April 23, 2020 • 38 mins
How do planets get atmospheres, and how long do they last? Will Earth one day run out of air?
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Episode Transcript
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Speaker 1 (00:08):
Hey, or hey, can you smell the spring in the air?
The air does say makes for fresh these days? I
think it's all those l A drivers in quarantine. Well,
you better enjoy that fresh smell while it lasts. Is
your particle collider going to create a black hole that
sucks it all the way? Why do you always blame
particle physicists for everything? Why would I not blame part
(00:29):
of the physicists. I mean, it's definitely not the cartoonist fault.
It's something happens point taken. But you know, the Earth
is losing its air, but this time it's not actually
our fault. I am Hornhammack, cartoonist and the creator of
(00:54):
PhD comments. I'm Daniel Watson. I'm a particle physicist, and
I'm not responsible for the end of the world, not yet,
Not this time. Don't you have to give that disclaimer?
Not this time? How many times? How many times are
you guys expecting to end there? Well, it's sort of
like running away from the bear, right, You don't need
to run faster in the bear. You just have to
run faster than your friend. So I just need to
(01:17):
be the second person to destroy the world, and then
I'm basically in a sense, because that makes no logical sense.
Well helps me sleep at night at least. So I
got into particle physics specifically because it has almost no
practical applications and therefore cannot be weaponized or anything like that.
So I would be devastated if it ended up destroying
(01:37):
the world. Has no practical applications, but it does have
practical implications we'll see. But welcome to our podcasts. Daniel
and Jorge Explain the Universe, a production of My Heart
Radio in which we give you a tour of all
the crazy, beautiful, nonsense insanity that's out there in the universe.
All the things that seem like they don't make sense
until we explain them to you, all the things out
(01:58):
there in space and all the things here on Earth
as well. We try to explain them so you can
understand and also kind of realize how precious they are.
Sometimes that's right, and we do our best to bring
you to the forefront of scientific thinking, because what scientists
are wondering about is what we are all wondering about.
We'd like to know how long will the universe be around?
What is everything made out of? End? How long can
(02:19):
we rely on that fresh spring. How long would it
all last? Any these days, it kind of seems like
not that long, but people are feeling up to before
Mega Maids sucks it all away. But no, you're right.
I think that the l a air, I think is
the cleanness it's ever been, maybe since the turn of
the century, the last century. That's true. When we take
our carefully socially distanced hikes and we get to a
(02:41):
nearby peak, we can see like all the way up
to Malibu. It's pretty impressive. And so I think, you know,
air is something that we probably all take for granted
because we've always had it. We have it all the time,
and it's something we definitely need to breathe and to
survive and which protects us from space. But people might
be surprised to hear that it's actually kind of fragile. Yeah,
I'm definitely pro atmosphere on that side of you. But
(03:04):
the thing that you realize when you're sort of standing
up on the top of a mountain and you're looking
at the curve of the Earth is that the atmosphere
is a tiny, tiny little layer on the surface of
a huge ball. I mean, it's like one quarter of
one percent of the radius of the Earth is our
atmosphere point five of the radio points to five to five. Wow,
(03:28):
So I've heard it say it's almost like a thin
layer of paint on a bone. Yeah, it's like the
most delicate little envelope surrounding a globe. If you're holding
the Earth in your hand, you probably wouldn't even notice it.
You know. Our oceans, for example, are like the thinnest
layer of water on the surface of a planet, and
the atmosphere is even more delicate. Right, Earth rocks, it's
(03:48):
mostly rocks, mostly rock, a little bit of a shine
to it, and a little bit of air surrounding it.
And that's different from other planets. You know, other planets
like Jupiter, there's like mostly atmosphere other place. Yeah. Well, yeah,
Jupiter is all gas. Well at its core, you know,
it still has a little bit of rock and there's
some metallic bits down there, but the the gaseous part
of it is, you know, it's a huge chunk of it.
(04:10):
So Earth is a little bit different from some of
the other planets, and so our atmosphere is especially thin
and especially fragile. It's like a very delicate tupe on
the top of a very bald head. Well, I guess
the question is why do we even have atmospheres? And
you know, as you said, we look around the Solar
System and we see that other planets don't have them.
They've actually lost their atmospheres, Like Marks, Yeah, Mars used
(04:35):
to have an atmosphere and now it's gone. And sort
of fascinating perspective on the universe is to imagine billions
of years ago when Venus and Earth and Mars used
to all be very similar. They had atmospheres, there's more
similar service temperatures, and now Earth is basically the only
place you would like to live. You know, Mars got
super cold and lost its air, and Venus got super
duper hot and its atmosphere is super dense. Well, it
(04:58):
kind of depends how hot you like it, Daniel. Nobody
likes it Venus hot except the Venusians. Yeah, exactly. I
wonder what it's like for them to take vacations on
the surface of the Earth. You know, they bundle up
even in southern California and you're like, oh my god,
this is so coolget but it's nine degrees on the
surface of Venus. They're like, wow, we can make snowballs
(05:18):
with wood water. That's crazy. But yeah, so it's it's
a big question how does the planet lose its atmosphere?
And I guess by consequence, how will Earth lose its atmosphere? Yeah?
Will Earth lose its atmosphere? It's just another question that
reminds you that on cosmic time scales, the Solar System
and the universe are quite dynamic. The Solar System didn't
(05:40):
always look this way. The Earth won't always look this way.
Other planets have changed. When you only look on a
hundred years or two hundred years time scale, things to
seem to move pretty slowly and you might be confused
and think that they're static. But things are changing actually
quite quickly on a cosmological time scale. Yeah, and so
I think scientists have lots of ways in which we
(06:00):
can lose our atmosphere. I mean, it's just this thin
layer of gas hanging on by gravity onto our giant
ball of rock. But recently there's been a study that
has a new crazy idea about how it could all
be gone. Yeah, it was a fascinating new idea and
it sort of adds to our understanding for how planets
can get rid of their atmospheres and also sort of
(06:21):
solves a mystery about exoplanets, and so do they on
the bark and we'll be asking the question, how can
the planet lose its atmosphere? You make it sound like
it just sort of like put it down, walked away
and came back and it was just gone, Like have
you seen my keys that were on the counter. In
terms of planetary scale time scales, it is sort of possible. Right,
(06:43):
one day, we could have an atmosphere. Next day it's
all gone. Somebody took it, right, and you're like, hey, Mars,
you didn't use to have an atmosphere, and then I
lost mine? Did you steal my atmosphere? That's another interesting question.
Oh yeah, you can planets steel atmospheres from each other
they get close enough, you know, like a black hole
sucking gas from a neutron star. Well, maybe we should
(07:04):
keep our social distance from Mars. That's right, that's right,
planetary distancing. Yeah, And so, as usually, we were wondering
how many people out there in the public knew whether
it was even possible to lose your atmosphere, or even
possible to lose it in the way that this new
study says that we could, and so I asked questions,
but in a sort of a new way. You see,
(07:24):
Irvine's campus is closed and we're all staying home to
stay safe, and so I reached down to the internet
to ask for volunteers to people who are willing to
answer random questions from a scruffy looking physicist. And the
internet didn't know you're a scruffy looking physicist. Did you
get more responses this this way? You know, my avatar
in the internet is the drawing you made in which
you made me look pretty scrappy looking. So I think
(07:46):
it's a fair representation. Oh man, Daniel, I am so
insulted that I did not draw that avatar reviews it
was another cartoon, is no, my avatar is the one
that you drew. I have one also from Saturday Morning
Breakfast Cereal that I is on Gmail. I see on
social media. It's your drawing of me podcasting some people,
you professor your favorite cartoons mean to other people it's
(08:09):
a different cartoons. But anyways, I've been cheating on you
with other cartoonists. Yes, anyway, I reached out to these
folks online and here's what they had to say. And
if you're interested in volunteering for a future round of
Internet random Questions right to us at questions at Daniel
and Jorge dot com and volunteer. I think next time,
(08:30):
maybe you should just pick up the phone book and
if you have a phone book, if the hymn exists
these days, but pick up something like a phone book
and just that all random numbers and see and ask
this question right, because we all love telemarketers, and this
is even better than telemarkers. It's telemarketers that make you
feel ignorant as a telephysicist. It could be a trade.
If you're like, Hi, I'm a physicist. If you have
(08:50):
any questions about the universe, I will answer it right now.
But first, all right, well here's what people had to say. Yes,
given the fact that Earth's atmosphere isn't do so great
at the moment, absolutely they can. Are magnetic field that
encompasses the Earth protects our Earth from the Sun's radiation
solar wind, and solar wind would blow the atmosphere away.
