Today we’ll be looking at a number of concepts
in terraforming, the field which looks at how to make other worlds more hospitable to
humans and other Earth life by making those worlds more Earth-like. If you’re a subscriber to the channel you
probably know the videos on the channel fall into two basic categories… the long ones…
and the incredibly long ones. This one is going to be of the second type,
because it is a long subject, so now probably would be a good time to grab a drink and a
snack. Also if you’re not a subscriber to the channel,
you can become one just by clicking the subscribe button in the lower right corner, and while
you’re down there you probably want to turn on the closed captions for the video. I can be a bit hard to understand even when
I’m not spouting technical terms and we will have a lot of those in this video. Since this is a summary video I will be including
both some links to other sources expanding on the subject in the video description as
well as referencing some other videos by myself and others, these we will usually appear as
thumbnail with a yellow box around them, most will appear again at the end of the video
but you can click on these any time and it should just pause this video and open that
one in another window. Just as an example, while we’ll talk about
Mars a great deal in this video it’s not our real focus and if you’re interested
in the nuts and bolts of getting to Mars and starting terraforming with only modern technology
Shaun Moss’s “The International Mars Research Station” is definitely a good place to get
started, and the attached video of his TED talk is a great introduction to getting to
Mars. Another person I’ll be referencing a lot
is Martyn J. Fogg, and if there’s anyone who knows more about terraforming them him
I haven’t met them. A link to his website on terraforming is below
in the video description and he literally wrote the book on the subject. We also all tend to hang around the same online
forums discussing these kind of subjects, so while I’ll try as always to answer any
questions you have in the comments section you may want to give those a try too. They tend to be friendly stomping grounds
for scientists, science fiction writers, hobbyists, and people just curious about the ideas. So one of the first things we need to discuss
is ‘what is terraforming?’ The word is plain enough, terra forming, terra,
Latin for Earth, or earth-forming. Historically it first popped up in a short
story by Jack Williamson called ‘Collision Orbit’ back in Astounding Fiction in 1942. This was the same story that saw the first
use of Anti-Matter in science fiction. Williamson also coined the term ‘genetic
engineering’, and probably tops the list of greatest and most influential science fiction
writers most people have sadly never heard of. In his story, the example of terraforming
is an asteroid just over a mile across with an artificial gravity field in it, so originally
it wasn’t a planet or even a large asteroid or moon. I stress that because ‘making a planet like
Earth’ tends to be the concept and image most think with terraforming but it’s not
limited to planets and hasn’t been since Day 1. Genetic engineering is of interest to us too
because there’s an alternate approach to terraforming, or one used in tandem with it,
sometimes called ‘bioforming’, and that’s where you aren’t changing the world to be
more Earth like to support Earth life but changing Earth organisms to be able to live
on an alien planet. Terraforming and Bioforming are two sides
of the same coin in some respects, and often assumed to be used together. Still, you often have people very opposed
to terraforming for wrecking an alien environment, inhabited or lifeless, or opposed to bioforming
because it involves genetic engineering. This isn’t an ethics class though, and it
also isn’t one on bioforming. Nor am I qualified to talk about it in real
detail since I’m not a biologist, so we won’t be discussing it in detail. Another term in common usage is Planetary
Engineering, a fairly straight forward term and in many ways better than terraforming
since its maybe a bit more on the nose. You’re engineer planetsing for habitability
by Earth life more than you’re trying to make the planet a close copy of Earth. You’ll also occasionally hear the term para-terraforming,
and this usually means just building domes on a planet. If taken to the extreme, so that the entire
planet is domed under, we call this a Worldhouse. Essentially a world-spanning greenhouse. Also paraterraforming is often used to reference
the first steps in most terraforming processes, where you’re setting up small living areas
like domes on Mars or floating cloud habitats on Venus to live in while you’re making
the planet more livable. If you’ve seen my original Megastructures
video or any of the follow ups discussing rotating habitats those are sometimes considered
para-terraforming examples too, especially if embedded in something like an asteroid. They replicate the conditions on Earth much
more closely than you could plausibly get on Mars for instance, because you can tailor
them to whatever you want. ‘Want’ is the key word there because not
everyone considers certain differences between Earth and another world as important to fix. They might not care, for instance, if the
gravity is a bit heavier or the day is 30 hours long. With rotating habitats you’re pretty much
able to tailor everything, but even though the original example of terraforming in fiction
was a small asteroid, building giant cylinder habitats inside asteroids normally isn’t
considered terraforming so we’ll look at those more properly in the Megastructures
videos. So Terraforming itself is a pretty simple
concept, make a place more like Earth, but which factors are most important? In which ones is a close approximation to
Earth okay? To a degree it’s an Eye of the Beholder,
Your Mileage May Vary kind of thing, especially when it comes to setting which differences
are priorities and how close to Earth is close enough. So what are the big differences that need
to be changed to make a world like Earth? We’re not focused on Mars or Venus but let’s
