We have gazed upon the Moon with
wonder since the dawn of humanity, and named its craters as seas, but
could those become true seas one day? Welcome to science and Futurism with Isaac Arthur,
and I am your aforementioned host, Isaac Arthur. Today we will be discussing if it could ever be
possible, let alone practical, to Terraform the Moon. To give it seas and sky and make it a
beautifully blue and green gem in our sky. The simple answer is yes, it can be done, though
it is a monumental task and how practical it is will depend a lot on both your available
technologies and how badly we want to do it. Today we’ll be discussing several different
approaches and what is involved in each. But let’s begin by laying out some basic
principles of terraforming, the main hurdles to doing it to the Moon, the advantages
it has, and some misconceptions involved. First, there’s two basic camps of terraforming,
which are meant to make them more Earth-like, and that’s terraforming and para-terraforming.
There’s no truly distinct line between the two but para-terraforming tends to manifest
in options like a dome on a planet full of pressurized and breathable air, or artificial
lighting to match Earth’s sunlight duration and spectrum. There’s also bioforming, which is when
you alter organisms to fit an alien environment. You might adjust everything’s biology to be
content with a 27 hour day on one planet, or more overtly, give humans and other mammals
gills so they could live on a water planet. With very few exceptions, we should assume
all of humanity’s efforts off of Earth will use a mix of all three options, both
over the course of the endeavor and in the final product. Even on earth we may opt
to para-terraform our tundras or deserts, and exact matches for Earth should be rare in the
galaxy. In nearly every case you have the ability to use one of those options far more heavily
than the others if you prefer that approach. For bioforming, you can probably cook up some
form of life that can live on a radiation scorched airless vacuum with sufficient effort, even
if it means a total overhaul of everything to use silicon-based life in place of carbon. You
can get heavy-handed with terraforming to take a planet with a 27-hour day and slow its rotation
to 24, by extreme efforts. For para-terraforming, we tend to view this as the active use of
technology to replicate Earth-like living conditions. You might alter daylight by use
of orbiting mirrors and shades, or gravity by centrifugal force. An extreme version of that
might be creating an incredibly elaborate virtual world like in The Matrix on some barren rock and
plugging everyone there into, while covering the rock in power collectors and robotic factories.
In all of these cases there’s likely to be a sweet spot for each planetary setup that varies by what
the colonists want and what their technologies make most economical or practical. And that is
likely to change with time. For instance, there are something like a million planets in just this
solar system – the 8 we talk about that no longer includes Pluto are the Major Planets, and that’s
basically the objects more massive than our Moon, Pluto is smaller and less massive than our Moon.
There’s a couple other moons bigger and more massive than our Moon too but there are probably a
hundred dwarf planets akin to Pluto kicking around the outer solar system and millions of minor
planets, a large portion of which are asteroids. In a future solar empire, every last one of
these will be para-terraformed in some fashion, and Earth will stand as the crown jewel, hub of
trade and knowledge. This will likely continue even as we expand out into billions of stars in
this galaxy, because almost every colony among the stars will maintain some sort of lifeline
with Earth. They would bring a lot of practical experience and knowledge about how to make
dead rocks livable and a lot of industrial might and manpower to the interplanetary economy.
Terraforming options will be very dependent on the resources you can commit to the project. If the
Moon is the brightest jewel in the heaven’s next to Earth, itself the center of a powerful
empire or confederacy of growing worlds, then the sheer amount of muscle they can throw at
the Moon is almost unimaginable. In the meantime, no place is closer to us and easier for
us to exert efforts on. We can get stuff to the Moon much easier than Mars or Venus.
