Terraforming Venus - The Latest Thinking

Michael Bloxham · 2007-09-10 05:18:20

What I am talking about is very localised heat pumping. A planetary scale system would be ridiculous and impossible.

But lets side-track from the subject of the topic and talk about actively cooling structures on the surface.

What I can imagine is large dome-type structures (for minimum surface area to volume ratio), lifted off the hot surface by insulating blocks. And I'm talking really big domes, as the more internal volume the better. Perhaps it could house a large internal heat sink, of either water or rock, to help stabilize internal temperatures, and to provide some thermal lag in the event that the active cooling system fails.

The cooling system would simply be a large heat pump, using CO2 as a refigerant. The CO2 would be circulated under the same external pressure as that of the interior of the dome (say 1 to 10 bar).

Fresh CO2 would be leaked in to a sealed compartment, pushing itself through a heat exchanger (on the inside of the dome), thereby cooling the internal heat-sink. The CO2 would then be compressed to slightly above external atmosphere levels, thereby expelling it out of the dome.

It would be a single pass system. No need to recirculate CO2.

Would this work?

Michael Bloxham · 2007-09-10 05:21:40

Actually, I can imagine super large domes, perhaps vacuum insulated also, that use pure CO2 in their atmosphere, for the purposes of growing plants only. That way, a heat exchanger is not required. All you would need is a dome, some insulating blocks, and a big pump.

Tom Kalbfus · 2007-09-10 07:49:11

I like your idea Tom. It's bizzare but ingenious. However, it would require an unimaginatively big planetary-scale effort to construct those plates. And what would happen if it were to rupture while under pressure?
What about actively cooling structures on the surface? Has any thought been given to using the CO2 gas as a refigerant?

Lets compare it to other planetary scale efforts, one is constructing the Sun shield inbetween the Sun and Venus to block sunlight from reaching Venus. One can dirty the atmosphere with dust to temporarily block sunlight to Venus, but eventually you need something more permanent because Venus receives too much sunlight, so some massive object is going to have to be constructed in space to shade Venus. Easily the surface area of such a Sunshade out beyond L1 is going to be more than the entire surface area of Venus, so the reasoning goes, if you can construct such a massive thing in space, why not do some massive construction works on the surface of Venus? The material for building the plates comes from Venus itself, perhaps the only resource allocation where mining material from Venus actually makes sense. The sunshade material however will probably come from an asteroid or two. To conserve material, the sunshade will probably be made of thin solar sail material and it will probably also let some sunlight through, reducing the levels of Solar Illumination to Earth levels or less. Probably temporarily reducing the light levels to that of Jupiter or the Asteroid belt might be a good idea for cooling the planet, while also leaving sufficient illumination to see by etc. The solar sail sunshade will park on the Sun side of the L1 point so that it can use light pressue to maintain its position against a pull of gravity that's toward the Sun.

The plate material to envelop Venus would be thicker, but you have alot more material to work with also coming out of Venus's crust. As for the 1,000 bars of CO2 pressure, make the plates heavy enough and their weight will contain it provided the plates are locked together airtight. One possible problem may be volcanoes, what happens if a Venusian volcano were to erupt under the plates, the pressure of that eruption would have to be contained as well, for Venus unlike Mars is very much volcanically active. The crust on Venus is probably thinner than on Earth, so the sort of eruption one is likely to find is more likely to be an oozing of lava rather than an explosion like Mt St Helens, but I'm sure we'll get both types of eruptions. These are engineering problems though, nothing insurmountable for a society capable of doing this sort of stuff. I think Venus if Terraformed this way is likely to end up as a sort of "city planet" maybe not all covered with towers, part of the planet will likely be set aside for agriculture as its cheaper to grow one's food on planet than off. Now if everybody were to move from Earth to Venus with plenty of infrastructure to accomodate all of Earth's billions, that can only do the natural environment on Earth some good, either that or we can make a "naturalistic" surface on Venus, but for all of that effort, I doubt it would be all for the bears and the birdies. Venus would be a brand new city as compared to Earth, with a thorougly modern infrastructure and transportation system since its entire surface would be artificial. There would likely be no air traffic above the surface of Venus except for people and ships arriving and leaving the planet, a system of evacuated maglev subways would sweep passengers to anypoint on Venus's surface in about an hour to 90 minutes, there would probably be at first more living space than people, the terrain would likely be flat with little variation in altitude, as the shell has to support all this weight. One could stand out on the surface and see a blue sky above and filtered sunshine shining down on one's face. Probably he'd also see neat rows of trees on the surface, some useful insects for pollenization and so forth, much agriculture, but as the initial population is likely to be small, much of the surface may be given over to neatly manicured parks, gardens and lawns.

