## Which planet in this solar system would be most appropriate to terraform?

 Quote by siiix but thats exactly my point , if you look at that picture if you move the moon father away from the planet the shadow would be bigger, obviously its impossible to make that huge of a disk , so its easier to just keep the disk at a bigger distance cant be to far either , it has to be the OPTIMAL distance to get the maximal possible effect
The further away you move it the less of the effect of the shadow. Think of the relation between Venus and the moon. When venus is in between the earth and the sun, it casts a shadow across the entire earth, yet you can't really tell, as far as temperature is concerned, I'll bet the effect is negligible.

Edit: I see where you are going after re-reading. You are arguing about getting the entire planet in the penumbra, while I was arguing about getting the entire planet into the Umbra.

 Quote by JonDE The further away you move it the less of the effect of the shadow. Think of the relation between Venus and the moon. When venus is in between the earth and the sun, it casts a shadow across the entire earth, yet you can't really tell, as far as temperature is concerned, I'll bet the effect is negligible. Edit: I see where you are going after re-reading. You are arguing about getting the entire planet in the penumbra, while I was arguing about getting the entire planet into the Umbra.
again i know , but thats TO far, it has to be the optional distance where the shadown is still effective , but big enough
 Wouldn't it be kind of difficult to keep a large object stationary relative to a planet if it isn't located in one of the Sun-Planet lagrange points?

 Quote by vemvare Wouldn't it be kind of difficult to keep a large object stationary relative to a planet if it isn't located in one of the Sun-Planet lagrange points?
its would be insanely difficult, far more difficult then building it (and that not easy either)

its not really stationery, it has to constantly move as both planet and the sun are moving, and it cant be in orbit as then it would need to be to big to be possible (about planet size)

maybe it would be easier to create millions of orbiting satellites with huge mirrors+solarpanels, powered my solar energy and all networked so they wont collide

but i dont know about this plan, because the ground pressure is still 95 x higher then earth, even if the temperature drops, to much "air" makes also takeoff and landing more difficult

and converting all that CO2 in to O would take how knows how many 100's or 1000's of years, also cant really convert it all there is just to much of it, lets say we do 50% oxygen 50% CO2 that would make the planet very flammable, and pressure would be still to high (estimating 60-70x earth), as there is no hydrogen O would not turn in to water, at least not much of it

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 Quote by siiix but thats exactly my point , if you look at that picture if you move the moon father away from the planet the shadow would be bigger, obviously its impossible to make that huge of a disk , so its easier to just keep the disk at a bigger distance cant be to far either , it has to be the OPTIMAL distance to get the maximal possible effect

Yes, the further the Moon, the larger the penumbra, however, this also decreases the "deepness" of the shadow. The amount of light striking each square meter would go up. This increase of Light level in the penumbra increases faster than the surface area tha the penumbra covers does. Moving the moon further away can only increase the total sunlight striking the Earth.

 Quote by vemvare Terraforming is of course extremely speculative. A "terraforming future" isn't a future with a couple of thousand NASA/ISA scientist-astronauts flying around the solar system, it is a future where millions of people live their lives in massive space stations, where thousands of people leave and return to Earth each day, and where asteroids are moved around, smashed to pieces and mined! As such, it is likely to be distant future, which of course means that huge advances will be made in science, so much of what we're speculating about here will be laughably wrong if read by the generation that actually start the terraforming process.
I agree, the timescales here are not centuries, but millenia. That's why we have to start the process soon, so that capacity keeps up with the projected growth of our civilization.

Because of this, I believe that Venus is a poor candidate for terraforming, as it will eventually be subject to the increasing luminosity of the sun as it finishes the main sequence. Earth, too, will be in danger, so it would be wise to select a planet that has a good chance of escaping the red giant phase if we really do intend to survive and prosper indefinitely.

Mars is quite appropriate for several reasons.

1) Reasonably similar gravity to earth's (0.376g)
2) Conveniently reduced escape velocity for transfer of materials to and from orbit
3) High oxygen content (in iron oxide)
4) Bearable temperature & pressure ranges
5) Proximity (~7 minute delay in communications, regular resupply from earth feasible)
6) Familiarity - we've already started exploring it and have the technology today for landing.

The easiest way to go about the terraformation would be to send over a probe full of our favorite lichen, moss, and (genetically modified?) microbes that would start clambering over the surface, devouring iron oxide and releasing heat & H20.

