Science fiction has told us again and again,
we belong out there, among the stars. But before we can build that vast galactic
empire, we’ve got to learn how to just survive in space. Fortunately, we happen to live in a Solar
System with many worlds, large and small that we can use to become a spacefaring civilization. This is half of an epic two-part episode that
I’m doing with Isaac Arthur, who runs an amazing channel all about futurism, often
about the exploration and colonization of space. Make sure you subscribe to his channel. This episode is about colonizing the inner
Solar System, from tiny Mercury, the smallest planet, out to Mars, the focus of so much
attention by Elon Musk and SpaceX. In the other episode, Isaac will talk about
what it’ll take to colonize the outer Solar System, and harness its icy riches. You can watch these episodes in either order,
just watch them both. At the time of this video, humanity’s colonization
efforts of the Solar System are purely on Earth. We’ve exploited every part of the planet,
from the South Pole to the North, from huge continents to the smallest islands. There are few places we haven’t fully colonized
yet, and we’ll get to that. But when it comes to space, we’ve only taken
the shortest, most tentative steps. There have been a few temporarily inhabited
space stations, like Mir, Skylab and the Chinese Tiangong Stations. Our first and only true colonization of space
is the International Space Station, built in collaboration with NASA, ESA, the Russian
Space Agency and other countries. It has been permanently inhabited since November
2nd, 2000. Needless to say, we’ve got our work cut
out for us. Before we talk about the places and ways humans
could colonize the rest of the Solar System, it’s important to talk about what it takes
to get from place to place. Just to get from the surface of Earth into
orbit around our planet, you need to be going about 10 km/s sideways. This is orbit, and the only way we can do
it today is with rockets. Once you’ve gotten into Low Earth Orbit,
or LEO, you can use more propellant to get to other worlds. If you want to travel to Mars, you’ll need
an additional 3.6 km/s in velocity to escape Earth gravity and travel to the Red Planet. If you want to go to Mercury, you’ll need
another 5.5 km/s. And if you wanted to escape the Solar System
entirely, you’d need another 8.8 km/s. We’re always going to want a bigger rocket. The most efficient way to transfer from world
to world is via the Hohmann Transfer. This is where you raise your orbit and drift
out until you cross paths with your destination. Then you need to slow down, somehow, to go
into orbit. One of our primary goals of exploring and
colonizing the Solar System will be to gather together the resources that will make future
colonization and travel easier. We need water for drinking, and to split it
apart for oxygen to breathe. We can also turn this water into rocket fuel. Unfortunately, in the inner Solar System,
water is a tough resource to get and will be highly valued. We need solid ground. To build our bases, to mine our resources,
to grow our food, and to protect us from the dangers of space radiation. The more gravity we can get the better, since
low gravity softens our bones, weakens our muscles, and harms us in ways we don’t fully
understand. Each world and place we colonize will have
advantages and disadvantages. Let’s be honest, Earth is the best place
in the Solar System, it’s got everything we could ever want and need. Everywhere else is going to be brutally difficult
to colonize and make self-sustaining. We do have one huge advantage, though. Earth is still here, we can return whenever
we like. The discoveries made on our home planet will
continue to be useful to humanity in space through communications, and even 3D printing. Once manufacturing is sophisticated enough,
a discovery made on one world could be mass produced half a solar system away with the
right raw ingredients. We will learn how to make what we need, wherever
we are, and how to transport it from place to place, just like we’ve always done. Mercury is the closest planet from the Sun,
and one of the most difficult places that we might attempt the colonize. Because it’s so close to the Sun, it receives
an enormous amount of energy. During the day, temperatures can reach 427
C, but without an atmosphere to trap the heat, night time temperatures dip down to -173 C. There’s essentially no atmosphere, 38% the
gravity of Earth, and a single solar day on Mercury lasts 176 Earth days. Mercury does have some advantages, though. It has an average density almost as high as
Earth, but because of its smaller size, it actually means it has a higher percentage
of metal than Earth. Mercury will be incredibly rich in metals
and minerals that future colonists will need across the Solar System. With the lower gravity and no atmosphere,
it’ll be far easier to get that material up into orbit and into transfer trajectories
to other worlds. But with the punishing conditions on the planet,
how can we live there? Although the surface of Mercury is either
