me two questions at Daniel and Jorge dot com. Trust me, it's fun. Here's what people had to say. I gotta guess from rocks during the heavy bombardment period when they guesses got released into the atmosphere. But the oxygen and atmosphere, which actually a lot higher today, came from I think it's Sanda bacteria, those rocks in Australia that the first thing is to photosymphasize and actually caused a huge distinction event um And the Earth was just formed. It was hot, and I think there were many chemical reactions going on away her atomic reactions and all. So maybe because of the reactions, I think probably they were just hydrogen and helium in the beginning, but then due to all these reactions, all the different gases will formed. Then maybe that's how we got that atmosphere. Let's say we have lots of nitrogen that prevents everything from blowing up. Then we have some oxygen and some argon. And that's about what I know about earth atmosphere. I can't really tell you where it comes from. I think the atmosphere came from volcanic activity when the Earth was young, and I know that the oxygen came from cyanobacteria producing it when life just got started on Earth. Well the proto or it was very very hot, so I would say that the burning and the temperature itself would cause gases to form that would accumulate around the Earth, being trapped in its gravitational field, and once the Earth cooled, the composition of the those gases must have changed, especially when life started to arise and would start to change the atmosphere and take out garbon dioxide and fill it with oxygen. I think they say Mars used to have an atmosphere. Maybe we stole mars atmosphere here have it on Earth now. Our atmosphere came from all the various eruptions on the Earth. In other words, the Earth's hot are the biggest contributor easy life. You fount organisms reciting the various chemicals from the atmosphere, apart from the atmosphere easily blanged by absorbing common trails and volcano emissions. I'm assuming, like ah, the formation of the Earth, there was a bunch of like dust and rocks and like just surrounding chemicals, and the Earth kind of lumped together. The rocks lumped together created kind of some strong gravity, and like particles and like air particles were like, hey, there's some gravity here. I guess let's like stick around, stick to it. And that's what happened. Alright. A lot of pretty detailed answers. You people have thoughts on the topic. Yeah, they have air, They have a lot of things to say about how we got our atmosphere. That's pretty cool. Do you think it's out there in the popular culture kind of the history of our atmosphere? Yeah? Or you know, maybe it's just so immediate people think about it. They literally breathe it in and out every day. So it's not some like weird, abstruse topic that only physicists wake up late at night thinking about. It's something everybody thinks about. And these days with all the discussion of global warming and climate change, it's something that people really do think about what's in the air and how we can influence it. And I guess it's kind of interesting that nobody was surprised. Nobody was like, what, we didn't always have an atmosphere? Like people seem to know that it came from somewhere. Yeah. Somebody even suggested we stole it from Mars. No way, what is it? Hot airror air? Hot exactly. They're gonna come looking for it, bring it pulled over with a vacuum and suck it all back up. So do you have a receipt for this atmosphere? I do. I just lost a seven billion years ago. Who keeps records that long anyway. Yeah, so it is an interesting story how we got our atmosphere, and so it's interesting to think that that wasn't always the case. You know, we were just a little barren rock floating out in space with some gas. Right. Yeah. It's really a fascinating story because the Earth has had different atmospheres through its history. Like if you took a time machine back to the very very early hot Earth, you'd experienced something very different from if you went back like three billion years ago or one billion years ago. So it's really it's a fascinating, very very dynamic story with lots of twists and turns. Yeah, and it's not just like a different temperature maybe, or like twists in the composition. It's like a totally different set of gas that was enveloping the Earth. Right, Yeah, we have like atmosphere three point oh these days we're not breathing the original atmosphere or even the second atmosphere. We're lacked on the third version of the atmosphere. It's been upgraded twice already. Well, do you think we got it this time or do you think we're do for an upgrade? I'm pretty happy with it. I got no notes like do we have to schedule the update? You know? Can we schedule it for like a billion years from now and when we're not around. Well that's the problem is sometimes you know, you're happy with your version of your operating system and then it updates itself and you're like, no, don't change anything. It was great. Do we have auto update on? Maybe we should turn that off because sometimes things don't work the same, you know, that's the solution of climate change. Rather just untake that box on the atmosphere operating system that says no updates please. All right, everybody stopped breathing for about a hundred years and then we'll get anyone. We're gonna reboot. Yeah, all right. Well, so you're saying this is not our first atmosphere. Um, we're in the third version. So what was the first version of the atmosphere? So