The Economics of Terraforming.

[GrandMasterTerwynn]

I know that there are stories written about it. I know that there are a fair number of us who theorize about it. My question, though, is how likely is it that we'll actually terraform other worlds (in the solar system)? Will it make economic sense to terraform a planet like Mars or Venus, or even the largest moons of Jupiter to suit our whims? Or are humans more likely to engage in less long-sighted projects, such as building colonies out of asteroids? After all, terraforming a planet will take many centuries and millenia of work, and massive and expensive feats of engineering to pull off.

So, does it make sense to terraform other planets?

[Zero]

One thing about terraforming a world is that if it's done successfully by a private organization, then they may be able to reap the rewards of an entire planet's work. An entire planet's production would be nice for any company, even if getting there would be a shithole.

I honestly doubt it will ever be done as anything besides a government program type of thing. I couldn't see a corporation wanting to put that much money into THAT long-term of an investment.

[Erik von Nein]

The only thing economical about terraforming is that it would, once the terraforming is complete, allow for cheaper housing to be built, since it would no longer need to be air-tight, provide it's own atmosphere, etc. They could also build bigger buildings and have larger cities. Otherwise I don't see much of a point.

[GrandMasterTerwynn]

One thing about terraforming a world is that if it's done successfully by a private organization, then they may be able to reap the rewards of an entire planet's work. An entire planet's production would be nice for any company, even if getting there would be a shithole.

I honestly doubt it will ever be done as anything besides a government program type of thing. I couldn't see a corporation wanting to put that much money into THAT long-term of an investment.

But what private corporation would have the resources needed to do something even as seemingly straightforward as terraforming Mars? To terraform Mars, you need to liberate a lot of greenhouse gases and water, and seed the planet with life to gradually kick up the oxygen content of the atmosphere. And depending on what scheme you're going with, you'll need a big mirror to reflect more sunlight on Mars to give things a bit of a boost. And Mars is the easy one. Terraform Venus? You need a way of cooling the planet and getting rid of 90% of its atmosphere. Terraform a Galilean? You'll need a giant mirror with many times the surface area of the moon, essentially an enormous Solar Death Ray the size of a planet with the moon at its focal point.

[Zero]

Even a planet that hasn't been terraformed will have resources, like raw materials and all that, and if we're sufficiently advanced that we're attempting such an endeavor, it isn't such a far assumption to believe that we may already have fusion power at our disposal. If this is so, the energy required would be less of an issue, and many of the raw materials for whatever tools you will require can be found on the barren planet itself. However, as I said, I doubt anybody would ever want to put in for an investment THAT long term, and THAT big. As I said, I believe the best chance of such a thing being done is through an effort put forth by a government program, or perhaps a program that several of the nations of the world buy into for the sake of having land on the new world.

[Zor]

Terraforming (for the in-system goals at least) in my opinion will most likely it will be some sort of government/joint governer project with plenty of corperate assistance and contracting. I don't think it could be profitable for a corperation. It would be much more profitable for them to build O'neil Island-IIIs (both open and closed types) and sell off plots of land to rich people and industrialists.

Zor

[wolveraptor]

On a similar note, wouldn't it be easier to build orbital colonies, since there would be no gravitational obstructions? Or would they be too susceptible to radiation and debris? Would the cost of making them spin to simulate gravity be too high?

[Zor]

On a similar note, wouldn't it be easier to build orbital colonies, since there would be no gravitational obstructions? Or would they be too susceptible to radiation and debris? Would the cost of making them spin to simulate gravity be too high?

For spinning them and there mirrors, it does not take all that much energy once you get them started, so i would not expect it to cost that much to spin.

Zor

[Lord Zentei]

Err. This depends a lot on the timeframe and total cost of these two kinds of project, and how soon the terraformers could ditch not only their pressure suits but their rebreathers also. Plus: the impact of living in low-gee for most of your lifespan needs to be better understood (since orbital colonies can be built with normal gee but terraformed planets and moons, obviously, cannot).

So: for now, "insufficient data", I guess.

[GrandMasterTerwynn]

Err. This depends a lot on the timeframe and total cost of these two kinds of project, and how soon the terraformers could ditch not only their pressure suits but their rebreathers also. Plus: the impact of living in low-gee for most of your lifespan needs to be better understood (since orbital colonies can be built with normal gee but terraformed planets and moons, obviously, cannot).

So: for now, "insufficient data", I guess.

A pronouncement of "insufficient data" tends to lend credence to the thought that terraforming will be thought of as enormously impractical for a long time to come.

