Terraformed Venus

[Ford Prefect]

I cannot comment on the plausibility of terraformation as a whole, and terraforming Venus would be a total chore, to put it mildly. But for my own satisfaction, could anyone comment on how a terraformed Venus would be different to Earth? I mean, say you put a ginormous sunshade at at the Venus/Sun lagrange point and you somehow got rid of all that CO2 and then rigged up a day shorter than a third of a year and got yourself some oxygen and oceans going on, what could it be like? How different would weather be, for example? What effect would a slow rotation and lack of tectonic activity have on the livable Venusian environment?

[Darth Raptor]

You have to introduce plate tectonics, unless you want to periodically lose the entire world in violent, melty resurfacing events. The good news is that the additions of oceans should stimulate the development of plates. Also, mirrors aren't just good for shading the planet, they can bring light to the night side. All told, it's not inconceivable for Venus to be every bit as livable as Earth when you're done with it (though, as you said, it would be a fucking chore).

[Count Chocula]

Imagine Death Valley temperatures and below sea level pressures, with no humidity and no wind, with the only benefit being a slightly lighter gravity.

In other words, Tatooine with one sun in the sky - a truly suckful place to be. And not a speeder in sight.

And to see just what an enormous task it would be, take a look at http://www.nineplanets.org.

[Ford Prefect]

You have to introduce plate tectonics, unless you want to periodically lose the entire world in violent, melty resurfacing events. The good news is that the additions of oceans should stimulate the development of plates. Also, mirrors aren't just good for shading the planet, they can bring light to the night side. All told, it's not inconceivable for Venus to be every bit as livable as Earth when you're done with it (though, as you said, it would be a fucking chore).

I was hoping someone wouldn't say that. Short of changing its very rotation, starting plate activity on Venus was one of those things I didn't really want to touch, even if I was fine with oceans* from nowhere. For one, I have no idea where to begin with that sort of project (whereas I have read more than a couple methods that could deal with Venus' atmosphere). It's not a situation you can just throw rocks at to get going. Compartively, constructing a fifty thousand kilometre wide sunshade in such away that the solarwind doesn't wrap it around your planet seems trivial.

*Carbonated.

[Darth Raptor]

Actually, it *is* a problem you can throw rocks at. Or comets, anyway. The same idea proposed to introduce oceans to Mars is to bombard the planet with lots and lots of dirty snowballs. Once that's out of the way, plate tectonics should start up all on its own.

[Ford Prefect]

That shows what I know about plate tectonics. While any venusian/martian ocean is going to come from space ice, I had no idea that oceans would eventually lead to tectonic activity. What sort of timeframe would we be talking about? I was erring on the far side of a thousand years, but sounds as though itm ight take a whole lot longer than that.

[Darth Raptor]

Centuries at least, a thousand years is probably a good estimate.

Also, it wouldn't start up tectonic activity on Mars because Mars is dead inside (there's no radioactive decay in the core any more).

[Count Chocula]

Raptor nailed it in one. Fling asteroids at Venus, make sure they impact tangentially and in the direction of Venus' current orbit. Reinforce its current slow retrograde orbit. Over time (decades? centuries? dunno) and with enought impacts, kinetic energy transfer will generate rotation, hence a magnetic field and all that lovely moving mass. The sun will rise in the West and set in the East. That is, if your comet impacts haven't knocked Venus off its orbit.

The dirty snowball asteroids, while having less mass than carbonaceous or nickel-iron asteroids, would introduce some much-needed H2O. At this point, we're still trying to terraform an as-yet unpopulated planet. Any upheavals we would cause to a hunk of useless rock to make it something useful to us would be irrelevant.

[Darth Raptor]

I contend that building orbital mirrors to induce artificial day is preferable to playing Spin the Planet.

[Ford Prefect]

Centuries at least, a thousand years is probably a good estimate.

Well, that's good. Admittedly, I'm fairly willing to handwave a lot of stuff, but I still want it to feel reasonable, if not actually plausible. If I was being plausible I would just ignore terraformation entirely in favour of more space habitats, but sometimes you just want another planet which isn't Earth.

Also, it wouldn't start up tectonic activity on Mars because Mars is dead inside (there's no radioactive decay in the core any more).

