# Terraforming Another Planet - Possible? When? **URL:** \ **Category:** Factual Questions\ **Created:** [June 4, 2017, 4:50pm UTC](https://boards.straightdope.com/t/terraforming-another-planet-possible-when/788117 "2017-06-04T16:50:18Z")\ **Posts on this page:** 20\ **Page:** 2
**Author:** ![SamuelA](https://avatars.discourse-cdn.com/v4/letter/s/c77e96/32.png) [@SamuelA](https://boards.straightdope.com/u/SamuelA)\ **Post date:** [June 4, 2017, 11:43pm UTC](https://boards.straightdope.com/t/terraforming-another-planet-possible-when/788117/21 "2017-06-04T23:43:05Z")
> [@Stranger\_On\_A\_Train](#): > > The short answer is no. > > The longer answer is that we do not currently have the capability and even with plausible extensions of existing or projected technologies such as nuclear fusion, the challenge of altering the atmospheric composition, surface soil, climate, et cetera of another planetary-type body is vastly beyond anything we could credibly perform. > > On the other hand, constructing rotating habitats using space-borne materials such as water ice, silicates, hydrocarbons, et cetera, is entirely plausible. They can be powered by light from the sun, mediated by shielding and insulation to prevent thermal overheating; spun to generate acceleration simulating gravity, and protected against most celestial hazards. These could be constructed with plausible advances in propulsion, in situ space material utilization and processing, and habitation technology, and supported by external supplies without spending millenia trying to establish a biosphere across an entire planet. It would be a vast (many trillions of dollars and decades of effort) effort to develop such technology but it is at least they don’t require magic pixie dust or altering physical laws, nor command of massive energies and sensitive control of biomes across hundreds of millions of kilometers of surface area. > > Stranger Stranger, do you think self replicating _nearly_ fully automated factories are plausible? I’d argue that it’s a straightforward extrapolation of existing tech that mere market forces will probably make happen within 20-50 years. (aka, no need for a government funded moonshot like you would need to make fusion work, we already have extensive factory automation and most of the advanced tools for neural network classifiers are readily available to even CS undergrads…) Note the nearly. Just like a neural network doesn’t classify 100% of the time or make the correct prediction 100% of the time, I would expect nonzero error rates. Every now and then the exact combination of circumstances would lead to an error the factory cannot automatically clear, and a human would need to intervene. And yeah, once you have them, you strip mine the Moon, build canisters full of refined raw materials, and orbit them with superconducting mass drivers. Hit the canisters with a laser beam to burn off a little mass and circularize their orbit after launch. Then use those materials to build the habitats in orbit. ---
**Author:** ![chargerrich](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chargerrich/32/5399_2.png) [@chargerrich](https://boards.straightdope.com/u/chargerrich)\ **Post date:** [June 4, 2017, 11:57pm UTC](https://boards.straightdope.com/t/terraforming-another-planet-possible-when/788117/22 "2017-06-04T23:57:35Z")
I like to use the 100 year window because we can see what amazing progress can be had in that length of time. Can you imagine if you had talked to the leading minds of 1917 about traveling to the moon, living in space for years at a time, the internet, nuclear fusion and fission, gps or self driving cars? I have to think that in 2117 there are technologies present that we can barely even grasp today. That gives me some belief that terraforming may in fact be possible. ---
**Author:** ![eburacum45](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/eburacum45/32/8690_2.png) [@eburacum45](https://boards.straightdope.com/u/eburacum45)\ **Post date:** [June 5, 2017, 12:10am UTC](https://boards.straightdope.com/t/terraforming-another-planet-possible-when/788117/23 "2017-06-05T00:10:29Z")
> [@Weisshund](#): > > Well, you do have studies on the effects of no gravity/micro gravity. > Loss of bone density, muscle mass etc. > Bone mass, growth and cell division seem to be some key things of importance. > So you could reasonably assume lesser outcomes for partial gravity. There is a lot of difference between low gravity and no gravity. Bone mass forms as a response