Want the convenience of Earth-like gravity? Terraform Venus. The problems, of course, are getting rid of well over 99% of the planet's carbon dioxide, cutting down its insolation (big sunshade), and supplying it with the water that nature conveniently drove off early in the planet's history. This would involve a lot of comets, one or two of the larger moons of the gas giants (Enceladus orbiting Saturn would do, but Enceladus seems to be geologically active, and a large lump of water that's warm enough to be active might have native primitive life on it.), or the hairy task of relocating a large Kuiper-belt object to the inner solar system (such as Pluto . . . that'd resolve the whole rabid debate about what to classify it as.)

Terraforming Mars would be easier, you just have to release all the CO2 locked up in the planet's rocks and polar ice caps. Except you'd have to substitute the CO2 with another species of greenhouse gas (and if that new greenhouse gas doesn't do the trick, you'll have to build an enormous space-going mirror to reflect more sunlight on Mars.) if you want your terraformers to ever take off their rebreathers. CO2 is decidedly toxic above a certain fraction. Failing that, you could eventually genetically engineer people to live on Mars, that opens the whole unpleasant can of worms over eugenics.

Terraforming Callisto or Ganymede (we'll assume the same concerns that lead to the decision to send Galileo screaming into Jupiter at the end of its life will result in the transformation of Europa into an enormous nature preserve,) would involve building a gigantic arrary of mirrors to quintuple the solar energy falling on the two moons. Their atmospheres will have to be thick (around 2-2.5 bars) and at least a third of it will be made up of methane. And that will only raise a third of the surface area of each moon above the freezing point of water. And there's that small problem of both moons having about the same surface gravity as the Moon, again possibly requiring some sort of genetic modification of the people living there (though one might see this as a logical offshoot of treatments for osteoperosis, arthritis, and poor cardiovascular function for Earthly people.)

So the total cost will be however much it costs to build an enormous mirror with the diameter of a planet (all terraforming schemes will require one. It's just a matter of the size and placement of the thing.) It will also be the cost of time and effort expended in moving large bodies around the Solar System. The total cost in time will be between a century and a millenium or two just to get the atmospheres to the point where we can begin the process of building a planetary ecology, and rendering the atmosphere both workable and breathable to humans and other large animals. The latter process will only move as fast as the organisms we engineer to take on the task. As biology is notoriously slow, this process will take millenia, though one could cut down the time considerably if they constructed enormous factories to help the process out via lots of brute-force non-biological chemistry. That requires lots of power though.

[Turin]

I'm going to go out on a limb and suggest that a corporation is more likely to attempt this sort of thing than a government. A government would have to deal with enormous political pressure from within... a government that is spending a lot of resources on terraforming will be attacked politically for not spending those resources on social programs, economic development with shorter timelines, the military, etc. A corporation could be spun off from a larger corporation with the explicit goal of terraforming. Investors who invest in such a corporation will be viewing it as the ultimate long-term investment - most likely the investors will be other corporations themselves rather than individuals.

[Lord Zentei]

Err. This depends a lot on the timeframe and total cost of these two kinds of project, and how soon the terraformers could ditch not only their pressure suits but their rebreathers also. Plus: the impact of living in low-gee for most of your lifespan needs to be better understood (since orbital colonies can be built with normal gee but terraformed planets and moons, obviously, cannot).

So: for now, "insufficient data", I guess.

A pronouncement of "insufficient data" tends to lend credence to the thought that terraforming will be thought of as enormously impractical for a long time to come.

Yes, I reckon that this would be the most likely answer at present.

Want the convenience of Earth-like gravity? Terraform Venus. The problems, of course, are getting rid of well over 99% of the planet's carbon dioxide, cutting down its insolation (big sunshade), and supplying it with the water that nature conveniently drove off early in the planet's history. This would involve a lot of comets, one or two of the larger moons of the gas giants (Enceladus orbiting Saturn would do, but Enceladus seems to be geologically active, and a large lump of water that's warm enough to be active might have native primitive life on it.), or the hairy task of relocating a large Kuiper-belt object to the inner solar system (such as Pluto . . . that'd resolve the whole rabid debate about what to classify it as.)

I imagine you would want a Hochmann transfer for that icy object... Even this would be bloody monstrous in terms of expense and time. Hell, its hard enough to engineer a randezvous with a goddamn tin can, much less a moon sized object. Any hope of harvesting the H2SO4? Or isn't there enough of this? Also, how exactly would the CO2 be gotten rid of?

As for the Sun-shield - this would have to be an object ca 20000 km in diameter with active attitude control systems. I'm wondering how this compares with a space habitat in terms of expense (probably less if you get a nearly-Earth sized planet).

