Venus / Mars

KaseiII · 2003-02-04 12:07:55

Which is better / easier to terraform? Mars or Venus? I heard somewhere it is probably easier to terraform Venus than it is to terraform Mars? Opinions....Comments...

Josh Cryer · 2003-02-04 13:16:21

They're both hard to terraform. Venus lacks water, Mars lacks atmosphere. Venus has a lot of light, Mars doesn't have enough.

Terraforming Venus could prove to be quite difficult, since you'd need to shade it some how so that the CO2 would freeze to the surface, allowing you to get rid of it somehow. Venus has a surplus of energy, though, with it being so close to the sun, so any work you do on (or around) Venus would be easier than Mars. Most of the Venus terraforming project would be done from space, though, due to how dense the atmosphere is.

Since there is no water in the inner solar system outside of gravity wells (ie, Earth, Mars), you have to go far into the outer solar system to get ice rich comets. 3001 The Final Odyssey begins with a person who is shipping ice to the inner solar system, to plunge it into Venus' atmosphere, which is a reasonable prospect.

All in all, I'd say they're equally hard. Though I would argue that we could terraform Mars faster than Venus, since it's easier to add than it is to subtract. On Mars, you have the requirement for inert gasses. On Venus, you need to get rid of CO2 and add water. Just an extra step.

RobS · 2003-02-04 16:17:54

The thinking about terraforming Mars is much more advanced (if "advanced" is the right word). You can't just bombard Venus with ice-rich comets; you end up making the atmosphere thicker and the greenhouse effect worse. You probably have to blow away 99% of the Venus atmosphere, and rather daunting prospect. If you could collide an object 500 miles in diameter with the planet, that might do it; but the entire planet's surface would be molten for a thousand years or so, and rather hard to terraform! The surface temperature is too high for carbonate rocks to be stable, so you can't fix the CO2 in the crustal materials, like on earth. Even if you could cut off the sunlight, it would take hundreds or thousands of years for the stored heat in the air and rocks to radiate to space.

-- RobS

el scorcho · 2003-02-04 16:37:01

Also, for a Venus terraforming project, you would need to speed up the orbit to something resembling a 24-hour day (since the current day is something like 253 Earth days). Then you would have to maintain the rotation speed somehow, probably by coming up with a moon or moons to orbit Venus. This could be accomplished by using massive electromagnets in low Venus orbit to pull at the planets core. I heard somewhere that the planet's rotation would increase to Earth levels in about 50 years with this approach.

If we were technologically advanced enough to do this, then why not go ahead and tow Mercury into Venus' orbit to create an artificial moon? Then we could tow them both further back from the sun to cool the planet.

Number04 · 2003-02-04 16:44:59

UH.. that sounds kinda scary. I don't really want to start playing god and moving the planets. So many problems could arise because of this that my head hurts.

Shaun Barrett · 2003-02-04 18:30:53

In my opinion, Venus is a basket case because of the water situation. Without very large-scale planetary engineering, involving sunshades and relocation of comets from the outer solar system, it's difficult to see how Venus could be rehabilitated.
Carl Sagan was one of the first (if not the first) to suggest dropping hundreds of tons of bacteria into the atmosphere. The idea, of course, being to consume the CO2 and reduce the greenhouse effect, while creating an oxygen rich atmosphere.
But Venus has only about 1/100,000th of the water Earth has, so oceans as a climate moderator are not an option and no hydrological cycle is possible. In addition, current theories suggest the lack of water might be responsible for the absence of plate tectonics. Earth's crust contains an enormous quantity of water, which acts as a lubricant for the movement of crustal plates and allows them to move relatively smoothly. Many volcanoes occur at plate boundaries due to various mechanisms, and much internal heat is vented and energy dissipated. It looks like Venus, without these natural means of 'letting off steam' (! ), suffers catastrophic crustal upheavals about every 700 million years from an orgy of pent-up volcanism!
How many comets would it take to supply enough water to not only produce surface oceans, but also to soak into the crust and restore tectonic activity?! And how many millions of years would the process take?

And El Scorcho's point about Venus's painfully slow retrograde rotation is important too. Who wants to live on a planet with a day longer than its year?!! And what would that do to atmospheric circulation, with one side of the planet in seemingly perpetual hot sunshine and the other in seemingly perpetual cold night?!
Maybe we could increase the rotation rate, as El Scorcho suggests - though I've never heard of the notion of doing it in 50 years. (Any links for this? ) But we're back into very heavy engineering again to achieve this sort of thing.

No. However hard Mars may be to terraform, for my money I think it'll be a walk in the park compared to Venus!

Josh Cryer · 2003-02-04 19:03:12

Hmm... I think rotation is unimportant to colonization.