to stress - in microgravity there is little or no stress, but in low gravity there is stress - you still put weight on your bones in 0.376g, just not so much. > [@](#): > > Except for the part where returning to earth would probably just about kill you, or at least make you wish it did. Sure, there would be problems for Martians (and Lunar colonists) who tried to come back to Earth. So they’d need to stay on their own worlds, or build low-gee rotating habitats. I’d expect them to use wheelchairs or the equivalent on Earth. > [@](#): > > Apparently breeding is a bit iffy in low gravity too. Cite? > [@](#): > > Not surprising though, we (life) have spent the better part of 3 billion years learning to live at 1g Small animals on Earth have need thinner bones, since the stresses involved are smaller. Children are less massive than adults, and they too have thinner bones for the same reason. ---
**Author:** ![Tim\_T-Bonham.net](https://avatars.discourse-cdn.com/v4/letter/t/46a35a/32.png) [@Tim\_T-Bonham.net](https://boards.straightdope.com/u/Tim_T-Bonham.net)\ **Post date:** [June 5, 2017, 12:19am UTC](https://boards.straightdope.com/t/terraforming-another-planet-possible-when/788117/24 "2017-06-05T00:19:09Z")
> [@Lemur866](#): > > Folks, setting up a self-sufficient autonomous colony on the summit of Mt Everest is going to be 100 times easier than a Mars colony. Given that the summit of Mt Everest is ‘about the size of a pool table’, it’s going to be one awfully crowded colony! ---
**Author:** ![Weisshund](https://avatars.discourse-cdn.com/v4/letter/w/ba8739/32.png) [@Weisshund](https://boards.straightdope.com/u/Weisshund)\ **Post date:** [June 5, 2017, 12:43am UTC](https://boards.straightdope.com/t/terraforming-another-planet-possible-when/788117/25 "2017-06-05T00:43:20Z")
> [@eburacum45](#): > > Cite? bones or breeding? BONE [https://www.nasa.gov/audience/foreducators/postsecondary/features/F\_Bones\_in\_Space.html](https://www.nasa.gov/audience/foreducators/postsecondary/features/F_Bones_in_Space.html) MAMMALIAN BREEDING > **[Detrimental Effects of Microgravity on Mouse Preimplantation Development In...](https://journals.plos.org/plosone/article?id=10.1371%2Fjournal.pone.0006753)** > > Sustaining life beyond Earth either on space stations or on other planets will require a clear understanding of how the space environment affects key phases of mammalian reproduction. However, because of the difficulty of doing such experiments in... > [@](#): > > Small animals on Earth have need thinner bones, since the stresses involved are smaller. Children are less massive than adults, and they too have thinner bones for the same reason. But, they are not thinner per se. We are talking about density, not “thickness” And little junior or mr whiskers would suffer the same effect. [Bones and microgravity](http://www.mainsgate.com/spacebio/modules/cb_resource/microgravity_cells.pdf) ---
**Author:** ![Weisshund](https://avatars.discourse-cdn.com/v4/letter/w/ba8739/32.png) [@Weisshund](https://boards.straightdope.com/u/Weisshund)\ **Post date:** [June 5, 2017, 12:44am UTC](https://boards.straightdope.com/t/terraforming-another-planet-possible-when/788117/26 "2017-06-05T00:44:25Z")
> [@t-bonham@scc.net](#): > > Given that the summit of Mt Everest is ‘about the size of a pool table’, it’s going to be one awfully crowded colony! Build up 😃 ---
**Author:** ![eburacum45](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/eburacum45/32/8690_2.png) [@eburacum45](https://boards.straightdope.com/u/eburacum45)\ **Post date:** [June 5, 2017, 12:51am UTC](https://boards.straightdope.com/t/terraforming-another-planet-possible-when/788117/27 "2017-06-05T00:51:51Z")
> [@Weisshund](#): > > bones or breeding? > > BONE > [https://www.nasa.gov/audience/foreducators/postsecondary/features/F\_Bones\_in\_Space.html](https://www.nasa.gov/audience/foreducators/postsecondary/features/F_Bones_in_Space.html) > > MAMMALIAN BREEDING > [Detrimental Effects of Microgravity on Mouse Preimplantation Development In Vitro](http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0006753) Nope, these are no use ; I want references about low gravity, not microgravity. Don’t bother looking - there are none. Martian gravity, at 0.376g, is not even particularly low, compared to the gravity on most of the solid bodies in the Solar System. ---