Terraforming Mars would be easier, you just have to release all the CO2 locked up in the planet's rocks and polar ice caps. Except you'd have to substitute the CO2 with another species of greenhouse gas (and if that new greenhouse gas doesn't do the trick, you'll have to build an enormous space-going mirror to reflect more sunlight on Mars.) if you want your terraformers to ever take off their rebreathers. CO2 is decidedly toxic above a certain fraction. Failing that, you could eventually genetically engineer people to live on Mars, that opens the whole unpleasant can of worms over eugenics.

I had in fact more of this possibility than the other scenarios; a greenhouse chain reaction was mentioned with the CO2 released by the terraforming process helping with said process (some suggested a very dark coloured GM algae that would darken the surface, reducing the albedo and be engineered to die off at a certain temperature. However as you point out, biology is slow, so this is probably not very practical).

As for the human modification: some exotic kind of reversible surgical/implant procedure could be used instead maybe, though obviously this is speculation on my part. If one goes the GM route, it might be a solution to the gravity problem, though then you have basically induced speciation (well, not quite, but for practical purposes). Not really an ideal solution.

Terraforming Callisto or Ganymede (we'll assume the same concerns that lead to the decision to send Galileo screaming into Jupiter at the end of its life will result in the transformation of Europa into an enormous nature preserve,) would involve building a gigantic arrary of mirrors to quintuple the solar energy falling on the two moons. Their atmospheres will have to be thick (around 2-2.5 bars) and at least a third of it will be made up of methane. And that will only raise a third of the surface area of each moon above the freezing point of water. And there's that small problem of both moons having about the same surface gravity as the Moon, again possibly requiring some sort of genetic modification of the people living there (though one might see this as a logical offshoot of treatments for osteoperosis, arthritis, and poor cardiovascular function for Earthly people.)

Frankly, I doubt that humans could thrive for long in a 0.16 g environment, though a moon-base may resolve that question more. With such a high concentration of methane, the rebreathers could not be dropped which means that for comfort the colonists would have to live inside enclosed areas. Not really worth it, unless the $$ cost of pressurising the habitats is greater than the terraformation.

So the total cost will be however much it costs to build an enormous mirror with the diameter of a planet (all terraforming schemes will require one. It's just a matter of the size and placement of the thing.) It will also be the cost of time and effort expended in moving large bodies around the Solar System. The total cost in time will be between a century and a millenium or two just to get the atmospheres to the point where we can begin the process of building a planetary ecology, and rendering the atmosphere both workable and breathable to humans and other large animals. The latter process will only move as fast as the organisms we engineer to take on the task. As biology is notoriously slow, this process will take millenia, though one could cut down the time considerably if they constructed enormous factories to help the process out via lots of brute-force non-biological chemistry. That requires lots of power though.

OK, so we need to consider the mass of the hardware versus the mass of the spaceborne habitats. Since the latter require extensive radiation shielding with a huge mass per protected volume, I think it is reasonable to surmise that hollowed out asteroids will be used instead, and the tunnels filled with pressurised units.

What would really be helpful is if we could make an estimate for the mass of payload that has to be launched from our production facilities (presumably located on the moon eventually) for each payload seperately, plus the energy needed to accomplish our missions (I'm looking at that Hochmann transfer for Enceladus here...).

So, for the payload, for a population of 1000, given 40 square meters of living space, cabin structure, say 2500 tons, 1000 tons of atmosphere, power plant, etc for another 2500 tons fir a total of 6000 tons. Let's be generous and give them 10000 tons (they'll need vehicles and machine shops, etc). Part of the bulk mass of the structure can be mined from the hollowed out asteroid, but then this is also true of the mirrors. So roughly 10 tons per colonist. Quite a lot actually.

For the mirror: lets give it a radius of 1e7 meters, thickness of 0.03 millimeters and made of aluminium, gives roughly 3e10 tonnes; which would be space habitat for some three billion people by the earlier estimate. Of course, a successful terraformation gives higher quality habitat, and there is the issue of the relative cost of active maintenance of the respective systems: huge mirror in the right place versus maintaining a pressurized area, as well as the issue of the timeframes involved.

[Lord Zentei]

Of course a huge mirror is much easier to manufacture

But at least this way we are a step closer to guesstimating by how much the mirror has to be cheaper. How long do we want to wait for such and such a benefit would be next.

[GrandMasterTerwynn]

Want the convenience of Earth-like gravity? Terraform Venus. The problems, of course, are getting rid of well over 99% of the planet's carbon dioxide, cutting down its insolation (big sunshade), and supplying it with the water that nature conveniently drove off early in the planet's history. This would involve a lot of comets, one or two of the larger moons of the gas giants (Enceladus orbiting Saturn would do, but Enceladus seems to be geologically active, and a large lump of water that's warm enough to be active might have native primitive life on it.), or the hairy task of relocating a large Kuiper-belt object to the inner solar system (such as Pluto . . . that'd resolve the whole rabid debate about what to classify it as.)