Tom Kalbfus · 2007-09-10 07:56:42

Michael Bloxham,
Hmmm now that is an interesting thought.
I wonder if you could use co2 as a refrigerant to cool the entire atmosphere?
A giant global air conditioner.
We would need a way to dump heat to space, but the compressor rates of a bar or two over the native atmosphere wouldnt be difficult.
Anyone have any ideas to dump the heat?

All that nasty hot carbon dioxide would be compressed and made even hotter under the plates, the sun shades interposed between Venus and the Sun would do much of the cooling, much of the heat would be conducted through the plates and radiated through the much thinner atmosphere above and into space. The amount of sunlight allowed to reach Venus would therefore have to be less than that reaching Earth to compensate for the heatflow coming through the surfaces of the plates. As all gasses do when they cool, the pressure underneath the plates will likely decrease as the gasses below cool, some thought has to be put into the engineering details so that the plates don't buckel as the pressure under them decreases. Perhaps a system of weights underneath can be dropped as the gas pressure decreases.

nickname · 2007-09-11 04:43:45

Michael Bloxham,

I'm not sure an air conditioner on a domed structure would work on the surface of Venus.

We could probably make a structure that was cooler than the outdoor temperature.

As a human habitation we would need a cooling differential of 400c and 90 bars pressure.
The power requirements would be off the scale and trying to dump heat from inside 2 bars 50c to outside 92 bars 450c would be problematic.
Not impossible though.

On the global scale its not as crazy as i first thought.

We could probably use the differential pressure and temperature from surface to upper atmosphere to make a very high speed chimney.

At first glance that seems quite silly because we would need to build a 30km high chimney from the surface and put a high magnetic charge on the gas, but a partical gun on the surface pointed up would create a virtual chimney and charge the gas.

Getting that co2 to the le grange point to meet up with asteroid debris in orbit would be a plus, as it would form a moon by itself after a few hundred years.
The first few hundred years it would act as an efficient sun shield.

Since c02 is one of the heaviest gasses on Venus and we draw from the surface we would keep most of the useful gasses on Venus.

nickname · 2007-09-11 05:01:27

Tom Kalbfus,

If we had a surface of Venus that co2 can be fixed to things permanently and we can mine for catalysts, why not just turn the atmosphere into carbon everything.?
Build the entire surface structure from fixed carbon and oxygen elements.
You could probably use it all up just doing that and not have to worry about the pressure problems.

Or an even simpler process is to create mass quantities of carbon smoke to change the way the atmosphere retains heat.
Then take your own sweet time to make carbon everything

Tom Kalbfus · 2007-09-11 13:24:52

Chemical processes take time, perhaps physically pushing the atmosphere aside or burying it might be faster.

nickname · 2007-09-11 15:45:43

Tom Kalbfus,

I agree, bury, expel, fix, create.
Anything we can do to decrease the atmosphere.

We could live in structures on a planet with a 92 bar atmosphere, but not one with a 450c surface.

The heat is enemy #1.

If the light doesn't make it to the co2 level neither does the heat retention of the co2.
If we could cool things just enough to get machines working on the surface we sure could produce a lot of thick smoke lighter than co2 with that 89 bars of co2 and 3 bars of nitrogen.

We could make 9 bars of nitros oxide from the atmosphere, a gas lighter than co2 with decent reflecting properties.

Suplhur dioxide etc etc, lots of options for gas combinations right on Venus.

Something like the smog filled atmosphere of titan might be a goal to aim for.
Venus can keep it 89 bars of co2, simply block it from being a heating factor.