the first version in the atmosphere formed when Earth formed itself. As we were saying before, everything in the Solar system came from the same basic constituents. You have this huge cloud of hydrogen mostly in a little helium and trace heavier elements, and that whole thing got sparked into a collapse, which led to the formation of the Sun of course, which is a huge ball of hydrogen. And then the planets gathered together and all basically came out of the same stuff, and you had planets formed because you had like little rocky cores that gathered together and gradually pulled other stuff along with it. And so what was Earth's atmosphere when it first formed, Well, the only gases around really were hydrogen and helium mostly, So just like Jupiter and the Sun and the other gas giants have big atmospheres mostly of hydrogen with a little bit of helium, Earth also had a helium hydrogen envelope around it when it first formed, right because I guess you know, the whole area in space was covered in hydrogen and helium and most of it went into the Sun, but I imagine some of it sort of hung out around the little rocky planets that were forming. Yeah, but not for very long. So what happens is these things are forming and they're collapsing, and there's sort of a race, Like the Sun is gobbling up a huge amount of this stuff, and the gas giants are out there, they're gobbling up a lot of it. And here in the inner Solar System, it turned out to be pretty hard to hold onto any gas because you're competing with the Sun that's slurping up all of the hydrogen as much as it can, and you don't have the gravity that like Jupiter has because the inner part of the Solar System is warmer, so there's no like rock ice to help you build a planet rapidly to grab some of that helium and that hydrogen. So out in the outer part of the Solar System where Jupiter was, you had rocks formed together but also with ice that let them see these larger planets that could hold onto their hydrogen. But here in the inner Solar System, Earth was just sort of like too small to really hang onto its hydrogen, so it was very short lived atmosphere. I guess maybe, like you know, lighter elements like hydrogen and helium, they get more easily sucked in by the Sun and other planets than the rocks that we have, right, that's kind of what happens is that you know, it's so light that they can just leave and get sucked in by the Sun. But whereas the rocks, it's harder for the Sun to have pulled us in that's exactly right. And there was also an opposite effect because once the Sun started burning, it was producing a solar wind, which is a huge amount of radiation that then blew off the rest of our atmosphere. Right, we had no magnetic field yet to protect ourselves from these things. Magnetic field is formed when layers inside the Earth are like mixing and blending and spinning. But the Earth was too young to have like differentiated and had these nicely divided layers that could produce a magnetic field. And so the solar radiation also blew off any gas that we did manage to grab. So initially we had a little bit of gas around our kind of brand new Earth, but then it quickly either left or it got blown away. Yeah, so this first atmosphere was very very short lived. I'm not even really sure you could say they was like settled down before it got slurped up by the Sun and then blown off by the solar radiation. Yeah. I feel like there's a lot of gas and wind in this story is getting a little um you know, gastric here, not just cosmic dig a tums. But there was a lot of stuff going on, like the early solar system was a very chaotic place, and it could have gone in lots of directions. You know, you could have had a planet here or a planet there. The reason we have a planet exactly here depends on a lot of very small chaotic factors that depended just on like the distribution of the initial stuff. But a little bit more clumpy or there, you would have got a different set of planets. All right, So then we had a little bit of hydrogen and helium, but then that quickly went away, and so what was our second atmosphere? So then the Earth was barren, right, we had just a ball of rock with really no atmosphere to speak of. Say this period here where the Earth is like naked. There's just no atmosphere protecting the surface of the Earth from basically space. And you know, interestingly, I talked to some geologists, and they don't see the Earth as naked in that sense. Like for them, the atmosphere is part of the crust. It's just like a different kind of crust, you know. They don't think of it as like the crust ends at the surface and then you have atmosphere. The atmosphere is just sort of like part of the crust. Because there's like constant interchange between the atmosphere and the surface, and it's just like you know, another layer of the earth. Sure, I guess two a geologist. They want it all, they want it all there like the air. That's part of my grant proposal as well. It's part of geology. Of course, humans where also geology. We are part of geology. Absolutely, we are part of the crust. And that's where this outer gas la or the crust that we call atmosphere came from when it was replenished. It was replenished from inside the Earth because volcanoes like the one in Iceland and the other ones around the Earth out gased like internal processes inside the Earth lead to these explosions and eruptions, which can produce enormous quantities of gas. Meaning like was all this gas forms inside of the Earth or it just got