I imagine you would want a Hochmann transfer for that icy object... Even this would be bloody monstrous in terms of expense and time. Hell, its hard enough to engineer a randezvous with a goddamn tin can, much less a moon sized object. Any hope of harvesting the H2SO4?

The atmosphere of Venus is 96.5% CO2 and ~3.5% N2, with everything else filling in the last fraction of a percent. The H2SO4 forms from photochemical reactions from the SO2 and H2O in the Venusian atmosphere, so the result is, there isn't water vapor and harvestable H2SO4 to produce a global layer of water more than a few centimeters deep. And all of that would be promptly locked up in the Venusian regolith.

Also, how exactly would the CO2 be gotten rid of?

The methods for doing so aren't elegant. You can boost the water content of Venus' atmosphere so it will support genetically engineered acid-resistant cyanobacteria and wait for a very long time for them to lock up the CO2. You can use enormous lasers tuned to the absorption bands of CO2, with the thought being that you can heat up the gas enough that it will achieve escape velocity and fly off into space. Of course, to liberate all the CO2 with this method will apparently require the input of 2.5x10E+28 joules of energy. To do that in a reasonable timescale will require the construction of a number of big, powerful lasers that, if seized by a band of terrorists, could just as easily be used to toast significant fractions of Earth. Or you could mine the stuff (using big scoopships, (carbon will eventually become very valuable stuff.) Failing that, you could simply keep the enormous mirror in place and wait until the atmosphere cools enough that it all precipitates out as dry ice. Though, since Venus happens to contain the Solar System's largest store of carbon outside the cores of the gas giants, the prospect of removing all that dry ice is enough to induce nightmares on its own.

As for the Sun-shield - this would have to be an object ca 20000 km in diameter with active attitude control systems. I'm wondering how this compares with a space habitat in terms of expense (probably less if you get a nearly-Earth sized planet).

The sun-shield would essentially be an enormous solar-sail. With the appropriate ballasting in place, it would be its own attitude control system. If you were so inclined, you could focus the reflected sunlight onto a massive solar power generation facility and use the energy to power your enormous atmosphere-boiling laser, or provide power for interplanetary beam-riders, recouping some of the costs, or making anyone inside the orbit of Venus very, very nervous.

As for the human modification: some exotic kind of reversible surgical/implant procedure could be used instead maybe, though obviously this is speculation on my part. If one goes the GM route, it might be a solution to the gravity problem, though then you have basically induced speciation (well, not quite, but for practical purposes). Not really an ideal solution.

Speciation is going to occur regardless. If we don't do it, eventually evolution will cause the people living on Mars to gradually adapt to the lower gravity and odd atmospheric composition. Since permanent Martian residents can't easily return to the crushing gravity of Earth, they will form a relatively isolated population (especially after the population growth by native birthrate exceeds the population growth through immigration.) Isolated populations under selection pressure produce new species.

Frankly, I doubt that humans could thrive for long in a 0.16 g environment, though a moon-base may resolve that question more. With such a high concentration of methane, the rebreathers could not be dropped which means that for comfort the colonists would have to live inside enclosed areas. Not really worth it, unless the $$ cost of pressurising the habitats is greater than the terraformation.

If one wants to colonize the Galilean moons in their natural state, they will need to live underground, since the radiation environment around Jupiter is fairly harsh. They will also need extensive networks of fusion reactions to supply them with the energy needed to grow crops and carry out the process of living. This will limit the extent of colonization.

If one wants to live on the moons, then terraforming is actually something of a viable option. The construction of giant mirrors reduces the need for native fusion reactors, since we'd be concentrating the energy from the big fusion reactor a couple billion kilometers away to useable intensities. And according to the National Academies Press Emergency and Continuous Exposure Limits for Selected Airborne Contaminants, Volume 1 (2000) methane has little toxicity (inducing mild depression and lethargy in concentrations of 50% to 90% in an atmosphere of oxygen . . . . I'm suggesting only using 20% - 25% methane in an atmosphere otherwise composed of N2 and O2) when oxygen is readily available. So the rebreathers might not be necessary, though it would be wise to dress warmly, and you'd have to genetically engineer cyanobacteria to lock up the photochemical smog that will otherwise form and turn a terraformed Ganymede or Callisto into a featureless smoggy orange ball. The density of the atmosphere will serve to partially attenuate the particle radiation induced by Jupiter's enormous magnetic field, reducing the need for shielding of one's habitats.