take a look at some of the key differences both have with Earth, in this chart. In some ways it’s a very Goldilocks, not
too hot, not too cold issue, too much air, too little air, but for neither is it what
we can breathe. You need to make them warmer or colder, so
how do we do that? You need add breathable air and remove unbreathable
air. How do we do that? Venus’s Gravity is just about right, Mars
has a Day Length that’s just about right, but its gravity is too low and Venus’s Day
Length is almost a year long. Can we change those? How? Can we even change things like gravity, or
year length or a planet’s axial tilt? The simple answer is that any planet, any
moon, any asteroid can be made very like Earth in most ways, how close depends on which quality
we’re talking about, what tools we have, how much of the tools we have, and how stubbornly
persistent we are at the goal. Even the most basic terraforming takes centuries
and must take centuries, as we’ll see, even if you’ve got something really neat like
near limitless energy or self-replicating robots. The good news is humanity has an impressive
track record of being stubborn and has been known to spend whole centuries working on
projects. From the pyramids and cathedrals to highway
systems, canals, and walls, we have shown a willingness to dedicate massive resources
and long term efforts to getting projects done, and we did most of those back when people
lived about half as long as we do now and with far less excess wealth to devote to them. People often wonder if we’d be willing to
devote centuries to projects like Terraforming and for my part, though I often get accused
of excessive optimism, I think the answer is a clear yes. So let’s start by talking about those three
most basic qualities a planet needs to have. The right temperature for life, the right
atmosphere for life, and water. Water’s actually quite easy, on the surface
anyway. It’s one of the most common molecules in
the universe because its constituents, hydrogen and oxygen, are the first and third most common
elements in the Universe and it’s a very simple molecule to form. Ironically in most cases it’s coming up
with the Hydrogen, the most plentiful substance in the Universe, and not the Oxygen, which
is the problem. Hydrogen tends to be a touch rare on rocky
planets, as is helium, the second most common atom. The reason for this is simple enough. Planets we’re interested in are hot, and
regularly hit by ionizing radiation, asteroids and other items that tend to help evaporate
atmospheres into space. I’ve mentioned in the past that people tend
to mistakenly assume places like Mars and our own moon have too little gravity to hold
atmospheres, and we’ll talk about that briefly in a little bit, but the key thing is that
the various means by which matter escapes from atmospheres, regardless of the various
physical mechanism being used, relies very heavily on the mass of the molecule. Hydrogen and helium molecules are quite light
and fly away quite easily. Hydrogen unlike helium can bind to other,
heavier atoms to form heavy molecules so even though it’s lighter as an atom than helium
it often remains in larger quantities. Still it will often find itself free from
molecular bondage to heavier kindred, either paired up with another hydrogen atom or kicked
free entirely by radiation in the upper atmosphere and can then be sent shooting off into space
much more easily than things like oxygen. Oxygen, being heavy, stays around, but actually
disappears from atmospheres in the other direction by getting sequestered into rock. Most rocks, be it sand or limestone or granite
or metal ores tend to be composed in large part of oxygen. If there’s not a lot of water or ice already
on a planet you can always get more oxygen by taking it out of those rocks. That’s quite energy intensive. It is so energy intensive that even if you
covered every inch of a planet with efficient solar panels that did nothing but cook oxygen
out of the rock by melting or electrolysis it would still take anywhere from many centuries
to many thousands of years to collect all the oxygen you need for even modest shallow
oceans and breathing air. Of course you also have to worry about keeping
that oxygen, if removed from dirt, from going right back into it. Separate iron oxide, rust, into iron and oxygen,
and the iron will just rusting again and sucking the oxygen back in. Still you can get oxygen out of it to make
air and water. But you’d still need hydrogen for water
and odds are you’ll need to bring it in from elsewhere. If the planet had large quantities it would
already have oceans. Now you could opt just to bring in water directly
as it is plentiful in the form of ice in the outer solar system and likely would be in
any solar system, but it’s debatable if this is much of cost saving exercise since
most of the weight of water is oxygen, nearly 90%, and moving that oxygen millions of miles
costs energy in a similar range to cooking oxygen out of rock. It also matters where you’re getting that
energy from. Planets we’re interested in terraforming
tend to be good places for solar power, places where ice is plentiful are obviously not. If they got a lot of sunlight they wouldn’t
have ice. The flip side is that there are places in
this solar system where hydrogen exists in massive quantities by itself instead of as
water or methane or ammonia, but these tend to have massive gravity wells. Gravity is never your friend when trying to
ship matter in bulk. We’ll talk about moving hydrogen when we
talk about air, since it’s a similar process for getting nitrogen, another thing not in
much supply on Mars for instance. Before we move on to that we’ve two other
big concerns that often get overlooked in terraforming where water is concerned. First, while Mars for instance isn’t a great
example because its crust is both similar in composition to Earth’s and has previously
had water on it, we need to remember that water dissolves stuff. Like continents. The rate water evaporates at, and therefore
rains at, isn’t too well related to the amount of it now on your planet in your early