**Author:** ![Weisshund](https://avatars.discourse-cdn.com/v4/letter/w/ba8739/32.png) [@Weisshund](https://boards.straightdope.com/u/Weisshund)\ **Post date:** [June 5, 2017, 1:16am UTC](https://boards.straightdope.com/t/terraforming-another-planet-possible-when/788117/28 "2017-06-05T01:16:15Z")
> [@eburacum45](#): > > Nope, these are no use ; I want references about low gravity, not microgravity. Don’t bother looking - there are none. Martian gravity, at 0.376g, is not even particularly low, compared to the gravity on most of the solid bodies in the Solar System. It’s .3 which is 1/3rd I would say that is particularly low as compared to earth, where we come from, which also determined how we were put together. Even Mercury is higher even if by a fraction at 0.38g Earth and Venus are highest at 1.0 and 0.9 respectively. And those are the 4 “Terrestrial” planets And there can only be microgravity studies because we have not had anyone hang out on the moon or what not for months on end unless you know something i do not. And if you look through some of the various studies, they do speculate on what the effects of a Mars environment might be. Not a hard hypothesis to make i would imagine? By the way, you are not talking “thinner” or “littler” bones, you are talking about something similar to osteoporosis. Even at 1/3rd g, having a porous brittle bone can not be a good outcome. ☹ ---
**Author:** ![eburacum45](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/eburacum45/32/8690_2.png) [@eburacum45](https://boards.straightdope.com/u/eburacum45)\ **Post date:** [June 5, 2017, 1:33am UTC](https://boards.straightdope.com/t/terraforming-another-planet-possible-when/788117/29 "2017-06-05T01:33:19Z")
> [@Weisshund](#): > > And if you look through some of the various studies, they do speculate on what the effects of a Mars environment might be. > Not a hard hypothesis to make i would imagine? Yes, it is a hard problem, since we have no data whatsoever about this. The NASA microgravity studies (and the bedrest studies, which are even further removed from the reality of 1/3 gravity) suggest very strongly that bone density would be reduced - but they say nothing about whether that would actually cause a problem to colonists living permanently on Mars. As I said in an earlier post- it would cause problems for anyone returning to Earth- the solution is - don’t return to Earth. ---
**Author:** ![LSLGuy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lslguy/32/5813_2.png) [@LSLGuy](https://boards.straightdope.com/u/LSLGuy)\ **Post date:** [June 5, 2017, 1:47am UTC](https://boards.straightdope.com/t/terraforming-another-planet-possible-when/788117/30 "2017-06-05T01:47:09Z")
> [@Quartz](#): > > Yes, though I would hope we would find a planet without complex life. The fate of the human race is at stake, remember. The survival of alien species is way down **the list**. Starting with no biosphere and building a facsimile of Earth’s is going to be way easier than adapting humans to an alien biosphere. Bolding mine. You misspelled “our list”. The aliens may have a different list of their own. ---
**Author:** ![Weisshund](https://avatars.discourse-cdn.com/v4/letter/w/ba8739/32.png) [@Weisshund](https://boards.straightdope.com/u/Weisshund)\ **Post date:** [June 5, 2017, 1:49am UTC](https://boards.straightdope.com/t/terraforming-another-planet-possible-when/788117/31 "2017-06-05T01:49:03Z")
> [@eburacum45](#): > > Yes, it is a hard problem, since we have no data whatsoever about this. The NASA microgravity studies (and the bedrest studies, which are even further removed from the reality of 1/3 gravity) suggest very strongly that bone density would be reduced - but they say nothing about whether that would actually cause a problem to colonists living permanently on Mars. > > As I said in an earlier post- it would cause problems for anyone returning to Earth- the solution is - don’t return to Earth. That would probably be the end solution for anyone going off world and spending long term in greatly reduced gravity, you can never come back. Surely, unlike in science fiction, any child born off world, in a significantly lower than earth gravity could never come here for that and other reasons. Atmospheric pressure might also be too much, unless they grew up in a pressurised environment. But the gravity alone would be unbearable. It would be like you suddenly going from 100 pounds to 300 pounds. Of course there is also the aspect of earth killing them ala war of the worlds. If the people that left were sterilised as best as humanly possibly a generation or two later may have lost all or most of the immunities we ignore every single day. Billions of wee beasties waiting to do in anything with out a membership card. Even worse, they may have learned to co-exist with wee beasties of their own that dont like us. ---
