What makes the Earth’s atmosphere so special? What makes the atmospheres of other planets so special? Why are atmospheres so special anyway? I discuss these questions and more in today’s Ask a Spaceman!
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EPISODE TRANSCRIPTION (AUTO-GENERATED)
We're always obsessed with the best, aren't we? We wanna know what the biggest thing is or the oldest thing is or the youngest or the most powerful, the most extreme or in general, we always want to know what is the most special. And when we look at the planets of the solar system and especially the atmospheres of the planets of the solar system, Earth always wins. What's so special about the Earth anyway? It's always it's always about life this and life that.
We're the only planet with life and living creatures and photosynthesis and blah blah blah. That's all anybody talks about. Life, life, life. Yes. The Earth is special, and there's something very special about its atmosphere.
There's lots of oxygen. There's lots of life, and there's so much oxygen in the Earth's atmosphere. It's the most oxygen in any atmosphere that we've ever detected, you know, percentage wise. But does that really make Earth the best? Does that really make Earth the most special?
Does that really make the atmosphere that you're breathing now the most extreme, the strangest, the weirdest, the most unique in the solar system? I don't know, man. I don't know. I'm I wanna take this episode. I'm gonna take a little tour of the solar system, and I'm gonna point out something special about each one of the planets and each one of the planet's atmosphere, something unique that no other planet shares.
Why? Because it seemed like a fun thing to talk about. And if aliens were to ever visit the solar system roll with me here. They they may be totally bored by the Earth. They may look at the Earth and say, okay.
Yeah. Nitrogen, oxygen, carbon dioxide, life. Okay. Whatever. Seen that before.
Give us something new. And then they look at you know, when they pick out, like, Neptune, they're like, oh my gosh. You need Neptune is the most unique planet in the entire galaxy that we've ever scanned. We can't let our biases get in their own way. Who knows what an alien would find special about our solar system?
We can't assume it's gonna be us. We might be boring. And so in a pursuit of the most extreme, the most special, the wildest weather in the solar system, let's go. Let's take a look. Let's give the other planets some love because they deserve it.
And we'll start with Mercury. The most special thing about Mercury's atmosphere is that it has any atmosphere at all. I mean, it has air, but not it's not quite an atmosphere. It's something called an exosphere because the world needs more random jargon words tossed around to confuse people. Here's the thing.
To make an atmosphere, you need a bunch of elements. The elements need to be floating around, but gravitationally bound to the planet, and they definitely need to be rubbing up against each other so that they behave like a gas, like a single fluid. Mercury has a and b. It has a bunch of elements floating around, gravitationally bound to Mercury, but it's just way too thin to act like a single entity. Hence, not atmosphere, exosphere.
How thin is the Mercurian Mercurial? I don't know. Mercurian atmosphere, it's one thousandth of a billionth of the Earth's air pressure. Okay. So it's not working with a lot, but it's something.
Okay? And for Mercury, that's pretty special. It's the usual suspects, hydrogen, oxygen, water vapor, blah blah blah, and also sodium and magnesium and and calcium, minerals, vitamins, nutrients. This is interesting. This is interesting.
And but before I dig into why the presence of sodium and magnesium is interesting in the exosphere of mercury, I should talk about the most surprising fact, which I hinted at, which is that it exists at all. Mercury is pretty close to the sun. Right? It's pretty hot. All the gas particles in the exosphere of Mercury are really, really hot and liable to escape.
Plus, there's this whole thing called the solar wind, this stream of energetic particles constantly oozing out of the sun. That's capable of stripping an atmosphere off of a planet, which is what we think happened to Mars a long time ago. So this atmosphere, as thin as it is, it exists. It shouldn't exist. It should have been blown away.
It should have just evaporated. It should have just gone away. Mercury should be as airless as the moon, but it's not. Something is replenishing the atmosphere on Mercury. Either the solar wind particles are getting trapped or radiation is hitting the surface and kicking up dirt, hence all the minerals like magnesium and calcium.
We're not exactly sure what is replenishing Mercury's atmosphere. And so that's what makes it special that it's able to survive that close to the sun, 10 times the solar radiation that the Earth gets, and still hang on to something. Good job, Mercury. You are special. Next, Venus.
Now where to start with Venus? We've done a whole episode on it, but Venus is just something else, isn't it? First off, I feel like you should note that Venus is blindingly white. I mean, it's the brightest object in the sky after the sun and the moon, and it's still tens of millions of miles away from us. So that should clue you in on just how reflective this thing is.