terraforming days. Long before you’ve swathes of ocean miles
deep you’ll have rainfall, lots of rainfall, because a thin puddle of water a few inches
deep evaporates water just as fast as deep trench with the same surface area. So long before the planet has anything like
the volume of water Earth has you’ll start getting serious amounts of rain. Especially if there’s not much atmosphere,
because water evaporates quicker in low pressures. Now lots of rain is good. Except rain dissolves dirt and there won’t
be any plant roots helping prevent erosion since plants need rain. And without pre-existing rivers you’ll end
up with floods and building destroying waves of mud. So terraforming requires you to either get
an atmosphere in place before there’s much water or requires you go out cutting spillways
and reservoirs all over the place. If you know the kind of engineering muscle
it take to keep the Mississippi river in check, or to prevent soil erosion of farmland, think
of that and multiply it by a thousand. That other issue is that you don’t just
want to keep toxic heavy metals out of your soil and water, but you also need to make
sure some other things are dissolving into it. Like salt, if you want seawater. Earth’s crust has a lot of sodium in it,
2-3%, similar to the salinity of our oceans. Sodium and Chloride though not terribly rare
aren’t going to be abundant on every planet’s crust and aren’t particular common in asteroids
either. So water, which initially seem simple, turns
out to be a bit more complex than we first thought. How about air? We’ve already mentioned one way to get air,
baking it from the rocks, or electrolyzing it from water if that’s very abundant. But that’s just oxygen. We need nitrogen too, for plants to live. Now on both Venus and Mars nitrogen is the
second most abundant component of air, right after carbon dioxide. But for Mars the atmosphere is quite thin
so that doesn’t equal much, only a small fraction what is needed, and it doesn’t
appear to have it in abundance in the rocks either. If we’re wrong on that, and we may well
be, then we can cook it out of the local rock. In Venus’s cases we have the reverse problem. Venus may only have about 3 or 4 % nitrogen
compared to Earth’s own nearly 80%, but Venus’s atmosphere is nearly a hundred times
more massive than our own and Venus is a bit smaller than us too, so it has few times more
nitrogen in its air than we need for an Earth-like atmosphere there. Now you need some more for in the dirt and
plants themselves but not much. So Venus is one place we can get Nitrogen
for Mars at, the other is Saturn’s moon Titan which has an atmosphere composed of
almost pure nitrogen and the rest mostly methane which is quite handy itself for terraforming
cold worlds like Mars because it’s a greenhouse gas and has a lot of hydrogen in it too. How do we move air from one place to another? How do we move hydrogen from a place like
Jupiter to Mars or Venus, which itself has very little hydrogen? Just imagining a giant ship moving billions
of tons from place to place is probably a bit unrealistic. A million tons of air at normal pressure takes
up about a cubic kilometer, and even a ship that big would need to make a few billion
trips to move a planet’s atmosphere. The biggest oil supertankers on Earth can
haul a few hundred thousand tons of oil, and if you were thinking of things that big, making
the round trip once a year for a thousand years, you’d need ten million of them in
service. Even when we’re talking about redirecting
comets at a planet we’re talking about needing hundreds of millions if not billions of them. If you’ve seen any of the Megastructures
videos on this channel you might be thinking of a few solutions. The first three episodes of that deal with
nothing but moving huge amounts of matter off of planets cheaply. And it needs to be cheap, for context if it
were costing only one dollar per ton you’d still spend over a quadrillion dollars, which
is more than our entire planet’s GDP for a decade. Don’t have many illusions about terraforming,
people often talk about how we can do something, then just sort of handwave how that goes from
in the lab to being done at the planetary scale. With the exception of para-terraforming, and
one of the reasons why it’s so popular, there’s not a single planet we could terraform
without having massively improved automation and power sources. Sometimes I’ll mention heating planets with
orbital mirrors the size of planets themselves, or rather many mirrors with a total size on
that scale, and people will object on the grounds that doing something like that would
be ludicrously expensive. Then they’ll turn right around and suggest
moving planet’s worth of air and water. Those planet sized orbital mirrors will be
thin sheets a few millimeters in thickness tops, so a planet sized one would not even
mass a trillion tons. Whereas Earth’s atmosphere weighs about
5,000 trillion tons. That doesn’t mean it can’t be done. The resources needed are in this solar system,
Jupiter has many times more hydrogen than Earth has rock, Titan and Venus both have
abundant nitrogen, and oxygen is plentiful everywhere in the inner solar system except
on Mercury. On a place like Titan we’d likely go the
mass driver route, filling metal pods about as thick as soda cans and as big as semi-trailers
full of high-pressure gas and just firing them off, one after another, from the surface. Titan’s gravity is so weak compared to Earth
that we can build structures miles long and high peeking out over the top of the atmosphere. Coming up with the metal for the structures
and pods isn’t too hard, Titan has a rocky metallic core and digging very deep on low-gravity
worlds is actually quite easy, especially when you’re mostly just melting your way
through ice until you get to the rock, and Saturn has other more rocky moons that could
be sources. Mass drivers are perfect for a place like
Titan, as are space elevators, except that Titan doesn’t get much sunlight for solar
power, only about 1% of what Earth gets per unit area, and isn’t likely to be abundant
in fissile materials like Uranium. So Titan is only a good source if you’ve