trapped as the Earth was sort of forming and all those rocks, actual rocks were coming together. Yeah, it's all in there, and it's all mixed together. You know, you have carbon, you have sulfur, as, you have oxygen. These are all the elemental ingredients of the Solar system, which are then compressed and mixed together. There's a lot of chemistry going on. So these elements all mixed together in the way that's like energetically most favorable. But then yeah, they get spewed up from underneath the earth, and you know, these rocks have gases dissolved in them sometimes and then those can come out when there's less pressure or I guess as maybe as things were sort of churning and coming up from the surface, then the gas was able to escape the rock. Exactly. Large gas bubbles exactly can make their way up through the crust and then emitted by the volcanoes. I mean, that's why volcanic eruptions happen, right. We talked about this in a recent episode on most massive volcanoes in the Solar System. When you have lava that has like a lot of silica dissolved into it, then it becomes like very sticky and it can absorb a lot of gas, and then the gas builds up the pressure and then it erupts and the gas can be freed. Right, And so that's how we got things like water of water, vapor and CO two and hydrogen open in the atmosphere. In that second atmosphere. Yeah, so the second atmosphere is mostly as you say, water, vapor, carbon dioxide, sulfur dioxide, and then a huge amount of just nitrogen. And very importantly, there was no free oxygen, no like O two molecules were floating around in the atmosphere. So this second atmosphere is not something we can breathe at all. It would be totally toxic. You took a time machine back to this volcanic period of the Earth and you took a deep breath as you stepped out, you would die pretty quickly. Great, not a great place to visit. No exactly what bring your space suit, you know, no big deal. Packs of oxygen. Just pack oxygen for fifty years. And there's one other source of sort of basic ingredients for our atmosphere. In those early days, it didn't just come from inside the Earth. There were some deposits from outside the Earth because during this period of chaos in the early Solar System, there's a lot of stuff moving around. The planets were switching positions and passing through the asteroid belt and passing through the asteroid belt in the other direction, which led to a lot of bombardment of the Earth by really big rocks. This is called the late heavy bombardment, and some of those rocks have water, and they have ice, they have other things frozen into them which then evaporated when they hit the Earth. Interesting, so those rocks had other sort of gaseous elements and then when they hit the Earth, they made it into our atmosphere. Yeah, just like we talked about how comets probably replenished the Earth's water in a very same way. Right, Earth had water when it formed, but then it boiled off because we our atmosphere is very hot surface, And we had a whole episode about how comics replenished the Earth's water in the same way. Asteroids and other things probably also replenished part of our atmosphere. Cool. All right, Well let's get into how we actually got breathable oxygen in our atmosphere and how we know all of these things. How do we know the history of our atmosphere? But first let's take a quick break. All right, we're talking about the history of air. Basically, right, where did air come from? And why is it so fresh to breathe? Yeah? Exactly, something it's all around us. It's something that we rely on, so we better understand why it's here and whether it's going away. Yeah. Do you think air is offended when we sneeze or like cough, like you know, get it out of my body? No, I think it's probably grateful. It's like, oh, that's much more interesting. Who wants to be inside of a wind warm human? All right, Well, we had one atmosphere, but then it was blown away by the sun and cosmic rays, and then we had got a second atmosphere that was burped up from the rock inside of the core of the Earth. And this atmosphere had a lot of oxygen, but it which just wasn't free oxygen like it was inside of C O two and H two O or s O two, but it was not something that we could use, like if we breathe it that you wouldn't be able to get that oxygen. Yeah, your lungs can't use that, right, even though there's oxygen c O two, if you step into a room that's pure CEO two, you're gonna fall unconscious pretty quickly. Yeah, not good. Alright, So then that's our second atmosphere. How do we get breathable oxygen? Then breathable oxygen came from life, right, This was terraformed by tiny, tiny, little microbes. But the first oxygen that was produced on Earth wasn't actually from those microbes. The very first came from ultra violet light that hit the Earth's atmosphere. When you v photons, these are just really high energy particles from the Sun and hit H two O molecules of water. They can break it up and you can get ozone formed in the atmosphere. And ozone is just a form of oxygen. It's an O three molecule and it forms in the upper atmosphere and it helps to actually shield us from ultra violet light. So ozone again not something you can breathe, but it's oxygen in the atmosphere which then shielded us from UV which helped life I think evolve a little bit interesting. So, like you just have water molecules H two os there and then when it gets hit by this light, it just breaks up, and I guess breaks up. But then the oxygen doesn't go into O