That includes signals, as signal lag from the Moon is only a bit over a second each way, not
many minutes like our inner solar system, hours for the outer system, or years to neighboring
stars. That means you can run robots on the moon controlled by people here on Earth. And while
more advanced AI seems certain in the future, ones able to work fairly autonomously even
if we limit it to very-subhuman intelligence, the sheer advantage of a more automated industrial
base makes everything about space travel and development enormously easier and gives you a
larger amount of resources to throw at projects. The Moon’s proximity to Earth and its low
gravity also makes it our natural first base to launch not just interplanetary colonization,
but build up efforts in Earth orbital space, as bulk raw materials and fuel can be gotten
off the Moon for just a few percent of the energy cost of getting off Earth with its thick
atmosphere and high gravity. For this reason, the Moon is likely to be heavily mined and home to
a lot of manufacturing, for the build up of space, and thus is likely to eventually have a lot
of muscle to turn efforts to improving its own livability, long before a place like Mars might.
Indeed, I would go so far as to argue the Moon will be the first place we terraform, even if it
might be a more heavy case of paraterraforming and thus might not be the first place to decently
approximate a naturally livable planet. Though again, unless we find some decent twin to Earth in
a neighboring solar system, every other candidate would also need a lot of para-terraforming,
with Venus maybe being the easiest, not Mars. This hardly makes it easy and we should begin
the major challenges for terraforming the Moon by mentioning that it is also an advantage. The Moon
is one of the few objects that gets Earth-parallel levels of sunlight. Mercury, Venus, and the
Aten Asteroid Group get more or equal lighting, but most objects are further away,
at least for most of their orbits. As such, the Moon is not just a place where
solar power is practical, but which needs no more filtering of sunlight than our own Atmosphere
provides us. However, nice as that is, there’s two problems with that lighting. First, that
filtering our atmosphere does is hardly trivial, if our air suddenly became transparent to all
that ultraviolet light and ionizing radiation we would be burned badly. Second, the sun
rises and sets on Earth and the Moon both, there is no dark side to the Moon except in the
sense of the back side of it being invisible to us here on Earth. The Moon orbits the Earth and
always shows it the same face and it does this once a month so that’s how long its day is too.
For the sake of discussion, yes it would be possible to unglue the Moon from its tidal locking
with Earth, and if it were terraformed with seas and sky they would act like a lubricant against
tidal breaking, cutting down on how much effort had to be exerted to keep the Moon at a 24
hour day. The rotational energy of a sphere rises approximately with the square of its angular
velocity. If you want to spin the Moon almost 30 times faster, so it rotated every day, you are
talking nearly a thousand times the rotational energy it has now but it’s actually very tiny
compared to Earth’s, it’s around 3 x 10^23 Joules, whereas Earth’s is almost a million times higher,
so even spun at Earth’s rate of once a day, it’s far lower mass and radius means it would still
only need a thousandth of the energy Earth did. And indeed that once-a-day Moon’s rotational
energy would be a little under the amount the Sun produces every second, and only a small fraction
of the sunlight hitting the Moon during a period it would need for tidal locking to reoccur if left
to its own devices. So keeping the Moon spinning once per day is entirely doable. This is arguably
still para-terraforming since it would require continuous technological effort to keep it from
slowing down, as opposed to simply putting various mirrors in shades in a 24-hour orbit of the Moon.
I think we need to acknowledge a conceptual difference with para-terraforming though, with the
idea that para-terraforming is where things are more immediately vulnerable to breakdown. A fleet
could come by and wipe out those orbital mirrors and shades. As could some Kessler syndrome event
of cascade collisions of orbital junk. Neither would be likely to spin a planet or moon
back down again to a lower rotation. While para-terraforming efforts might need regular
maintenance, a breakdown of civilization for a century or two after some collapse of an
empire or disaster isn’t going to result in that planet de-terraforming. This is obviously a
very gray and somewhat arbitrary distinction too, but I think a degree of vulnerability or
time-sensitivity is implied with para-terraforming and that its absence tends to be where we
consider it more in the line of terraforming. So could we spin the Moon up?