OK, so we need to consider the mass of the hardware versus the mass of the spaceborne habitats. Since the latter require extensive radiation shielding with a huge mass per protected volume, I think it is reasonable to surmise that hollowed out asteroids will be used instead, and the tunnels filled with pressurised units.

An asteroid habitat could concievable recoup some of the costs of its construction by processing the minerals extracted in the process of hollowing it out. Since this takes energy and time, the amount of costs recouped will be reduced.

For the mirror: lets give it a radius of 1e7 meters, thickness of 0.03 millimeters and made of aluminium, gives roughly 3e10 tonnes; which would be space habitat for some three billion people by the earlier estimate. Of course, a successful terraformation gives higher quality habitat, and there is the issue of the relative cost of active maintenance of the respective systems: huge mirror in the right place versus maintaining a pressurized area, as well as the issue of the timeframes involved.

The mirrors and sunshades and what-have-yous also require maintenance. I suppose it would be instructive to compare the costs of maintaining an asteroid colony versus the maintaining of a terraformed world. Get it right, and the atmosphere will generally maintain itself, provided the insolation doesn't exceed or fall below certain tight tolerances.

[Turin]

Speciation is going to occur regardless. If we don't do it, eventually evolution will cause the people living on Mars to gradually adapt to the lower gravity and odd atmospheric composition. Since permanent Martian residents can't easily return to the crushing gravity of Earth, they will form a relatively isolated population (especially after the population growth by native birthrate exceeds the population growth through immigration.) Isolated populations under selection pressure produce new species.

What's the the selection pressure if you've got the colony equipped with rebreathers and good medical care? Conditions aren't likely to be fatal enough to prevent breeding, just enough to reduce lifespan. Unless that reduction is enough to drop it close to the age of reproduction, there's no selection pressure.

[Plushie]

A few quick questions:

1. What about Titan?

2. If we were to begin a fusion reaction or a hundred in a very hydrogen and deuterium rich environment, would the reaction become self-sustaining? (If you can guess what I'm getting at, you get a cookie and a chance to call me crazy)

3. Couldn't we use very light electrical currents to cause a lot of Venus' atmosphere to become charged and just use some kind of massive space-vacuum that uses something akin to a statically charged swiffer brush to move it all away? How feasible is this versus other options?

4. How feasible is it to, er, move a planet? As in change the orbit?

[GrandMasterTerwynn]

A few quick questions:

1. What about Titan?

What about it? It's much farther away from the Sun than Jupiter's moons are. You would need a much, much bigger mirror to provide the sort of insolation needed. (Instead of being just five times the surface area of Ganymede or Callisto, it would be twenty-five times the surface area of Titan (as the intensity of sunlight is inversely related to the square of the distance. Saturn is about twice as far from the Sun as Jupiter, so it recieves only a quarter of the sunlight. Therefore, a mirror big enough to warm Ganymede is only a quarter the size needed to warm Titan.) A mirror that large would have something like half of Saturn's diameter.

2. If we were to begin a fusion reaction or a hundred in a very hydrogen and deuterium rich environment, would the reaction become self-sustaining? (If you can guess what I'm getting at, you get a cookie and a chance to call me crazy)

No. Fusion reactions require immense pressures and temperatures. Suggesting that one could create a runaway fusion reaction in a simple hydrogen rich environment is about as absurd as the belief that setting of a nuclear bomb will cause the atmosphere and ocieans of Earth vanish in an enormous conflagration. Turning a gas giant into a sun is an idea best left in the realm of mastubatory fantasy. (Sure you could create a brown dwarf warm enough to heat its moons to habitable temperatures, but this would involve introducing between fifteen to forty Jupiter-masses of extra hydrogen to Jupiter. Where you would get this gas, how you would move it, and how you would cope with the gravitational effects of suddenly transforming the Solar System into a close binary are very daunting problems.)

3. Couldn't we use very light electrical currents to cause a lot of Venus' atmosphere to become charged and just use some kind of massive space-vacuum that uses something akin to a statically charged swiffer brush to move it all away? How feasible is this versus other options?

You're talking about ionizing the atmosphere of Venus. You could do it locally, by extending long charged tethers into the atmosphere, dangling from orbiting spaceships. You would need a bloody lot of space-ships, though.

4. How feasible is it to, er, move a planet? As in change the orbit?

Depends on how much energy you're willing to spend, and how long you want to wait. If you were willing to wait millions of years, you could move an entire planet with enough encounters with a modest-sized asteroid. (By timing the encounters correctly, you increase the planet's angular momentum at the expense of the asteroid's, or you decrease it by using the asteroid to steal some of it away. That's how gravitational slingshots work. The Voyager probes were accelerated by stealing some of the angular momentum from the planets they flew by. However, as a space probe weighs a ton, and a gas giant weighs several trillion-trillion tons, the change to the gas giant's orbit is statistically insignificant. The asteroid, of course, would require some manner of rocket motor bolted onto it, so you can adjust its trajectory and speed between encounters.)