scorching or freezing, NASA’s MESSENGER spacecraft turned up regions of the planet
which are in eternal shadow near the poles. In fact, these areas seem to have water ice,
which is amazing for anywhere this close to the Sun. You could imagine future habitats huddled
into those craters, pulling in solar power from just over the crater rim, using the reservoirs
of water ice for air, fuel and water. High powered solar robots could scour the
surface of Mercury, gathering rare metals and other minerals to be sent off world. Because it’s bathed in the solar winds,
Mercury will have large deposits of Helium-3, useful for future fusion reactors. Over time, more and more of the raw materials
of Mercury will find their way to the resource hungry colonies spread across the Solar System. It also appears there are lava tubes scattered
across Mercury, hollows carved out by lava flows millions of years ago. With work, these could be turned into safe,
underground habitats, protected from the radiation, high temperatures and hard vacuum on the surface. With enough engineering ability, future colonists
will be able to create habitats on the surface, wherever they like, using a mushroom-shaped
heat shield to protect a colony built on stilts to keep it off the sun-baked surface. Mercury is smaller than Mars, but is a good
deal denser, so it has about the same gravity, 38% of Earth’s. Now that might turn out to be just fine, but
if we need more, we have the option of using centrifugal force to increase it. Space Stations can generate artificial gravity
by spinning, but you can combine normal gravity with spin-gravity to create a stronger field
than either would have. So our mushroom habitat’s stalk could have
an interior spinning section with higher gravity for those living inside it. You get a big mirror over it, shielding you
from solar radiation and heat, you have stilts holding it off the ground, like roots, that
minimize heat transfer from the warmer areas of ground outside the shield, and if you need
it you have got a spinning section inside the stalk. A mushroom habitat. Venus is the second planet in the Solar System,
and it’s the evil twin of Earth. Even though it has roughly the same size,
mass and surface gravity of our planet, it’s way too close to the Sun. The thick atmosphere acts like a blanket,
trapping the intense heat, pushing temperatures at the surface to 462 C. Everywhere on the planet is 462 C, so there’s
no place to go that’s cooler. The pure carbon dioxide atmosphere is 90 times
thicker than Earth, which is equivalent to being a kilometer beneath the ocean on Earth. In the beginning, colonizing the surface of
Venus defies our ability. How do you survive and stay cool in a thick
poisonous atmosphere, hot enough to melt lead? You get above it. One of the most amazing qualities of Venus
is that if you get into the high atmosphere, about 52.5 kilometers up, the air pressure
and temperature are similar to Earth. Assuming you can get above the poisonous clouds
of sulphuric acid, you could walk outside a floating colony in regular clothes, without
a pressure suit. You’d need a source of breathable air, though. Even better, breathable air is a lifting gas
in the cloud tops of Venus. You could imagine a future colony, filled
with breathable air, floating around Venus. Because the gravity on Venus is roughly the
same as Earth, humans wouldn’t suffer any of the side effects of microgravity. In fact, it might be the only place in the
entire Solar System other than Earth where we don’t need to account for low gravity. Now the day on Venus is incredibly long, 243
earth days, so if you stay over the same place the whole time it would be light for four
months then dark for four months. Not ideal for solar power on a first glance,
but Venus turns so slowly that even at the equator you could stay ahead of the sunset
at a fast walk. So if you have floating colonies it would
take very little effort to stay constantly on the light side or dark side or near the
twilight zone of the terminator. You are essentially living inside a blimp,
so it may as well be mobile. And on the day side it would only take a few
solar panels and some propellers to stay ahead. And since it is so close to the Sun, there’s
plenty of solar power. What could you do with it? The atmosphere itself would probably serve
as a source of raw materials. Carbon is the basis for all life on Earth. We’ll need it for food and building materials
in space. Floating factories could process the thick
atmosphere of Venus, to extract carbon, oxygen, and other elements. Heat resistant robots could be lowered down
to the surface to gather minerals and then retrieved before they’re cooked to death. Venus does have a high gravity, so launching
rockets up into space back out of Venus’ gravity well will be expensive. Over longer periods of time, future colonists
might construct large solar shades to shield themselves from the scorching heat, and eventually,
even start cooling the planet itself. The next planet from the Sun is Earth, the
best planet in the Solar System. One of the biggest advantages of our colonization