(09:12):
If we didn't have the electro magnetic field around the Earth,
then we would have no atmosphere, similar to Mars. I
believe they can lose their atmosphere if they're too close
to their Sun. I don't know. Really depends who was
living there at the time. I think definitely, Yes, can
be caused by an external can be a supernova, asteroid,
(09:34):
or internal might be losing your manic the field. I mean,
I know that we are constantly losing gases um without
space due to atmospheric escape. But whether we could lose
the whole atmosphere, I'm not so sure about that. I'm
not sure how that would work. I definitely think so.
(09:55):
If we know anything about the Earth, is we have
like a core that's that's causing us to have a
magnet at an atmosphere, and that protects us from like
the solar winds, and we have like theories and ideas
of how that amphair started. But I can definitely see,
you know, a situation where on some certain planet the
core stop spinning and the magnetism field stops, and elements
(10:15):
of the atmosphere can just be blown away by a
sun's wind, like a solar wind. Yes, I certainly think
it's possible for a planet to lose its atmosphere m Mars,
I think lost. It's a lot of the atmosphere once
it's cool cooled down on the magnetic field fight in
the Sun's blew a lot of the atmosphere away. Yeah. Absolutely, Um,
(10:39):
Mars lost its atmosphere. Yes, a planet can definitely lose
its atmosphere. All right, some pretty good answers there. Yeah,
a lot of people have different ideas about how we
can lose our atmosphere. Yeah, and these are all our
podcast listeners, and so they've probably heard us talking about
magnetic fields and solar winds and Mars. Do you think
they cheated? Know? I'm saying, I'm proud that our listeners
(11:02):
have learned something about astrophysics and space physics and that
they have absorbed some knowledge. They're better educated on average
on these topics than your random you see, Irvine undergrad
Welcome to Daniel and Jorge University, the only university is
still standing these days. But what I was interested in
and was surprised by it was by how people need
(11:24):
about all the different ways that we can lose our
solar systems. So maybe let's start with that. Daniels, walk
us through what are some of the ways in which
we can lose our atmosphere? Well, the first way that
people talked about, and the first thing that probably comes
to your mind. And the way that we've talked about
a lot in this podcast is that it can just
get blown away. Like the Earth is surrounded by this
ball of gas and it's held on by gravity. But
(11:44):
there are winds out there in the Solar System that
can help sort of sweep away particles from our atmosphere.
Sometimes it's hard to remember that, you know, we're just
a giant ball of rock floating in space, you know,
and that the air that we breathe, our atmosphere is
isn't it attatched to us. It's just hanging on by gravity.
So if something comes over and blows it away, we
(12:04):
could lose it, that's right. And this isn't like, you know,
a hurricane blowing the wind to knock over your ice
cream or anything most tortured analogy. Ever, the wind we're
talking about here is the Solar wind, and the solar
wind is not like the motion of the air on Earth.
It's a stream of particles and radiation emitted by the
Sun and so it's mostly protons, but it's also high
(12:26):
speed electrons and other stuff. And what happens when these
particles impact the Earth's surface is that they can knock
off particles of gas. Because these things hit it really
high speed. They hit it like a million miles per hour.
It's like point one percent of the speed of light.
And so it might knock the atmosphere particles and then
(12:46):
throw them into space and then we'll lose them. Yeah, exactly.
It's like a big billiard ball hits another one and
they both go flying off into space because it has
a huge amount of energy and it shares some of
that energy with these particles of our atmosphere, and then
they both have enough energy to escape. Okay, So that's
not good. And so that that can happen like if
there's a solar flare or something, or just it can
(13:07):
happen anytime. It can happen anytime. It's happening all the time.
Now during solar flares it can happen much more dramatically.
But we have a shield, right, We have this like
literal force field in space that mostly protects us from
this method, and that's our magnetic field. Because most of
the solar wind are charged particles, protons and electrons, their
(13:27):
ions were not like being shot by neutral atoms of hydrogen.
And that means that when they hit a magnetic field,
they bend. That's what magnetic fields do. And so our
magnetic field tends to deflect a lot of the solar wind.
It's like we have a little envelope and the solar
wind bends around us. But I heard there's a problem
with polar winds that like that might make them vulnerable. Well,
(13:50):
the magnetic field is not a perfect bottle, right that
we have north pole and a south pole, and the
magnetic field lines come out from the North pole and
go down to the South pole and want to charge
particle reaches the magnetic field line, it tends to bend
left or right depending on its charge. But they can
move along the field lines, and so what happens is
that some of them get blown out into space, a
lot of them, but some of them get funneled along
(14:11):
those field lines up to the North pole and the
South pole. And that's what causes the Northern lights and
the Southern lights is energized particles hitting the atmosphere and
making it glow. So basically the North Pole in the
South Pole get a lot more of this cosmic radiation.
You can get these plumes of gas leaving the atmosphere
on the North pole and the south leaving, leaving the atmosphere. Yeah,
(14:32):
just like when you know the solar wind, it hits
the atmosphere, blows off particles. Most of the Earth is
protected because of our magnetic field. But it's like we
have these weak spots in the North Pole, in the
South Pole, and then then then so there's gas leaving
the Earth. But then and then it doesn't come back.
It doesn't come back. You get these big plumes of
gas and that's because you get really high energy particles
hitting our atmosphere there where we're not protected and knocking
(14:56):
particles off, and then and then we lose them forever
because the Earth moves off forever, the Earth moves on. Yeah,
and so you take these pictures you can see during
solar flares especially, but all the time you see these
plumes of gas being leaked at the north and the south.
You know, like if we were the death Star, the
north Pole in the South pole is where you would want,
you know, to send your ex wing because that's our
(15:16):
little weakness. Maybe we are maybe we are the Empire,
Maybe we are the bad Everybody grows up to be
their parents, right, just like the rebels will grow up
to be to build their own death star, and then
they'll realize we're just like our father. Welcome to Daniel
Jorge process, Daniels daddy issues. But there's there's a bit
of a controversy here because you know, some people think
(15:38):
our magnetic field protects us, and that makes sense for
all the reasons we just talked about. It deflects the particles.
Some other scientists those say that maybe your magnetic field
actually sometimes it bends particles towards the planet and it
ends up focusing it like catches a huge larger swath
of the solar wind than you otherwise would like. Your
profile is much larger, focuses all those to shoot down
(16:00):
near the poles, and you end up losing more atmosphere
on these polar plumes than you would otherwise. So there's
a little bit of controversy of whether or not the
atmosphere is The atmosphere is definitely good for us, but
there's a bit of a controversy about whether the magnetic
field is in the end protecting us or or helping
us lose our atmosphere. I think most scientists think is protection,
(16:23):
but there is controversy and discussion in the field. In
the field bump bump. And you know, we should specify
that Earth has a nice magnetic field, which we think
mostly protects us. But if you look nearby to Mars,
for example, Mars doesn't have a magnetic field, and Mars
is totally vulnerable to solar winds, and every time there's
(16:44):
a solar flare, there's a huge flux of particles and
it blows off a lot more of mars atmosphere. Alright, well,
it sounds like there are a couple of ways in
which we can lose our atmosphere, and there's one more
way and then actually some pretty interesting seeing dynamics that
can happen depending on the size of your planet. So
let's get into that. But first let's take a quick break,
(17:16):
all right, Daniel, So our atmosphere is not a given
in our planet. We can lose it. It can blow
away by solar winds, but it can also sort of
explode out of our planet. Yeah, we're talking about impacts
from like tiny little particles. The solar wind is a
huge stream of tiny little particles. But you can also
get hit by bigger stuff, right, like an asteroid. Yeah,
(17:37):
you see shooting stars at night, that's a huge big
rock hitting our atmosphere. You know what happens when you
throw a rock into a pool as you make a splash,
and so if you throw a big rock into our atmosphere,
you make a splash and some of that splash drifts
off into space. Yeah, so it's another way we can
lose our atmosphere is we get we could get pelted
by rocks and those blow the atmosphere away. Yeah, you
(18:00):
can think of the atmosphere is like a cushion or
like a force field against rocks, right, because it slows
them down, it heats them up, it it immolates them
before they hit the surface, which is nice. And that's
why Earth doesn't have a lot of craters because we
have this atmosphere. But it's not forever, right, we can
use it up. If Earth get hits by a lot
of asteroids, then it depletes the atmosphere unless you're lucky.
(18:21):
You're unlucky enough to get hit by comets, which are
actually like cosmic snowballs that can deliver water or gas
when they melt in your atmosphere. And you know, this
is not a big factor today, but we don't know.
Some people think that this was a big factor in
how Mars lost its atmosphere not just to the solar wind,
but also to a lot of impacts. Well, I guess
(18:42):
it's kind of a runaway effect, like if you start
to lose it because of one thing, then you have
less protection against the other kind. Yeah, exactly. And the
estimates are that Mars lost more than two thirds or
its atmosphere due to either impacts or the solar winds,
and that solar wind effect is called sputtering by the
signs is and so early on they think that that's
that's the dominant way that Mars lost its atmosphere, but
(19:05):
today there's actually something else going on on Mars. Al right, Well,
it sounds like these are kind of maybe the basic
ways in which you can lose your atmosphere, but there
are sort of two new ways maybe that people are
thinking about, right, like depending on the size of your planet.