**Author:** ![wolfpup](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/wolfpup/32/10618_2.png) [@wolfpup](https://boards.straightdope.com/u/wolfpup)\ **Post date:** [June 5, 2017, 2:11am UTC](https://boards.straightdope.com/t/terraforming-another-planet-possible-when/788117/32 "2017-06-05T02:11:43Z")
> [@John\_Mace](#): > > If we can terraform planets in this century, we won’t need to worry about Climate Change anymore. We can just terraform Terra. Right, and not only are we unable to do so, no one has even the remotest idea of how we might be able to do it in the future, notwithstanding wild ideas about geoengineering and infeasible or non-scalable schemes for carbon sequestration. Here’s the way to put it in perspective. Our climate troubles – and they are serious troubles indeed – result from a bit more than a 100 ppm increase in atmospheric CO2. Granted, that’s about a 35% increase over where it should be, but (as skeptics deceptively like to point out) still a mere 0.04% of the atmosphere. And there’s not a damn thing we can do about it except try to cut further emissions and hope for the best. Mars, OTOH, (a) has an atmosphere that is almost all CO2, (b) has almost no oxygen, and (c) has lethal toxins like carbon monoxide in it. It’s also not clear what resources can be extracted from Mars, if any, to even start a terraforming process assuming we were within sight of any kind of technology to do any of it. Right now we can’t even get there without spending a good chunk of global GDP. Yeah, good luck with that. > [@Stranger\_On\_A\_Train](#): > > The short answer is no. > > The longer answer is that we do not currently have the capability and even with plausible extensions of existing or projected technologies such as nuclear fusion, the challenge of altering the atmospheric composition, surface soil, climate, et cetera of another planetary-type body is vastly beyond anything we could credibly perform. Exactly. ---
**Author:** ![Weisshund](https://avatars.discourse-cdn.com/v4/letter/w/ba8739/32.png) [@Weisshund](https://boards.straightdope.com/u/Weisshund)\ **Post date:** [June 5, 2017, 2:22am UTC](https://boards.straightdope.com/t/terraforming-another-planet-possible-when/788117/33 "2017-06-05T02:22:34Z")
> [@wolfpup](#): > > Granted, that’s about a 35% increase over where it should be, but (as skeptics deceptively like to point out) still a mere 0.04% of the atmosphere. And there’s not a damn thing we can do about it except try to cut further emissions and hope for the best. Could try to find a use for it, something you can build that would use carbon, and lock the carbon. 0.04% is still probably a nice pile of free material? ---
**Author:** ![eburacum45](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/eburacum45/32/8690_2.png) [@eburacum45](https://boards.straightdope.com/u/eburacum45)\ **Post date:** [June 5, 2017, 2:37am UTC](https://boards.straightdope.com/t/terraforming-another-planet-possible-when/788117/34 "2017-06-05T02:37:40Z")
Let’s go back to the OP and try to answer some questions. > [@](#): > > 1. Do we currently have or would have the technology in 50 years to colonize Mars, Titan or any newly found earth like planet especially given the will and focus that unanimous agreement would bring? Not a chance. We are hundreds of years away from developing the technology to terraform Mars. here’s Robert Zubrin’s scheme to terraform the Red planet [http://www.users.globalnet.co.uk/~mfogg/zubrin.htm](http://www.users.globalnet.co.uk/~mfogg/zubrin.htm) timescale about 900 years - plus another hundred or so to develop the capacity to even start the project. Here’s a timescale estimate for SamuelA’s self-replicating devices from Robert Freitas > **[Terraforming Mars and Venus Using Machine Self-Replicating Systems (SRS)](http://www.rfreitas.com/Astro/TerraformSRS1983.htm)** > > HTML Editor: Robert J. Bradbury 350 years - but first we need to develop highly advanced self-replicators that would work on Mars and not poison themselves with their own waste products (like bacteria tend to do). Such advanced tech is hundreds of years in the future. > [@](#): > > 1. Colonizing seems infinitely easier than Terraforming. Can you even Terraform AFTER colonization? I wouldn’t like to be a colonist on Mars while Zubrin was raining icy asteroids down on