We are really good at burning things and creating smog without really trying
Imagine how good we would be if we tried

Michael Bloxham · 2007-09-12 04:35:33

Nickname, perhaps a problem with this is that the atmosphere and surface of Venus store a great deal of heat energy. I bet that if you were to block the entire planet from the sun, it would take hundreds or thousands of years for it to cool. However, this is just my assumption. I bet you could do the calculations quite easily. Just figure out the mass, temperature, and specific heat capacity of the Venus' atmosphere, and also maybe the first 10 meters depth of its rocky surface, find the total heat energy stored, then work from there.

nickname · 2007-09-12 05:21:11

Michael Bloxham,

I seem to remember a long discussion about blocking the sun from Venus here.

If i remember right if you were to completely block the sun it was about 1 - 2 years for Venus to cool below 50c at the surface at least the atmosphere.

The surface rock is sure to be 450c decreasing at about the same temperature earths rock does, about 5c meter.

That layer of hot surface rock will take much longer to cool.
More like 10 -20 years on a 100% sun blocked Venus.

I think the best we could ever hope for is maybe 75% sun block, that would be with an orbital sun shield, maybe a temporary L1 shield and manmade upper atmospheric reflective smog.

At 75% the numbers are more like 40 years for the atmosphere and 140 years for the surface rock to cool below 50c.
Machines could arrive on the surface and start work about year 10 - 15.

Keeping an L1 shield in place for many years would be the hard part, the other two Shields are pretty easy to maintain.

If we could simply pump c02 to the le grange, each day on Venus the temperature would decrease and the heat retention would decrease.
140 years sounds about right for that process anyway, maybe longer.
1/2 a bar a year from surface to le grange point seems possible.

Tom Kalbfus · 2007-09-12 21:12:30

Nickname, isn't there something called a Solar Sail?

Couldn't a Solar Sail block the Sunlight if it was an especially large solar sail or a fleet of solar sails?

Since a solar sail is propelled by sunlight, it could accelerate indefinitely against Solar gravity just so long as the light pressure on the Solar Sail and the gravity minus centripetal force balance out.

So long as the Solar Sail is further away from Venus than L1 in the direction of the Sun, and it moves at the right velocity, it can keep its shadow on Venus. The great thing about Solar Sails is that they are very thin and thus economical of materials. Now if we can get a Solar Sail that can reflect 75% of the Solar radiation, we'd end up with Mars-like illumination reaching Venus. The current surface temperature would then be too high to be maintained with only a quarter of the radiation Venus gets today, so the atmosphere would cool. The surface would remain hot for a time longer, but you could then set down machinery on its surface. Dump some water on Venus and you can add microorganisms to convert Venus's CO2 into oxygen. Keep the shipments of comet water coming and you'd gradually fill in an ocean. Microorganisms would make free oxygen, building up a surplus of it. The excess oxygen can then be soaked up by shipments of hydrogen from Jupiter's icy moons after seperating out the oxygen in water ice by electrolysis, or perhaps Titan is a better candidate.

Basically we uses plants to remove the carbon from carbon dioxide, take the oxygen and add hydrogen to it to make water, then we add to Venus Ocean. I read a series of books about this by Pamela Sargent. Basically it was this long Soap Opera thing that took place under the backdrop of terraforming Venus. Pamela had this "magic wand" where she used spinning micro black holes to spin up Venus, otherwise the process was realistic. The timespace of three books over multiple generations was not enough to see the terraforming project to completion, so the heroes took an interstellar jaunt to a distant star system to investigate an alien signal only to find out it was nothing but a beacon with nothing significant to tell, so they returned to the Solar System millenia later to find Venus completely terraformed and Earth having hung up a "do not disturb" sign for these interstellar travellers from the past.

I think terraforming Venus is a hobby for some super-civilization with too many resources on its hands and nothing better to do with them. The best way to enjoy a terraformed Venus is take a long interstellar journey while someone else terraforms Venus, and then return when the Job is done.

So what about a Venus that rotates as slowly as it does now? Changing the planet's rotation is the hardest part, so what if we dispense with that, could Earth's organisms adapt to such a long day/night cycle?

I suspect it could, humans would need shades in their windows so they could get some sleep during the day, while at night, they would need some illumination.