And one of them is kind of this interesting new
study that maybe planets can eat their atmosphere. That's right, Yeah,
(19:27):
we'll get to that in a little bit. But it
turns out that the way that Earth is losing its
atmosphere is mostly not due to polar wind or solar
wind or meteor impact it's something wait wait wait wait
wait wait wait wait, So we are losing our atmosphere.
We are losing our atmosphere. Yes, really, as as we
speak right now, we have less atmosphere right now than
before we started talking. Oh. Man, see I knew, I knew.
(19:50):
We're just blowing hot air here, Daniel. And that's making
it worse because the reason Earth is losing its atmosphere
is that it's literally just boiling off the planet it wow, Okay,
so step us three here. So if the planet is
too small, you're saying, the atmosphere can just gradually boil away.
And that means kind of like when you put water
on the stove, the particles that are on the surface
(20:12):
that you get energized and they fly away. Yeah, it's
that kind of what would Yeah, just like you know,
water evaporates from a puddle, right, our atmosphere can just
evaporate off into space. What is keeping the atmosphere on
the planet is only gravity. So if your planet is
too small, like, the smaller your planet is, the harder
time it has hanging onto its atmosphere. Like why does
(20:34):
the Moon have no atmosphere? Well, it's basically just too
small to hold onto anything. Even if we created an
atmosphere and shipped it to the Moon and put it
on there, it would just drift away in you know,
tens of years. Really, it would just drift away. It
would just it would hang out for a bit for
but eventually would it would all evaporate? Yeah? Well, the
same laws of physics that applied to you have also
(20:55):
applied to little particles. And just like how it's easier
to leave the surface of the Moon, take a run
and a jump and you could float off into space.
Where that's is that true? Okay? Well not really. I
mean you'd have to be super strong. You have to
go like two kilometers per second. So I guess if
you're iron man, maybe if you had any athletic ability,
for hey, you would be able to drop off off
(21:17):
of Mars the moon. Mars will be much harder to
jump off of the Moon might be possible, But the
same is true of little particles. Right, Earth is much
better holding onto little particles than Mars is. Then the
Moon is right and Jupiter much much better. And so
if your planet is too small, it's just hard to
hold onto your atmosphere. Interesting, but I guess you know,
(21:38):
if even if things float away, why wouldn't they just
come back due to gravity, because is it because we're
moving through space and we sort of miss it. Well,
once things float away, they don't come back. I mean
that's what escape velocity is, right. Escape velocities how much
speed you need to essentially be able to neglect the
gravity of that object. Like if you shoot a satellite
off into space and it reaches escape velocity, it doesn't
(21:59):
come back like voyage or whatever. Isn't just on its
way back. It's got some trajectory away from us, and
the gravitational power is just weakening and weakening and weakening.
And in the same way, if a particle has enough
velocity to leave the Earth's atmosphere, there's no reason for
it to come back unless it gets deflected, it bounces
off the moon or you know that alien mother ship
that's orbit orbiting quietly for the last few years. Okay,
(22:22):
so then it would help to be heavier because then
you can keep more of your atmosphere, that's right. So
lighter planets tend to lose their atmosphere, and we also
tend to lose different gases at different rates, like we
lose hydrogen on Earth and helium, but we don't lose
oxygen nearly as much because oxygen is heavier, and so
that's why it falls to the bottom. Well, that's why
(22:43):
Earth has very little hydrogen naturally occurring in our atmosphere
because morbid bubbles away, whereas the heavier stuff, you know,
xenon or oxygen or neon. That stuff is heavier, and
Mars doesn't have the gravity to hold onto the same
kind of things that we can, and so water vapor,
for example, on Mars can easily reach escape velocity, whereas
Earth has enough gravity to hold onto it because Mars
(23:05):
is smaller than Earth. Mars is a lot smaller than
Earth and it has weaker gravity. And so today the
dominant process for how Mars is losing its atmosphere is
not sputtering. It's not the solar wind. It's actually just
being boiled off. And Mars is still losing its atmosphere
at a rate of like one and a half kis
per second. We need to kind of like a put
(23:27):
a lit on it, I guess. So, I mean, if
we're ever going to move to Mars, we need to
provide a new atmosphere, and then we need to somehow
prevent it from just leaving, right. We talked about terraforming,
needing some sort of like huge new magnetic field to
prevent sputtering to prevent the solar wind from blowing that
atmosphere way, but we also need to sort of just
keep it somehow on there. Yeah, although of course the
(23:49):
process of atmosphere loss on Mars is very slow, so
your new atmosphere would stick around for a long time
before actually getting blown away. And so I don't know
if you've seen spaceballs or emper, but they have this
huge planet wide envelope to keep their atmosphere in place,
no waste. Baseballs foresaw this situation thirty years ago. Spaceballs
(24:10):
could foresee the future. I was trying to come up
with a quote from the movie, but I can't. That's ludicrous.
That's there, you go. And so that's how Mars is
losing it tout this yere now right, These hot gases
basically just boil off. The same thing is happening here
on Earth. So we're so we're losing our atmosphere. That's
shocking news. Every every breath we take there's less air. Yeah,
(24:31):
and it's not at a tiny rate like Earth is
losing three kilograms per second of hydrogen fifty grams per
second of helio and so this adds up, you know,
to like tons and tons of gases every year per
second three kilograms, how much is that? Like a teaspoon?
M a kilogram is a leader of water, right, So
(24:52):
we're losing three liters of water is worth of hydrogen
every second. Every second, it's just boiling out into space.
Where where are people not more alarmed? Well, you know,
we have a lot of hydrogen. Unfortunately, we're a big planet.
And it turns out that by the time we lose
most of our hydrogen, other things will have happened. Like
(25:15):
we think in about a billion years, by the time
we've lost significant atmosphere, you know, the sun will be
ten brighter than it is today. And at that point
we'll have other big problems. For example, you'll heat the
planet up and the oceans will boil and break into
water vapor, and probably all that hydrogen will also get
lost into space. But all right, we're talking a billion
(25:37):
years until we have to worry about Yes, exactly. You
don't need to worry about your kids having enough air
to breathe, or your kids kids or your kids, kids, kids.
It's it's a lot of generation. I think in that
time scale, wouldn't we evolve probably to breathe differently? Right
in a billion years to biology would probably adapt. Yeah,
perhaps we would. Perhaps we could breathe differently, or perhaps
we will have just left this rock and explore the
(25:58):
universe and found other places to live. Or we could
do you know, geoengineering and protect the Earth from getting
hotter and fabricate new new hydrogen, new oxygen and and
you know, curate microbe that can produce more oxygen as
we need it. Or something like a billion years is
a long time to figure this stuff out. I mean,
(26:19):
who knows. Maybe in a year, physicist bal end the
year the planet all by ourselves with plenty of eric despair.
You sound like you're rooting for that option, and I'm
just trying to so I'm just trying to prepare mentally, Daniel,
so it doesn't surprise me. I see. This is a
classic relationship technique. It's called pre assignment of blame. This
(26:41):
happens we agree it's your fault that we don't have
to argue about it. I see you're a big fan
of that, right, I'm a big fan of pre assignment
of blame. Yes, well, if it does happen, we'll blame me. Yes,
you can come to my house after I destroy the
Earth and shout at me with plenty of air to
shout at you. Fortunately. Right, So boiling off gases is
(27:03):
basically what's happening here on Earth now, and it's now
the dominant process on Mars also because the atmosphere is
much more dilute there, and so this is something I
wasn't even really aware of that this is a big
factor in how you can lose your atmosphere. And so
all of this is if your planet is small or
too small to kind of have enough gravity to keep
it all in, and so other things can happen if
(27:26):
your planet is too big. So we'll get into that,
but first let's take a quick break. All right, Daniel,
we're losing our atmosphere, but it's not something to worry about.
(27:48):
It's it's happening very slowly, maybe in a billion years,
but by then we have other things to worry about.
But there's a new study you were telling me earlier
that talks about what can happen if your planet is
too big, Because apparently you can lose your atmosphere in
other ways if you are to be Yeah. Well, first
of all, the title of this study is awesome. It's
called Why Planets Eat their Own Skies and will include
(28:10):
a link to the study in the episode of information
that you can read it for yourself. It's from Stanford. Yeah,
not a bad school. I hear it's a junior college.
So I hear they give PSDs to cartoonists as well,
So yeah they do. It's been on a down cycle
ever since, then, said the Berkeley graduate. Of course, Man,
go cow, go col Cow. How many football games have
(28:32):
you been to with Cal Danny? Oh, I've been to
a lot. Yeah, No, football games are a lot of fun.