got Nuclear Fusion. Without that you might still be able to run
mass drivers, solar can be concentrated with thin mirrors and lenses for instance, but
it wouldn’t be easy and we’re talking about shifting trillions of tons of matter
to another planet every year just to get enough to finish the job in a timeline of centuries. If we’re imagining those pods, say containing
ten tons of nitrogen gas, you’d have to launch one every second for thirty million
years to get about the right amount of nitrogen to Mars. That means needing a lot of mass drivers and
a lot of energy to get it done on any timeline worth doing and the entire solar energy budget
of Titan if we wrapped the thing in solar panels is only around a billion megawatts,
compared to Earth’s own 200 billion megawatts. Even with very efficient conversion of that
light straight into kinetic energy you need several thousand megawatts per ton of matter
flow you’re trying to get into space and off to Mars and that level of efficiency is
not too realistic. But if you achieved that you could move enough
nitrogen to Mars in several centuries to get the job done, lower efficiency, longer timelines,
and more panels and mirrors all needing maintenance and needing it for longer. Needless to say nuclear fusion makes things
much easier if you’ve got it, and it makes terraforming Titan much more plausible too,
which you might want to do too if you if you’re planning to hang out there for centuries pumping
off gas anyway. For Venus and Jupiter the game’s a bit different. You could put floating mass drivers in the
upper atmosphere, shooting nitrogen and carbon dioxide off Venus, and hydrogen from Jupiter,
but for Jupiter you have the advantage that it’s got a very strong magnetic field, and
if you’ve seen the video on skyhooks you know that those ideally operate by regenerating
their momentum by using electricity to shove off a planet’s own magnetosphere using a
process called Electrodynamic Tethering. So they can rotate down, drop off empty pods
at floating refineries, pick up full ones, fling them off to their destination, and end
a little lower in the process from friction and momentum transfer. They then shove off the magnetosphere to get
back up. Hypothetically you can mine Jupiter’s moons
for the metal for the pods, fling them to Venus, which catches them, steals momentum
in the process, empties their hydrogen into Venus’s atmosphere and fills the pods with
nitrogen that then get flung to Mars. And rotating skyhooks – often called rotovators
in this context – can still work on Venus since it does have some magnetic field and
there’s abundant solar power, and other ways to regenerate momentum too. But since there is it might be easier to just
use floating mass drivers. When it comes to floating structures, ones
being held up same as a blimp, a thing to remember is they can be very big and that
the top can be higher than the bottom so you could build a mass driver where the refineries
and launch point are lower down where the air is thicker while the exit point and solar
panels running it are up higher where there’s less air to cause drag on the projectile and
attenuate sunlight. We’ll look at Venus in a bit more detail
in a moment but I want to give a quick mention to Wormholes. Wormhole are obviously another way to move
mass fast, same as artificial gravity is a great way to adjust a planet’s gravity to
Earth-normal and nuclear fusion is a great source of cheap and abundant power. Of the three of these only the last, Nuclear
Fusion, appears has much chance to appear in the near future for us, and personally
I don’t hold out much hope we’ll ever have the other two. This video is about all the options though
so it wouldn’t be right to skip mentioning them. Fusion is quite likely to be available for
us to help in Terraforming, and will help a lot, but we’ll try in this video to address
options without using it. Ditto, nanotechnology or genetically engineered
organisms able to eat rock and spit out gas on an otherwise airless world would be very
helpful too, but none of these things allow super-rapid terraforming because of Thermodynamics. As we discussed when talking about nanomachines
and grey goo in the Fermi Paradox Apocalypse How video, every mechanical process, or chemical
or electrical process, generates heat. When you start running the numbers on this
stuff you find that planetary transformations like terraforming usually generate way more
heat regardless of the method than the planet gets in several years of Earth-like sunlight
so you can’t go too fast or you’ll melt everything including your machines in all
the excess heat. Even with things like wormholes you have to
consider how all that mass transfer is going to effect pressure and heat. We won’t look at these options much though
because not only are they outside the realm of the near future but they also make the
subject pretty boring. If you can dump a vial of nanomachines on
a planet and just come back to it ready made in a couple of decades there’s not much
to discuss. Similarly if you’ve got functioning wormholes,
then you can not only open them to places with abundant water or air, and open them
to places with pre-existing industry to make transport of people and infrastructure easy,
but you could also open them near or maybe even in your own sun, which is obviously a
pretty handy way to get more light on Mars or more hydrogen on Venus and would give you
a power source on at least on par with nuclear fusion. Also while discussing nuclear fusion I’d
be remiss if I didn’t mention the one working form of nuclear fusion we currently have,
and its application for terraforming. Thermonuclear bombs, or fusion bombs, have
a long history with terraforming contemplations. You can use them to blow off the excess air
on a planet or rapidly cook air out of a planet’s soil. Needless to say you’ve got fallout issues
but the bigger bombs generate almost all their energy from fusion which isn’t a big radioactive
fallout generator anyway. A lot of people flinch away from terraforming
Mars by starting with a nuclear bombardment that would eclipse the worst Cold War scenarios