Perhaps we can one day slingshot magnetic materials around it at ridiculous speeds to jump-start the core and provide a magnetosphere to boot... if not, we'll find a way to generate the shielding we need.

Eachus said some very interesting things about starting in Martian valleys. I think that process could start within a year if we applied ourselves. Mars One estimates the cost of sending 4 crewmembers to Mars permanently to be $6 billion, about as much as the U.S. spends on defense every 2-3 days in 2012 money - so the resources are there if we can find common ground for cooperation. Don't forget, the asteroid belt is right next door to Mars. Once we get a foothold on and around the red planet, it will be that much easier to access those resources and relieve scarcity even back home. The moons of the gas giants will be great resources for a network of space stations throughout the solar system, but terraformation will be much less feasible owing to the gravitational stripping of their atmospheres caused by the planets they orbit. With the limitations we experience here, I can't help looking past earth and imagining an interstellar future for humankind. Our homeworld will always be sacred, but future lies among the stars. Mentor Blog Entries: 1  Quote by mofobro I agree, the timescales here are not centuries, but millenia. That's why we have to start the process soon, so that capacity keeps up with the projected growth of our civilization. Welcome to the forums, what projections are these? Considering the demographic transition of the developed world and the increasing development of everywhere else I can't see population growth being a global problem (and increasingly becomming less of a local problem). This is all mainly thanks to modern medicine ensuring children reach adulthood, contraceptives ensuring pregnancy is optional, female education and emancipation freeing women from being babymakers and childcarers and the labour requirements of post-industrial economies that reduce the need for mass unskilled labour in favour of skilled (read: expensive to train) labour.  Quote by mofobro Because of this, I believe that Venus is a poor candidate for terraforming, as it will eventually be subject to the increasing luminosity of the sun as it finishes the main sequence. Earth, too, will be in danger, so it would be wise to select a planet that has a good chance of escaping the red giant phase if we really do intend to survive and prosper indefinitely. The increasing luminosity of the sun is a problem so far in the future that it dwarfs the age of our species by several orders of magnitude. I highly doubt homo sapiens will be extant when this is a problem.  Quote by mofobro Mars is quite appropriate for several reasons. 1) Reasonably similar gravity to earth's (0.376g) How is 37% reasonably similar? Indeed without further research into the effects of low-gravity on embryology, development and general health of all necessary species within a human supporting ecology how can we even begin to claim what is reasonable?  Quote by mofobro 4) Bearable temperature & pressure ranges The average temperature on mars is -50C and the pressure 5-10millibars that really doesn't seem bearable to anything but extremophiles. Sure there may be areas where the temperature peaks to above zero but that does not a healthy environment make.  Quote by mofobro The easiest way to go about the terraformation would be to send over a probe full of our favorite lichen, moss, and (genetically modified?) microbes that would start clambering over the surface, devouring iron oxide and releasing heat & H20 Unless you want any chance of a biome within several hundred million years or more you're going to have to do more than dropping extremophiles onto the planet and waiting for it to change. It took billions of years for enough free oxygen to be liberated on Earth for larger organims to exist. That's not to mention the hellishly complex task of constructing an ecosystem from scratch on a world with different characteristics. Ecosystems are not modular systems you can just build up species by species, they are (at minimum) complex, dynamic trophic webs that rely on the interaction of thousands of species to remain somewhat sustainable.  Quote by mofobro Perhaps we can one day slingshot magnetic materials around it at ridiculous speeds to jump-start the core and provide a magnetosphere to boot... if not, we'll find a way to generate the shielding we need. Off the top of my head that's going to require some serious amounts of energy i.e. significant fractions of the solar output for a significant amount of time. I'd be interested to see some math on that.  Quote by mofobro Eachus said some very interesting things about starting in Martian valleys. I think that process could start within a year if we applied ourselves. Mars One estimates the cost of sending 4 crewmembers to Mars permanently to be$6 billion, about as much as the U.S. spends on defense every 2-3 days in 2012 money - so the resources are there if we can find common ground for cooperation.
I'd take Mars One's estimate with a massive pinch of salt. Bear in mind that we're only at the stage where after years of work by tens of thousands of experts can land a <1 tonne probe some of the time. And what we're talking about is the mass development of multiple academic fields with an increase in industrial capability that greatly dwarfs what we have today (the social effects of which would be very interesting). There's so many critical paths of R&D involved that even allowing for as much funding as humanly possible the task is by no means guarenteed to be attempted well for a long time.
 Quote by mofobro Don't forget, the asteroid belt is right next door to Mars. Once we get a foothold on and around the red planet, it will be that much easier to access those resources and relieve scarcity even back home.
IIRC from LEO there is little difference between going to Mars and going to the belt. We don't need Mars to mine asteroids. Also for space mining to be profitable there would need to be huge advances in automation and in situ resource allocation, so much so that I highly doubt we'll need humans for anything more than troubleshooting from afar.
 Quote by mofobro With the limitations we experience here, I can't help looking past earth and imagining an interstellar future for humankind. Our homeworld will always be sacred, but future lies among the stars.
I can't see what we could get from living off the Earth than we could get from Earth given the resources and technology needed to achieve the former. I'm not opposed to the aesthetic value but I've never seen a reasonable argument that we need to.
 Now that's a prime example of "chickity-check yourself before you wrickity-wreck yourself." Thanks for the warm welcome, I look forward to improving my phys-fu. I only speak in relative terms of the "reasonable" attributes of Mars. It's not like we have a hard day/night split like on the moon, and the gravity is neither crushing nor negligible. You're absolutely correct about what you've said, though. I'll have to be better prepared next time before I go around declaring my opinions.