Were a little encapsulation of the old bear rivalry right
here on Oh man, it's it's scientists versus engineers. It's
Cal versus Stanford. What else, bananas versus not bananas. That's right.
We satisfy all of your rivalry needs here on the program.
You know this. Lots of people contributed this study, not
(28:54):
just from Stanford. It was led by Edwin Kite at
the University of Chicago, and they noticed something really interesting,
they know, is that when we see other planets in
other solar systems, which is now this thing we can
do right as we can look at planets going around
other stars, and we can measure two things about those planets.
We can measure their mass and we can measure their radius,
(29:15):
and that tells us like roughly what's going on in
those planets. We can tell like how dense they are
based on the mass and the radius information. And so
the radius we can tell by looking at it, but
the mass we tell by either orbits or something. Yeah.
You can tell the radius by like how much of
the star's light is being blocked, and you can tell
the planet mass by how much it makes its star wiggle. Oh.
(29:37):
This is a study of exoplanets out there in space.
And what they noticed is that they see a bunch
of planets sort of Earth sized, and they see a
bunch of gas giants. But there's kind of a gap,
like you go up to about like three times the
size of the Earth what they call, you know, Neptune
sized planets, and then bigger than that, there's like a gap.
(29:58):
There's no like planets in between Neptune size and Jupiter size,
and naturally you would expect sort of like you know,
a big continuum. You expect like a smooth distribution that
their planet is everywhere. Yeah, like a big rocks, smaller rocks, rocks.
But you're saying that there's a gap there. There's just
cut off before the gas giants and after sort of
the Neptunes or the super Earth's. And they were trying
(30:20):
to understand why, and it turns out that they came
up with this cool explanation that if a planet gets
big enough but not too big, and it has a
rocky surface, then that rocky surfaces like lava, so you
have like flava flowing on this hot surface, then it
can actually absorb its own sky. The gas in the
atmosphere gets sucked into these oceans of liquid magma because
(30:42):
of the gravity. Well, the gravity is certainly part of it, right,
But that's not happening on Jupiter, right. Jupiter also has
a lot of gravity but still has vast atmospheres of gas.
But it's something about this chemical interaction between the liquid
magma ocean and the gas in the atmosphere. Oh, I see,
And you're saying doesn't happen on Earth because we don't
have magma and lava on our surface, because we are
(31:06):
what not hot enough or not heavy enough. Both you
need the liquid magma on the surface, and then you
also need more gravity because you need the pressure. You
need the gas to be like squeezed down onto this
liquid magma that can sort of force it into it.
And so they find that basically these planets just eat
their atmosphere that stops them from growing bigger. Like, the
reason Jupiter is so big is because a huge part
(31:28):
of it is its atmosphere. Right on Earth, point to
five of the radius of the Earth is the atmosphere.
Jupiter is like a third or a half of Jupiter
is atmosphere. Okay, so you're saying that, like, we see
planets out there, and they get bigger and bigger in
terms of the size, but we don't know how big
the rock inside of them are, but you sort of
see the size. And so at some point if the
(31:50):
Earth suddenly grew in rocky nous in size, you're saying
that at some point the first of all, the surface
of Earth would turn into lava or that's not necessary,
it's necessary for this to happen. I think in these larger,
rockier planets, it's hotter, right, is more pressure because there's
more gravity and so the surface is more likely to
(32:10):
be magma, and then that pressure squeezes the gas down
onto the surface of that magma and basically forces it
in and it gets it dissolved in into the lava
I see, into the like it traps. Yeah, so you
get like carbonated lava, like sparkling lava, sparkling lava. It's
(32:31):
like mountain dew, but literally made out of mountain. There's
this whole new beverage trend, you know, sparkling water and
sparkling this and sparkling that. Nobody has thought about selling.
Sparkling lava, sparkling lava. Well, there you go. That's that's
the new market. Yeah exactly. And so basically it forces
you know, the gravity and the pressure forces the gas
into the rock, and that keeps the planet from really
(32:52):
growing inside because when your planet, you get to count
the extent of your atmosphere as part of the planet. Right,
And so where are the planets that are just bigger rocks?
Why is there a gap or are they saying that
suddenly at some point the planets grow in size because
of their atmosphere, not because of the rock. Planets grow
in size because of their atmosphere. Like the way to
get a really big planet is to have a small
(33:16):
icy core and then accumulate a lot of gas. You
accumulate too much rock, then you can't really grow anymore
because you can't attract anymore gas. But why can't I
just have a Jupiter size rock floating around the Solar System?
You know, I didn't say you couldn't. Go ahead, like
do whatever you like. You can, you can, you can,
(33:36):
but you know, there's just not that much rock. Like
most of the material in the Solar System is gas,
So if you want to get big, you got to
include that in your budget. So like, if you just
look at rocky centers, they maybe taper off, like they
get bigger, bigger about the Earth, the size of Earth,
three times the size of Earth, and then they don't.
They don't. You don't see them get bigger. But you
do see planets get bigger because then they start to
(33:57):
accumulate atmosphere. Yeah, that's right. But if your rocky or
is too big, then it can prevent you from growing
a big atmosphere because it can suck it into the
liquid magma in the core. I see, all right, So
probably the bigger planets we see out in the universe. There,
they don't have a rocky center bigger than ours. They
have smaller rocky nuggets inside, but they're bigger because of
the gas, and adding enough gas can turn any rocky
(34:20):
object into a gas giant. We don't really know the
size of the rocky cores and some of the big
gas giants in exoplanet systems, but most of the volume
is gas. That's why they are bigger. And if you
look at the internal structure of Jupiter, it has a rocky,
icy core, but it's pretty small. You know, it's not
enormously vast. After that, it's like metallic hydrogen and all
(34:41):
these things because of the high pressure and then vast,
vast clouds of just gaseous hydrogen, and that's the way
to go. But you know, there's even still a lot
of questions about how planets like Jupiter form, Like how
do you get so much gas accumulated. You need to
have some sort of rocky core that forms rapidly enough
that has time to accumulate all that gas because the
(35:01):
gas is pretty light, and so it takes a while
for gravity to gather that together. So we're still learning
about how all these planets form you know, in ten
years we could have a lot of new ideas for
how any of these planets form. And I think we
talked on another podcast about like should Jupiter sized planets
form always in the outer Solar System or only in
the inner Solar System? You know? Can they move back
(35:24):
and forth? And so we're learning so much about our
planet and other planets and how it all puts together
just by studying other Solar systems. It's it's a fascinating time.
And so they call it eating your atmosphere, eating your sky,
because in a way, you're sort of like absorbing the gas, right,
Like if your rock is big enough, it sort of
absorbed the atmosphere. Yeah, it sucks it into itself, and
(35:45):
it prevents it from getting bigger. It's like you sucking
your stomach in, right, it keeps you from from looking
larger than I don't think how do I think that
works in real Physicsdanu, I'm surprised. All right, Well, it
sounds like we should once again be lucky that we
are just the right size, because if we were heavier,
if the Earth was bigger, we wouldn't have an enmoshere,
(36:05):
or if we were smaller, we wouldn't have an atmosphere either. Yeah,
it's just another way that the Earth seems to be
at this weird sweet spot. Right. We're just the right
distance from the Sun, we have just the right amount
of atmosphere, we have just the amount of stuff to
hold onto that atmosphere, but not too much. We're like
far enough away from the center of the galaxy to
not be fried, but not so far away. But that
(36:27):
there's no planets out there, and so it's it's amazing
how many ways we seem to be lucky, you know,
and it raises questions about about how many how many
other planets are out there that could have as many
lucky factors. Yeah, you can be too big or too small.
You got to be just right, all right. Well, we
hope you enjoyed that. And maybe when you go out
(36:48):
there and breathe this new clean air that we're all
enjoying because of where we are these days, um, think
about how precious that breath of air is. In how
it's we were a little bit different in this planet,
we wouldn't have that nice fresh year and count your
breaths because you only got about a billion years left
to enjoy them. Depending if Daniel ends Universe and thanks
(37:10):
to my friend and colleague and geologists Steve Davis for
sending me to study and the idea for this podcast. Yeah,
if you are a physicist out there listening to this
program and you see a fun paper, send it to Daniel.
I will definitely look forward to hearing again from him
about it. But we want to hear about all your
thoughts and all your questions. So if you have a
question about anything going on in the universe or a
study you see on the internet, please write to us
(37:30):
at questions at Daniel and Jorge dot com. We do
love our listener mail. See you next time. Thanks for listening,
and remember that Daniel and Jorge Explain the Universe is
a production at by Heart Radio. From more podcast from
my Heart Radio, visited my Heart Radio, papp Apple Podcasts,
(37:53):
or wherever you listen to your FILI shows. No
Hey, or hey, can you smell the spring in the air?