two, it goes straight into OH three. Yeah. In these chemical processes, you always get a mixture of everything, but primarily this is how ozone is formed, and you also get some other stuff forming. You know, you get a little bit of O two but that's only responsible for like one per cent of the oxygen in the atmosphere. That's certainly not enough for us to breathe, all right, but it did sort of form enough O two then that you've kind of had to shield around Earth so that you could, you know, evolve little organism that did make well, it made O three, which is ozone, which is primarily the shield. But exactly it provides a shield to protect us from UV and that can like protect the DNA of delicate little critters as they're evolving on the Earth. All right. So then that's how we got most of our oxygen then, is through bacteria and things like that. Yeah, so bacteria have been around for quite a while, turning away in the oceans of the Earth, and at some point they evolved the ability to do photosynthesis, right, to take sunlight and to combine the energy from sunlight with C O two and water and to produce oxygen. And when this happens, they're essentially producing fuel for themselves. And so this is a really cool little thing that they evolved. It's called cyanobacteria that first evolved this ability to basically drink energy from the sun. And this started about two points seven billion years ago, and that's a very efficient way to turn c O two and H two O into oxygen us. Maybe the you know, in the primordial soup, you know, the earth was you know, inhospitable, but there were little tiny things that could grow in this environment in the oceans, and then that started turning out O two. But that wasn't very beneficial for them, right, No, it actually poisons them. Cyanobacteria are killed by the presence of O two, and so if they make too much of it, they kill themselves off. And again they don't need O too. It's like a byproduct. It's a waste product for them. But they wanted the CEO two, right. Plants breathe CEO two and produce oxygen. Animals like us breathe O two and produce c O two and cyanobacteria they're not plants. They're like the precursors of photosynthesis in plants. So they made a lot of oxygen, but that's not quite the oxygen we breathe today, right, that's right. The oxygen that was made by cyanobacteria originally didn't stick around in the atmosphere because oxygen is super duper reactive. It doesn't usually just hang out like if it can react with anything around it, it will. So you have this fresh earth covered in rocks, and these rocks are very reactive with oxygen. Like imagine a bunch of iron out there and you combine it with oxygen. When you get you get rust. And so basically most of the oxygen produced by the Earth and the first few hundred million years was then breathed in by the rocks on the Earth. They like sucked it all up. Wow, Like the Earth was, you know, shiny and nice looking, and then suddenly these bacteria breathed oxygen and everything rusted. Yeah, it was like hundreds of millions of years where the Earth was getting like a weatherized by all the oxygen that was being produced. And you know how you talk about like free radicals, etcetera in your body maybe causing damage and causing cancer. That's all because of oxygen. Oxygen is very reactive. It's like a crazy thing. It's going to touch and break things near it. And so that's what happened when cyanobacteria started pumping O two into the atmosphere, is that it's starting to get absorbed by all these rocks and break them down and weatherize them. And as you say, rust the entire planet. I guess that's a process that they had to happen, you know what I mean, Like, you can't just have like a shiny, brand new rust free Earth and also have oxygen. Like you're gonna put oxygen in the atmosphere, you have to first, you know, rust everything before you can breathe it. Yeah, everything is going to drink of that oxygen. So if you want enough floating around in the atmosphere for other things like animals to breathe, then you've got to sort of like fill up all the reservoirs out there that are just going to gobble the oxygen so that there's enough to float around. It's sort of like electrons and a semiconductor. You've got to fill up all the lower energy levels so you can have some floating around in the conduction band and conduct electricity. Right, That was the first analogy I was going to go with. I think these cyanobacteria are super amazing, and I love how plants basically co opted them because you know, the cyanobacteria, they evolved photosynthesis, and now when we look inside plants, we see these little objects inside a plant cell that can do the same thing, these chloroplasts. But those things are basically cyanobacteria. They got co opted by plants. The plants like eight them and said, okay, come do that work for me now. So the cyanobacteria should get all the credit for evolving this incredible ability to plants just to like took it over. They're like the managers. Or you could look at it the other way, right, you could say that cyanobacteria, you know, kind of form plants around themselves kind of to do all the hard work. They just have to sit back and get a plan. Exactly. You can look at anything in two ways, I guess. All right, So then we had to wait until everything was rusted before we got our third atmosphere. Yeah, it wasn't until everything was rusted that the oxygen being produced by cyanobacteria and then later also by plants could just sort of hang out in