[Plushie]

Ok, since 1 and 2 seem out, I'll just continue on with 3 and 4.

3. How does this method compare in efficiency and energy requirements with the other methods? Could it be used in conjunction with any number of the other methods?

4. Would it be possible to destablize a planet's orbit with a heavy-handed application of a very large number of very powerful nuclear devices and then "catch" it when it entered the desired orbital slot with another nuclear stockpile?

[Lord Zentei]

I imagine you would want a Hochmann transfer for that icy object... Even this would be bloody monstrous in terms of expense and time. Hell, its hard enough to engineer a randezvous with a goddamn tin can, much less a moon sized object. Any hope of harvesting the H2SO4?

The atmosphere of Venus is 96.5% CO2 and ~3.5% N2, with everything else filling in the last fraction of a percent. The H2SO4 forms from photochemical reactions from the SO2 and H2O in the Venusian atmosphere, so the result is, there isn't water vapor and harvestable H2SO4 to produce a global layer of water more than a few centimeters deep. And all of that would be promptly locked up in the Venusian regolith.

I knew it was little, but well, that's not going to cut it.

And at 8.40e+19 kg, moving Enceladus is pretty fucking hefty in terms of energy requirement. And by "pretty fucking hefty" I mean "astronomical". We're talking about, what? 1e+28 to 1e+29 joules or somesuch madness? Of course that is what you estimated for the laser method of liberating the CO2

The methods for doing so aren't elegant. You can boost the water content of Venus' atmosphere so it will support genetically engineered acid-resistant cyanobacteria and wait for a very long time for them to lock up the CO2. You can use enormous lasers tuned to the absorption bands of CO2, with the thought being that you can heat up the gas enough that it will achieve escape velocity and fly off into space. Of course, to liberate all the CO2 with this method will apparently require the input of 2.5x10E+28 joules of energy. To do that in a reasonable timescale will require the construction of a number of big, powerful lasers that, if seized by a band of terrorists, could just as easily be used to toast significant fractions of Earth.

By "very long" I imagine you are talking millennia - which is beyond our racial attention span barring some serious life extension. Terrorists aside, the laser sounds more attractive. Though it's a pain to loose all of that carbon.

Or you could mine the stuff (using big scoopships, (carbon will eventually become very valuable stuff.) Failing that, you could simply keep the enormous mirror in place and wait until the atmosphere cools enough that it all precipitates out as dry ice. Though, since Venus happens to contain the Solar System's largest store of carbon outside the cores of the gas giants, the prospect of removing all that dry ice is enough to induce nightmares on its own.

I'm not sure how such scoopships would be implemented - perhaps these ideas could somehow be combined using smaller mirrors to create "cold areas" that allow precipitation and a large half-mirror to lower the temperature overall (substantially), thus causing the CO2 to precipitate in designated areas. Don't know how practical that is.

The sun-shield would essentially be an enormous solar-sail. With the appropriate ballasting in place, it would be its own attitude control system.

Yes, I reckoned as much - I was more thinking in terms of the requirement for active maintenance of the orbit; it's not a passive system, unlike bulk mass as for a hollowed out asteroid or an ideal atmosphere. Keeping as many essential systems passive is better, in the case of possible future economic collapse.

If you were so inclined, you could focus the reflected sunlight onto a massive solar power generation facility and use the energy to power your enormous atmosphere-boiling laser, or provide power for interplanetary beam-riders, recouping some of the costs, or making anyone inside the orbit of Venus very, very nervous.

Mercury, pfft. If we go to the outrageous trouble of terraforming Venus it will be because low gee worlds are bad for human physiology in the long-run. At least I can't see any other reason to go to all that trouble. So one of the big questions is whether low-g environments such as Mars are habitable in the long-run.

OK how's this: we have H in the regolith and CO2 in the atmosphere. We also have a big-ass mirror and laser. Would it be feasible to use the mirror to do the following:

1) Lower the temperature to Earth levels.
2) Power immense electrolysis machines that sift the C from the O2 in the atmosphere.
3) Power H2 harvesters that mine the regolith.

Burn the extracted H2 with the O2 and dump the C in designated areas.

Speciation is going to occur regardless. If we don't do it, eventually evolution will cause the people living on Mars to gradually adapt to the lower gravity and odd atmospheric composition. Since permanent Martian residents can't easily return to the crushing gravity of Earth, they will form a relatively isolated population (especially after the population growth by native birthrate exceeds the population growth through immigration.) Isolated populations under selection pressure produce new species.