The air does say makes for fresh these days? I
think it's all those l A drivers in quarantine. Well,
you better enjoy that fresh smell while it lasts. Is
your particle collider going to create a black hole that
sucks it all the way? Why do you always blame
particle physicists for everything? Why would I not blame part
(00:29):
of the physicists. I mean, it's definitely not the cartoonist fault.
It's something happens point taken. But you know, the Earth
is losing its air, but this time it's not actually
our fault. I am Hornhammack, cartoonist and the creator of
(00:54):
PhD comments. I'm Daniel Watson. I'm a particle physicist, and
I'm not responsible for the end of the world, not yet,
Not this time. Don't you have to give that disclaimer?
Not this time? How many times? How many times are
you guys expecting to end there? Well, it's sort of
like running away from the bear, right, You don't need
to run faster in the bear. You just have to
run faster than your friend. So I just need to
(01:17):
be the second person to destroy the world, and then
I'm basically in a sense, because that makes no logical sense.
Well helps me sleep at night at least. So I
got into particle physics specifically because it has almost no
practical applications and therefore cannot be weaponized or anything like that.
So I would be devastated if it ended up destroying
(01:37):
the world. Has no practical applications, but it does have
practical implications we'll see. But welcome to our podcasts. Daniel
and Jorge Explain the Universe, a production of My Heart
Radio in which we give you a tour of all
the crazy, beautiful, nonsense insanity that's out there in the universe.
All the things that seem like they don't make sense
until we explain them to you, all the things out
(01:58):
there in space and all the things here on Earth
as well. We try to explain them so you can
understand and also kind of realize how precious they are.
Sometimes that's right, and we do our best to bring
you to the forefront of scientific thinking, because what scientists
are wondering about is what we are all wondering about.
We'd like to know how long will the universe be around?
What is everything made out of? End? How long can
(02:19):
we rely on that fresh spring. How long would it
all last? Any these days, it kind of seems like
not that long, but people are feeling up to before
Mega Maids sucks it all away. But no, you're right.
I think that the l a air, I think is
the cleanness it's ever been, maybe since the turn of
the century, the last century. That's true. When we take
our carefully socially distanced hikes and we get to a
(02:41):
nearby peak, we can see like all the way up
to Malibu. It's pretty impressive. And so I think, you know,
air is something that we probably all take for granted
because we've always had it. We have it all the time,
and it's something we definitely need to breathe and to
survive and which protects us from space. But people might
be surprised to hear that it's actually kind of fragile. Yeah,
I'm definitely pro atmosphere on that side of you. But
(03:04):
the thing that you realize when you're sort of standing
up on the top of a mountain and you're looking
at the curve of the Earth is that the atmosphere
is a tiny, tiny little layer on the surface of
a huge ball. I mean, it's like one quarter of
one percent of the radius of the Earth is our
atmosphere point five of the radio points to five to five. Wow,
(03:28):
So I've heard it say it's almost like a thin
layer of paint on a bone. Yeah, it's like the
most delicate little envelope surrounding a globe. If you're holding
the Earth in your hand, you probably wouldn't even notice it.
You know. Our oceans, for example, are like the thinnest
layer of water on the surface of a planet, and
the atmosphere is even more delicate. Right, Earth rocks, it's
(03:48):
mostly rocks, mostly rock, a little bit of a shine
to it, and a little bit of air surrounding it.
And that's different from other planets. You know, other planets
like Jupiter, there's like mostly atmosphere other place. Yeah. Well, yeah,
Jupiter is all gas. Well at its core, you know,
it still has a little bit of rock and there's
some metallic bits down there, but the the gaseous part
of it is, you know, it's a huge chunk of it.
(04:10):
So Earth is a little bit different from some of
the other planets, and so our atmosphere is especially thin
and especially fragile. It's like a very delicate tupe on
the top of a very bald head. Well, I guess
the question is why do we even have atmospheres? And
you know, as you said, we look around the Solar
System and we see that other planets don't have them.
They've actually lost their atmospheres, Like Marks, Yeah, Mars used
(04:35):
to have an atmosphere and now it's gone. And sort
of fascinating perspective on the universe is to imagine billions
of years ago when Venus and Earth and Mars used
to all be very similar. They had atmospheres, there's more
similar service temperatures, and now Earth is basically the only
place you would like to live. You know, Mars got
super cold and lost its air, and Venus got super
duper hot and its atmosphere is super dense. Well, it
(04:58):
kind of depends how hot you like it, Daniel. Nobody
likes it Venus hot except the Venusians. Yeah, exactly. I
wonder what it's like for them to take vacations on
the surface of the Earth. You know, they bundle up
even in southern California and you're like, oh my god,
this is so coolget but it's nine degrees on the
surface of Venus. They're like, wow, we can make snowballs
(05:18):
with wood water. That's crazy. But yeah, so it's it's
a big question how does the planet lose its atmosphere?
And I guess by consequence, how will Earth lose its atmosphere? Yeah?
Will Earth lose its atmosphere? It's just another question that
reminds you that on cosmic time scales, the Solar System
and the universe are quite dynamic. The Solar System didn't
(05:40):
always look this way. The Earth won't always look this way.
Other planets have changed. When you only look on a
hundred years or two hundred years time scale, things to
seem to move pretty slowly and you might be confused
and think that they're static. But things are changing actually
quite quickly on a cosmological time scale. Yeah, and so
I think scientists have lots of ways in which we
(06:00):
can lose our atmosphere. I mean, it's just this thin
layer of gas hanging on by gravity onto our giant
ball of rock. But recently there's been a study that
has a new crazy idea about how it could all
be gone. Yeah, it was a fascinating new idea and
it sort of adds to our understanding for how planets
can get rid of their atmospheres and also sort of
(06:21):
solves a mystery about exoplanets, and so do they on
the bark and we'll be asking the question, how can
the planet lose its atmosphere? You make it sound like
it just sort of like put it down, walked away
and came back and it was just gone, Like have
you seen my keys that were on the counter. In
terms of planetary scale time scales, it is sort of possible. Right,
(06:43):
one day, we could have an atmosphere. Next day it's
all gone. Somebody took it, right, and you're like, hey, Mars,
you didn't use to have an atmosphere, and then I
lost mine? Did you steal my atmosphere? That's another interesting question.
Oh yeah, you can planets steel atmospheres from each other
they get close enough, you know, like a black hole
sucking gas from a neutron star. Well, maybe we should
(07:04):
keep our social distance from Mars. That's right, that's right,
planetary distancing. Yeah, And so, as usually, we were wondering
how many people out there in the public knew whether
it was even possible to lose your atmosphere, or even
possible to lose it in the way that this new
study says that we could, and so I asked questions,
but in a sort of a new way. You see,
(07:24):
Irvine's campus is closed and we're all staying home to
stay safe, and so I reached down to the internet
to ask for volunteers to people who are willing to
answer random questions from a scruffy looking physicist. And the
internet didn't know you're a scruffy looking physicist. Did you
get more responses this this way? You know, my avatar
in the internet is the drawing you made in which
you made me look pretty scrappy looking. So I think
(07:46):
it's a fair representation. Oh man, Daniel, I am so
insulted that I did not draw that avatar reviews it
was another cartoon, is no, my avatar is the one
that you drew. I have one also from Saturday Morning
Breakfast Cereal that I is on Gmail. I see on
social media. It's your drawing of me podcasting some people,
you professor your favorite cartoons mean to other people it's
(08:09):
a different cartoons. But anyways, I've been cheating on you
with other cartoonists. Yes, anyway, I reached out to these
folks online and here's what they had to say. And
if you're interested in volunteering for a future round of
Internet random Questions right to us at questions at Daniel
and Jorge dot com and volunteer. I think next time,
(08:30):
maybe you should just pick up the phone book and
if you have a phone book, if the hymn exists
these days, but pick up something like a phone book
and just that all random numbers and see and ask
this question right, because we all love telemarketers, and this
is even better than telemarkers. It's telemarketers that make you
feel ignorant as a telephysicist. It could be a trade.
If you're like, Hi, I'm a physicist. If you have
(08:50):
any questions about the universe, I will answer it right now.
But first, all right, well here's what people had to say. Yes,
given the fact that Earth's atmosphere isn't do so great
at the moment, absolutely they can. Are magnetic field that
encompasses the Earth protects our Earth from the Sun's radiation
solar wind, and solar wind would blow the atmosphere away.
(09:12):
If we didn't have the electro magnetic field around the Earth,
then we would have no atmosphere, similar to Mars. I
believe they can lose their atmosphere if they're too close
to their Sun. I don't know. Really depends who was
living there at the time. I think definitely, Yes, can
be caused by an external can be a supernova, asteroid,
(09:34):
or internal might be losing your manic the field. I mean,
I know that we are constantly losing gases um without
space due to atmospheric escape. But whether we could lose
the whole atmosphere, I'm not so sure about that. I'm
not sure how that would work. I definitely think so.