the surface. But with luck you might find a space space on the surface somewhere. > [@](#): > > 1. How many decades or centuries are humans away from having the ability to Terraform a planet? (I personally like to look at the technology available in 1917 and compare to 2017 as a belief that we may have the ability in 100 years). Why not look at 1967 and compare it to 2017? In some ways we’ve gone backwards - where are the moonrockets today? Advances in the next 100 years are more likely to be in the realms of information technology and biotech - that’s why I’m fairly confident about whether humans could be adapted to live on Mars. But if information technology advances in the way I think it will in the next 100 years, we probably won’t even think about Mars as a destination for humans any more- we’ll probably be retreating into cyberspace instead. > [@](#): > > 1. What types of hypothetical technology would be needed that we do not have now to Terraform a planet and create an atmosphere? Is nuking polar caps REALLY feasible? It seems it would take 1000s or more nukes to even begin to create a real atmosphere and without a magnetic core, it would just get blown away by the Sun, right? Zubrin’s scheme uses nukes to divert icy asteroids onto Mars- this uses gravity to amplify the effect significantly. So I doubt we’ll ever use nukes directly on Mars. As far as the magnetic field goes, there is a scheme that might provide some relief from the Solar onslaught; a magnetic shield see > **[NASA Might Use Magnetic Shield to Grow Life-Sustaining Atmosphere on Mars](https://www.inverse.com/article/28574-nasa-mars-magnetic-shield-solar-winds)** > [@](#): > > 1. Under the best case scenarios and with probably uninvented technologies, could a planet be Terraformed to create a breathable atmosphere in 50 or 100 years? I left the best till last - the late Paul Birch sketched out a scheme to terraform Mars in less than a hundred years, using gigantic devices that would probably take hundreds of years to create > **[TerraformingMarsQuickly.pdf](https://www.orionsarm.com/fm_store/TerraformingMarsQuickly.pdf)** > > 1790.20 KB The end result is a planet where the atmosphere is barely breathable, and the gravity is still tiny; hardly worth doing in the long run. ---
**Author:** ![eburacum45](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/eburacum45/32/8690_2.png) [@eburacum45](https://boards.straightdope.com/u/eburacum45)\ **Post date:** [June 5, 2017, 2:42am UTC](https://boards.straightdope.com/t/terraforming-another-planet-possible-when/788117/35 "2017-06-05T02:42:46Z")
Concerning the magshield mentioned above, I should perhaps mention that I came up with a similar idea more than ten years ago - > **[Lagrange Magshield, The](https://www.orionsarm.com/eg-article/4851d85e0791b)** > > Interplanetary Age concept, which was developed from research into magsails and Ram-assisted magscoops. there’s even a certain amount of similarity between my image and the one in the article above. > **[NASA Might Use Magnetic Shield to Grow Life-Sustaining Atmosphere on Mars](https://www.inverse.com/article/28574-nasa-mars-magnetic-shield-solar-winds)** You only need a measly 10 petawatts to make it work… ---
**Author:** ![Quartz](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/quartz/32/267_2.png) [@Quartz](https://boards.straightdope.com/u/Quartz)\ **Post date:** [June 5, 2017, 8:33am UTC](https://boards.straightdope.com/t/terraforming-another-planet-possible-when/788117/36 "2017-06-05T08:33:52Z")
> [@Weisshund](#): > > You on the other hand know what will come of those one day. > Would you not terminate with extreme prejudice anything that strolled on by deciding otherwise? Ponder this: you have a choice between the extinction of Terran life - including humanity - and the extinction of an alien biosphere. Your choice. ---