the atmosphere that those levels could climb to the point where like animals could breathe them. And so now we're up to the atmosphere that we have today, which is you know, still mostly nitrogen. It's like seventy eight percent nitrogen, but a good of our atmosphere is O two wow. And it was all made by bacteria and plant basically right like before and like you know, we didn't get that we made that. Yeah, it was made by living creatures. And it took a long long time. Right, So if you're imagining, like let's go to Mars and produce enough oxygen for the atmosphere for us to walk around and breathe, like, it takes a long time. Even when you got like jillions of tiny little machines pumping out of oxygen, it took millions and millions of years. Yeah, it took like four hundred million years actually to be precise. And in a way, they sort of ruined the planet for themselves a little bit, right, or do you think they were co evolving as they were changing the atmosphere. They're definitely co evolving. And cyanobacteria are still with us. They still produce half of the oxygen that we have on the Earth currently, like half of it is made by plants and half of it is made by cyanobacteria. So they're still around in the oceans. Yeah, And so that's how we got our atmosphere and it's not I mean it's a lot, obviously, because we have a lot to breathe, but in terms of the scale of the Earth, it's a really small fliver or a small coating of air that we have on the planet. Yeah. The whole Earth, of course, is six thousand kilometers in radius. The atmosphere where we considerately the atmosphere is you know, just like thirty or fifty kilometers high, so it's a very very thin ver near It's like a very thin coating of water on a billiard ball. Yeah, because like what the Earth is, what like ten thousand kilometers in radius or something like that kilometers in radius, but only the last thirty kilometers are atmosphere. Yeah, And where exactly you say the atmosphere and depends really just on where you want to say it ends. Some people say it's up to a hundred kilometers because you know, it falls off very smoothly as you go out into space. But of the mass of the atmosphere, like most of the stuff in the atmosphere is within the first thirty kilometers. The geologists also claim space as geology as well. They're like, you know, I just keep going. Their atmosphere is geology, space is geology. Galaxies geology. When they say we are one with the universe, they mean it literally, like the universe is just all part of the Earth. We are one, and that one is you got below the surface and above the surface, and it's just two parts to the whole universe. Or no, it's it's all one big surface geologist. But it's actually quite interesting. There are lots of like really fascinating layers to the atmosphere. Like you might imagine as you go higher up, the air gets thinner and thinner and colder and colder until you get out into space and it's like super freezing. But actually the temperature like varies and it gets hotter and colder and hotter and colder as you go up really depending on like the composition or did you just get like pockets of stuff, Yeah, depending on the composition. They're all these fascinating layers. Like as you go up, you know, you go above like Mount Everest, for example, things get colder and colder and thinner and thinner. But then when you get to like this ozone layer, things turn around and start to get hotter. As you go past the stratosphere, things actually start to get hotter and hotter and hotter, not quite back up to like surface levels, but you know, getting kind of warm before they turn around again and then get colder as you go up through the is a sphere and then it turns around again and it actually gets hotter and hotter as you go into space, right, Yeah, because I guess those are the layers that are absorbing a lot of the sunlight. Is that what's happening. They are absorbing a lot of the sunlight and they are evaporating, Right, what's going to be leaving the Earth? What's going to be making it out there to the higher levels are the faster moving particles, and so the Earth is sort of like differentiating. We are losing our atmosphere constantly. We had a whole podcast about that, and primarily we lose the hotter atoms, the faster moving ones. So while it's not very dense up there, there's not a lot of heat, you have faster moving particles, which are the ones that are escaping, and so it technically it is hotter. Yeah, the hotter ones that are always the first ones to leave, for sure. And there's also sort of like radioactive elements out there in our atmosphere too, right, Like some pretty not saying stuff out there. Yeah, absolutely, one percent of our atmosphere is actually are gone. You know, You've got like seventy percent nitrogen oxygen, and then one percent are gone, which is sort of weird. It's this radiogenic argon forty which comes from the decay of potassium forty. And it's really interesting actually, because mostly which you have out there in the universe, like made by stars is aregon thirty six, which is, you know, a different isotope of argon that's made in the fusion inside stars. But here on Earth, most of the argon in our atmosphere is argon forty, which comes from this radioactive decay. And it took people a long time to figure out that that's where it came from and how it worked, and it was a fun puzzle that was solved a few decades ago. And there's also some pretty interesting elements like krypton and neon and methane, And our