RobS, have any round figures for how long it would really take for CO2 to freeze? I thought Venus let off a lot of thermal radiation. Reflecting 100% sunlight should cool the thing quite fast.

And you don't have to turn the CO2 into oxygen, you just turn it into solidified carbon somehow... then ship it off.

soph · 2003-02-04 19:31:28

even cutting off sunlight, i believe there is so great of a greenhouse effect as to keep venus hot for a long time. as for solidified carbon, i believe that would take a REALLY long time.

and then you have a temperate planet. now find water, and make it sutiable for settlement! At this point, venus is at the stage of mars today. so youre talking about at least another few centuries in time needed for venus colonization. although, i wonder if we could capture venusian greenhouse gases and ship them to mars! it would still take a long time for both though, while i think mars is the better choice.

Echus_Chasma · 2003-02-04 21:55:53

i think mars is the better choice.

Yeah, Mars is a hell of alot easier to terraform. Unlike Venus, we can land on the surface, which should make the process easier than terraforming in orbit.

KaseiII · 2003-02-05 01:34:27

The only LARGE problem I see with Mars is the ONE continent is so big , and most of the south has no large areas of water; isn't it going to turn into a Giant Russia ir Arid Antarctic Desert, making most of the southern hemisphere rather useless.

But you all see right, Mars will probably be easier to terraform.

And the estimates for freezing the CO2 is 120 years at latest guess and it will take about 90 years to speed up Venus' rotation at latest guess.

RobS · 2003-02-05 16:06:17

I have not seen the estimate for how long it would take to freeze Venus's atmosphere. Someone could calculate it, I suppose.

You are right, the best thing to do would be to (1) freeze out the atmosphere; (2) place terawatt fusion reactors on the cold and near-airless Venus surface; (3) use the power to split the CO2 into oxygen and carbon; (4) bury the carbon under a layer of regolith to keep it away from the oxygen; (5) bombard the place with comets to add water (I'd blow the comets to smithereens with nuclear bombs an hour or two before impact, so that Venus is hit by snow rather than solid objects).

The pressure of the Venus atmosphere is about 100 times the pressure of the Earth's atmosphere. Pressure is equal to weight, which is a function of mass and gravity. The Earth's atmosphere weighs 10 tonnes per square meter, so Venus's atmosphere must weigh more like 1000 tonnes per square meter (assuming the same gravity as Earth, which isn't quite true). CO2 is 32/44 = 73% oxygen and 12/44 = 27% carbon. Thus the surface of Venus would have to be covered with something like 270 tonnes of carbon per square meter. If that carbon has a density equal to water, that means the pile would be 270 meters (885 feet!) high over the entire surface of the planet. And Venus would still have an atmospheric pressure 73 or so times higher than the Earth's air pressure, and it would all be pure oxygen. Such a pressure would be utterly toxic to life and would cause almost anything that can oxidize to catch on fire.

So I think the scheme still would have some problems! You either have to wait thousands of years for the oxygen to oxidize rocks or expell the oxygen from the planet.

-- RobS

Shaun Barrett · 2003-02-11 01:03:05

Hi RobS !
I love those little back-of-the-envelope calculations! It sure helps to clarify the enormity of the CO2 problem on Venus. And your mathematics doesn't even deal with the problem of separating the carbon from the oxygen - imagine the energy input you'd need to do that!

Others have simply visualised freezing out the CO2, as is, onto the surface. If you managed to achieve this engineering marvel, you'd have roughly 900 to 1000 tonnes of solid CO2 covering each square metre of the surface. You'd then have to dig through it just to find some regolith to pile on top of it!!
And this stuff is potentially very dangerous to work with. An accident which allowed the temperature to rise too much (always a worrying possibility at only 108 million kms from the Sun! ), would result in an explosive release of expanding, gaseous CO2!

As you suggested, Rob, the only real solution might be to direct impactors onto the surface and blast the atmosphere off into space. Current wisdom is that this worked accidentally on Earth about 3.8 billion years ago (stripping off the primordial reducing atmosphere), so maybe it could be made to work deliberately on Venus today.
Better to wait a thousand years for the surface to cool after such a bombardment, than to try to cope with all that excess carbon and oxygen.

I think this Mars versus Venus debate is so one-sided as to be a 'no contest'!
Give me Mars any day!!

Josh Cryer · 2003-02-11 11:49:12

I was thinking that the best way to get rid of the carbon, is to create hydocarbons out of it. Have huge floating platforms in the upper atmosphere or whatever, growing tons of plants a day. Of course, there are issues with water, but if we could get a fair shipment coming regularly, and if we had some space elevators (ones which just reached the floating platforms, not the ground, just to make it easier), I think it could be dooable.

Venus, if I'm thinking right, gets like 4 times as much sunlight as Earth. So I don't think we'dhave an issue with energy.