So long as it doesn't start melting rihgt beneath my feet, I'm fine with that.

Spinning the planet is almost certainly out. In my rough idea in my head, it just seems like too much trouble when polar mirror arrays can manage the same thing. I mean, costs have got to be cut somewhere.

[Count Chocula]

Orbital mirrors to Sunside of Venus would reduce the insolation caused by Venus' dense atmosphere and closer proximity to the Sun, but wouldn't to anything to introduce a Van Allen belt. If I remember my college astronomy, it's the magnetic lines induced by the Earth's rotation that create the Van Allen belt, which prevents most harmful solar radiation (it's a continuous nuclear fusion explosion, after all) from pelting the Earth. Without that protection, a Venus at 1g, 29.92mb atmosphere pressure, and a perfect 59 degrees F temperature would still be uninhabitable.

[Ford Prefect]

Magnetic fields are one of those issues I've been side-stepping for some time, only to have two seperate people bring it up within ten minutes of each other. However, a going theory in regards to Venus' magnetic field is that it lacks the convection needed, which plate tectonics would provide. Thisi s not a subject I can pontificate on, as it is well out of my own expertise.

[Gil Hamilton]

Imagine Death Valley temperatures and below sea level pressures, with no humidity and no wind, with the only benefit being a slightly lighter gravity.

In other words, Tatooine with one sun in the sky - a truly suckful place to be. And not a speeder in sight.

And to see just what an enormous task it would be, take a look at http://www.nineplanets.org.

Hah hah hah. No. Venus makes Death Valley look like Great Lakes island on a sunny spring day. As far as I know, the atmosphere in Death Valley isn't carbon dioxide at 92atm with sulfuric acid rains, with extensive calderas and other volcanic activities.

It's not just an enormous task to terraform it. Mars is an enormous task. Venus just isn't worth it.

[Ford Prefect]

Hah hah hah. No. Venus makes Death Valley look like Great Lakes island on a sunny spring day. As far as I know, the atmosphere in Death Valley isn't carbon dioxide at 92atm with sulfuric acid rains, with extensive calderas and other volcanic activities.

Strictly speaking, the acid rains aren't a problem because they evaporate well before they hit the peak of Maxwell montes.

It's not just an enormous task to terraform it. Mars is an enormous task. Venus just isn't worth it.

Obviously in real life it's a fool errand, but far more unlikely things happen in science fiction all the time, and I would rather learn what a habitable Venus could be like as opposed just hearing 'the effort required is monumentally titanic'. I know that it's so difficult to be next to impossible, but let's assume for a moment that God Himself is your ecological engineer and he's got a great deal on twelve squillion tons of cometary ice.

[Count Chocula]

My bad, my Tatooine premise was based on cooling Venus enough and throwing enough icy meteorites at it to provide at least a marginal oxy/nitrogen atmosphere at no more than 2 bars. Got a little ahead of the curve there...

[Lord of the Abyss]

I mean, say you put a ginormous sunshade at at the Venus/Sun lagrange point and you somehow got rid of all that CO2

One idea for doing this that I read in a sci-fi short; block off ALL the sunlight from Venus until the atmosphere freezes, then toss the excess frozen atmosphere elsewhere with mass drivers. Using solar power from the sunshade, perhaps.

I contend that building orbital mirrors to induce artificial day is preferable to playing Spin the Planet.

Especially since you will need to leave some mirrors in place to keep Venus from overheating and de-terraforming, anyway.

[starslayer]

As has been said, in real life, terraforming Venus is a fool's errand, but if you seriously want to do it, here's how I would:

First and foremost, we have to reduce the atmosphere somehow. More than anything, reducing the pressure to about one-ninetieth the current pressure will be essential if we want people running around unprotected. And someone turn down the Sun, please. In order to do this, we must either cart off vast sections of the Venusian atmosphere, or introduce viable oceans to dissolve the carbon (there may be another way, but I don't know it). Either one of these methods is re-goddamn-tardedly hard. Speeding the retrograde rotation heavily and thus reducing the day length will help, as this will lower the temperature somewhat by reducing the time for the dayside to heat, and allowing it cool much sooner. As Venus stands now, the temperature shows little variation between day and night. Oh, and we have to get rid of that damned sulfur.