 Quote by siiix i dont think it has to be as big as the planet as the sun is far away, you just have to position the disk at an optimal distance between the sun and the planet AND move the disk so the sade of the disk is constantly covering the planet < and thats the hardest part
The optimal point was mentioned as L1, which fixes the distance and necessary size. I'd think a massive light-collecting array could produce power to maintain obliquity through thrusters and etc.

I still see Mars as an attractive option for permanent settling. It would be within the range of current technology (though perhaps not within political sentiment for funding) to construct a series of probes that attach to comets with favorable intersect orbits with mars. Boosting up to comet speed is energy intensive but small adjustments using solar powered ion thrusters or plutonium reactors over a reasonably long period of time would do the trick to have the comet captured by Mars and eventually impact.

Say, aren't the poles of Mars covered with frozen CO2 and H20? Wonder how much of an atmosphere we could get out of those with a few 1000-megaton equivalent impacts.
 Also, a nice sobering read for the difficulties of humans "making it in space" http://physics.ucsd.edu/do-the-math/...why-not-space/ (somewhat related to the grand vision of terraforming)

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 Quote by H2Bro Also, a nice sobering read for the difficulties of humans "making it in space" http://physics.ucsd.edu/do-the-math/...why-not-space/ (somewhat related to the grand vision of terraforming)
I have a lot of respect for Tim Murphy and really enjoy reading his blog. I disagree with him on some aspects but IMO he is right on the money here. The prevailing narrative of the 1950s/60s that space is the next-big-thing has lasted long past the time where it was clear something was wrong with it.

As I said above I'm by no means opposed to the idea that people might one day live in space in significant numbers but I don't see it happening any time soon and I don't see any reason to do it other than for the panaché.
 It is my belief that no terraforming project will be sustainable if it is based solely in that name of "science" and done under the auspices of some tumorous government entity like NASA. There has to be some economic benefit that will attract private sector entrepreneurs into space, otherwise the project will be a huge money-pit with nothing to show except a few dirt samples. I'm not saying there are no economically attractive attributes of outer space (read Lewis' book Mining the Sky), I'm saying it's a waste to do it in the name of some government bureaucracy.

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 Quote by Hercuflea It is my belief that no terraforming project will be sustainable if it is based solely in that name of "science" and done under the auspices of some tumorous government entity like NASA. There has to be some economic benefit that will attract private sector entrepreneurs into space, otherwise the project will be a huge money-pit with nothing to show except a few dirt samples. I'm not saying there are no economically attractive attributes of outer space (read Lewis' book Mining the Sky), I'm saying it's a waste to do it in the name of some government bureaucracy.
Terraforming would require such a radically different political, social and economic climate that speculating on whether or not private or public enterprise would do a better job is basically groundless.