atmosphere is not just like nitrogen and air and oxygen. Do you remember that everything in our solar system came from those same basic soup of ingredients. Inside the Sun, of course you have fusion making new heavy elements, but outside of the Sun, everything is just a mixture of the same elements that went in. Right, we have no fusion happening on Earth. All the elemental like crypton or neon, or hydrogen or oxygen or all the other weird stuff that we have came from fusion in side some star somewhere else. Our solar system is a population one solar system, which is the third generation in our universe. So all of these atoms of oxygen and other stuff were formed inside a star billions of years ago, which then blew up and led to the formation of this dust cloud, which eventually became our solar system. That means we're all a little bit cryptonian, right, a little bit. Yeah. All of these things that were made of that we're breathing, that we're relying on, all came from somewhere else, were fused inside a star somewhere, and so that's how we got our atmosphere through a lot of burpaying by the Earth and surviving some winds and a lot of bacteria making it. And that's how we got the air that we have today. And thank goodness, because it smells pretty good. You could have smelled that, right, you guys. We're lucky that the Earth smells good. It probably did smell pretty bad for long periods. You know, they're probably some pretty stinky times when Earth the stinker scene, I think it's called, you know, teenagers they never smelled, Introduce them to deodorant, and then things pick up from there. All right, let's get into how we know this interesting history of our atmosphere and what it could mean for the future of Earth and people breathing in it. But first, let's take another quick break. All right, we're talking about the history of our atmosphere and we're kind of in our third atmosphere, is what you're saying, Like we you know, we're not in our starter home, we're not in our second home. We're like in our our vacation home. Unless we've been working on this for a while. We're living the dream right now, breathing the dream. We are we are And I love hearing those kinds of stories when you look around and you don't really know what the history of the Earth is, and then you discover through various like really subtle clues and awesome detective work that things have changed, that the Earth used to be really really different. Because you know, your naive assumption is like I don't know the earth form that had it to have spirits always been like this, that's the simplest story, and science always prefers the simplest story. But it's super fun when you discover that the story is more complicated than it has twists and turns. But you can't just like tell that story. You gotta find the clues. You've got to discover that story. Yeah, because that's a big question. It's like, how do we know all these details? I feel like that was a very detailed story of how we got our atmosphere, but there was nobody around really to sort of measure the oxygen or to see what was happening. So how do we know all of these things? Yeah, we have to look for clues in the geological record, and so the rock record, like rocks that were formed five hundred million years ago or a billion years ago or two billion years ago, how they formed, and which kinds of rocks formed tell us about what atmosphere there was around, because some kind of rocks can only form in the presence of oxygen, and other kind of rocks can only form if there's no oxygen. So as you look at the rock layers, you can look like back in time and get a sense for like what was going on, right, because I guess the rocks are stead of changing, right, they're churning, they're flipping over. They sort of build up as they're growing, right, So then then that's where you get the record. Yeah, if you drive through the desert, for example, and you see canyons, etcetera, you can see these stripes in the rocks. Right, where do those stripes come from? Those are layers of rocks that have been laid down over millions and billions of years. As you say, the surface is like active stuff is coming out from underneath and then creating new layers which get laid down and then pushed down, and sometimes those layers then break and get pushed back up to the surface and revealed, and so we can see that history. That's why like dinosaurs are buried in the earth, because we're constantly laying down new layers of rock on top of the old ones. And so that's super cool because it's basically like a snapshot of what was going on on the planet back in the day. And as you can look at those rocks and see patterns in them, then you can get a clue is to like what was going on in the atmosphere because all those rocks, as we were saying before, interacted with the atmosphere that leaves an imprint on the rock basically like if they was a lot of oxygen or not, or other kinds of gases than the rocks a little different. Yeah, And one of the most important clues are these formations called banded iron. And these are really beautiful. You should google them and check them out because they are basically these rocks with these thick red stripes in them, this oxidized iron stripes, And that tells us a lot about when this oxygen nation event happened, when the cyanobacteria started pumping oxygen into the atmosphere, because it started to bind with the iron that was out there and get weatherized and make these layers and layers of basically rushed inside the