Yes, and we might too. We could do the same with Venus, to give it a day length
like Earth’s instead of its backwards day-night cycle longer than its own year, but since
Venus is nearly as massive and wide as Earth we would need to give almost three-quarter’s Earth
rotational energy to match our day. Alternatively, Mars, at a tenth our mass and half our radius
would have only a fortieth Earth’s rotational Energy for the same day length, and already
has one only about half an hour longer, so it already has about 95% of that energy.
For Mars, we might add to its rate of spin, and angular momentum, by dropping comets on it to
bring it valuable volatiles like water, ammonia, and methane. It would not be hard to coordinate
all your incoming drops of those to add angular momentum to Mars. That’s no small task but if
you’re planning to add those to Mars you might as well do it that way and get the free rotational
bump. Especially since dropping an object onto it to add spin means it impacts at a slightly lower
velocity, since it’s coming in near the equator and in the direction of existing spin. Less
crash damage. Doing it the other way around, to subtract spin, would produce stronger impacts.
But you can also magnetically drain a planet’s rotation as a power source, by building a
planet-sized dynamo around the planet. You can add spin that way too, but must pay energy in.
You also have the option of launching material off a planet, or Moon, and using that momentum
to shove your planet’s rotation up or down. When we think of exporting large amounts of raw
material off the Moon, or Venus for that matter, we can imagine a large mass driver or
space catapult that launched so as to add or subtract spin. Two opposing launchers
could ensure that the spin remained the same, adding when one launched and subtracting when
the other did, so you could get a body to the right spin then keep it there. A directed energy
beam from the Sun could do it too, though radiant pressure alone is not your best option. A beam
of ionized particles or concentrated solar wind isn’t a great thing to hurl at a planet with an
atmosphere you want to keep either, but would also work on an initially airless planet.
You could build big towers up into space with giant reflectors on them, or deflecting
magnets – it’s quite easy to do without any gravity or air constraints -- and use them
like a big solar windmill to spin the Moon, or any other body for that matter. However, I
think you would opt for timing your landings and launches so they added inertia. And a big mining
hub like the Moon in an automated Kardashev Scale civilization might be belching out entire megatons
of matter every moment at interplanetary speeds, while receiving large amounts of other materials,
which is a lot of inertia changing hands. In any event, the key notion there is that you are
likely to try to piggyback a lot of terraforming operations onto existing projects to save effort.
I would not be surprised if we saw rotational changes done while terraforming planets, and
you might piggyback off the para-terraforming effort too. Our vastly cheaper alternative
to spin a planet, at least in the short term, is erecting a big solar shade and mirrors to
keep the normal sunlight off the planet and bounce it down in a proper 24-hour pattern. This
is ideal for a place like Venus as we can then cool it down over a couple centuries and make
it livable and use mirrors to bring in a 24-hour day at Earth-level of intensity and warmth.
You can make them wavelength selective too. This lets you add more light of a given wavelength
to a planet for other stars than our own, or to remove most of the harmful ultraviolet
light. Given that such shades and mirrors need to be only a few micrometers thick, even though
they must have a combined surface area similar to the planet or Moon they are on, this is not a
big investment of mass. Over time they may become a hassle to repair and replace and be viewed as
not as good as the real thing. In which case, such shades might be large power collectors and
you could beam that energy down to the planet as a power source for the people and industries below.
A shade like that would represent a huge amount of power and a constant one, there’s no night time
or weather at some planet’s L1 Lagrange point, so you could use your surplus power as your
civilization grew, or from outside your peak hours, to help spin that planet up, and when
you get there you just recycle your orbital shades and mirrors and enjoy a natural day.
Or most of them anyway, this sort of orbital infrastructure is likely to be a common feature
on any planet or moon we settle on as it has so many advantages and is relatively cheap to deploy.