 Quote by Ryan_m_b The prevailing narrative of the 1950s/60s that space is the next-big-thing has lasted long past the time where it was clear something was wrong with it.
The 1950's/60's narrative was more like going into space proves that we are better than the Russians. Once the US planted a flag on the moon, and the Russian economy was in no position to match that, there really wasn't any point any more.

One very interesting thing to read the *entire* "let's go to the moon" speech

http://www.jfklibrary.org/Research/R...y-25-1961.aspx

Space was item 9, and the famous quote "I believe that this nation..." has been taken wildly out of context. If you read the whole speech it was clearly, "I think that we should go to the moon, but we need to talk about this, and if we decide not to then lets give up right now rather than go half way."

 As I said above I'm by no means opposed to the idea that people might one day live in space in significant numbers but I don't see it happening any time soon and I don't see any reason to do it other than for the panaché.
Also it would seem to me that if the goal is to have large populations in space, that terraforming a large planet would be the worst thing that you would want to do. You just spent a huge amount of effort getting out of a gravity well. What's the point into jumping back into to one. Once you get out of the earth's gravity well, you can go anywhere in the solar system if you willing to wait long enough.

 Quote by Ryan_m_b Terraforming would require such a radically different political, social and economic climate that speculating on whether or not private or public enterprise would do a better job is basically groundless.
The other big problem is that a civilization with the capacity to do planetary scale construction would also have the capacity to do planetary scale destruction. If humans had the ability to make Venus suitable for life, then we'd also have the ability to make Earth unsuitable for it.

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 Quote by twofish-quant The 1950's/60's narrative was more like going into space proves that we are better than the Russians. Once the US planted a flag on the moon, and the Russian economy was in no position to match that, there really wasn't any point any more. One very interesting thing to read the *entire* "let's go to the moon" speech http://www.jfklibrary.org/Research/R...y-25-1961.aspx Space was item 9, and the famous quote "I believe that this nation..." has been taken wildly out of context. If you read the whole speech it was clearly, "I think that we should go to the moon, but we need to talk about this, and if we decide not to then lets give up right now rather than go half way."
Interesting. You're right competition and national pride (along with a legitimate worry about loosing out to possible military domination in/via space) had a lot to do with it. It's interesting though how this bigger, better, faster, more idea of space as our future is pervasive in spite of evidence to the contrary.
 Quote by twofish-quant Also it would seem to me that if the goal is to have large populations in space, that terraforming a large planet would be the worst thing that you would want to do. You just spent a huge amount of effort getting out of a gravity well. What's the point into jumping back into to one. Once you get out of the earth's gravity well, you can go anywhere in the solar system if you willing to wait long enough.
Tbh if you have the industrial and economic capacity to terraform getting out of a gravity well is a negligable cost.
 Quote by twofish-quant The other big problem is that a civilization with the capacity to do planetary scale construction would also have the capacity to do planetary scale destruction. If humans had the ability to make Venus suitable for life, then we'd also have the ability to make Earth unsuitable for it.
I'd say we have the capacity for destruction now. We could if we wanted to bomb most of the Earth's surface with very powerful nuclear weapons and let the destruction, fallout and ash take care of any surviving organisms.

The ability to destroy in most cases is far easier than the ability to maintain or build.

 Quote by twofish-quant Also it would seem to me that if the goal is to have large populations in space, that terraforming a large planet would be the worst thing that you would want to do.
Usually, the goal is more along the lines of simply spreading out, though, it seems to me. An extension of the drive that leads all species to try and colonize new habitats when the opportunity arises, as well as wars of conquest and the traditional capitalist "stagnation equals regression" mindset among humans. From that point of view, what matters first and foremost is carrying capacity per unit of effort that has to be extended to create habitable conditions, and planets do pretty well for themselves, in those terms.

 Quote by Ryan_m_b I'd say we have the capacity for destruction now. We could if we wanted to bomb most of the Earth's surface with very powerful nuclear weapons and let the destruction, fallout and ash take care of any surviving organisms.
Human life, probably. But even to wipe out "just" all mammalian life, we'd need to devote a lot of industrial effort, for a long time, to building bombs. The impact that, per conventional wisdom, killed the dinosaurs (but, one notes, not the mammals), was the equivalent of millions of hydrogen bombs, says the 'pedia article. And to kill off things like ants and cockroaches, we'd need to try another whole lot harder than that. I wonder if there's actually enough accessible uranium on Earth to use that method...

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