Earth's atmosphere. So you can look back at these first earliest layers of rust and pinpoint when oxygen starts to be produced. That makes me think of like a heavy metal band or something bad. Iron first rust. There you go, red rusted rage. It's super cool because it's sort of like rings on a tree because you can see these bands. It's not just like, oh, oxygen turned on, start to be produced, and then everything after that is just rusted iron. You have these bands where it's like rusted iron and then none, and then rusted iron and then none, like turned on and off and on and off. You can be like, oh, look at the earth just burped here or just past wind. Yeah, what happens is that this oxygen that these bacteria produced is actually poisonous to them, right. Cyanobacteria do not like a lot of oxygen, so they produced a bunch of oxygen and some cases there was like a lot of iron around in the water to grab that oxygen and then sink back down to the ocean floor and form a band. But sometimes the cyanobacteria would produce too much oxygen it couldn't all get breathed in by this iron, and then they would poison themselves and like kill themselves off, and then they wouldn't be producing as much anymore, and so there wouldn't be as much iron deposited. But then the conditions were favorable again for a cyanobacteria, which would then grow back and produce a huge amount of oxygen, which would they create another band and sort of this sort of cycle effect where they overproduced and kill themselves and then grow. That's kind of what's happening to us right now. I mean, we are creating so much c O two. Every time we breathe out, we create c O two, And so we didn't have all these other processes to repleashes the O two, we would be basically poisoning ourselves, right, breathing ourselves out of a planet. Yeah, we could have a sort of similar effect we have, like human civilization builds up and then poisons itself with c O two, and then you have like a com period on the Earth for a million years, while you have like small bands of humanity surviving, rebuilding civilization to poison ourselves. Again. I can see your brain just writing the sci fi novel there. I think I've read that one. But I guess maybe a question is like, how do we, you know, correlate that to time. Like we can see these bands in the rock, but how do we know that band took place or was formed, you know, three hundred million years ago or six billion years ago? How do we get that calibration of the rings in the tree? Oh yeah, great question. It's like how do we know the age of any rock? You know? And I remember thinking about this as a kid, wondering, like what does it even mean the age of a rock? You know, because like love is lava, rock and melt or flow. It's like asking how old water is. But when you talk about the age of a rock, you're not talking about like when the chemical elements or even the elements inside the rock were formed, because that happened inside a star billions of years ago. We're talking about like when this crystal was created. Because rocks are a solid formation of these elements, right, like cooled together to form a solid object. So you can measure that age of the rock, which is when did this thing become a solid object? How long ago was this thing fluid? When did it transition to becoming solid? And you can measure that because when that happens, it captures things inside of it, these crazy little crystals, and those crystals, some of them are radioactive and they like decay very slowly over time. You can measure how many of those are and calibrate them. And that's when you do to measure the age of rocks. I see, like when the rock forms, they capture like a taking clock almost inside of them. It's sort of similar to carbon dating, which we can use to age like things that were once alive because they have certain ratios of carbon in them. But here we're talking about things that are much much older. So we use these radiometric dating methods based on the natural radioactive decay of things like potassium and carbon to date these ancient ancient events. I would different rocks. That's a terrible joke. I apologist for them. So yeah, so that's how we know then, how the history of our atmosphere. Yeah, because we can look at this record and so that's one piece of evidence is these banded iron formations. You know this that's a big influence on like our civilization because Detroit, for example, is in a location where there used to be an ocean with huge colonies of cyanobacteria depositing lots of bands of iron and so like that's why a huge fraction of the steel deposits available on Earth are like near Detroit, and that's why we have a car industry near Detroit because of this cyanobacteria. So I love these like connections from the ancient times back to like you know, modern zivilization and even politics. They always talk about the rust belt, right exactly, they should be talking about the cyanobacteria belt. Really, yeah, nobody wants to be in that political group. But this also lines up with other pieces of evidence. Again, we look into the record to see what could happen with oxygen and what could happen without oxygen. And there are other minerals like pyrite, this thing called fools gold, which can only form when there's no oxygen in the atmosphere. It's it's oxygen around and the elements that would otherwise make pyrite tend to make other things instead. And so you can say, like, oh, pyrite was only created until about a certain date several billion years ago. So that's