Well that really depends on the level of intercommunication, doesn't it? If we manage something like a orbital elevator, transit between the worlds may be sufficient to offset this.

If one wants to colonize the Galilean moons in their natural state, they will need to live underground, since the radiation environment around Jupiter is fairly harsh. They will also need extensive networks of fusion reactions to supply them with the energy needed to grow crops and carry out the process of living. This will limit the extent of colonization.

If one wants to live on the moons, then terraforming is actually something of a viable option. The construction of giant mirrors reduces the need for native fusion reactors, since we'd be concentrating the energy from the big fusion reactor a couple billion kilometers away to useable intensities. And according to the National Academies Press Emergency and Continuous Exposure Limits for Selected Airborne Contaminants, Volume 1 (2000) methane has little toxicity (inducing mild depression and lethargy in concentrations of 50% to 90% in an atmosphere of oxygen . . . . I'm suggesting only using 20% - 25% methane in an atmosphere otherwise composed of N2 and O2) when oxygen is readily available. So the rebreathers might not be necessary, though it would be wise to dress warmly, and you'd have to genetically engineer cyanobacteria to lock up the photochemical smog that will otherwise form and turn a terraformed Ganymede or Callisto into a featureless smoggy orange ball. The density of the atmosphere will serve to partially attenuate the particle radiation induced by Jupiter's enormous magnetic field, reducing the need for shielding of one's habitats.

OK, but are there long-term problems with methane? We are talking about people living in a smoggy environment for basically their entire lives. If there are no adverse problems with this (and not forgetting the biological effects of the low gravity) then I agree this will certainly be possible in principle. To quadruple the sunlight would then require a mirror ca 6000 km in diameter... easier than the Venus one. Plus methane is also a good greenhouse gas; useful to maintain the temperature.

For the mirror: lets give it a radius of 1e7 meters, thickness of 0.03 millimeters and made of aluminium, gives roughly 3e10 tonnes; which would be space habitat for some three billion people by the earlier estimate. Of course, a successful terraformation gives higher quality habitat, and there is the issue of the relative cost of active maintenance of the respective systems: huge mirror in the right place versus maintaining a pressurized area, as well as the issue of the timeframes involved.

The mirrors and sunshades and what-have-yous also require maintenance.

Yeah, that's what I was going for.

I suppose it would be instructive to compare the costs of maintaining an asteroid colony versus the maintaining of a terraformed world. Get it right, and the atmosphere will generally maintain itself, provided the insolation doesn't exceed or fall below certain tight tolerances.

With Venus I imagine that a permanent sunscreen could not be made redundant.

[GrandMasterTerwynn]

Ok, since 1 and 2 seem out, I'll just continue on with 3 and 4.

3. How does this method compare in efficiency and energy requirements with the other methods? Could it be used in conjunction with any number of the other methods?

You'd have to use a number of methods in combination. For a certain monetary value of carbon, the terraformation of Venus will be a fortuitous side-effect of its atmosphere being mined for its carbon (though it would likely be easier to merely track down and process every single high-carbon asteroid in the asteroid belt.)

4. Would it be possible to destablize a planet's orbit with a heavy-handed application of a very large number of very powerful nuclear devices and then "catch" it when it entered the desired orbital slot with another nuclear stockpile?

Um, while in principle it would be possible; in practicaility, imparting that much energy on a planet at once will most likely smash it to pieces. And of course, by "nuclear" I would assume you actually mean "annihilating an enormous fortune of antimatter (over a hundred million metric tons of the stuff.)"

[CoyoteNature]

I think it would be a gradual process, as the colonists on Mars spread out, harvesting resources maybe they would then deliberately begin terraforming.

Or why does it have to be deliberate at all?

Of course if you have the technology to survive for the amount of time it would take to terraform, then its rather silly to even begin it, by the time you get to the point where you have acheived it you have already adapted to it.

I'm not sure if any government or corporation could do it, I mean how long do any of these last anyway? Maybe a thousand years, if you use past examples, and thats the good ones.

Perhaps fusion torches in the gas giant's atmosphere could provide the extra illumination.

[nickolay1]

Wouldn't 20% methane in an oxygen atmosphere be easily ignited?

[GrandMasterTerwynn]

Wouldn't 20% methane in an oxygen atmosphere be easily ignited?

No. Methane only ignites when the concentration of gas is high enough to sustain combustion, but not so high that the combustion reaction finds methane molecules, and not enough oxygen molecules to complete the reaction. An atmosphere comprised of 20% methane is much too methane-enriched for it to easily ignite, or ignite at all. It's just like the fuel-air mixture in an automobile engine. Too lean, and the engine loses power. Too rich, and the engine floods.