(09:55):
If we know anything about the Earth, is we have
like a core that's that's causing us to have a
magnet at an atmosphere, and that protects us from like
the solar winds, and we have like theories and ideas
of how that amphair started. But I can definitely see,
you know, a situation where on some certain planet the
core stop spinning and the magnetism field stops, and elements
(10:15):
of the atmosphere can just be blown away by a
sun's wind, like a solar wind. Yes, I certainly think
it's possible for a planet to lose its atmosphere m Mars,
I think lost. It's a lot of the atmosphere once
it's cool cooled down on the magnetic field fight in
the Sun's blew a lot of the atmosphere away. Yeah. Absolutely, Um,
(10:39):
Mars lost its atmosphere. Yes, a planet can definitely lose
its atmosphere. All right, some pretty good answers there. Yeah,
a lot of people have different ideas about how we
can lose our atmosphere. Yeah, and these are all our
podcast listeners, and so they've probably heard us talking about
magnetic fields and solar winds and Mars. Do you think
they cheated? Know? I'm saying, I'm proud that our listeners
(11:02):
have learned something about astrophysics and space physics and that
they have absorbed some knowledge. They're better educated on average
on these topics than your random you see, Irvine undergrad
Welcome to Daniel and Jorge University, the only university is
still standing these days. But what I was interested in
and was surprised by it was by how people need
(11:24):
about all the different ways that we can lose our
solar systems. So maybe let's start with that. Daniels, walk
us through what are some of the ways in which
we can lose our atmosphere? Well, the first way that
people talked about, and the first thing that probably comes
to your mind. And the way that we've talked about
a lot in this podcast is that it can just
get blown away. Like the Earth is surrounded by this
ball of gas and it's held on by gravity. But
(11:44):
there are winds out there in the Solar System that
can help sort of sweep away particles from our atmosphere.
Sometimes it's hard to remember that, you know, we're just
a giant ball of rock floating in space, you know,
and that the air that we breathe, our atmosphere is
isn't it attatched to us. It's just hanging on by gravity.
So if something comes over and blows it away, we
(12:04):
could lose it, that's right. And this isn't like, you know,
a hurricane blowing the wind to knock over your ice
cream or anything most tortured analogy. Ever, the wind we're
talking about here is the Solar wind, and the solar
wind is not like the motion of the air on Earth.
It's a stream of particles and radiation emitted by the
Sun and so it's mostly protons, but it's also high
(12:26):
speed electrons and other stuff. And what happens when these
particles impact the Earth's surface is that they can knock
off particles of gas. Because these things hit it really
high speed. They hit it like a million miles per hour.
It's like point one percent of the speed of light.
And so it might knock the atmosphere particles and then
(12:46):
throw them into space and then we'll lose them. Yeah, exactly.
It's like a big billiard ball hits another one and
they both go flying off into space because it has
a huge amount of energy and it shares some of
that energy with these particles of our atmosphere, and then
they both have enough energy to escape. Okay, So that's
not good. And so that that can happen like if
there's a solar flare or something, or just it can
(13:07):
happen anytime. It can happen anytime. It's happening all the time.
Now during solar flares it can happen much more dramatically.
But we have a shield, right, We have this like
literal force field in space that mostly protects us from
this method, and that's our magnetic field. Because most of
the solar wind are charged particles, protons and electrons, their
(13:27):
ions were not like being shot by neutral atoms of hydrogen.
And that means that when they hit a magnetic field,
they bend. That's what magnetic fields do. And so our
magnetic field tends to deflect a lot of the solar wind.
It's like we have a little envelope and the solar
wind bends around us. But I heard there's a problem
with polar winds that like that might make them vulnerable. Well,
(13:50):
the magnetic field is not a perfect bottle, right that
we have north pole and a south pole, and the
magnetic field lines come out from the North pole and
go down to the South pole and want to charge
particle reaches the magnetic field line, it tends to bend
left or right depending on its charge. But they can
move along the field lines, and so what happens is
that some of them get blown out into space, a
lot of them, but some of them get funneled along
(14:11):
those field lines up to the North pole and the
South pole. And that's what causes the Northern lights and
the Southern lights is energized particles hitting the atmosphere and
making it glow. So basically the North Pole in the
South Pole get a lot more of this cosmic radiation.
You can get these plumes of gas leaving the atmosphere
on the North pole and the south leaving, leaving the atmosphere. Yeah,
(14:32):
just like when you know the solar wind, it hits
the atmosphere, blows off particles. Most of the Earth is
protected because of our magnetic field. But it's like we
have these weak spots in the North Pole, in the
South Pole, and then then then so there's gas leaving
the Earth. But then and then it doesn't come back.
It doesn't come back. You get these big plumes of
gas and that's because you get really high energy particles
hitting our atmosphere there where we're not protected and knocking
(14:56):
particles off, and then and then we lose them forever
because the Earth moves off forever, the Earth moves on. Yeah,
and so you take these pictures you can see during
solar flares especially, but all the time you see these
plumes of gas being leaked at the north and the south.
You know, like if we were the death Star, the
north Pole in the South pole is where you would want,
you know, to send your ex wing because that's our
(15:16):
little weakness. Maybe we are maybe we are the Empire,
Maybe we are the bad Everybody grows up to be
their parents, right, just like the rebels will grow up
to be to build their own death star, and then
they'll realize we're just like our father. Welcome to Daniel
Jorge process, Daniels daddy issues. But there's there's a bit
of a controversy here because you know, some people think
(15:38):
our magnetic field protects us, and that makes sense for
all the reasons we just talked about. It deflects the particles.
Some other scientists those say that maybe your magnetic field
actually sometimes it bends particles towards the planet and it
ends up focusing it like catches a huge larger swath
of the solar wind than you otherwise would like. Your
profile is much larger, focuses all those to shoot down
(16:00):
near the poles, and you end up losing more atmosphere
on these polar plumes than you would otherwise. So there's
a little bit of controversy of whether or not the
atmosphere is The atmosphere is definitely good for us, but
there's a bit of a controversy about whether the magnetic
field is in the end protecting us or or helping
us lose our atmosphere. I think most scientists think is protection,
(16:23):
but there is controversy and discussion in the field. In
the field bump bump. And you know, we should specify
that Earth has a nice magnetic field, which we think
mostly protects us. But if you look nearby to Mars,
for example, Mars doesn't have a magnetic field, and Mars
is totally vulnerable to solar winds, and every time there's
(16:44):
a solar flare, there's a huge flux of particles and
it blows off a lot more of mars atmosphere. Alright, well,
it sounds like there are a couple of ways in
which we can lose our atmosphere, and there's one more
way and then actually some pretty interesting seeing dynamics that
can happen depending on the size of your planet. So
let's get into that. But first let's take a quick break,
(17:16):
all right, Daniel, So our atmosphere is not a given
in our planet. We can lose it. It can blow
away by solar winds, but it can also sort of
explode out of our planet. Yeah, we're talking about impacts
from like tiny little particles. The solar wind is a
huge stream of tiny little particles. But you can also
get hit by bigger stuff, right, like an asteroid. Yeah,
(17:37):
you see shooting stars at night, that's a huge big
rock hitting our atmosphere. You know what happens when you
throw a rock into a pool as you make a splash,
and so if you throw a big rock into our atmosphere,
you make a splash and some of that splash drifts
off into space. Yeah, so it's another way we can
lose our atmosphere is we get we could get pelted
by rocks and those blow the atmosphere away. Yeah, you
(18:00):
can think of the atmosphere is like a cushion or
like a force field against rocks, right, because it slows
them down, it heats them up, it it immolates them
before they hit the surface, which is nice. And that's
why Earth doesn't have a lot of craters because we
have this atmosphere. But it's not forever, right, we can
use it up. If Earth get hits by a lot
of asteroids, then it depletes the atmosphere unless you're lucky.
(18:21):
You're unlucky enough to get hit by comets, which are
actually like cosmic snowballs that can deliver water or gas
when they melt in your atmosphere. And you know, this
is not a big factor today, but we don't know.
Some people think that this was a big factor in
how Mars lost its atmosphere not just to the solar wind,
but also to a lot of impacts. Well, I guess
(18:42):
it's kind of a runaway effect, like if you start
to lose it because of one thing, then you have
less protection against the other kind. Yeah, exactly. And the
estimates are that Mars lost more than two thirds or
its atmosphere due to either impacts or the solar winds,
and that solar wind effect is called sputtering by the
signs is and so early on they think that that's
that's the dominant way that Mars lost its atmosphere, but
(19:05):
today there's actually something else going on on Mars. Al right, Well,
it sounds like these are kind of maybe the basic
ways in which you can lose your atmosphere, but there
are sort of two new ways maybe that people are
thinking about, right, like depending on the size of your planet.
