Terraforming: Forging New Worlds
This episode is brought to you by Brilliant There are trillions of planets in this galaxy, but nature probably didn’t hand us any other pre-made worlds we can just move into, so we’ll have to forge them into livable worlds, but as they say if you want something done right, you have to do it yourself. So today we return to our Becoming an Interplanetary species Series to look at Terraforming and Para-Terraforming. In the previous 5 episodes we followed the National Space Society Roadmap to Space Settlement, which is linked in the episode description, and which breaks it into 6 parts. We covered the first 5 in each of the previous 5 episodes.
However, part 6 is a bit broader, consisting of more separate topics and I felt the Topic of Terraforming needed its own episode. It’s a topic we have looked at before but I wanted to discuss our available Techniques for Terraforming, along with what certain advanced technologies might permit, as well as discuss the motivation for doing it. Terraforming is changing a planet to be livable for Earth-based life forms, it literally means to form a world to be Earth-like. Alternatively, we have Bioforming, which is the adaptation of life to live on a new planet, rather than altering the planet.
In practice we would expect a mixture of the two, rather than a pure use of just one, but either should be possible if you are willing to go to the effort. One key notion from the outset, terraforming is all about how much effort you’re willing to throw at a planet – not that we’re limited to planets – and while some of the processes are gradual improvements you can do in steps, others are all-or-nothing procedures that you have to commit to from the beginning. For some of the processes, it would be little different and little easier to terraform a world to be like Earth than it would be to construct a planet in its entirety, like one of the Megastructures we often discuss on the Show, entirely artificial worlds ranging from the size of an island to the size of a galaxy. You can build a planet, though it is obviously no easy feat, and in truth terraforming one can be just as hard.
It just depends on how far you need to go and how far you are willing to go. We have two terms, para-terraforming and terraforming, the former usually meaning doing things more along the lines of building pressurized domes and creating ecologies inside, but there is no distinct line between the two or between a megastructure built as an artificial habitat and a planet that has been terraformed. Indeed, many of our terraforming processes will involve the use of megastructures. Let us start with that basic variety though, domes over large areas, potentially over an entire planet, what sometimes gets called a Worldhouse. Conceptually this is easy enough and likely a common process to start on worlds.
You build transparent or translucent domes over an area and just build more and more of them, until you have covered an area like a film of soap bubbles. This is easily accomplished in-situ as well, as we can make transparent materials out of many substances but silicon and oxygen, the main constituents of glass, are generally going to be abundant on any rocky surface be it the Moon or Mars or a random asteroid. Transparency is not necessarily your goal either, as you might be getting too much light or too much of certain spectrums. Regular glass for instance does not allow much ultraviolet light through, and in many cases you will need to block ultraviolet light.
Ultraviolet is one of the primary spectrums of the electromagnetic spectrum, and comes in three types UV-A, UV-B, and UV-C. UV-A is what we mostly encounter on Earth, and is often called Soft UV. UV-B is mostly blocked by our atmosphere, while UV-C is completely blocked and a good thing too as it's germicidal and hard on lifeforms. Nor is it the only type of radiation our atmosphere blocks, and it takes more than a few hundred meters of air to do that. Even worlds farther from our Sun that get less light, still get far more of these dangerous frequencies of radiation than we do, simply because they have nothing filtering it out, so any domes need that protection too. Atmospheres also help to minimize debris hitting Earth, as it burns up before reaching the ground.
Planets will generally be hit by millions of kilograms of random space debris in a given year and every gram of it moving faster than any bullet from a gun. Whatever the escape velocity of the planet you're on is, you can assume that without an atmosphere a piece of space debris will strike the ground with at least that velocity, as it will pick up that much speed just from entering the gravity well of the planet. Your typical bullet fired from a gun has less than a hundredth the kinetic energy it would have moving at Earth’s escape velocity, and the space debris is mostly very small, far more tiny rocks than big ones, so in a given year a planet might get peppered with billions of tiny pebbles carrying more force than a bullet without an atmosphere.
Now that’s not as bad as it sounds, a dome about the size of a house is only a hundred square meters or so, whereas planets generally have hundreds of trillions of square meters of surface area, so even if a billion bullets fell from the sky every year a dome that size would only have about a 1 in thousand chance of being hit. If you’re building thousands of domes though, let alone millions or billions, some will get hit. Nonetheless without an atmosphere you need to be building sturdy domes and you want to keep them small.