but it is a lot more manageable than you might think in terms of irradiating a planet beyond
habitability. Truth be told it gets a lot of mention in
terraforming conversations exactly because it is such a good approach in spite of the
radiation issue. And there’s really just no such thing as
non-destructive terraforming, that’s why there’s such a bioforming versus terraforming
ethics debate. Let’s get back to Venus. Often overlooked in favor Mars it’s easy
to forget that Venus has a lot more going for it in some areas. Its gravity is nearly the same as Earth’s,
it’s got plenty of nitrogen, and it’s got plenty of light. Those last two are actually the big problem. Venus is very hot and its atmosphere is nearly
a hundred times more massive than Earth’s and it’s mostly carbon dioxide, which is
heavier than nitrogen and oxygen air. Short term, in the para-terraforming sense,
that atmosphere is so thick you can float normal air in it. Conveniently in the upper atmosphere of Venus,
by the time the pressure drops to earth normal the temperature also drops to something comfortable
too. At about 200 miles up you can float a balloon
made of normal human-breathable air at normal human temperature and pressure and still have
lifting power since its less dense then carbon dioxide. Now that needs to be in a metal shell and
support some weight but if you’re not clear on how lifting power of gases works it’s
pretty straight forward. You just take a given volume of your local
air and figure out its mass for that pressure and temperature, than subtract the mass of
an equal volume of your lifting gas at the same pressure and temperature, or at a higher
temperature for a hot air balloon for instance. Whatever mass is left over is the mass you
have to work with for your shell holding the gas inside and for your payload. The advantage of using normal air is that
you can use the entire volume of your object instead of attaching something separate like
you need to do with helium, and you have a reserve of breathable air. If you’re curious, for air and carbon dioxide
that difference is about 700 grams a cubic meter or about 44 pounds for a 10x10x10 foot
cube of a thousand cubic feet. So if you made an aluminum balloon, for instance,
200 meters in diameter, that gives you a volume of about 4.2 million cubic meters or about
3 million kilograms or 3000 tons of lifting force. It also means your shell is 125,000 square
meters and a millimeter thick sheet of aluminum weighs just under 3 kilograms per square meter. So if you were willing to devote half you
lifting mass to making the shell it would be about 4-5 millimeters or a fifth of an
inch thick. Now if you double that diameter you get 8
times the volume and lifting force, but only increase the surface area by a factor of four,
so you can get double the thickness on your shell or use the same thickness but only needs
a quarter of your payload to be the shell, not half. And that keeps going, as volume always rises
faster than surface area, so you can make some fairly impressive floating structures
on Venus, especially if you’re bringing in hydrogen which has even more lifting power. You could have whole floating continents,
like tied together rafts. This doesn’t work as well on gas giants
because they are made of hydrogen and helium so your breathing air has to part of your
payload, not your lifting gas, which would probably need to be hot pure hydrogen to be
even a little feasible. But it works on Venus, and worlds like Venus,
just fine. Problem is, what next? Well there doesn’t need to be a next necessarily,
same as you could just dome over Mars as a Worldhouse you could swath all Venus in floating
cities and even if you took all the nitrogen away, to use on other worlds, you’d actually
float a little better since it would be make the air outside your balloons a little denser
by removing it. But if you want to live on the surface and
slowly remove the super-dense atmosphere you’re going to eventually need transition out from
those floating habitats and that would probably mean supporting them from underneath with
pylons. For Venus those would need to be a couple
hundred miles high. If you saw the video on mass drivers and launch
loops you might recall at the end we discussed space fountains, giant thin structures that
can be built to heights far beyond what normal building materials allow. These would be an example of how you could
keep holding those habitats up while you made Venus’s atmosphere thinner and cooler. How would we do that? Well one option is to just transport it away,
bit by bit. Another option for cooling the planet is to
erect giant solar shades between Venus and the Sun. At the kind of pressures Venus’s atmosphere
has, by the time it hit about Earth Temperature the Carbon dioxide will reach its supercritical
point and start falling down and forming seas of carbon dioxide. It’s only at Earth pressures that carbon
dioxide has no liquid phase, going straight from dry ice to gas. At pressures five times higher than Earth’s
it forms a liquid, and Venus’s pressure is ninety times Earth’s, not just 5. So you get seas of carbon dioxide. You just keep shading the planet then, dropping
its temperature below Earth’s by not letting much or any sunlight in. Soon it will drop to temperatures too cold
for life, and at 217 Kelvin, or -70 Fahrenheit, those oceans will freeze into dry ice. And you just pave over them. When Paul Birch ran the calculations on this
cooling time, it worked out to be only a couple hundred years. You could speed even that up by erecting cooling
towers rising from the lowest and hottest places to higher places. So for instance our floating cities could
wait till the atmosphere cooled enough near the ground to build towers, space fountains,
to hold them up and use those to pump heat off Venus faster. While you’re cooling the planet you steal
nitrogen from the air and bring in water or hydrogen to make water. In a couple hundred years you pave over the
dry ice frozen seas and then remove some but not all of your solar shades to bring the
temperature back up to Earth normal. The 1991 paper by the late Paul Birch, “Terraforming