It's also a bit trickier on a moon than a planet since the Moon’s own L1 Lagrange point is with
Earth, not the Sun, and the same for it’s L2, so you need to orbit them around the Moon at a
radius of about 6000 miles or 10,000 kilometers for a period of one day. You would likely use
the same big thin sheets for mirror and shades, and just give them some internal power collectors
and gyros so they could rotate themselves to either bounce light away from the Moon or add
light to it, and they’d spin to reflect light away when in between the Moon and Sun. This
amounts to building a micro Dyson swarm around the Moon to keep light out and I suspect you would
instead try for an orbital ring around the Moon that just had a big opaque circular shade on it
moving to interpose with the Sun, and a similar approach is probably a good pick for Mercury due
to its decidedly strange days. You just open or close your sun shade or mirror on that ring
to the amount needed to match what you want. This is a decidedly clunky approach though,
and combined with the vastly lower energy requirement to achieve proper spin, is why I think
we might see that brute force rotation adjustment occur. Which would make for some impressive
tides once we got air and water in place, as Earth would cause a lot more tidal warping
on the Moon than the Moon does to us, which is why it’s tidally locked in the first place.
We obviously haven’t got time today to run through all our options for terraforming in the
same length, but this topic is one we have tended to skim over in our other terraforming videos like
Planetary Terraforming Techniques, and I think it applies more to the Moon. Alternatively, we
devoted an entire episode to get a magnetosphere around Mars – which is much easier than folks tend
to assume and doesn’t involve nuking its core. And the same options can be applied to our Moon.
But it brings up our other challenge for terraforming the Moon, and that’s the issue that
things aren’t very heavy on the Moon because of its low gravity, and that combined with its lack
of a magnetosphere makes giving it an atmosphere very hard. Or rather having it keep an atmosphere
once put on. If we just opened a magic wormhole to the Moon and dumped an atmosphere on it, it
would not instantly fly off, but the leakage would be awful. We can’t model that well enough to
give useful figures but while it might be several lifetimes before any appreciable drop occurred,
it wouldn’t be the same geologically long process it was on Mars of a few hundred million years.
And if you spent a thousand years shipping in an atmosphere and have to replace your atmosphere
every several millions years, then that just means you went from having 10,000 mega-freighters
dropping air off every month to just one swinging by to replenish miniscule losses. Alternatively
if you needed to replenish it on a timeline of centuries, I think that becomes unsustainable, and
we don’t know what that timeline would look like for a terraformed Moon. It also represents a lot
of air, as you need more air over any given area on a lower gravity planet than on Earth,
because the lower gravity makes the same amount of air have less weight and generate less
pressure down on the surface. You get a very tall atmosphere as a result, and a thicker one in
terms of there being much more air above you, which would change the visual properties of
the sky, particularly near dawn and dusk. Now the reality is this atmospheric loss issue
is a hard problem to solve, there are several mechanisms for atmospheric loss and they all
happen faster when you have lower gravity, or are hotter, or have no magnetosphere protecting
you. The Moon has lower gravity than Mars, is closer to the Sun than Mars and has it shine
on spots for two weeks straight to further heat things, and has no magnetosphere of note.
The easy para-terraforming fix is basically to dome over everything. As we saw recently in our
episode the Domes of Mars, it is indeed possible to build diamond hard domes – diamond is just
carbon after all – with multiple panes that are crystal clear, filter out harmful sunlight, and
help protect against micrometeors. You could make them sturdier than the steel armor on a battleship
if you wanted and in that episode we detailed a number of backup and emergency protocols to make a
dome a safer place to live than under an open sky. Which is part of the problem. I’m not sure you
would ever not have those domes up given the advantages they have if big and crystal clear.
Indeed so long as they are tall enough to hold in a normal atmospheric depth, so that
the pressure was much lower near the top, you would not only still get weather but
have very slow leakage out of a given dome even if a huge hole was punctured into it.