efforts will be to get heavy industry off our planet and into space. Why pollute our atmosphere and rivers when
there’s so much more space… in space. Over time, more and more of the resource gathering
will happen off world, with orbital power generation, asteroid mining, and zero gravity
manufacturing. Earth’s huge gravity well means that it’s
best to bring materials down to Earth, not carry them up to space. However, the normal gravity, atmosphere and
established industry of Earth will allow us to manufacture the lighter high tech goods
that the rest of the Solar System will need for their own colonization efforts. But we haven’t completely colonized Earth
itself. Although we’ve spread across the land, we
know very little about the deep ocean. Future colonies under the oceans will help
us learn more about self-sufficient colonies, in extreme environments. The oceans on Earth will be similar to the
oceans on Europa or Enceladus, and the lessons we learn here will teach us to live out there. As we return to space, we’ll colonize the
region around our planet. We’ll construct bigger orbital colonies
in Low Earth Orbit, building on our lessons from the International Space Station. One of the biggest steps we need to take,
is understanding how to overcome the debilitating effects of microgravity: the softened bones,
weakened muscles and more. We need to perfect techniques for generating
artificial gravity where there is none. The best technique we have is rotating spacecraft
to generate artificial gravity. Just like we saw in 2001, and The Martian,
by rotating all or a portion of a spacecraft, you can generated an outward centrifugal force
that mimics the acceleration of gravity. The larger the radius of the space station,
the more comfortable and natural the rotation feels. Low Earth Orbit also keeps a space station
within the Earth’s protective magnetosphere, limiting the amount of harmful radiation that
future space colonists will experience. Other orbits are useful too, including geostationary
orbit, which is about 36,000 kilometers above the surface of the Earth. Here spacecraft orbit the Earth at exactly
the same rate as the rotation of Earth, which means that stations appear in fixed positions
above our planet, useful for communication. Geostationary orbit is higher up in Earth’s
gravity well, which means these stations will serve a low-velocity jumping off points to
reach other places in the Solar System. They’re also outside the Earth’s atmospheric
drag, and don’t require any orbital boosting to keep them in place. By perfecting orbital colonies around Earth,
we’ll develop technologies for surviving in deep space, anywhere in the Solar System. The same general technology will work anywhere,
whether we’re in orbit around the Moon, or out past Pluto. When the technology is advanced enough, we
might learn to build space elevators to carry material and up down from Earth’s gravity
well. We could also build launch loops, electromagnetic
railguns that launch material into space. These launch systems would also be able to
loft supplies into transfer trajectories from world to world throughout the Solar System. Earth orbit, close to the homeworld gives
us the perfect place to develop and perfect the technologies we need to become a true
spacefaring civilization. Not only that, but we’ve got the Moon. The Moon, of course, is the Earth’s only
natural satellite, which orbits us at an average distance of about 400,000 kilometers. Almost ten times further than geostationary
orbit. The Moon takes a surprising amount of velocity
to reach from Low Earth Orbit. It’s close, but expensive to reach, thrust
speaking. But that fact that it’s close makes the
Moon an ideal place to colonize. It’s close to Earth, but it’s not Earth. It’s airless, bathed in harmful radiation
and has very low gravity. It’s the place that humanity will learn
to survive in the harsh environment of space. But it still does have some resources we can
exploit. The lunar regolith, the pulverized rocky surface
of the Moon, can be used as concrete to make structures. Spacecraft have identified large deposits
of water at the Moon’s poles, in its permanently shadowed craters. As with Mercury, these would make ideal locations
for colonies. Our spacecraft have also captured images of
openings to underground lava tubes on the surface of the Moon. Some of these could be gigantic, even kilometers
high. You could fit massive cities inside some of
these lava tubes, with room to spare. Helium-3 from the Sun rains down on the surface
of the Moon, deposited by the Sun’s solar wind, which could be mined from the surface
and provide a source of fuel for lunar fusion reactors. This abundance of helium could be exported
to other places in the Solar System. The far side of the Moon is permanently shadowed
from Earth-based radio signals, and would make an ideal location for a giant radio observatory. Telescopes of massive size could be built
in the much lower lunar gravity. We talked briefly about an Earth-based space
elevator, but an elevator on the Moon makes even more sense. With the lower gravity, you can lift material