It's so reflective that if you were in orbit around it, you wouldn't even be able to look at it without filters, also known as sunglasses. But it's bright. It's a bright reflective object, and it's very, very white. Venus's atmosphere is choking and thick and toxic and altogether nasty. It's the thickest of the atmospheres of all the rocky worlds.
It's mostly carbon dioxide, but also a lot of sulfur. Sulfur. On Venus, sulfur plays a similar role that water does here on Earth, and especially the sulfur on Venus that comes in the form of sulfuric acid, AKA acid rain, AKA pure nastiness. There are clouds of water on the Earth. There are clouds of sulfuric acid on Venus.
On Earth, you might find a a hazy morning fog. On Venus, there's an entire layer in the atmosphere that is completely fuzzed out by all the sulfuric acid. On Earth, you have raindrops falling on your head. And Venus, there is precipitation of sulfuric acid, aka acid rain, but it doesn't even reach the surface because it gets too hot and it just evaporates. It's just acid rain, acid clouds, acid air, acid everything.
Like I said, Venus is nasty, which makes it special if you're a fan of sulfur. I'm gonna skip the Earth because that's the whole point of this episode. And next up is Mars. I've talked a lot about the atmosphere and general conditions on Mars before. The short version, it's cold, dried up, and very red forward.
It still has a thin atmosphere, about 1% the air pressure of the Earth, and it's mostly carbon dioxide because, apparently, that's nature's favorite gas. But here's something I didn't mention before, the methane. Methane is in the Martian atmosphere, and methane is very unstable. There's UV radiation from the sun. It just breaks up methane, knocks it apart.
And methane just really likes to react with the other gases in the Martian atmosphere and turn into other things. So in other words, if you dumped a bunch of methane on Mars, it would quickly transform itself into decidedly non methane stuff. But we see methane in the Martian atmosphere, not tons, but a decent amount. Odd. Odder still is that one of the biggest sources of methane on Earth is cow farts, and bacteria farts, and and and generally farts, you know, just in general.
Life farts. And when it farts, it farts methane. Earth's atmosphere has a decent supply of methane due to all the eating and farting going on by life. So if methane shouldn't last long on Mars, Mars, but is apparently hanging around long enough for us to measure it, and we know that life can make regular supplies of methane, then another strange thing. The methane on Mars varies with the seasons.
Methane ramps up in the summer and fall and then collapses in the winter and spring, you know, just like on Earth because of life. While the methane on Mars could be produced by life, it's not the only potential source. As long as you can find a chemical way to generate hydrogen, then hydrogen can meet up with some c o two and make methane. While the exact processes seem pretty unlikely, the truth is we don't really understand Martian geology or chemistry well enough to rule them out. So we can't say for sure that the methane on Mars is caused by some interesting, but not life based, Martian chemistry going on.
We can't rule it out. We can't say for certain. The Martian methane could be caused by Mars farts. Either way, the abundance of methane on Mars makes it special. Just plug your nose.
Okay. Jupiter, the king of the planets, the big bully. Jupiter is so big that it makes the sun swing in a little circle. Like, the gravity of Jupiter is big enough when Jupiter's on one side of the solar summit pulls the sun in one direction, then Jupiter's on the other, and the sun goes swinging in the opposite direction. And it's big enough that we can measure it.
And that's big. Okay. So Jupiter's big. The first thing of particular note about Jupiter's atmosphere is its sheer bulk. It's huge.
Jupiter is two and a half times bigger than all of the other planets combined. If you removed all the other planets from the solar system, every asteroid, every rock, every speck of dust, every comet, Jupiter has so much mass, you would basically still have the solar system. We are a rounding error in the planets of the solar system because it's all sucked up by Jupiter. It's just ridiculous. And the weather on Jupiter is, well, violent.
Winds rip around at hundreds of miles per hour as some of them get caught up in giant vortices. On Earth, we give these massive storms cool, threatening names like hurricanes or typhoons. On Jupiter, they're called spots. Spots. Fine.
And the most famous spot of all is the Great Red Spot. It's large, it's red, and it's a spot, great red spot. This is a storm. The Great Red Spot is a storm, a hurricane, that's been blowing for as long as we've been able to see it. Galileo and his telescopes didn't have the power to spot the spot, but his successor, Giovanni Cassini, definitely noticed something funky going on with Jupiter in 1665.
That's almost four hundred years ago. Now there are some gaps in the observational record. We don't know if the spot we see today is the same one that Cassini found or if his storm eventually dissipated and reformed or what. But let's assume it's the same storm that he saw in 1665 because that's way more awesome to believe, and we're allowed to have fun. The storm is, in all senses of the word, ridiculous.
