When it comes to the colonization of the other planets, most eyes are on Mars.
And on the surface, Mars does seem like the most hospitable planet in our solar system.
But we shouldn’t overlook our “sister planet” Venus. Someday, human scientists and perhaps even
civilians might find their home high above Venus’s surface in its upper atmosphere.
This is Unveiled, and today we’re answering the extraordinary question;
what if humans lived in cloud cities?
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Since at least the 1970s, scientists have contemplated the possibility of human habitation
in the Venusian clouds. It’s an exciting and tantalizing idea: a floating city, constructed
from an interconnected web of airships. The planet’s surface is wildly inhospitable,
boasting surface temperatures close to 900 degrees Fahrenheit, and its atmosphere is bursting with
carbon dioxide. The atmospheric pressure on the surface is ninety times that on Earth.
Venus has earned the nickname “Earth’s evil twin” because of its similar size, gravity,
and deadly climate. But in the upper cloud belt, while the air is thick with carbon dioxide and
wouldn’t be breathable, it’s just friendly enough to support a floating city. In fact, such an
aerial metropolis would have Earth-like gravity, protection from radiation, and temperatures as
reasonable as 86 degrees Fahrenheit. However, a first run at building a cloud
city on an alien planet sounds a little ambitious – perhaps too ambitious. So, could the same thing
be done on Earth first as a proof of concept? Almost certainly, yes, but it wouldn’t be easy.
In fiction, the most famous flying city is arguably Columbia, from the video game “BioShock
Infinite”. But though the buildings in Columbia do have balloons and other propulsion systems,
they’re suspended by a brand-new, quantum particle that certainly does not exist. This single
particle, called a Lutece Particle, has tremendous anti-gravity properties; suffice it to say,
we’re yet to prove that anti-gravity can actually exist, so this isn’t something we want to bet on.
But all is not lost – after all, we’ve already built plenty of large, flying objects that could,
in theory, support a human population indefinitely: airships. First built in the 1850s,
airships were one of the best ways to travel long distances before the development of commercial
airliners. Unlike regular ships, airships were capable of crossing both land and sea, traveling
much faster and more efficiently. However, there are many reasons that they’re not in use anymore.
For a start, the compartment underneath, called a gondola, only holds a few dozen people, even on
the biggest ships. Hindenburg-class airships were the biggest ever made, and only held roughly 100
people including crew. If we’re defining a true “city” as a settlement of over 100,000 people,
then to build a city out of Hindenburg-sized ships, you’d need 1,000. That would take 7
billion cubic feet of lifting gas to keep afloat. The best lifting gas on Earth is helium because,
unlike the hydrogen the actual Hindenburg carried, it’s not flammable – but it’s rare
and incredibly expensive. It’s because of this expense that there are only around 25
blimps operational worldwide. With about 1170 billion cubic feet of helium left on Earth,
using that to fuel a floating city, and only briefly at that, would be ludicrous.
Luckily, some of these problems are avoided when we skip the trial run and go straight
to building a cloud city on Venus. For a start, Venus’s atmosphere is still made
up almost entirely of CO2, even high up. This means that we can’t breathe there whatsoever,
but it also means that regular, Earth air is lighter than Venus’s. Crucially, the gas in
a container needs to be less dense than the gas outside the container for it to float. On Earth,
we need helium and hydrogen to do this, but on Venus, oxygen and nitrogen will suffice.
And we’ll already need to have a large supply of oxygen and nitrogen simply for us to breathe.
This also means that we don’t have to rely on the gondolas underneath to provide our living space;
we can just live inside the airship balloons themselves. The gondolas would still be useful,
providing scenic views, helping navigation, and being a way to get from one airship to another,
but the enormous balloons would be all the living space we would need. This also means
we’d need fewer ships for a larger population. In a city like this, the most vital part of the
infrastructure would be hydroponics. Initially, when we construct the first Venusian cities,
it makes sense to import air from Earth until a proper, enclosed ecosystem can be set up.
To create such an ecosystem, we’ll need to grow a lot of plants, not only for food but for oxygen.
The good news is that hydroponics is an integral part of any space colonization mission, and we’ve
already been growing plants on the International Space Station in preparation for this. If we go to
Mars instead of Venus, we still need hydroponics to provide air and fresh food. And because Venus’s
upper atmosphere still affords solid protection against solar radiation – unlike Mars’s incredibly
thin atmosphere – we don’t really have to worry about radiation contaminating our food and water,
or about radiation cladding too much. All we need to do is keep the sulfuric rain away so
that it doesn’t destroy our airships. Luckily, the Soviet Union already did research into this
decades ago when scientists first experimented with sending balloons to Venus. It turns out
that all you need to do is line the balloons with Teflon and you’ll be completely fine.
Over time, the city could evolve to be more similar to a settlement on Earth. You could
have enclosed walkways and cable cars to bridge the gaps between different gondolas,
making it relatively easy to get from one to the other. And filling just some of the balloons with
helium could enable them to carry heavier, larger loads, since helium is even lighter, creating more
standard living structures. Essentially, if you’re not building anything too heavy
and it’s not open to the Venusian atmosphere, it can probably be part of this city. It just
might take you a while to get from one side of the city to the other, but the same is true of
a normal city on Earth, which is why we need infrastructure solutions like public transport.
But what would it really be like? Even if you were surrounded by 100,000 other people, it
could still be a very lonely experience living on Venus simply because of how far away from Earth it
is. And because cities grow slowly over time and, until very recently, weren’t meticulously designed
with a population of millions in mind, it would take a long time to reach that 100,000 anyway – if
at all. Unless we can find enough resources on Venus and a cheap, safe way to extract them,
there wouldn’t be any point in putting an entire city there, at least not at first.
Living on Venus would therefore be more similar to living with a few thousand
people on a cruise ship that never docks. It could even be more like living on a submarine,
totally cut off from the outside world, or like living on an Antarctic research base.
In the early days of our Venusian city, it’s doubtful that anybody would live there full-time
even if it was totally climate-controlled. Just like any other future space colony,
it would be a dangerous and difficult mission. In any case, only if something happened to make
Earth even more toxic than Venus would we ever realistically consider moving enough people there
to build a city, since it probably wouldn’t be worth the expense otherwise. But if something
like that did happen, we could be the architects of an interplanetary network of cloud cities able
to weather the harshest environments, learning invaluable lessons about how to survive in space.
There is one other reason we’d have to do so cautiously, however.
Venus’ clouds might already have microbial life of its own that needs to be preserved.
The idea that there might already be life floating about in the Venusian atmosphere was first
seriously considered in 1950. Since then, several missions have discovered possible biomarkers that
could indicate the presence of life. If there is microbial life on Venus, we would have to be
careful not to contaminate it as we studied it and built our dwelling in the clouds.
It would be a remarkable place to live and potentially one of the safest locations for
a space colony in the solar system bar Earth – but it could be so expensive and hard to maintain
that it might remain a fantasy. And that’s what would happen if humans lived in cloud cities.
What do you think? Is there anything we missed? Let us know in the comments, check out these other
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