another clue. And I imagine also there's a lot of it is sort of theoretical, kind of based on models of how the Earth form, right, for example, we can only go back so much. But these methods, like when you're talking about before, like you know, our early or first atmosphere getting blown away by the solar wind. That's you know, we don't have evidence for that, but you know, from what we know how the planets get formed, that's probably what happened and we know the solar wind exists. We can measure the solar wind, and so we can model what would happen if we didn't have a magnetic field. So yeah, well there's a lot of things we can do to validate those models. But absolutely there's modeling going on all over the place in all of these studies. And you know, we try to make assumptions and then they would trying to find ways to check them and to validate those assumptions. Absolutely. You know, another thing we do is we think about, like how life could have evolved. A lot of the basic chemical building blocks of life couldn't have formed if we had oxygen in the atmosphere, right, So life produced oxygen, but in lots of cases it's inhibited by the presence of oxygen. That kind of life that me and you are, this aerobic kind of life that relies on oxygen, is fairly late showing up in the evolutionary record. And so if we had had oxygen, like outgassed by those volcanoes, we might not have formed life, right because the earliest life, like our ancestors, were anaerobic, right, they didn't like oxygen. Yeah, they're poisoned by oxygen, and not just the life itself, like the chemical building blocks, a lot of those amino acids that they need to just like bump together in a weird way in the primordial soup. Those couldn't have formed if there was oxygen, because oxygen is just like so excited. It bonds to everything and it prevents other things from happening. So if we've had oxygen around, we could have made those building blocks, and maybe life itself wouldn't have started sort of crazy. So it's a good thing we didn't have oxygen then, but it's a good thing that we have it now, Yes, exactly. And it's like such a delicate balance, right. We needed oxygen to not be around, and then we needed these other life to exist for a while, and then to produce a bunch of oxygen so that we could evolve. It's a crazy story, right, but I guess it's all one constant evolution. Right. You can't just ask, like, we wouldn't be here if we didn't have oxygen, but maybe some other anaerobic beans would be here having a podcast breathing out less hot air than we are, at least less mellie air. Maybe. Yeah, absolutely, it's just that our particular path relied on all of these things happened in a particular order. Really, if things have been different, you know, you could have evolved life in lots of other different ways. Well, I guess I'm glad that it worked out this way. And it's good to know these things also because not just because maybe we want to change other planets, but we may also want to find other planets like ours that have an atmosphere, and so knowing these things might help us find or maybe our second or fourth home or retirement home maybe for humanity. Yeah, we are just now able to probe the atmospheres of planets around other stars by seeing how light passes through them as they block their stars. And understanding how a planet forms its atmosphere and how the atmosphere evolves is really crucial to answering the question like is there one out there we could land on? Because there might be a planet out there in the habitable zone, meaning it's like warm enough to melt water on the surface, but there might not be an atmosphere, and that's not terribly useful because you can take millions and millions of years. Even if you like plants cyanobacteria in the water on an alien planet to produce enough oxygen. So it's a really interesting question, like how long does this take? Is it unusual on Earth? Could happen faster on other planets? Is it already happening on other planets out there right now with primitive life producing oxygen. It's a really interesting and deep question and one that might be really important for the future of humanity. Yeah, you don't want to pack up all of your things move halfway across the gaxy and then when you get there, that wouldn't be good. And also for our neighbors. You know, Elon Musk talks a lot about moving to Mars and making it a second home for humanity, but it's going to take a long time before you can walk on the surface of Mars and like take a deep breath and survive, not to mention even enjoy it. All right, Well, it kind of makes you grateful for the air that we have, because you know, this is kind of the only thing we have to breathe and the only place in our Solar System and maybe in our galaxy that we know of right now where we could comfortably walk around outside and breathe the air. I'm very grateful. I'm full of it. You're full of hot air and cold air and all the air. I'm putting them all on at the same time, and burping them and doing other contributions to the air all at the same time, and speaking Icelandic very badly into a microphone for other people to hear. All right, Well, that's the history of our atmosphere and we hope you enjoyed that. Thanks for joining us, See you next time. Thanks for listening, and remember that Daniel and Jorge explained. The Universe is a production of I Heart Radio or more podcast for my heart Radio, visit the I Heart Radio app, Apple Podcasts, or wherever you listen to your favorite shows. Ye