You might want them multi-layered too so that an object striking one of the outer panes can shatter and lose energy before striking the other layers. You might even fill them with something denser and clear like water. Alternatively, the light on most worlds won’t match what we have either. The Sun is weaker on Mars and Stronger on Venus, for instance. So you might decide instead to live under an opaque and thick armored dome, something like a mushroom, with a clear stalk and thick stone above as the cap, and mirrors around it to shine light inward.
We also need to remember that you can’t just build a dome above a piece of dirt and start farming. Our soil on Earth – as opposed to Regolith on other worlds – is very weathered and soft from untold centuries of erosion and biology, and the latter results in many important microbes in that soil too that help it live. Alien Regolith might be quite toxic too, beyond just having sharp flakes, so you don’t just dome above but place floor below, and build your ecology over that floor after carefully processing the regolith. You would crush and mix and separate it till it had a safe chemical composition and then probably dump it into big vats of churning water with algae and microbes till you got yourself a nice muddy brew of soil to use.
We have a notion of dropping comets on planets to add water, and nitrogen too – oxygen is always plentiful on rocky planets even if it is tied up in those rocks – and you can do this but it is easy to forget how much mass you are talking about moving. The Biblical story of Noah and the Flood, or other flood tales, is either the work of an omnipotent being or mythology, and thus the mechanics involved in actually doing that aren’t terribly relevant but they would be if we were trying to do it ourselves. If it rained 10 centimeters or 4 inches of water every day for forty days, planet wide, you would only have raised the sea level 4 meters or 13 feet. The average depth of Earth’s oceans is around a thousand times that, so you would have to rain at that rate for around a century to add that much water[a]. You could certainly add it faster, but keep in mind what we said early about objects striking a planet having at least the speed of that planet’s escape velocity.
If you try to add a meter, or 1000 kilograms, of water to a given square meter of Mars’ surface every day, at an incoming speed of say 10 kilometers per second, that means you are adding 50 billion joules of energy to it every day and 580,000 joules a second, or 580 kilowatts. That is around a thousand times the energy places like Mars and Earth get from the Sun on a given square meter of land and also more than enough heat to boil all that water, indeed it is a good deal more energy than an equal amount of gasoline or jet fuel has. You wouldn’t think of warming Mars up by hitting it with icy comets but that is what you would do. If you limited yourself to just 100 watts per square meter of incoming mass, which would probably let you avoid burning or boiling everything on that planet to death, that would let you add about 6 centimeters of water to Mars per year, and achieve the Earth-average Ocean depth in a mere 50,000 years. Terraforming is not a fast process and ironically the major delay is more likely to be heat dissipation issues than manpower or resource limitations. In all the talk I hear about adding mass or water or even air to a planet, nobody ever seems to bring up that whole heat issue of raining all that material down.
Air is a lot lighter than water to be sure, and our oceans mass about 300 times what our atmosphere does, but that still means you need to take centuries to import that mass of gas to avoid overheating the place. Though if the place is already fairly cold like Mars would be, much of that heat might be absorbed into the upper levels of rock so long as you give it time. Of course changing the temperature of rock also changes its size, materials expand and contract with temperature changes and if you are massively altering the temperature of a planet because it's too cold for people, or too hot, expect a lot of shaking and shattering and shifting as the ground expands or contracts, plus all the flash floods and erosion of adding air and water. Terraforming is not a gentle process on a planet and is not something that makes the place look the same except for seeming to spray paint it with ocean blue, plant green, and cloud white. This is remaking whole continents, you are going to mess with the geography as much as if you engaged in asteroid orbital bombardment or flat out nuking the surface, even if you are doing things slow.
Incidentally we often do talk of nuking planets as part of terraforming them, usually in humorous tone but it’s not actually a joke, that is one of the cheaper ways to terraform in terms of rapid atmosphere generation and warming, and lifeless planets are generally already radiation scoured hellholes so temporarily irradiating the surface when you plan to plow that all under anyway while making your soil is not really a big deal. Fall out is fairly short term before decaying, and even if you didn’t bury it under meters of rock as shielding it would be long gone as a threat before that planet was some place people walked around on in shorts and t-shirts eating fruit grown on trees under an open sky. You also aren’t just dropping a few comets on a planet to bring it water and air.