And one of them is kind of this interesting new
study that maybe planets can eat their atmosphere. That's right, Yeah,
(19:27):
we'll get to that in a little bit. But it
turns out that the way that Earth is losing its
atmosphere is mostly not due to polar wind or solar
wind or meteor impact it's something wait wait wait wait
wait wait wait wait, So we are losing our atmosphere.
We are losing our atmosphere. Yes, really, as as we
speak right now, we have less atmosphere right now than
before we started talking. Oh. Man, see I knew, I knew.
(19:50):
We're just blowing hot air here, Daniel. And that's making
it worse because the reason Earth is losing its atmosphere
is that it's literally just boiling off the planet it wow, Okay,
so step us three here. So if the planet is
too small, you're saying, the atmosphere can just gradually boil away.
And that means kind of like when you put water
on the stove, the particles that are on the surface
(20:12):
that you get energized and they fly away. Yeah, it's
that kind of what would Yeah, just like you know,
water evaporates from a puddle, right, our atmosphere can just
evaporate off into space. What is keeping the atmosphere on
the planet is only gravity. So if your planet is
too small, like, the smaller your planet is, the harder
time it has hanging onto its atmosphere. Like why does
(20:34):
the Moon have no atmosphere? Well, it's basically just too
small to hold onto anything. Even if we created an
atmosphere and shipped it to the Moon and put it
on there, it would just drift away in you know,
tens of years. Really, it would just drift away. It
would just it would hang out for a bit for
but eventually would it would all evaporate? Yeah? Well, the
same laws of physics that applied to you have also
(20:55):
applied to little particles. And just like how it's easier
to leave the surface of the Moon, take a run
and a jump and you could float off into space.
Where that's is that true? Okay? Well not really. I
mean you'd have to be super strong. You have to
go like two kilometers per second. So I guess if
you're iron man, maybe if you had any athletic ability,
for hey, you would be able to drop off off
(21:17):
of Mars the moon. Mars will be much harder to
jump off of the Moon might be possible, But the
same is true of little particles. Right, Earth is much
better holding onto little particles than Mars is. Then the
Moon is right and Jupiter much much better. And so
if your planet is too small, it's just hard to
hold onto your atmosphere. Interesting, but I guess you know,
(21:38):
if even if things float away, why wouldn't they just
come back due to gravity, because is it because we're
moving through space and we sort of miss it. Well,
once things float away, they don't come back. I mean
that's what escape velocity is, right. Escape velocities how much
speed you need to essentially be able to neglect the
gravity of that object. Like if you shoot a satellite
off into space and it reaches escape velocity, it doesn't
(21:59):
come back like voyage or whatever. Isn't just on its
way back. It's got some trajectory away from us, and
the gravitational power is just weakening and weakening and weakening.
And in the same way, if a particle has enough
velocity to leave the Earth's atmosphere, there's no reason for
it to come back unless it gets deflected, it bounces
off the moon or you know that alien mother ship
that's orbit orbiting quietly for the last few years. Okay,
(22:22):
so then it would help to be heavier because then
you can keep more of your atmosphere, that's right. So
lighter planets tend to lose their atmosphere, and we also
tend to lose different gases at different rates, like we
lose hydrogen on Earth and helium, but we don't lose
oxygen nearly as much because oxygen is heavier, and so
that's why it falls to the bottom. Well, that's why
(22:43):
Earth has very little hydrogen naturally occurring in our atmosphere
because morbid bubbles away, whereas the heavier stuff, you know,
xenon or oxygen or neon. That stuff is heavier, and
Mars doesn't have the gravity to hold onto the same
kind of things that we can, and so water vapor,
for example, on Mars can easily reach escape velocity, whereas
Earth has enough gravity to hold onto it because Mars
(23:05):
is smaller than Earth. Mars is a lot smaller than
Earth and it has weaker gravity. And so today the
dominant process for how Mars is losing its atmosphere is
not sputtering. It's not the solar wind. It's actually just
being boiled off. And Mars is still losing its atmosphere
at a rate of like one and a half kis
per second. We need to kind of like a put
(23:27):
a lit on it, I guess. So, I mean, if
we're ever going to move to Mars, we need to
provide a new atmosphere, and then we need to somehow
prevent it from just leaving, right. We talked about terraforming,
needing some sort of like huge new magnetic field to
prevent sputtering to prevent the solar wind from blowing that
atmosphere way, but we also need to sort of just
keep it somehow on there. Yeah, although of course the
(23:49):
process of atmosphere loss on Mars is very slow, so
your new atmosphere would stick around for a long time
before actually getting blown away. And so I don't know
if you've seen spaceballs or emper, but they have this
huge planet wide envelope to keep their atmosphere in place,
no waste. Baseballs foresaw this situation thirty years ago. Spaceballs
(24:10):
could foresee the future. I was trying to come up
with a quote from the movie, but I can't. That's ludicrous.
That's there, you go. And so that's how Mars is
losing it tout this yere now right, These hot gases
basically just boil off. The same thing is happening here
on Earth. So we're so we're losing our atmosphere. That's
shocking news. Every every breath we take there's less air. Yeah,
(24:31):
and it's not at a tiny rate like Earth is
losing three kilograms per second of hydrogen fifty grams per
second of helio and so this adds up, you know,
to like tons and tons of gases every year per
second three kilograms, how much is that? Like a teaspoon?
M a kilogram is a leader of water, right, So
(24:52):
we're losing three liters of water is worth of hydrogen
every second. Every second, it's just boiling out into space.
Where where are people not more alarmed? Well, you know,
we have a lot of hydrogen. Unfortunately, we're a big planet.
And it turns out that by the time we lose
most of our hydrogen, other things will have happened. Like
(25:15):
we think in about a billion years, by the time
we've lost significant atmosphere, you know, the sun will be
ten brighter than it is today. And at that point
we'll have other big problems. For example, you'll heat the
planet up and the oceans will boil and break into
water vapor, and probably all that hydrogen will also get
lost into space. But all right, we're talking a billion
(25:37):
years until we have to worry about Yes, exactly. You
don't need to worry about your kids having enough air
to breathe, or your kids kids or your kids, kids, kids.
It's it's a lot of generation. I think in that
time scale, wouldn't we evolve probably to breathe differently? Right
in a billion years to biology would probably adapt. Yeah,
perhaps we would. Perhaps we could breathe differently, or perhaps
we will have just left this rock and explore the
(25:58):
universe and found other places to live. Or we could
do you know, geoengineering and protect the Earth from getting
hotter and fabricate new new hydrogen, new oxygen and and
you know, curate microbe that can produce more oxygen as
we need it. Or something like a billion years is
a long time to figure this stuff out. I mean,
(26:19):
who knows. Maybe in a year, physicist bal end the
year the planet all by ourselves with plenty of eric despair.
You sound like you're rooting for that option, and I'm
just trying to so I'm just trying to prepare mentally, Daniel,
so it doesn't surprise me. I see. This is a
classic relationship technique. It's called pre assignment of blame. This
(26:41):
happens we agree it's your fault that we don't have
to argue about it. I see you're a big fan
of that, right, I'm a big fan of pre assignment
of blame. Yes, well, if it does happen, we'll blame me. Yes,
you can come to my house after I destroy the
Earth and shout at me with plenty of air to
shout at you. Fortunately. Right, So boiling off gases is
(27:03):
basically what's happening here on Earth now, and it's now
the dominant process on Mars also because the atmosphere is
much more dilute there, and so this is something I
wasn't even really aware of that this is a big
factor in how you can lose your atmosphere. And so
all of this is if your planet is small or
too small to kind of have enough gravity to keep
it all in, and so other things can happen if
(27:26):
your planet is too big. So we'll get into that,
but first let's take a quick break. All right, Daniel,
we're losing our atmosphere, but it's not something to worry about.
(27:48):
It's it's happening very slowly, maybe in a billion years,
but by then we have other things to worry about.
But there's a new study you were telling me earlier
that talks about what can happen if your planet is
too big, Because apparently you can lose your atmosphere in
other ways if you are to be Yeah. Well, first
of all, the title of this study is awesome. It's
called Why Planets Eat their Own Skies and will include
(28:10):
a link to the study in the episode of information
that you can read it for yourself. It's from Stanford. Yeah,
not a bad school. I hear it's a junior college.
So I hear they give PSDs to cartoonists as well,
So yeah they do. It's been on a down cycle
ever since, then, said the Berkeley graduate. Of course, Man,
go cow, go col Cow. How many football games have
(28:32):
you been to with Cal Danny? Oh, I've been to
a lot. Yeah, No, football games are a lot of fun.