off the surface and into lunar orbit using cables made of materials we can manufacture
today, such as Zylon or Kevlar. One of the greatest threats on the Moon is
the dusty regolith itself. Without any kind of weathering on the surface,
these dust particles are razor sharp, and they get into everything. Lunar colonists will need very strict protocols
to keep the lunar dust out of their machinery, and especially out of their lungs and eyes,
otherwise it could cause permanent damage. Although the vast majority of asteroids in
the Solar System are located in the main asteroid belt, there are still many asteroids orbiting
closer to Earth. These are known as the Near Earth Asteroids,
and they’ve been the cause of many of Earth’s great extinction events. These asteroids are dangerous to our planet,
but they’re also an incredible resource, located close to our homeworld. The amount of velocity it takes to get to
some of these asteroids is very low, which means travel to and from these asteroids takes
little energy. Their low gravity means that extracting resources
from their surface won’t take a tremendous amount of energy. And once the orbits of these asteroids are
fully understood, future colonists will be able to change the orbits using thrusters. In fact, the same system they use to launch
minerals off the surface would also push the asteroids into safer orbits. These asteroids could be hollowed out, and
set rotating to provide artificial gravity. Then they could be slowly moved into safe,
useful orbits, to act as space stations, resupply points, and permanent colonies. There are also gravitationally stable points
at the Sun-Earth L4 and L5 Lagrange Points. These asteroid colonies could be parked there,
giving us more locations to live in the Solar System. The future of humanity will include the colonization
of Mars, the fourth planet from the Sun. On the surface, Mars has a lot going for it. A day on Mars is only a little longer than
a day on Earth. It receives sunlight, unfiltered through the
thin Martian atmosphere. There are deposits of water ice at the poles,
and under the surface across the planet. Martian ice will be precious, harvested from
the planet and used for breathable air, rocket fuel and water for the colonists to drink
and grow their food. The Martian regolith can be used to grow food. It does have have toxic perchlorates in it,
but that can just be washed out. The lower gravity on Mars makes it another
ideal place for a space elevator, ferrying goods up and down from the surface of the
planet. Unlike the Moon, Mars has a weathered surface. Although the planet’s red dust will get
everywhere, it won’t be toxic and dangerous as it is on the Moon. Like the Moon, Mars has lava tubes, and these
could be used as pre-dug colony sites, where human Martians can live underground, protected
from the hostile environment. Mars has two big problems that must be overcome. First, the gravity on Mars is only a third
that of Earth’s, and we don’t know the long term impact of this on the human body. It might be that humans just can’t mature
properly in the womb in low gravity. Researchers have proposed that Mars colonists
might need to spend large parts of their day on rotating centrifuges, to simulate Earth
gravity. Or maybe humans will only be allowed to spend
a few years on the surface of Mars before they have to return to a high gravity environment. The second big challenge is the radiation
from the Sun and interstellar cosmic rays. Without a protective magnetosphere, Martian
colonists will be vulnerable to a much higher dose of radiation. But then, this is the same challenge that
colonists will face anywhere in the entire Solar System. That radiation will cause an increased risk
of cancer, and could cause mental health issues, with dementia-like symptoms. The best solution for dealing with radiation
is to block it with rock, soil or water. And Martian colonists, like all Solar System
colonists will need to spend much of their lives underground or in tunnels carved out
of rock. In addition to Mars itself, the Red Planet
has two small moons, Phobos and Deimos. These will serve as ideal places for small
colonies. They’ll have the same low gravity as asteroid
colonies, but they’ll be just above the gravity well of Mars. Ferries will travel to and from the Martian
moons, delivering fresh supplies and sending Martian goods out to the rest of the Solar
System. We’re not certain yet, but there are good
indicators these moons might have ice inside them, if so that is an excellent source of
fuel and could make initial trips to Mars much easier by allowing us to send a first
expedition to those moons, who then begin producing fuel to be used to land on Mars
and to leave Mars and return home. According to Elon Musk, if a Martian colony
can reach a million inhabitants, it’ll be self-sufficient from Earth or any other world. At that point, we would have a true, Solar
System civilization. Now that you’ve heard how to colonize the
inner planets, come on over for part 2, Colonizing the Outer Solar System, and we will start
with the Asteroid Belt and work our way out the Oort Cloud.