Michael Bloxham · 2007-09-13 02:28:32

Tom, perhaps you could use the solar sail you envision to control the day-night cycle.

nickname · 2007-09-13 05:19:14

Tom Kalbfus,

At first glance the L1 sun block looks ideal to cool Venus.
A solar sail will work if it is big enough, but it is big enough to block the sun from the path to Venus it is also big enough to feel even the tiniest solar storm.

An L1 sun block no matter what you make it from will require lots of fuel to keep it in place.
A solar sail might be the cheapest way to go for fuel though as you can direct it somewhat.

Collecting hydrogen from the gas giants is such a long process.
To collect 1 bar of hydrogen and return it to Venus with a pretty modest plan was about 10,000 years work.

I personally think its easier to just get 1 decent sized ice kb for Venus
when the atmosphere is about 20 bars.
The introduction of masses of water would soak up lots of co2 and sulphur and immediately make a home for bacteria.

Karov had an interesting idea about collecting hydrogen from solar storm activity near Venus with magnetics.
Doing the same thing from the L1 point as sun shield and solar storm re director really sounds interesting.

I don't think the spin of Venus will be much of a worry for Bacteria or plants.
They both do pretty well in the far north and south here on earth with long days and nights.
The people do put up curtains

The more i think about just dumping c02 to the le grange the more attractive it becomes.

C02 is a great greenhouse gas, it is also a pretty decent heat mirror.
With a layer of c02 at the le grange we might not have to worry to much about the light levels.
Most of the light passing through the le grange c02 layer would be converted to heat energy that the c02 on Venus would reject back to space.

Maybe enough heat rejected that we don't need any other cooling or shading process?
We really need some good math on that.

Tom Kalbfus · 2007-09-13 10:26:39

Tom Kalbfus,
At first glance the L1 sun block looks ideal to cool Venus.
A solar sail will work if it is big enough, but it is big enough to block the sun from the path to Venus it is also big enough to feel even the tiniest solar storm.
An L1 sun block no matter what you make it from will require lots of fuel to keep it in place.
A solar sail might be the cheapest way to go for fuel though as you can direct it somewhat.

I'm not good at graphics so please bear with me.

S-------------S--------------V
U-------------A----L1-------E
N-------------I--------------N
---------------L-------------U
-----------------------------S

The Solar Sail is not at the L1 point but beyond it, the Sun is pulling more strongly on it gravitationally than Venus because it is further than the L1 point where the forces of the Sun's gravity and Venus's balance out at this orbit. Basically L1 is the minimum distance for any solar sail shade. If the Sail was exactly at L1 the Sun's light would push it towards Venus and there would be no countervailing gravitational attraction toward the Sun as it would be balanced out by Venus's gravity, the Sail would be pushed toward Venus by light pressure and as it got closer to Venus than L1 it would also be pulled more strongly by Venus' gravity, a minor detail, but an important one. It is important that the Sun's gravity extert a stronger gravitational pull on the Sail than Venus', with that and an active structure the Sail can automatically position itself between L1 and the Sun by becoming more or less selectively transparent or reflective.

Micromachines or nanomachines can arrange the fibers of the Solar Sail actively so as to regulate the reflectivity and transparency of various parts of the whole sail or sails. By becoming more transparent, the sail will become less reflective and fall towards the Sun. By becoming more reflective and less transparent the Sail will be pushed away from the Sun. By becoming more reflective in part of the sail and less on another part, the sail can turn and reflect away from the sun, moving either forward in its orbit, or back, or perpendicular to its orbit around the sun, so as to maintian its position between Venus L1 and the Sun so as to cast a shadow on Venus, and it does this without expending any propellent of its own. Solar Sails rely on photons as both energy and reaction mass. With an intelligent structure and built in circuits, you can have a "smart" solar sail that "knows" where it is supposed to be, and if its position deviates in any way, the intelligent structure can maneuver to correct its position.

Collecting hydrogen from the gas giants is such a long process.
To collect 1 bar of hydrogen and return it to Venus with a pretty modest plan was about 10,000 years work.