I'm writing a story about people who actually do this. In it, Venus is the supplier of everyones plastics (because the worlds fossil supplies have long since run out, landmass on Earth is hard to come by, and basically, society has many uses for plastic). Water is shipped to Venus via comets, which are processed at one of Venus' Lagrange Points.

Of course, many of you may not wish to ascribe to the characters in my story, since it's actually a prison camp, but whatever.

tim_perdue · 2003-02-11 15:25:51

The easiest solution for terraforming venus is to wait until "gravity shielding" (aka Podkletnov) techology is ready. Then lay a good-sized gravity shield on the surface of venus and let the atmosphere bleed off above it - like a smokestack effect.

We could be 5-10 years away from such a device - and it would be light enough to send there and plop on the surface relatively cheaply. Then just let time do the work.

A similar strategy could be used to increase the spin of venus - you just place one of these magic "gravity shields" at the lagrange point between the sun and venus, and break the gravity between the sun/venus on only one edge of the planet. That edge would then be attracted less to the sun and would spin away faster than the unshielded side.

Now all we need is a podkletnov device that actually works.

Shaun Barrett · 2003-02-11 18:32:49

Don't forget that energy can neither be created nor destroyed, Tim.
The kind of gravity shielding you're talking about is the equivalent of the fictional "Cavorite" from H.G. Wells' "The First Men in the Moon". It's a fine concept but it contravenes the laws of thermodynamics, which basically tell us there's no such thing as a free lunch!
Even a wildly successful Podkletnov device, capable of 100% gravity shielding, will still require a power input. Whatever 'work' that device does, say like elevating billions of tonnes of CO2 out of Venus's gravity well, as you suggest, will take energy ... LOTS of energy! And you will have to provide that energy from somewhere.
Under the heavy clouds of Venus, with sunlight too weak to power solar panels, I imagine you'll have to resort to large numbers of very high output fission reactors. (And all those dead greenies chained to them will be very bad publicity! )

Besides, the last time I heard anything about the Podkletnov device, NASA had pulled the plug on Ron Koczor's research efforts. A pretty cavalier attitude with $600,000 of taxpayers money!!! :angry:

Does anyone know if this situation has changed? ???

Hi Josh!
When you say turn the CO2 into hydrocarbons, do you mean hydrocarbons or carbohydrates? I don't follow your line of reasoning with this.
(I guess this smilie is for
confusion - I'm not sure.)

Josh Cryer · 2003-02-12 21:27:30

Shaun, hydrocarbons and carbohydrates are somewhat synonymous, only hydocarbon generally means whatever is made of hydrogen and carbon- fossilized carbohydrates or whatever; whereas carbohydrate means more the plant-based forms of carbon oxygen, and hydrogen compounds.

When all the fossil fuels run out, we'll have to find a new place to make plastics (assuming all plasic is used up, and recycling is either cost-prohibited or not feasible because, well, it's in use). Most plastic, like polyethylene, are made of hydrogen and carbon, it suffices to call them hydrocarbons. The primary sources for hydrocarbons is petroleum. Petroleum is merely fossilized plantlife. Plantlife then, would be the obvious place to find new hydrocarbons to make plastics. And we're assuming that all good land which to grow planet life is taken up on Earth. It's all sued to grow food, or whatever.

So it seems obvious that people would grow plants on Venus, in the upper atmosphere on huge floating platforms. And actually, you wouldn't have to ship water, just ship them hydrogen. They can make water since they'll have plenty of oxygen to go around. Heck, perhaps have solar wind collectors which collect hydrogen from the solar wind (don't know if that's feasible, though).

Josh Cryer · 2003-02-12 21:32:44

Oh, BTW, not just plastic, mind you, but anything in the polyol group or whatever. Which is quite expansive. We practically have a use for every last drop of petroleum. Which is why it's so valuable, actually; it goes much much further than being a fuel.

What's ironic is that it's easier to get polyols from biomass than it is petroleum.

soph · 2003-02-12 21:54:07

Who needs plastic, when one day we might have nanotubes to do the job :laugh:

but seriously, plastic facilities could utilize biomass to produce plastic.

another comment-I think people are more willing to terraform Mars, which can have a breathable atmosphere in the next century if we get there within the next few decades, and which is pretty sure to have oceans of water that aren't too hard to tap. People can see Mars as another Earth far more readily, easily, and quickly, than Venus, which will surely require more effort to terraform.

Josh Cryer · 2003-02-12 22:24:01

Hah, nanotubes aren't very resiliant... for instance, check out this story I read in New Scientist awhile ago: http://www.newscientist.com/news/news.jsp?id=ns99992219

But yes, that's the point I'm trying to make. Biomass will have to ultimately replace petroleum and other hydrocarbons in the future. We'll need plastics, fuels, antifreezes, fibers, etc. The list goes on and on.