The entire Asteroid Belt is only two or three times as massive as Earth’s Oceans, for all its millions of rocks, and wouldn’t have enough ice for it. You need to add around a billion cubic kilometers of water to a planet to get to Earth levels and your typical big comet might get you a millionth of the way there. Fortunately there is no shortage of ice, even at this scale, out in the Kuiper Belt and Oort Cloud, water is one of the most common molecules in the Universe.
Though you might find it cheaper to import in hydrogen from gas giants and bind it to locally available oxygen to make your water. Alternatively a dome is a lot easier, you only need to add about a kilogram of air per square meter of floor for every meter of height the thing has. You probably only need a few hundred larger comets rich in ammonia for the nitrogen to provide all the air, and water, that you would need to fill up a domed-over planet of gardenscapes and shallow lakes. That is a lot more manageable and something you can build incrementally. Eventually you will leak enough air from them all to create an atmosphere, but if you want that ocean you need to leak a lot more and you might want to be thinking about making your domes mobile or buoyant, since they do need floors anyway.
Atmospheres on planets leak for a variety of reasons and leak faster the thicker they are, but the main method of losing air and water is from hydrogen atoms, when some bit of radiation or chemistry breaks them free, to be bounced out of the atmosphere. Wrapping the planet in a magnetic field causes them to deflect back down and be recaptured. Magnetospheres are made naturally by having a ton of molten metal spinning around in the core of a planet but are hardly the only way to make a magnetic field and not a good way of doing it either. If we’re considering trying to protect Mars from the solar wind our Sun generates, as the major cause of atmosphere depletion, then we need not even give Mars a magnetic field, we could just stick a big electromagnet at Mars’ own L-1 Lagrange point with the Sun, run on solar power, and rely on that to deflect the already weaker solar wind away.
Calculations vary but something in the 1 gigawatt range should be sufficient and that’s the equivalent of a modern nuclear reactor or about a square kilometer of solar panels. It’s also nothing compared to the energy budget of terraforming in general, remember we were talking about adding water at a rate of half a billion joules per cubic meter, and needing a billion-billion of them, and that’s way more energy than it would take to run that Lagrange Magnetic Shield for the entire lifetime of this solar system. Alternatively you can also put your magnets in orbit or even in big loops around the planet underground.
We often talk about using active support structures like the Orbital Ring to create super-strong shells for hollow planets, what we call Shellworlds, and those are essentially giant electromagnets and easily convertible into magnetospheres. So if you are building your world that way, making a shell you plan to fill with cheap hydrogen gas or something more exotic like dark matter or black holes to generate your gravity, you already have the magnetosphere built into it. Though for that matter a shell-planet built around a spinning dead star, be it black hole, old neutron star, or old and cold white dwarf, do have an awful strong magnetic field all on its own. This is why you don’t bother drilling into some planet’s core and nuking the heck out of it to create a magnetic field around the planet.
Indeed about the only reason you would ever drill down to some big rock’s core is if you were planning to make a hollow chamber down there and stick a black hole in it for generating artificial gravity. That’s a pretty extreme thing to do, and of course requires you be able to make artificial micro black holes, but is one way to add gravity to a planet. As a heads up, it doesn’t matter how big a planet is, or asteroid or moon, it takes the same mass per area of surface to generate Earth-like gravity, about 12 billion kilograms per square meter. Gravity falls off in strength as the inverse square of distance while the surface area of a sphere rises with the square of distance, so they counter each other out. However mass does not rise with the square, but rather the cube of radius, and various bits of solid and mundane matter occupy only a range of about a ton per cubic meter, like ice, to 20 times that, for fairly rare and dense materials like gold and osmium.