I don't know what assumptions you are using for the transportation network to get hydrogen from where ever in the outer Solar System. I suspect that it might be easier to obtain hydrogen from the ice in Jupiter's icy moons than from Jupiter itself, even though there is chemical processing involved to extract pure hydrogen from water ice and possibly hydrocarbons. The further out from the Solar System a body is, the less the velocity change that is required to get that body hurling towards Venus, but time is also money, it might make sense to obtain hydrogen from the outer asteroids than from Neptune or the Oort Cloud, although gravitationally the Oort Cloud would be easiest. Humans only have so much patience. The nearest source of hydrogen to Venus is the Earth with its oceans and icecaps. Since those ice caps may be melting and flooding our coastal cities, we can probably space some of our water hydrogen and send it over toward Venus, later on we can extract water from the asteroids and take out the hydrogen from that. Hydrogen from the asteroids takes longer to arrive than from Earth, later on, we can remove hydrogen from the Jovian system, and then the Saturnian system. Those closer in bodies are to get the hydrogen flowing towards Venus as soon as possible, but after the hydrogen has been coming in for a while, the hydrogen starts arriving from Jupiter, Saturn, Uranus, and Neptune. After a century has passed, the first supplies of comet derived hydrogen starts arriving. Once the outer bodies hydrogen starts arriving, we can shut down the extraction process from the inner bodies. The inflow of hydrogen has to match the excess liberation of free oxygen from micro organisms, and Venus' water supplie will build and build.

It makes no sense to fling out oxygen in the form of Carbon dioxide, and also add more oxygen in the form of water at the same time. I think the carbon in carbon dioxide can be made into some solid material and the liberated oxygen can be combined with hydrogen to make water for the oceans. The oceans will absord alot of oxygen in their creation, and I think we can get the atmosphere down to 1 bar by turing much of that excess oxygen into water. Moving oxygen atoms on and off of Venus is a waste of energy.

I personally think its easier to just get 1 decent sized ice kb for Venus
when the atmosphere is about 20 bars.
The introduction of masses of water would soak up lots of co2 and sulphur and immediately make a home for bacteria.
Karov had an interesting idea about collecting hydrogen from solar storm activity near Venus with magnetics.
Doing the same thing from the L1 point as sun shield and solar storm re director really sounds interesting.
I don't think the spin of Venus will be much of a worry for Bacteria or plants.
They both do pretty well in the far north and south here on earth with long days and nights.
The people do put up curtains
The more i think about just dumping c02 to the le grange the more attractive it becomes.
C02 is a great greenhouse gas, it is also a pretty decent heat mirror.
With a layer of c02 at the le grange we might not have to worry to much about the light levels.
Most of the light passing through the le grange c02 layer would be converted to heat energy that the c02 on Venus would reject back to space.
Maybe enough heat rejected that we don't need any other cooling or shading process?
We really need some good math on that.

I think Venus got the way it is because it was too close to the Sun, and that triggered a runaway greenhouse effect. Had Venus formed in Earth's orbit, that runaway greenhouse effect would not have been triggered and a balance similar to Earth's would have been achieved.

That Sunshade is going to have to stay there I'm afraid if Venus is to remain terraformed after we've terraformed it. That said, I think Venus will make a nice city-planet, since we would have to rework it so much, we should try to maximize human habitation capability to maximise the return on our enourmous investment.

Cities can have their own aritificial illumination, they can be enclosed structures where the air is exchanged with the outside for breathing purposes. People will tend to live in vast enclosed spaces where the illumination and day/night cycle will be regulater artificially to a 24 hour period, and on occasion, people will venture outside into the natural sunlight filtered by the distant sun shade, and they will see a blue sky with some white clouds, and a Sun that slowly moves toward the east over a period of so many weeks, or sometimes they'll step out under a starry sky, the constellations will wheel about very slowly, a blue double star or Earth and a greenish star of Mars will be visible, and a large number of artificial structures would wheel about more quickly in orbit around Venus. There would be no Moon of course except for those artificial moons we place there. At night the ground may be covered with snow and ice, and people will see their breaths under the floodlights of the nearby cities, and have to wait weeks for the next sunrise in the west. So long as people live indoors and don't do too much camping, the long day/night cycle need not impact them too much.

Spatula · 2007-09-13 22:26:30

I think the main problem with these Venus threads is that people see how close the planet is to the Sun, and they immediately assume it would be hot without the thick atmosphere.