Venus Quickly” goes into more details on floating cities, atmosphere cooling, solar
shades, and the works. It’s fairly short and Birch had a knack
for putting in all the technical details while still making papers readable without understanding
those, so I do recommend it and it is linked below. Now giving Venus a day as long as Earth’s
is another matter and we’ll come back to that later. First I want to talk briefly about the opposite
case, places where this isn’t enough air, like Mars or our own moon. I mentioned earlier that people tend to mistakenly
assume these places are too small to hold an atmosphere. There’s some truth to that but not the way
they think. Air, depending on what it’s made of and
how hot it is, has a speed associated to it. That speed, essentially the average speed
of gas molecules for a given mass and temperature, is called the root mean square speed. The equation I’ve got up shows you how to
calculate that, and this table shows you what it is for various common gasses at roughly
Earth Temperatures. Take a moment to note that the temperature
is in Kelvin, and speed rises with its square root. So if you wanted to double the speed you’d
need to quadruple the Temperature. We live at around 300 Kelvin, quadruple that
is 1200 Kelvin, which is even hotter than Venus or Mercury. But even doubled, most of these would still
have a speed far, far short of escape velocity from even a place like the Moon where the
escape velocity is just over a fifth of Earth’s. Now not all particles will be moving at the
same speed, some will move faster, following a Boltzmann distribution curve, and this is
called the Jeans Escape Mechanism. A very small fraction of the gases will be
moving much faster, at any given time about a millionth of them will be moving four times
faster than normal. Meaning for Earth free hydrogen and helium
gases will occasionally be moving at sufficient speed to leave. Earth loses an estimated hundred thousand
tons of gas a year this way, almost all of it hydrogen and helium. If a planet is cooler, like Mars, it would
lose less, and if it’s got a lower escape velocity, like Mars, it would lose more. But as huge as a hundred thousand tons a year
sounds like, Earth’s atmosphere masses about 50 billion times that. Even places like Mars or our moon would take
geological timescales to shed an atmosphere via Jeans Escape. But that’s not the only way to lose air. We know of two others, planets can leach air
into rock and dirt, called sequestration. It can also lose it to being blown off by
nukes, and of course comet and asteroid impacts can do the same. Another way, a bigger way, is for the individual
particles to be hit by radiation and slammed clean free of the atmosphere. If you picture a helium atom kicking around
the thin upper atmosphere of a planet, that then gets hit by a powerful photon like a
gamma or X-ray particle, it just soaked up that photon’s entire momentum. If we’re looking at a helium atom on the
terminator of the planet spinning away from the sun then it’s got some additional momentum
already from the planet’s spin. Same as we launch rockets west to east to
take advantage of Earth’s own spin to get into orbit. If that helium atom is already moving in that
direction, as many will be, and has the planet’s own spin, and gets hit by photons which are
also moving in that direction, the combined energy and momentum can send it zipping off
into space. This is generally going to throw off far more
atmosphere than Jeans Escape. This is also why you hear about the importance
of Magnetospheres to making planet’s habitable. It’s not just that the radiation off the
sun, before it’s been filtered by our own air and magnetosphere, is inimical to life. It’s that without a magnetosphere to help
counter the highest energy particles you’d have more air particles getting launched away,
and magnetospheres can also deflect charged particles, like a lone hydrogen, nitrogen,
or oxygen atom, back down into the atmosphere. There’s more to it than that, for instance
Venus has a very dense atmosphere in spite of being way hotter than Earth and having
no appreciable magnetosphere, but that’s all the more time we can spend on it today. Summary form, any planet or moon massive enough
that its escape velocity is a couple thousand meters a second can hold an atmosphere for
a very long time by human standards so long as you shield the planet from high energy
particles and radiation. You do that with a magnetosphere, though there
are other ways we’ll also discuss. Now you occasionally hear people suggest you
could get Mars’ core spinning again to produce a sufficient Magnetosphere, and that is possible,
but it is way harder than just dumping a nuke down a very long shaft. If you’ve seen the movie the Core, where
Earth’s core stops spinning and they travel down to get it started again, then just ignore
every single thing in that film mentioned as science. Honestly I’ve seen better science in some
of the old 50’s scifi serials like Commando Cody where they walk around on the moon without
spacesuits or take off in rockets with rolling chairs in them. You can, of course, dump millions of nukes
off to reheat and re-spin a planet’s core. You wouldn’t want to be on that planet while
this was happening though since things tend to expand when heated and the kind of Earthquakes
that would set off would make a major Earthquake on Earth seem like a light ground tremor and
they’d probably go on like that for centuries. So you’d probably go the artificial route. You can make a magnetosphere by doing rings
of solar powered satellites around a planet generating magnetic fields. This is a lot more power and energy efficient
than melting millions of trillions of tons of iron and nickel in a planet core. Similarly, just like with solar shades, you
can stick magnetic deflectors out at a planet’s L-1 Lagrange point with its sun and deflect
solar wind away. The other option is to just use straight matter
to stop radiation. Same as you can stick thick domes overhead
on a planet to cut it down, you could litter the planet’s orbit with many concentric