The Moon’s low gravity is still a good deal higher than what is needed to hold particles of
air moving at room temperature velocities. That’s generally a few hundred meters per second and
the escape velocity of the Moon is around 2400 meters per second. Some particles will move faster
than that but the distribution of speeds falls off very sharply, especially for heavier molecules
like nitrogen, oxygen, argon, and carbon dioxide. What’s mostly going to strip them off is high
speed ions. Typically a hydrogen atom or lone proton from the Sun ramming them at roughly a
million miles per hour, which is not hyperbole. A strong magnetic field bends most of those
out away from a planet, or moon, and prevents all those collisions, and thus is even more
important than gravity for holding atmospheres. Again, see that episode about making a
Magnetosphere for Mars for details on how, though there we recommend deploying a solar
powered magnet at the Martian L1 with the Sun, and have the same problem as solar shades for
applying this to a Moon, so you would probably use the alternative approach of a large orbital
ring to generate a magnetic field, which could also serve as useful landing and launch platform.
It would be a lot less visually intrusive than the solar shade and mirror approach too.
I am generally of the opinion that an artificial magnetosphere would be installed
almost everywhere we settled too, and even Earth might deploy one just to further cut down on
the ionized particles coming in – which represent dangerous radiation to those on space stations
or ships. This is a paraterraforming option, and one where if it breaks down you aren’t in
immediate danger, so not a jugular vein option, and neither are very tall and strong domes
on the Moon, which if nice and clear don’t represent any sort of visually unpleasant effect.
I suspect that even with a magnetosphere and an economy able to import air to replace that lost
by slower leakage, you might still have those domes up. I think it would come down to the
net leakage rate and if the cost of replacing that was higher than maintaining domes. You would
likely keep that artificial magnetosphere anyway. This would minimize energetic particles hitting
your domes which would cut down on their own wear and tear and cut down on losses from cracked or
leaking domes. You would probably have a very thin atmosphere above the domes anyway just from
leakage. This also means if you have short domes, which get all their pressure from being a
sealed container stuffed with air, rather than by weight of air like on earth, that when cracks
or ruptures do occur your air spilling out is not being stripped off by solar wind very quickly
and can be recovered from this over-the-dome atmosphere and pumped back down into domes.
But that circumvents the gravity issue a bit, which is our last big problem. As we discussed in
Moon: Megacity, if we could develop the ability to artificially create black holes then you
could stick one in the center of any body, be it an asteroid or a modest planet like Mars
and pump hydrogen and helium into that to generate power and add mass. You just surround it with a
shell so your black hole is separate. You can also skip on doing this at the core in favor of placing
many of them at a shallower depth in a grid around the planet or Moon. We discussed black hole
tech more last week, and again Moon: Mega City, covers your gravity options in more detail.
As noted there, if you wanted full Earth-like gravity on the Moon, which has 7.4% of Earth’s
surface area, you would need 7.4% of Earth’s mass, and the Moon only has 1.2% of Earth’s
mass, so you would need to add 6.2% to it, roughly 5 times what it has now. That’s a lot of
hydrogen and helium to ship in from Jupiter but isn’t even a thousandth of Jupiter’s mass, and we
might do this to Jupiter’s 4 big Galilean Moons, which are all comparable to our Moon in size,
and much closer to Jupiter for shipping purposes. Adding mass to the Moon would also raise tides
on Earth, though at the level of planetary engineering we’re discussing, the increased
erosion on Earth from that would be miniscule to correct for compared to everything else.
This obviously would help a lot for maintaining an atmosphere and one more like Earth’s.