They also see the slow rotation and think 'ah, much hotter days.'

Without any atmosphere, the predicted temperature for the planet is around 25 degrees C.

The disparity in temperature between days and nights would not be significantly greater than Earth's.

When the concept of exoplanets that were tidally locked to their stars came up, it generated a lot of interest, and the scientific community spent quite a bit of time modeling these to see if life would be possible on them. It was thought for a long time that earthy atmospheres would simply get blown off from the turbulence, but apparently the presence of a water cycle, and greenhouse gases, is sufficient at distributing heat and keeping the prevailing wind speeds down.

nickname · 2007-09-14 05:01:18

Spatula,

I see an early Venus more in the 50c range with a few bars of co2 and 3 of nitrogen.

I also see a problem for that atmosphere trying to boil off its oceans to get to the 92 bars we see today.

The math of oceans turning into free oxygen that combines with free carbon makes seance, then hydrogen just lost to space.

The trouble with that idea is if we run the clock backwards before the process, the quantity of ocean on Venus would have resisted the heating.

Once you have vast oceans on Venus its near impossible to boil them away, especially with a sun 10% dimmer.

If it was oceans boiling away why doesn't Venus have vast quantities of sulphur dioxide?
Why so little nitros oxide and nitrogen dioxide?
They would have been formed in quantity with masses of free oxygen.

In my opinion Venus had some water to begin with, but the bulk of the co2 was expelled by volcanos.
The sulphur content of the upper atmosphere and the extreme volcanic activity all over Venus gives some evidence of that.

The evidence of oceans of water on Venus is only a good fit when trying to make math fit an atmosphere we see.
Maybe Venus was just a very volcanic place for a few billion years.

A 25c temperature on a Venus with a nitrogen oxygen atmosphere like ours seems pretty straight forward.
Interesting to know that if we did teraform Venus it would tend to stay that way.

Not so sure about the day night side staying equal.
A teraformed Venus would have pretty cool nights and pretty hot days.
Those temperature difference are sure to cause some pretty intense weather.

Then again those sort of temperature differentials exist on earth between poles and equator, so Venus might be no more weather challenged than earth.
We are sure to get some pretty persistent prevailing winds on Venus though as the weather patterns will be east west, not north south like on earth.

nickname · 2007-09-14 05:29:22

Tom Kalbfus,

What is your best guess for size of a solar sail to block light to Venus?
I think a position would exist between the sun and the L1 for such a sail, we would just have to figure out where.

The hydrogen collection from the outer solar system was on a long ago topic here.

With current technology its about a 20 year trip to collect hydrogen then deliver it to Venus.

Cant remember exactly how the 10,000 year per bar was arrived at.
It seemed pretty reasonable with a few people hacking away at the math.
That was for a pretty intense collection program with a fleet of big hydrogen collectors.

Other than cooking up a way we can collect hydrogen from solar storms all the other locations for hydrogen collection in the solar system will take as long.

Other than donations from earth.
I'm pretty sure we wont donate, we gave at the office

Trouble with adding hydrogen to Venus to create water is we need 30+ bars of hydrogen to deal with the c02 content.

Even if we had it and could deliver it all at once we would just create steam on the current Venus.

We need a Venus with surface temperature below 110c the boil point of water on Venus to add water.

Adding either hydrogen or ice ball before that would just make Venus a hotter place.
So cooling is the first think we need for venus to do anything productive.

I think we have a hope of cooling Venus with it's own nasty atmosphere.
A shell of c02 at the le grange point would stay in place for eons.
I'm just not 100% sure it would convert enough of the light to heat before it arrives at Venus to make the co2 atmosphere work as a heat reflector.

Antius · 2007-09-14 07:30:41

Tom Kalbfus,
What is your best guess for size of a solar sail to block light to Venus?
I think a position would exist between the sun and the L1 for such a sail, we would just have to figure out where.
The hydrogen collection from the outer solar system was on a long ago topic here.
With current technology its about a 20 year trip to collect hydrogen then deliver it to Venus.
Cant remember exactly how the 10,000 year per bar was arrived at.
It seemed pretty reasonable with a few people hacking away at the math.
That was for a pretty intense collection program with a fleet of big hydrogen collectors.
Other than cooking up a way we can collect hydrogen from solar storms all the other locations for hydrogen collection in the solar system will take as long.
Other than donations from earth.
I'm pretty sure we wont donate, we gave at the office
Trouble with adding hydrogen to Venus to create water is we need 30+ bars of hydrogen to deal with the c02 content.
Even if we had it and could deliver it all at once we would just create steam on the current Venus.
We need a Venus with surface temperature below 110c the boil point of water on Venus to add water.
Adding either hydrogen or ice ball before that would just make Venus a hotter place.
So cooling is the first think we need for venus to do anything productive.