And that's what my story is about (which hopefully I'll be able to use in a game). I'm trying to keep it somewhat realistic, beacuse I believe Venus will eventually become this way, prison aspect aside.

Terraforming Venus is way hard, would cost a ton, and wouldn't benefit us as much as not terraforming and exploiting the gaseous CO2 to grow biomass. We'd only resort to terraforming Venus a very long way down the road, once population levels got up there and people decided it was feasible from a technological and cost perspective.

tim_perdue · 2003-02-14 21:05:03

Don't forget that energy can neither be created nor destroyed, Tim.
The kind of gravity shielding you're talking about is the equivalent of the fictional "Cavorite" from H.G. Wells' "The First Men in the Moon". It's a fine concept but it contravenes the laws of thermodynamics, which basically tell us there's no such thing as a free lunch!
Even a wildly successful Podkletnov device, capable of 100% gravity shielding, will still require a power input. Whatever 'work' that device does, say like elevating billions of tonnes of CO2 out of Venus's gravity well, as you suggest, will take energy ... LOTS of energy! And you will have to provide that energy from somewhere.

Podkletnov's device doesn't break the so-called "law" of thermodynamics. It takes more energy to power the device than you gain in potential energy. (assuming it isn't a total fraud)

Anyway, centrifugal force will do some of the work to throw the CO2 out of the atmosphere. All you're doing is stopping it from falling back to the surface. I'm no mathematician, but a gigawatt or two should let you shield at least a few hundred square meters of the surface. That would be one hell of a huge chimney.

You're right - as far as changing the rotation, you can forget about that with any conceivable power supply we have now, but it's no different than the huge electromagnets some people were mentioning.

Bleed off the atmosphere and knock a few comets into the planet and you've got a pretty good start.

dickbill · 2003-02-15 11:29:54

Another point to prefer terraforming Mars is how's gonna be the sun in the future ?, maybe unstable, maybe hot enough that you don't want to stay too close like in Venus.
As little as 1% increase of sun output would be bad for a globally warming earth, so imagine Venus.

Shaun Barrett · 2003-02-15 22:12:12

Three points:-

Josh, the very best of good luck with the story you're writing. It's an interesting angle and I don't reacall anyone having done anything similar. Hope it's a raging success!!

Tim, I hope I wasn't shooting from the hip as far as your Podkletnov solution to the Venusian problem is concerned. In retrospect, it seems I was preaching to the converted. At least mentally, you had indeed factored in the need for a substantial energy supply. This wasn't apparent to me at the time - my apologies, no offence intended!!
Actually, I'm a big fan of researching things like the Podkletnov device and only wish the people at NASA would get off their ***es and get on with it!

Good point, Dickbill! Though I'm hopeful that any significant change in the Sun's output will be extremely gradual and therefore negligible for many millions of years yet!
:;):

dickbill · 2003-02-16 10:58:34

Though I'm hopeful that any significant change in the Sun's output will be extremely gradual and therefore negligible for many millions of years yet!

Hi shaun,

maybe yes maybe not. Do we have any certitude that the sun couldn't start to fluctuate a little bit, as soon as in 10 years for example ?
Our model of the sun tells us that the sun is stable for billions of years, I've heard that a slightly hoter sun is expected only in 500 millions years , but stable at what scale in terms of output ?
Is a 0.5 % output fluctuation is predictidable in that model ? and what could be the impact on our planet ? Certainly bad for us and disastrous for any terraformed Venus.

Josh Cryer · 2003-02-16 15:44:04

A terraformed Venus would undoubtedly require some sort of shade. Or at least, lots of reflectors on the ground or something silly like that! You have to get rid of that excess heat.

So, since it would need a shade, I see no problem with merely closing the blinds, if you will, if and when the sun grows brighter. Of course, that doesn't help Venus as the sun grows bigger, but that won't occur for quite a long time.

Shaun Barrett · 2003-02-16 21:58:10

Dickbill, you're quite correct, of course, in saying that significant fluctuations in solar output could possibly occur in relatively short time frames.
Those fluctuations could be disastrous for Earth and even more catastrophic for a terraforming endeavour on Venus.
I suppose all we can do is look at the history of life on Earth for clues as to how stable the sun really is. Most of the mass extinctions we see evidence for in the fossil record appear to be traceable to volcanic and/or impact events. To the best of my knowledge (such as it is), no major extinction episodes have been attributed to large and sudden changes in insolation, though I suppose attitudes could alter with the advent of new data.

In any event, we just have to go about our business on the assumption that things will remain much as they are now. If we were to base all our planning on the assumption that a major disaster could befall us any minute, I guess we'd just huddle together in the basement, hold hands, and wait for armageddon!
In other words, I think we have to be optimistic and hope for the best.

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Re: Venus / Mars

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Re: Venus / Mars

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