layers of thin material or do the same at the Lagrange Point. All of these approaches need maintenance too,
parts replaced, but they’d be a tiny fraction of the mass of a planet core and a lot of
planets would already have various small moons in orbit that could just be pulverized carefully
to generate such a shield. Superconducting magnets are a lot easier to
keep working in space in many respects, so as these hopefully get better and cheaper
with time an artificial magnetosphere becomes a lot saner as an option. We’re already looking at this as a protective
system, like in the tethered magshield design, for interplanetary spacecraft to get both
their radiation protection and some artificial spin gravity. If you saw the video on orbital rings then
you already know the idea of a giant superconducting ring around a planet is pretty feasible, a
lot more feasible then reheating a planet core, and also lets us do it for place like
our own Moon that couldn’t realistically produce enough on its own anyway. It’s also good for options like Venus where
the day is so long that you don’t have much magnetosphere even though the entire planet
is molten, not just the core. Same issue for Terraforming Mercury. Yes it’s really close to the Sun, yes it
is even less massive than Mars, yes its day is a couple months long, and yes it could
be terraformed too. Solar shades, artificial magnetosphere, solar
mirrors to bounce light around so night and day doesn’t last months. Paraterraforming on a place like Mercury isn’t
terribly bad either. If you want to build a base on Mercury, where
there’s no air to transfer heat, you stick you base up on stilts of sturdy materials
that don’t conduct heat well and you stick a shiny thin metal umbrella over it to shade
it. I sometimes call this a mushroom habitat. Mercury’s surface gravity is about the same
as Mars has, almost identical, because while Mercury is smaller than Mars it’s also denser. It’s denser because almost all the light
elements have baked away so you can’t expect to get your water and air locally. Now we don’t really know if Mars and Mercury’s
surface gravity is really enough for people in the long term, it probably is, but as I’ve
mentioned in the past you could build your bases there to spin and combine natural and
spin gravity to get something more comfortable. If you’re already built up on stilts and
under an umbrella spinning a base through a near non-existent atmosphere isn’t that
big a deal. You could forego that setup by just placing
solar shades in orbit or at the Lagrange point too, and give the planet a few decades to
chill out. Most solar system expansion ideas usually
call for Mercury to be mined until there’s nothing left to make artificial habitats out
of, so I don’t usually spend much time thinking about terraforming the place, but even then
you’d need thousands of years minimum to rip the place apart so bases on stilts under
mushrooms makes a lot of sense. If you’re using a planet’s own sunlight
to extract its minerals for offworld export then even with maximum efficiency you are
talking timelines of many thousands of years to do that even for a place like Mercury with
far less gravity and mass than Earth and far more sunlight than Earth. We’ve mentioned daylight too. Most planets don’t have day lengths we’d
find comfortable. Mars has a day very similar to Earth’s own,
but Venus and Mercury definitely don’t, and most large moons like Ganymede or Europa
or our own take many days or even weeks to complete one day for themselves. We talked about the example of moons with
Earth-like days in the third video on in the Habitable Planets series, but most moons don’t
have 1 day orbits and don’t have Earth-like mass. So what do you do to get a 24-hour day if
the planet doesn’t have one? We mentioned mirrors, and it is possible to
use a combination of orbital mirrors and shades to produce a 24 hour day on a planet, in terms
of its night and day length not its actual spin. This gets pretty muscular and complicated
but it’s nothing like as muscular as changing a planet’s spin. Still it can be done. You can change a planet’s spin without needing
any super-science. This isn’t easy but it’s not any harder,
and in some ways easier, than trying to screw with the planet’s core to make a magnetosphere. If a planet is spinning too fast, as many
would be – the Earth’s day used to be 12 hours long after all - you can actually
harvest that energy to power your terraforming while slowing the planet. Earth’s current rotation energy is about
2x 10^29 Joules of energy. Which is a lot of juice, for comparison, it’s
equal to all the energy the sun shines on the Earth for a trillion seconds, or about
30 years. That also tells you how long you’d need
to power something like that strictly off solar power or how long you need to spend
to avoid dumping so much energy on a planet you’d melt the place. The energy involved doing this is fairly comparable
to what you’d to spend to get a planet’s core spinning to generate a decent magnetosphere. How would you do that? Well you could attach rocket thrusters right
to a planet or detonate millions of nukes but a better route would be to build giant
towers over the planet’s atmosphere and point orbital mirrors at them, like a big
water mill. Or aim those same mirrors at one edge of the
planet and use the energy to bake air out of the soil while you’re at it. This is going to take a long while but that’s
okay because increasing the spin rate of a planet should be done slowly to give stuff
a chance to settle. Slowing it down, same concept, but you could
potentially power things with that. A planet’s spin isn’t the easiest thing
to tap for energy but waste not, want not. Same concept for adjusting the year, except
if you want to adjust a planet’s year you’re also changing the sunlight it gets. Only thing is Earth’s Orbital energy around
the sun is about 10,000 times its rotational energy around its own axis. Even ignoring the energy issue, or how to
get that much energy, it’s hard to do this in a non-destructive way in less than many
millions of years. You’d normally use a gravitational tractor,