**Author:** ![Francis\_Vaughan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/francis_vaughan/32/3093_2.png) [@Francis\_Vaughan](https://boards.straightdope.com/u/Francis_Vaughan)\ **Post date:** [June 5, 2017, 9:51am UTC](https://boards.straightdope.com/t/terraforming-another-planet-possible-when/788117/37 "2017-06-05T09:51:00Z")
I always ask one question. Where is the energy coming from? Self replicating factories are not self powering. The energy needed for any of the possible scenarios is orders of magnitudes greater than pretty much anything we have any clue how to create. You can posit exponential bootstrap processes that can do interesting things - like build solar array systems with areas that dwarf that of the entire Earth. But your lead time to even getting such a venture to break even, let alone to growth is not going to be measured in just decades. Of course we already have self replicating intelligent factories, and they are self replicating with no AI or high tech assistance at all. The only question is efficiency. I very much doubt the great AI revolution some think is upon us will deliver any sort of AI tech that is quite as energy efficient as a human brain. Market forces don’t always deliver a demand for the destruction of jobs. Someone has to pay for what is made, and those people need jobs to pay for it. cf - Kurt Vonnegut’s Player Piano. ---
**Author:** ![MichaelEmouse](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/michaelemouse/32/101_2.png) [@MichaelEmouse](https://boards.straightdope.com/u/MichaelEmouse)\ **Post date:** [June 5, 2017, 11:17am UTC](https://boards.straightdope.com/t/terraforming-another-planet-possible-when/788117/38 "2017-06-05T11:17:20Z")
> [@Francis\_Vaughan](#): > > I always ask one question. Where is the energy coming from? Cold fusion. Which we’ll figure out how to do the very microsecond following the singularity. Which is just around the corner now that we’ve had some major recent breakthrough. ---
**Author:** ![Pantastic](https://avatars.discourse-cdn.com/v4/letter/p/3bc359/32.png) [@Pantastic](https://boards.straightdope.com/u/Pantastic)\ **Post date:** [June 5, 2017, 1:00pm UTC](https://boards.straightdope.com/t/terraforming-another-planet-possible-when/788117/39 "2017-06-05T13:00:07Z")
The “20 to 50 years” timeframe some are using is pretty amusing, since I remember seeing that kind of time frame a lot in the 80s from stuff that had been written in the 70s or earlier. Even ignoring that, I’m not sure how getting the technology to create a complete functioning, self-sustaining ecosystem with 100 years of work is supposed to happen in the next 50 years - wouldn’t you need at least 100 years just to run one complete test of the theory of how to terraform a planet? The energy levels and materials needed to modify a planetary environment are staggering, and just saying ‘oh, self-replicating machines will handle it’ isn’t anything more than hand waving. The world’s ecosystem is incredibly complicated and has multiple chaotically ineracting systems that we don’t understand, the idea that we’ll go to a barren rock, slap some algae down, and have a well-tuned ecosystem that sustains itself and is suited for human habitation without even testing the process first is… more than optimistic. > [@Francis\_Vaughan](#): > > I always ask one question. Where is the energy coming from? The waste heat from the huge energies involved is also a big problem that doesn’t seem to get addressed. Even if you assume that you have amazing nanomachines that you can launch a rocket full of at a planet and let them go to work, and you assume they’re super 99.9% energy efficient, you end up with so much waste heat that it would take centuries or longer to get the planet back to human habitable temperatures. ---
**Author:** ![Mangetout](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mangetout/32/19_2.png) [@Mangetout](https://boards.straightdope.com/u/Mangetout)\ **Post date:** [June 5, 2017, 1:39pm UTC](https://boards.straightdope.com/t/terraforming-another-planet-possible-when/788117/40 "2017-06-05T13:39:32Z")
> [@Pantastic](#): > > The “20 to 50 years” timeframe some are using is pretty amusing, since I remember seeing that kind of time frame a lot in the 80s from stuff that had been written in the 70s or earlier. Even ignoring that, I’m not sure how getting the technology to create a complete functioning, self-sustaining ecosystem with 100 years of work is supposed to happen in the next 50 years - wouldn’t you need at least 100 years just to run one complete test of the theory of how to terraform a planet? Especially as you will probably be dealing with systems that contain significant hysteresis - it’s no use if you can spin up a warm, breathable atmosphere in a century, if that warm breathability is just a momentary state that exists on a continuum of change that ends soon after with it being warmer, and not-so-breathable, like Venus. [Previous page](https://boards.straightdope.com/t/terraforming-another-planet-possible-when/788117.md?page=1) [Next page](https://boards.straightdope.com/t/terraforming-another-planet-possible-when/788117.md?page=3)