Winds at the edge blow at around 250 miles per hour. And if you don't know what a mile is, let's just go with fast. The storm itself is wider than the entire planet Earth. I don't think you really heard me and appreciate that, so I will repeat it. The storm itself is wider than the entire planet Earth.
Period. At its peak a hundred years ago, it could have swallowed the entire Earth three times over. That's right. It used to be bigger. Since then, it's shrunk for unknown reasons, but that's kind of part of the ridiculousness that you can have a giant hurricane that goes from three Earths to just over one Earth, and we don't know why.
I guess that does make it slightly less ridiculous because it's, you know, not as big as it used to, but, hey, it's still pretty awesome. The top of the storm sits five miles above the rest of the clouds, and you've all seen massive thunderstorms or satellite images of hurricanes. Imagine a storm taller than Mount Everest. It is just ridiculous. Sometimes it's red.
Sometimes it's more of a pale white. Why is it changed? We have no idea. Well, we do have some ideas, probably interaction of ultraviolet rays from the sun with some organic compounds going on in the atmosphere, but it's complicated. The storm is so powerful that it creates sound waves that heat the atmosphere above it by a few hundred degrees up to 500 miles.
So the air sitting above the storm, 500 miles above the storm is heated by a few hundred degrees because of the sound waves. Like, you know how loud a storm can get. Right? Imagine sitting in that great red spot. Actually, you can't imagine it because not only would it deafen you, the sound waves would literally obliterate you.
This is a power of a storm. Like I said, it's ridiculous, and that makes Jupiter special. So Saturn. Saturn has a hexagon. Seriously, look it up.
I'm not kidding. Saturn has a hexagon in its atmosphere. It's basically the last thing you would ever expect on any planet anywhere in the entire universe, and there is Saturn sitting there with a hexagon on its North Pole. Look it up. I'm not joking.
Look at a picture of Saturn. It has a hexagon. What is a geometric figure doing on Saturn? Yes. We have an explanation.
So the the North Pole of Saturn, there's a giant vortex. There's a giant storm, a constant circulating hurricane that just sits in the North Pole, and it's whipping around super fast as storms are want to do. As you move further and further south, as as you go from the North Pole down the latitudes down towards the Equator, the winds get slower and slower and slower because that's what it does. So at northern latitudes near the pole, you have fast winds, and southern latitudes near the Equator, you have slow winds. And anytime you have a fluid, like a gas, atmosphere, or, like, water or whatever, where there's a region of it, a patch of it that's moving really fast, and it's next to a part of that is moving not so fast, you get turbulence.
The fluid starts to fold in on itself. And there's a very specific latitude on Saturn as you start to move south from the North Pole, where the turbulence has set in between two layers of winds, and it's formed vortices, like little mini hurricanes. And you can get any number of hurricanes you want. Sometimes, like, 10 will form or three. In Saturn's case, six individual hurricanes formed just beneath the North Pole.
And because they're low pressure regions, they they resist each other, so they spaced themselves out equally in a ring near the North Pole of Saturn. So it's like imagine on Earth, a storm constantly spinning at the North Pole, a giant vortex, and then you pick some more southernly latitudes, say the line that goes through, I don't know, like The United States and Southern Europe and Russia and China. Like, pick that latitude. And then each one of these regions gets a storm. So North America gets a storm, and Europe gets a storm, and Asia gets a couple storms because it's really wide, and the Pacific gets a few storms.
And they're all equally spaced in a line like, like jewels on a necklace. So you've got this setup. You've got the vortex happening in the center at the North Pole, and then at a more southerly latitude, you've got this string of storms. You still have all these winds, but what the winds encounter when they reach one of these storms is the storm passes off the wind to the next storm. Like a bunch of people standing in a circle, tossing a Frisbee around.
Even though the people form a circle, even though the storms form a circle, they pass the Frisbee off in straight lines, segment by segment, person to person to person. And so these vortices, even though they form in a circle, they pass the winds off in a straight line. Saturn formed six storms, and so it makes a hexagon. Just like six people standing in a circle, they play Frisbee. The Frisbee traces out six straight lines and makes a hexagon.
We think. We've been able to recreate this in some sense in laboratories with, like, spinning up fluids inside of bottles and taking pictures of it. Obviously, we can't recreate Saturn's atmosphere itself in a laboratory. Saturn's northern hemisphere is the only place in this in the entire solar system where this happens. Why didn't it happen at the Southern hemisphere?