I think we have a hope of cooling Venus with it's own nasty atmosphere.
A shell of c02 at the le grange point would stay in place for eons.
I'm just not 100% sure it would convert enough of the light to heat before it arrives at Venus to make the co2 atmosphere work as a heat reflector.

A floating solar sail would rapidly lose orbit due to sunlight pressure. Another solution is to manufacture trillions of tiny aluminium balloons filled with a lifting gas (hydrogen , helium, nitrogen, etc) and inject them into the upper atmosphere. Eventually, these could be manufactured using native Venusian resources. As the atmosphere cools, CO2 will begin to liquify into seas on the surface. It could gradually be bottled and buried.

Tom Kalbfus · 2007-09-14 07:48:06

Sunlight is not a gas. If the solar sail is angled to deflect sunlight in a direction opposite of its path around the sun, the sail will move away from the sun as it accelerates and moves to a wider orbit.

If the Solar Sail is angled to deflect sunlight in the direction of its motion, then it will slow down and fall into a closer and faster orbit around the sun.

The Solar Sail I'm talking about is not a passive object, it is powered by the sun and propelled by the sun, and by moving tiny motors among the fibers of the sail it can cause the sail to be more or less reflective in various parts of the sail, and the differences in light pressure resulting on the sail will cause the sail to turn, and deflect sunlight in a specific direction to cause thrust for maneuvering. There would be sensors in the sail that would detect where Venus and the Sun are in relation to it, and if Venus was in the wrong spot, it would instruct its servo-motors to angle the sail in such a way as to maneuver the sail back in the right spot so as to shade the planet Venus. There is an automatic feedback mechanism at work here to keep the sail in place. I'm not sure trillions of balloons or particulates are the right answer as they will always have to be replenished, and the balloons especially will cause a "garbage problem" on the surface of Venus. Those balloons which won't float forever will eventually fall to the ground creating a layer of deflated balloons on the surface of Venus which would kill plants by blocking the sunlight, and would really create a mess that would need to be picked up. At least the Solar Sail would stay up there and not create litter. Give a hoot, don't pollute!

nickname · 2007-09-14 15:05:15

Antius,

Wouldn't high altitude smog do the same thing as trillions of tiny aluminium balloons ?

With the raw products at Venus, oxygen, carbon, nitrogen and sulphur I'm sure we can make a pretty thick light reflecting smog and deliver it to the upper atmosphere.
The beauty of creating natural smog made from elements found on Venus is we wouldn't need to bring anything special to Venus to start and maintain the process.

Spatula · 2007-09-14 20:45:08

Spatula,
I see an early Venus more in the 50c range with a few bars of co2 and 3 of nitrogen.
I also see a problem for that atmosphere trying to boil off its oceans to get to the 92 bars we see today.

Right, and that's right. My 25 C figure is in reference to Venus without any atmosphere at all. It's an estimate though, for situations where the planet is a greybody with a similar composition to earth on the crust. As a blackbody, reflecting nothing that hits it, the temperature increases quite a bit. Add oceans, and that completely changes too.

A 25c temperature on a Venus with a nitrogen oxygen atmosphere like ours seems pretty straight forward.
Interesting to know that if we did teraform Venus it would tend to stay that way.

Unfortunately, with 1 bar of atmosphere the planet would probably be hotter than 25 C. The oceans would be below 25 C, in no danger of boiling off, but the atmosphere might be in the borderline uncomfortable range, 35 C or higher maybe. Such a planet would only be comfortable in the temperate regions or poles. We could take measures to artificially cool it though. Extra atmospheric oxygen, possibly. Maybe just make the atmosphere thinner, I'm just throwing ideas out!