Were a little encapsulation of the old bear rivalry right
here on Oh man, it's it's scientists versus engineers. It's
Cal versus Stanford. What else, bananas versus not bananas. That's right.
We satisfy all of your rivalry needs here on the program.
You know this. Lots of people contributed this study, not
(28:54):
just from Stanford. It was led by Edwin Kite at
the University of Chicago, and they noticed something really interesting,
they know, is that when we see other planets in
other solar systems, which is now this thing we can
do right as we can look at planets going around
other stars, and we can measure two things about those planets.
We can measure their mass and we can measure their radius,
(29:15):
and that tells us like roughly what's going on in
those planets. We can tell like how dense they are
based on the mass and the radius information. And so
the radius we can tell by looking at it, but
the mass we tell by either orbits or something. Yeah.
You can tell the radius by like how much of
the star's light is being blocked, and you can tell
the planet mass by how much it makes its star wiggle. Oh.
(29:37):
This is a study of exoplanets out there in space.
And what they noticed is that they see a bunch
of planets sort of Earth sized, and they see a
bunch of gas giants. But there's kind of a gap,
like you go up to about like three times the
size of the Earth what they call, you know, Neptune
sized planets, and then bigger than that, there's like a gap.
(29:58):
There's no like planets in between Neptune size and Jupiter size,
and naturally you would expect sort of like you know,
a big continuum. You expect like a smooth distribution that
their planet is everywhere. Yeah, like a big rocks, smaller rocks, rocks.
But you're saying that there's a gap there. There's just
cut off before the gas giants and after sort of
the Neptunes or the super Earth's. And they were trying
(30:20):
to understand why, and it turns out that they came
up with this cool explanation that if a planet gets
big enough but not too big, and it has a
rocky surface, then that rocky surfaces like lava, so you
have like flava flowing on this hot surface, then it
can actually absorb its own sky. The gas in the
atmosphere gets sucked into these oceans of liquid magma because
(30:42):
of the gravity. Well, the gravity is certainly part of it, right,
But that's not happening on Jupiter, right. Jupiter also has
a lot of gravity but still has vast atmospheres of gas.
But it's something about this chemical interaction between the liquid
magma ocean and the gas in the atmosphere. Oh, I see,
And you're saying doesn't happen on Earth because we don't
have magma and lava on our surface, because we are
(31:06):
what not hot enough or not heavy enough. Both you
need the liquid magma on the surface, and then you
also need more gravity because you need the pressure. You
need the gas to be like squeezed down onto this
liquid magma that can sort of force it into it.
And so they find that basically these planets just eat
their atmosphere that stops them from growing bigger. Like, the
reason Jupiter is so big is because a huge part
(31:28):
of it is its atmosphere. Right on Earth, point to
five of the radius of the Earth is the atmosphere.
Jupiter is like a third or a half of Jupiter
is atmosphere. Okay, so you're saying that, like, we see
planets out there, and they get bigger and bigger in
terms of the size, but we don't know how big
the rock inside of them are, but you sort of
see the size. And so at some point if the
(31:50):
Earth suddenly grew in rocky nous in size, you're saying
that at some point the first of all, the surface
of Earth would turn into lava or that's not necessary,
it's necessary for this to happen. I think in these larger,
rockier planets, it's hotter, right, is more pressure because there's
more gravity and so the surface is more likely to
(32:10):
be magma, and then that pressure squeezes the gas down
onto the surface of that magma and basically forces it
in and it gets it dissolved in into the lava
I see, into the like it traps. Yeah, so you
get like carbonated lava, like sparkling lava, sparkling lava. It's
(32:31):
like mountain dew, but literally made out of mountain. There's
this whole new beverage trend, you know, sparkling water and
sparkling this and sparkling that. Nobody has thought about selling.
Sparkling lava, sparkling lava. Well, there you go. That's that's
the new market. Yeah exactly. And so basically it forces
you know, the gravity and the pressure forces the gas
into the rock, and that keeps the planet from really
(32:52):
growing inside because when your planet, you get to count
the extent of your atmosphere as part of the planet. Right,
And so where are the planets that are just bigger rocks?
Why is there a gap or are they saying that
suddenly at some point the planets grow in size because
of their atmosphere, not because of the rock. Planets grow
in size because of their atmosphere. Like the way to
get a really big planet is to have a small
(33:16):
icy core and then accumulate a lot of gas. You
accumulate too much rock, then you can't really grow anymore
because you can't attract anymore gas. But why can't I
just have a Jupiter size rock floating around the Solar System?
You know, I didn't say you couldn't. Go ahead, like
do whatever you like. You can, you can, you can,
(33:36):
but you know, there's just not that much rock. Like
most of the material in the Solar System is gas,
So if you want to get big, you got to
include that in your budget. So like, if you just
look at rocky centers, they maybe taper off, like they
get bigger, bigger about the Earth, the size of Earth,
three times the size of Earth, and then they don't.
They don't. You don't see them get bigger. But you
do see planets get bigger because then they start to
(33:57):
accumulate atmosphere. Yeah, that's right. But if your rocky or
is too big, then it can prevent you from growing
a big atmosphere because it can suck it into the
liquid magma in the core. I see, all right, So
probably the bigger planets we see out in the universe. There,
they don't have a rocky center bigger than ours. They
have smaller rocky nuggets inside, but they're bigger because of
the gas, and adding enough gas can turn any rocky
(34:20):
object into a gas giant. We don't really know the
size of the rocky cores and some of the big
gas giants in exoplanet systems, but most of the volume
is gas. That's why they are bigger. And if you
look at the internal structure of Jupiter, it has a rocky,
icy core, but it's pretty small. You know, it's not
enormously vast. After that, it's like metallic hydrogen and all
(34:41):
these things because of the high pressure and then vast,
vast clouds of just gaseous hydrogen, and that's the way
to go. But you know, there's even still a lot
of questions about how planets like Jupiter form, Like how
do you get so much gas accumulated. You need to
have some sort of rocky core that forms rapidly enough
that has time to accumulate all that gas because the
(35:01):
gas is pretty light, and so it takes a while
for gravity to gather that together. So we're still learning
about how all these planets form you know, in ten
years we could have a lot of new ideas for
how any of these planets form. And I think we
talked on another podcast about like should Jupiter sized planets
form always in the outer Solar System or only in
the inner Solar System? You know? Can they move back
(35:24):
and forth? And so we're learning so much about our
planet and other planets and how it all puts together
just by studying other Solar systems. It's it's a fascinating time.
And so they call it eating your atmosphere, eating your sky,
because in a way, you're sort of like absorbing the gas, right,
Like if your rock is big enough, it sort of
absorbed the atmosphere. Yeah, it sucks it into itself, and
(35:45):
it prevents it from getting bigger. It's like you sucking
your stomach in, right, it keeps you from from looking
larger than I don't think how do I think that
works in real Physicsdanu, I'm surprised. All right, Well, it
sounds like we should once again be lucky that we
are just the right size, because if we were heavier,
if the Earth was bigger, we wouldn't have an enmoshere,
(36:05):
or if we were smaller, we wouldn't have an atmosphere either. Yeah,
it's just another way that the Earth seems to be
at this weird sweet spot. Right. We're just the right
distance from the Sun, we have just the right amount
of atmosphere, we have just the amount of stuff to
hold onto that atmosphere, but not too much. We're like
far enough away from the center of the galaxy to
not be fried, but not so far away. But that
(36:27):
there's no planets out there, and so it's it's amazing
how many ways we seem to be lucky, you know,
and it raises questions about about how many how many
other planets are out there that could have as many
lucky factors. Yeah, you can be too big or too small.
You got to be just right, all right. Well, we
hope you enjoyed that. And maybe when you go out
(36:48):
there and breathe this new clean air that we're all
enjoying because of where we are these days, um, think
about how precious that breath of air is. In how
it's we were a little bit different in this planet,
we wouldn't have that nice fresh year and count your
breaths because you only got about a billion years left
to enjoy them. Depending if Daniel ends Universe and thanks
(37:10):
to my friend and colleague and geologists Steve Davis for
sending me to study and the idea for this podcast. Yeah,
if you are a physicist out there listening to this
program and you see a fun paper, send it to Daniel.
I will definitely look forward to hearing again from him
about it. But we want to hear about all your
thoughts and all your questions. So if you have a
question about anything going on in the universe or a
study you see on the internet, please write to us
(37:30):
at questions at Daniel and Jorge dot com. We do
love our listener mail. See you next time. Thanks for listening,
and remember that Daniel and Jorge Explain the Universe is
a production at by Heart Radio. From more podcast from
my Heart Radio, visited my Heart Radio, papp Apple Podcasts,
(37:53):
or wherever you listen to your FILI shows. No
Hosts And Creators
Daniel Whiteson
Kelly Weinersmith
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