I’d emphasize rare because most dense materials are pretty rare and valuable to be wasting on generating gravity compared to hydrogen and helium, which make up nearly all the mass of normal matter in the Universe. Terraforming very large shell planets, like Saturn whose gravity at the edge of its atmosphere is equal to Earth’s, can use cheap hydrogen and helium gas compressed under its own gravity, but if you want to make some place like Mars have Earth-like gravity then you’d have to hollow out the core and replace it with something dense like Osmium or Gold, or otherwise use an artificial black hole or some sort of degenerate matter you found a way to keep stable, like a white dwarf or neutron star. Those are kept stable at their density because they have the whole mass of a star pulling them together without any fusion going on to push them apart anymore, but it is conceivable you might be able do that electromagnetically, and if you could do that, or create black holes, then you could arrange for Earth-like gravity on any decently sized rock, even a fairly modest asteroid, and the same would apply if you figured out a way to generate artificial gravity with electricity. We have no idea how but there is a decent chance it is possible to generate gravity without mass. Indeed the term “Terraforming” was coined by sci-fi author Jack Williamson in regard to making asteroids have Earth-like gravity via an artificial gravity device.
One way around having to use 12 billion kilograms of matters per square meter of living area, with known technology, is to simulate gravity by rotation, but if you like your planets spherical and your gravity natural you do have the option of building multiple layers of surface, concentric shells, what we call a Matrioshka Shell World, see that episode for details. You might be saying isn’t all this a little high-tech and resource intensive? How about simpler methods? And that is kind of the problem, the simple methods all involve the brute application of raw mass and energy too, we can just cheat sometimes by using what’s already there or automation – including biological automation such as genetically engineered microbes – to get the job done. We can make a device that will turn a rock into oxygen and either glass or metal.
Your typical rock is just oxygen plus silicon or iron or aluminum or such after all. It takes a lot of energy, but we could probably engineer a microbe that did that and used photosynthesis to power it. That sort of approach is a popular notion too, but often makes folks think it would happen fast. In practice biology is less efficient than some giant machine we might build to do the same thing but using solar power. So given that photosynthesis is usually less than 1% efficient, and probably a good deal less if we were measuring that efficiency in terms of converting sunlight into oxygen and soil, it means your typical planetary budget for biological terraforming is going to be on the order of a billion megawatts at most.
Which sounds huge, and indeed is, but is planet-wide, and you need around 30 megawatts to get a kilogram of oxygen per second, so you are generating about a quadrillion kilograms a year – though that is probably optimistic – and you need around a thousand times that, plus whatever is leaking back into solid form through oxidation. So it is viable but it isn’t quick. It really would be faster to carpet-nuke the place and wait for the fallout to decay. A machine will be more efficient and thus faster.
But machines don’t build themselves, microbes do, so are preferable, if you have the time, unless you’ve got self-replicating machines. Of course we probably will have those inside the century so it mostly comes down to practical application and preference, and the line between self-replicating machines and biological lifeforms, especially ones genetically engineered to exist on some dead planet, is fairly blurry and probably fairly arbitrary. Critical notion though, whether you’re building giant rotating orbital habitats or terraforming planets or outright fabricating shell-worlds and megastructures, automation is the key, and one of the reasons we tend to favor rotating habitats is because it uses so much less mass per unit of living area, which also makes them faster to build.
You have to terraform the insides of those too and that is not just a matter of dumping in rock and water and air, you will go through many epochs of complexity as you build from simple organisms that can live without a complex and diverse ecosystem to slowly altering it into something big plants and animals and people can live in. Fortunately epochs, when we’re talking microbes, are quick things, lifespans of days not decades, so you can move up the complexity chain faster, and you’re not waiting on evolution either. You probably are looking at massive dirt factories involved in any terraforming project that are using the kind of energy and automated manpower that would dwarf our whole modern industrial infrastructure though. Fundamentally para-terraforming, whether its big domes or big spinning cylinders, is your incremental approach, and thus the one you are likely to use.