[AMX]

Wouldn't 20% methane in an oxygen atmosphere be easily ignited?

No. Methane only ignites when the concentration of gas is high enough to sustain combustion, but not so high that the combustion reaction finds methane molecules, and not enough oxygen molecules to complete the reaction. An atmosphere comprised of 20% methane is much too methane-enriched for it to easily ignite, or ignite at all. It's just like the fuel-air mixture in an automobile engine. Too lean, and the engine loses power. Too rich, and the engine floods.

Sure?
Remember, we're dealing with a low-gravity environment, where you'd likely have less total pressure, thus a higher relative amount of O2 to maintain the partial pressure necessary to make it breathable.
If you're "lucky", you might put the CH4/O2 relation right back into the explosive range

[GrandMasterTerwynn]

I knew it was little, but well, that's not going to cut it.

And at 8.40e+19 kg, moving Enceladus is pretty fucking hefty in terms of energy requirement. And by "pretty fucking hefty" I mean "astronomical". We're talking about, what? 1e+28 to 1e+29 joules or somesuch madness? Of course that is what you estimated for the laser method of liberating the CO2

Yeah, about that. And you can only apply it so fast, lest you destroy the moon before you can get it somewhere useful. Might be better to find something in the Kuiper-belt with a long, slow orbit. Less kinetic energy to cancel out. However, slowing it down after the long fall into the solar system is going to be tricky, since you don't want something that big to hit Venus so hard that most of it, and a sizeable fraction of the planet to boot, ends up rebounding back into space.

By "very long" I imagine you are talking millennia - which is beyond our racial attention span barring some serious life extension. Terrorists aside, the laser sounds more attractive. Though it's a pain to loose all of that carbon.

I suppose one would have to scoop as much of it up as possible, though getting in the way of a laser potent enough to drive off the atmosphere in human timescales might not be the brightest idea.

I'm not sure how such scoopships would be implemented - perhaps these ideas could somehow be combined using smaller mirrors to create "cold areas" that allow precipitation and a large half-mirror to lower the temperature overall (substantially), thus causing the CO2 to precipitate in designated areas. Don't know how practical that is.

In this scheme, atmospheric circulation will dictate that the CO2 will naturally settle at the poles, forming growing CO2 polar ice-caps.

Yes, I reckoned as much - I was more thinking in terms of the requirement for active maintenance of the orbit; it's not a passive system, unlike bulk mass as for a hollowed out asteroid or an ideal atmosphere. Keeping as many essential systems passive is better, in the case of possible future economic collapse.

If one has an economic collapse deep enough and long enough that it lasts past the time the mirror system will remain stable on its own, then one probably has much bigger problems to worry about than the fate of some unlucky Venusian colonists.

Mercury, pfft.

Heck, the terraforming laser will probably be a threat to most everything in the Solar System that's within the laser's field of view.

OK how's this: we have H in the regolith and CO2 in the atmosphere. We also have a big-ass mirror and laser. Would it be feasible to use the mirror to do the following:

1) Lower the temperature to Earth levels.
2) Power immense electrolysis machines that sift the C from the O2 in the atmosphere.
3) Power H2 harvesters that mine the regolith.

Burn the extracted H2 with the O2 and dump the C in designated areas.

This would probably be feasible, but only after you reduce the surface atmospheric pressure to levels that are slightly less lethal to equipment. Or design complex equipment to operate for decades or centuries under up to 90 atmospheres of pressure.

OK, but are there long-term problems with methane? We are talking about people living in a smoggy environment for basically their entire lives. If there are no adverse problems with this (and not forgetting the biological effects of the low gravity) then I agree this will certainly be possible in principle. To quadruple the sunlight would then require a mirror ca 6000 km in diameter... easier than the Venus one. Plus methane is also a good greenhouse gas; useful to maintain the temperature.

Actually, we're going to want to aggressively scrub the smog from the atmosphere. Like the photochemical smog on Titan, the smog on our terraformed Jovian moon will dampen the greeenhouse effect if you allow enough of it to accumulate. And methane's potency as a greenhouse gas is why I picked it. It's relatively easy to obtain or manufacture (compared to exotic CFCs) and it isn't toxic or corrosive like large quantities of CO2 or ammonia would be.

I suppose it would be instructive to compare the costs of maintaining an asteroid colony versus the maintaining of a terraformed world. Get it right, and the atmosphere will generally maintain itself, provided the insolation doesn't exceed or fall below certain tight tolerances.

With Venus I imagine that a permanent sunscreen could not be made redundant.

Not for very long, I suspect.