But if you are using domes and artificial magnetospheres this question comes
down to whether or not lower gravity is biologically adaptable. If it is, I suspect
you don’t try messing with the Moon’s mass. We know zero gravity is bad for our health, we
have no idea what lower gravity does and how much is enough, but we tend to assume the Moon’s
gravity isn’t optimal for our health or those of other terrestrial flora and fauna, though that
low gravity might make for some trees so tall that they laughed at redwoods. This is an example where
we just don’t know yet. You are likely to see a large change in how ecosystems work in low gravity
though, see our life on low gravity planets episode for discussion of that, but as a simple
example, ecological balances might shift a lot if your trees are taller and flying is easier, and
indeed running changes in low-gravity too, as each springing step takes longer to lower your foot
down to the ground for the next one. So a given predator-prey relationship might change massively
and disrupt ecologies you try to put in place. This is where bioforming might be a better
option than para-terraforming or even terraforming options. You genetically tweak
organisms to better handle lower gravity and re-balance your ecosystems. As we mentioned,
it is likely that every place we settle will have its own unique blend of terraforming,
bioforming, and para-terraforming that it uses, and which might change at any time. A given planet
or moon might not have a unified government able to make policy decisions on terraforming and
that’s why paraterraforming will often work better. It’s a lot harder to complain if one of
the countries on your planet is using domes than it is to if they’re mass altering genetics
or bringing in tons of cometary bodies or putting a black hole in your planet.
And my assumption is that by the time most larger bodies like the Moon, Mars, or
Venus have enough people to justify a planet wide terraforming operation, rather than
habitation domes and their parallels, that they will also have developed multiple
governments, be they sovereign or simply large sub-divisions with different opinions than their
neighbors on where their planet or moon should go. That time, intent, and willpower equation
is the last big aspect of terraforming, as while it might seem like a monumental task
to bring in a quadrillion of tons of nitrogen from Venus or the outer solar system, and many
times that in water or hydrogen to make seas, it is in some ways easier to ship that than
to decide to keep doing it. If I need to bring in 100 quadrillion tons of water to give
the Moon nice deep seas in those craters, then that’s something like a trillion oil tanker
deliveries of water or ice, and if you had one arriving every single second of every single day,
that’s about 30,000 years’ worth of deliveries. All the while folks who might have been building
their homes and towns in those craters might be having second thoughts about how much you really
need a sea there and if it really needs to be full depth. Though with Earth hanging huge in their
sky, far larger than the Moon is in our sky, they might have that as a constant reminder
of what terraforming success looks like. It’s a long term project but in a civilization in
which mass automation makes mega-projects viable and which would likely see the Moon second
in power and influence in the interplanetary settlement era only to Earth, I think the
resources would be there. Indeed you might maintain willpower simply because radical life
extension technology might make it so people survived from the earlier days who still
dreamed of completing the project. While others might be quite used to the lower gravity
and the monochrome wasteland beyond the domes and prefer dwelling underground anyway. They
might object to terraforming further. Later generations might push the project once more
and seek to terraform the Moon after a pause. Inevitably the question comes down to how
Earth-like you want your new home to be, and how Earth-like your descendants want
it when it’s been made more habitable but they’ve adjusted too. Time will tell where the
happy medium lies. The political landscape of those descendants will shift as the physical
landscape shifts. It will also shift with the capabilities of technology to reshape a world,
and the balance point of practical and possible, will all help determine the fate of our Moon
and of all those other worlds we come to. But we saw today the many ways the Moon might
be terraformed, so we know it can be done. And for my part, I think a day will come
on Earth when we look up at that Moon in the sky and see another sky, of white
clouds over blue seas and green lands. We were discussing the differences between
terraforming and para-terraforming today and part of that line between them is their
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risk-free with Nord’s 30-day money-back guarantee. So that wraps us up for today but we have
a bonus episode this weekend, Sunday, February 25th, on the topic of Vacuum Trains and
other hyperfast transit systems. Next week we’ll be finishing the month on February 29th, as we
leap into the topic of life on colony ark ship carrying people to new worlds that will carry
us ahead into this leap year and into March, where we’ll head back to the dawn of time
for a look at Primordial Planets. Then we’ll continue our discussion of terraforming
by asking if it is ethical and when, and what sorts of challenges future civilizations
will face on deciding whether or not a planet should be terraformed and to what degree.
If you’d like to get alerts when those and other episodes come out, make sure to hit the
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