Why didn't it happen on Jupiter or Uranus or anywhere else? What is so special about Saturn's northern pole? We don't know. That that makes it special. Right?
I mean, it's the only planet with a hexagon. I would say that's pretty dang special. Next up is Uranus. And okay, at first glance, Uranus is by far the most boring planets, and it's an almost perfectly uniform greenish haze. There's very little variation, very few storms, just lame.
But that's just on the surface. Below, there's a lot more going on, we think. You see, there haven't exactly been a lot of observations of Uranus. We had the Voyager probe forty years ago, and then well, you see, we we, and then, you know, and, nothing. Nothing.
We've only visited this planet once. It actually drives me nuts how Uranus and Neptune combined have gotten just, like, a couple of visits, and that's it in all of human history. Where's the next generation of probes to this part of the solar system? Why is no one else interested in it? Maybe it's because they look boring.
I don't know. It looks boring on the surface. A lot of what we know about the your Eurasian no. That can't be right. Your Urani Uranusian, someone help me out here, about the atmosphere of Uranus comes from simulations and from computer work, from theory.
And what we know tells us that the atmosphere of Uranus is boring. Well, I guess at least near the top, but in the depths below, we think something funky is going on. There are four different cloud layers. You have to go deep several hundred miles down where the pressures are 200 times that on Earth. And and it's just crazy to think about.
Here on Earth, we have clouds, but there's just one layer of clouds in the atmosphere. You go to Venus, and there there are the sulfuric acid clouds, and there's just a single cloud layer. That's it. You go to Mars. Mars has some carbon dioxide clouds, but there's just one layer.
Uranus has four layers of clouds. At the deepest level, you find the good old fashioned water clouds, the same as you find on Earth. So let that sink in. If you were to go a hundred hundreds of miles beneath the surface of Uranus, where the air pressures are 200 times that on the Earth, you will find water clouds. But above that, it gets smellier.
There's a layer of clouds of ammonium hydrosulfide, which is the good old fashioned stink bomb chemical. And above that, you have a cloud deck of ammonia clouds, and ammonia is, you know, fertilizer. And above that, you have a cloud deck of clouds made of hydrogen sulfide, which is the classic smell of rotten eggs. So Uranus has four cloud necks. Three of them are outright stinky.
There are very obvious Uranus and stinky gas jokes to make here. I'm just gonna be more mature than that and move right along and say, Uranus, you are special. Okay. Neptune. Neptune is the last of the major planets.
Shepherd and shaper, the Kuiper Belt. It's the green one. And Neptune has a lot going for it that Uranus lacks, and you can see it right on the surface. There's lots of storms coming and going, a lot of circulation, a lot of activity, a lot of warmth. Wait, hold up.
Warmth? Neptune is 50% further away from the Sun than Uranus is, gets only 40% of the sunlight, but it's over twice as warm as Uranus. In fact, Neptune radiates two and a half times the energy it gets from the Sun. It radiates more energy than it receives, and it has the fastest winds in the solar system. That requires a lot of energy.
That requires a heat. How does Neptune stay so warm? One explanation is its leftover heat from the formation of Neptune. What we now call Neptune, all the little bits and pieces used to be spread out over an incredible volume, then those bits and pieces over the incredible volume coalesced into a small dense object that we call Neptune. That process releases a lot of heat.
A lot of that heat got trapped inside and slowly leaks away over the eons. And that sounds reasonable of, okay, Neptune's warm because it formed a worm, and it's just still warm. But then why is Uranus so cold? What what cooled off Uranus but kept Neptune warm? One possibility is diamond rain.
You can take methane, which is made of hydrogen and carbon, add a little bit of pressure that knocks the hydrogen loose, and you're just left with the carbon. The carbon squeezes get together and under enough pressure, a bunch of carbon becomes diamond. Exactly what happens inside the Earth, but in the atmosphere of Neptune. This process of forming diamond rain releases heat. You squeeze a bunch of carbon together, this just this is a process that releases heat, and so it can potentially keep Neptune warm.
And it also means you literally have rain made out of diamonds. At the in the upper layers of the atmosphere, the where the pressures are just right, you get little diamond droplets, and they fall further down into the pressures are so extreme that it even obliterates the diamonds themselves. Then the little carbon oxygens reform into methane, make their way up top, and the cycle starts again. That's kind of cool. You get diamond rain.
But diamond rain may also happen on Uranus. So once again, why is Neptune so warm? What's going on? Well, we don't know. And that's something special about Neptune.