Not so sure about the day night side staying equal.
A teraformed Venus would have pretty cool nights and pretty hot days.
Those temperature difference are sure to cause some pretty intense weather.

An atmosphere of 0.1 bars is enough to stabilize the temperature on both sides to an earthy range, but there is some variation in the models. Some show ice caps forming on on the night side. It's difficult to be certain. Part of it is that the planet is simply hotter. It will take longer to lose heat on the night side through blackbody radiation, because there's more of it.

Part of it is that the planet has no axial tilt, so the yearly temperature variation would be the same as Earth's equator, everywhere. No seasons. There are other small details.

nickname · 2007-09-15 07:26:24

Spatula,

Yeah difficult to model what a Venus with a similar atmosphere to earths would be like.
The water quantity on Venus would be a big factor i think.

I think your pretty close to the 35c day temperatures on the day side, maybe a bit hotter in specific locations.

The night side all depends on how much atmosphere and water you had, its sure to get cool on the long nights.

Moving ice caps on the night side probably wouldn't be a bad thing for Venus, a pretty good temperature regulator for the globe.

One other thing to think about on a teraformed Venus is the persistent rain.
With all that additional energy from being closer to the sun the evaporation cycle with be much faster than on earth.
Lots of rainy days and lots of clouds will lower the global temperature and scrub c02 much faster than on earth.
With persistent cloud cover we could find that Venus is as cool as earth.
Thick cloud cover could keep the chill of the night side and stop overheating on the day side.

Wonder if it would rain or snow on the night side?

Tom Kalbfus · 2007-09-15 08:36:45

With all that additional energy from being closer to the sun the evaporation cycle with be much faster than on earth.
Lots of rainy days and lots of clouds will lower the global temperature and scrub c02 much faster than on earth.
With persistent cloud cover we could find that Venus is as cool as earth.
Thick cloud cover could keep the chill of the night side and stop overheating on the day side.
Wonder if it would rain or snow on the night side?

The Venusian Day is about 116 Earth days long with the Sun rising in the West and setting in the East, so Each Venusian hour is 4.83 Earth days long. Your can divide the Venusian day into 4 one-month seasons, each season is the length of the month of February during a leap year (29 days)

"Winter" would probably be from 10 p.m. to 4 a.m.

"Spring" would be from 4 a.m. to 10 a.m.

"Summer" would be from 10 a.m. to 4 p.m.

and "Autumn" would be from 4 p.m. to 10 p.m.

Each Venusian day is about the same length as there is hardly any tilt to the Venusian axis of rotation so the Sun would set and rise at approximately the same time each day. Remember each Venusian hour we are talking about is the equivalent to 4.83 Earth days, so in the course of a work week on Venus, the Sun would move 15 degrees in its arc across the sky.

If Venus is being shaded the Sun would likely show a larger disk, but the intensity of sunlight per angual unit of area would be less. Another thing to consider is that an Earthlike atmosphere on Venus would stack higher on Venus than on Earth, even assuming the same atmospheric composition, the terraformers would probably desire the total illumination reaching Venus to be a little less than on Earth. Considering how short the Venusian growing season is, they'd probably prefer to maximise their growing season to take advantage of the full 3 Earth-months worth of sunlight, so the climate would only get cold enough to snow after sunset., and would melt quickly with each Sunrise, so planting can begin as quickly as possible, it would probably only snow near the poles, while the majority of the climate would be tropical. Venus would have no permanent ice caps, as no doubt the terraformers would want to inhabit one of the two main continents, Ishtar Terra, which straddles the Venusian arctic. Thank's to the lack of tilt though, a day in the aretic would last about as long as a day at the equator. The high mountain ranges of Maxwell Montes would probably have permanent snow on top though, or at least until the next eruption.

Terraformer · 2007-09-15 10:10:39

Permenant snot?

What about setting up an exchange with Earth. Earth sends water for food crops under domes. Plants use up load of CO2. Venus swops the plants for water.

Tom Kalbfus · 2007-09-15 10:35:50

I hate this keyboard! I type one letter and out comes another, 't' for 'w'.

We don't want too much carbon on Earth either, as there is no shortage of carbon on Earth for making plants out of.

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