which is where you stick something, like our own moon, in orbit around the planet and shove
that object away from the planet when it is one the far side of the sun then back toward
the planet when it is near the sun. That keeps the object in the same relative
position to the planet while pushing the planet further away from the sun. Do the reverse to bring the planet closer. You could do this with a giant solar sail
being hit by sunlight, or many of them, but you can’t make them too thin or dump too
much energy on them at a time or they’ll fly off. This is a lot like the Shkadov Thruster I’ve
discussed before in the Megastructures or Dyson Dilemma videos as a way to move entire
suns. Moving planets, moving stars, moving whole
galaxies, isn’t the realm of super-science it’s just the realm of brute force. It’s the difference between stacking a few
stones across a creek to make a small pool one afternoon and building the Great Wall
of China. Same process, just way more time and effort. The key thing to remember is even if you have
an infinite power source you can’t move the planet too fast without heating the planet
up. Your average planet’s orbital energy tends
to be on a similar scale to what you’d need to vaporize a planet so you can’t be applying
this all at once. The other aspect is that since it is similar
to the energy needed to vaporize the planet someone’s going to point out that it makes
way more sense to just convert the entire planet into trillions of orbital habitats
with a million times the living area. Earth’s rotational Energy is comparable
to the sunlight it receives over thirty years, its orbital energy is more like half a million
years. Energy used in such processes is going to
see a big chunk dissipate as heat so if you don’t want to roast the planet you need
to go very slow even if you have the energy to go faster. Needless to say it’s always going to be
both faster and easier to use orbital mirrors or shades to replicate the effect so moving
planets is probably the sort of thing you’d only ever do with a planet to move it away
from its own star as it heats up over its lifetime. You can take billions of years to do that
and would want to anyway, slowly moving a planet further from its star as the star gets
hotter. Now axial tilt can be adjusted in a similar
fashion but is more like adjusting day length then year length. Same sort of concept, you use gravitational
tractors or various other means. Takes time, it’s very brute force, but it
can be done. Gravity is harder. If you don’t like a planet’s gravity you
can only add or remove mass. If the gravity is lower than Earth’s than
you can make spinning habitats that combine natural and spin gravity. If the gravity is higher the only way to do
it is to hang some material like ultra dense deuterium or neutronium over your city to
locally negate some of the gravity. This isn’t necessarily completely undoable,
but people might feel a little nervous living under a billions tons of matter hanging over
their heads. On the other hand if you live in the lower
floor of a skyscraper you live with thousands of tons of matter hanging over your head anyway
and a thousand, a million, or a trillion, you’re basically just as dead if it falls
down. Gravity’s also very hard to bioform around,
because while low gravity would likely not be a big issue high gravity is. Slip and fall in the shower a high-gravity
world and you’d shatter every bone in your body. We discussed in the launch loops and mass
drivers video how the big limitation on mass drivers launching people is that we just can’t
handle high acceleration, which is the same as gravity according to Einstein. So barring someone inventing the cool artificial
gravity most scifi tv shows have… because it’s hard to film in zero gravity… world’s
with much higher gravity than Earth aren’t good for terraforming, and even for paraterraforming
unless you’re cool with transferring your mind into a cyborg body with titanium bones. Which to be fair, a lot of us would be fine
with, especially the generally pro-science sorts who probably make up the majority of
my audience, but I usually try to focus on the routes that don’t involve cyborging
people up or tinkering a lot with their genes even though I’m basically a transhumanist
or extropian. Key thing, if you get a way of generating
or negating gravity, same as if you get wormholes or perpetual motion machines, the entire landscape
changes so much I don’t see much point analyzing it. Same as in my Dyson Dilemma video, where I
mentioned we might find a way to just open portals to uninhabited parallel Earths and
if we did you can pretty much write off any space exploration not done specifically for
scientific research or ‘because we can’ prestige efforts like climbing Mount Everest. We climbed that mountain many a time, nobody
has ever built a city up there. Now, we’ve looked at a lot of terraforming
notions but we haven’t even scratched the surface. I may came back and do some more videos on
this subject in the future if people seem interested, and I’ll continue to mention
planet-specific options in the Habitable Planets series, but for more information take a peek
at some of the links below and videos I’ve attached. We’ll be looking at alternatives to terraforming,
in the form of building worlds and mega structures in the Megastructures series too. I can’t give you any good links on bioforming,
I’m not qualified to evaluate biology and genetic engineering but if you happen to be,
feel free to leave some comments or links below. Next in the video series we’ll be taking
a look at Rogue Planets in the Interstellar Void, where terraforming can only be done
with artificial power sources like fusion, then doing another stand alone video discussing
early interstellar colonization concepts like we did with interplanetary colonization here. After that we’ll be diving into Rotating
Habitats as an alternative to Terraforming. If you’ve enjoyed this video, which I assume
you have if you’ve made it this far, make sure to subscribe to the channel and like
the video, and try out some of my other videos as well. As always, thanks for watching, and have a
great day!