It's freaky, unexplained warmth. I know Pluto isn't a planet. It's I mean, it's a dwarf planet, but you know what? It still has a really cool atmosphere, and we gotta talk about it. It's very thin.
It's mostly nitrogen. Same nitrogen as the Earth's atmosphere, which gives it a very lovely blue color. It's extremely extended, you know, because Pluto isn't very big, so it's a tough time holding on to any kind of atmosphere. If you were to put Pluto at the center of the Earth, then Pluto's atmosphere would actually stretch further out than the surface of the Earth. It's pretty big.
But Pluto is freezing cold. It's way out here most of the time beyond the orbit of Neptune. How is Pluto able to create an atmosphere in the first place? It should all be ice. It should all be solid.
How can something exist as a vapor, as a gas? Maybe it does it by contributing to Patreon. Go to patreon.com/pmsudder to learn how you can create your very own atmosphere in the depths of space and also help keep the show going. That's patreon.com/pmsutter. We think one explanation for the atmosphere of Pluto is that it has an elliptical orbit.
Sometimes it's closer to the sun. Sometimes it's further away. Sometimes it's so close it's within the orbit of Neptune. It just got done recently doing that and is now slinking its way back out. So it's close to the sun, but only temporarily.
It might get close enough to the sun that some of the ices that are on the surface convert, sublimate, can turn into an atmosphere, into a gas. The gas hangs around for a while, and then as it goes back out, the gas settles back down into a solid form as ice on the surface. It's currently snowing on Pluto. Now that snow is methane, so I wouldn't exactly try to catch a snowflake on my tongue, but it's still snowing on Pluto, which is pretty awesome. And that's special.
Before I go, I do have to bring in an honorable mention. I have to mention Titan. Titan is the largest moon of Saturn, and it is not a planet, duh, but it is a rocky world in the solar system, and it is second to Venus in terms of density of atmosphere around a rocky world. And it's the only world besides Earth and Pluto with a nitrogen rich atmosphere. And this atmosphere is so thick, it's 50% denser than the Earth's atmosphere.
There's also a bunch of other stuff. Methane, ethane, propane, propane accessories, acetylene, just all the good stuff. And it's raining on Titan, but not water. It's not water rain. Why?
It's too cold. It's it's a hundred Kelvin. It it's 300 degrees below zero Fahrenheit or approximately Celsius. But when it's just that cold, they're basically the same thing. It's not rain of water.
It's rain of methane. There are methane lakes, methane rivers, methane droplets splashing on your head way out here in the outer regions of the solar system. And one of my favorite things about Titan is that you can make a reverse blowtorch. Check this out. If you want a blowtorch on Earth, if you wanna light something on fire, you need a can of fuel, you know, like a can of propane.
Then that fuel needs to react with oxygen to make a fire. The oxygen is just hanging around in the atmosphere doing its thing, minding its own business. Then you open the valve on your fuel tank. The fuel starts squirting out. You spark it, give it a little bit of an ignition, and that sets off a chain reaction.
The fuel combines with the oxygen, releases a little bit of heat, enough heat to get the next round started. And as long as you can keep pumping fuel in it into it, you can keep your blowtorch going. On Titan, it's the reverse. On Earth, the oxygen is in the environment, and the fuel is in your can. On Titan, the fuel is in the atmosphere.
You've got methane just hanging around, so you need to take a tank of oxygen. And you need to open the valve, let the oxygen out, light a spark so that the oxygen reacts with the fuel just hanging around in the environment. The process releases a little bit of heat and get the next round going. And as long as you can keep supplying the oxygen, you can keep your reverse blowtorch going. And that's pretty awesome, which makes Titan special, which is why I needed to meet it.
And the lesson we've learned, hopefully, is that when it comes to the atmospheres of the planets in the solar system, everybody is special just like you. Thanks to Saul c for the question that led to today's episode and, of course, my top Patreon contributors, Matthew k, Justin z, Justin g, Kevin o, Duncan m, Corey d, Barbara k, Newdoo, Chris c, Robert m, Nate h, Endref, Chris l, John Cameron L, Nalia, Aaron s, Kirk t, and doctor Johnny Fever for making this show possible along with all the other space cadets. You can join them. That's patreon.com/pmsuder. Look up all the various tiers and the rewards and all the cool stuff you get for joining, and you get to keep this show going.
And don't forget, I do have a book coming out June 2020, How to Die in Space, a Journey Through Dangerous Astrophysical Phenomena. I mean, it just sells itself, doesn't it? It's available for preorder. Check it out. You can go to pmsudder.com/book.
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And I will see you next time for more complete knowledge of time and space.