When we want to terraform a promising planet in another solar system, it’s likely to be the last place in that solar system colonists move onto, as they get all their other habitats and industry built up off-world, while carrying out the long and energy intensive process of terraforming that planet as some sort of crown jewel. In general you are better off not having anyone living on that planet until terraforming is well under way too, as noted, the process is very destructive, especially when done quickly. It's also not likely to ever be something where folks cared if it was made natural and eternal, no natural planet is a static thing anyway, but you are far more likely to see solutions like that LaGrange Magnetic Shield, or the use of giant swarms of mirrors or shades to increase or decrease the sunlight and temperature of a world, than doing stuff like nuking the core or moving the planet closer or further from its sun, because it’s the difference between wanting to keep your yard a bit shadier by planting a tree or erecting a shade umbrella, versus moving a mountain to just shade your yard. The mountain will shade your lawn much more naturally and require no maintenance once it's done, but replacing a shade every couple years or planting a new tree every few decades is still way less effort than moving that mountain. If your civilization has enough energy and automation it might not care, but there are plenty of other awesome things you can do with that energy too, so someone talking about moving whole planets around to make them warmer or mashing two together to make one bigger planet with better gravity is likely to have folks asking why you don’t just tear the planets apart to make trillions of rotating habitats given that it would be faster, easier, and provide a million times the living room for people or nature preserves or whichever.
This doesn’t mean we’re not terraforming in the future, it’s just recognizing that you have a whole sliding scale of effort, and it is probably way easier to engineer an ecology around living on a planet with lower gravity, a different day and year length, and relatively shallow lakes rather than oceans, than it is to adjust all those. Adding air is not too hard, adding that protective magnetosphere is not either, and lakes a few meters deep get most of the weather and ecology options that oceans kilometers deep offer. Replacing and repairing your solar shades and mirrors is easier than dragging that planet around.
So I think that is what we’ll mostly see for terraforming, para-terraforming of most places to create human comfortable environments, and bioforming everything to cover the remaining gap. For purists who hate bioforming, there’s always O’Neill Cylinders and those can be made continent sized if need be. Mars will probably be terraformed, as will Venus, and possibly some of the Moons of Jupiter, we looked at the specific approaches in our Springtime on Mars, Winter on Venus, and Summer on Jupiter episodes, but terraforming beyond this solar system is likely to be either very heavy on bioforming, and very heavy on the engineering side to the point of being effectively megastructures as much as planets, or be limited to those planets a lot closer in mass and makeup to Earth than Mars or even Venus are. The good news is that there are probably billions of planets that are better picks for terraforming out there in the galaxy than Mars and Venus.
Of course it’s a long trip to get there, to claim those billions of worlds and terraform them, and to do that we have to become more than an Interplanetary Species, we have to become an Interstellar Species, and we’ll look at that in the next and final episode of this series. Whether our future will be on Terraformed Planets, Artificial Cylinder Worlds, Virtual Paradises, or any of the scenarios we discuss on the show, one thing that seems certain is that the key to unlocking it will be with ever improving science and technology, and as we head into the holidays, if you’re still looking for gifts, I’d suggest the gift of knowledge and problems solving skills. If you know an inquisitive investigator that loves asking “Why?”, our partner, Brilliant may be just the thing for you, and them. Brilliant is a problem solving based website and app with a hands-on approach, with over 60 interactive courses in math, science, and computer science, like their course on scientific thinking, which helps show scientific principles and how valuable they are to have in your problem solving toolbox. It’s a great course to introduce you to Brilliant’s fun and thought-provoking approach to learning, and from there you can go on to any of their 60+ other great courses. If you are looking to improve your own skills in math, science, and computer science, and want to help support our show and have fun while you’re doing it, or know someone else who would, you can try Brilliant out, for free, or get is as a gift for a loved one, by going brilliant.org/IsaacArthur.
So we’ll be finishing our series on Becoming an Interplanetary Species, along with finishing the year 2020, with a look at Becoming an Interstellar Species, but before that we’ll be looking at how to navigate interstellar space, and also how we might begin the process of going beyond being an interplanetary species in this solar system, as we look at Low-Tech Kardashev-2 Civilizations. We also have our monthly livestream Q&A coming up on Sunday, December 27. If you want alerts when those and other episodes come out, make sure to subscribe to the channel, and if you’d like to help support future episodes, you can donate to us on Patreon, or our website, IsaacArthur.net, which are linked in the episode description below, along with all of our various social media forums where you can get updates and chat with others about the concepts in the episodes and many other futuristic ideas.
Until next time, thanks for watching, and have a great week! [a]As an interesting aside, this is the reason terraformed planets will probably have quite shallow oceans--the flatter geologiclly dead terrain and the relatively less native water.