Once the atmosphere is down to an acceptable level, and the oceans are in place, and the entire thing has reached a much colder equilibirium, detailed atmospheric chemistry must be considered. Photosynthetic organisms first, to produce lots of nice oxygen, and then artificial removal of carbon dioxide. Because Venus is closer to the Sun, we must have less CO2 in the air to keep the warming down. Genetically engineered organisms will be key here, because they may need to survive below plants' current 150 ppm threshold. Water, of all things, will be a problem too. Water vapor is a strong greenhouse gas, and oceans will generate a lot of it. Luckily, Venus' very tall mountains may provide more condensation than on Earth; I'm not sure though, and I doubt the effect would be significant enough for our purposes. And if God is on our side, we can magic away the excess, or put it back into the oceans artificially (something that should be well within the terraformers' capabilities anyways).

Next, we must induce plate tectonics, and find some way to keep it going, rather than have Venus form a one-plate surface again. The first reason we need this is to create make Venus a significant magnetic dipole; this will siphon away most dangerous solar wind particles, and prevent the destruction of the ozone layer (this will form automatically due to the presence of oxygen in the upper atmosphere; the solar wind, however, has a nasty habit of stripping it away faster than it can be formed). The next, however, is more esoteric; we need plate tectonics to regulate the atmosphere, and keep CO2 levels high enough. In fact, without plate tectonics, the Earth's CO2 would disappear into the oceans in a few million years, IIRC.

Once you've done all that, and have a functioning biosphere, Venus is ready for human habitation. And then you have to move the damned thing farther out, because the Sun's too hot. Fucking Sun brightening over its life cycle...

Orbital mirrors to Sunside of Venus would reduce the insolation caused by Venus' dense atmosphere and closer proximity to the Sun, but wouldn't to anything to introduce a Van Allen belt. If I remember my college astronomy, it's the magnetic lines induced by the Earth's rotation that create the Van Allen belt, which prevents most harmful solar radiation (it's a continuous nuclear fusion explosion, after all) from pelting the Earth. Without that protection, a Venus at 1g, 29.92mb atmosphere pressure, and a perfect 59 degrees F temperature would still be uninhabitable.

Not quite. The Van Allen Belts themselves are not responsible for our protection; what is is our planet's wonderful magnetic field. When solar wind particles hit it, they are strongly affected by it, being charged and moving at quite a clip (F=qvBsinθ), and tend to be funneled towards the poles. Some, however, get stuck in a "magnetic bottle" around the field's equator (not the Earth's), and these form the Van Allen Belts, as I understand it (Wyrm'll be along any second now...). High-energy photons get stopped by the atmosphere, not the magnetic field. We've our 12-foot thick sheet of aluminum equivalent to thank for us not being fried by UV, X, and γ rays from the Sun and elsewhere.

The good news is that the additions of oceans should stimulate the development of plates.

How so? The introduction of large amounts of water shouldn't do much to start the mantle convection currents necessary for plate tectonics, unless my rudimentary geophysical intuition is far off base.

The whole problem of starting plate tectonics is starting the mantle convection; generating core convection is probably required for this, and coincidentally is required to produce the strong magnetic field we want. I don't see any way to do either, unless oceans really are that significant to a planet's internal processes.

Especially since you will need to leave some mirrors in place to keep Venus from overheating and de-terraforming, anyway.

No, you don't. Keep a close enough eye on atmospheric chemistry, or simply play solar system engineer (you'll have to do this to keep Earth in the game, anyways), and Venus shouldn't suffer a runaway greenhouse effect like it once did.

Anyways, wrt the OP, life wouldn't be all that different on a sufficiently terraformed Venus. Assuming a 24-hour day/night cycle, and we haven't played Spin the Planet very much, the trade winds and jet stream would likely be extremely weak, and cyclonic storms probably wouldn't be able to form very well (tornadoes being an exception). If we have spun up Venus, and thus don't need the mirrors, it would be much like Earth, except the Sun would rise in the West and set in the East.

[Ariphaos]

In Solar Storms I throw a dwarf planet the size of Mars at it.

A thousand years and a lot of effort later, you have the beginnings of a livable world.

The resulting moon is of course named Neith.

[Ford Prefect]

Anyways, wrt the OP, life wouldn't be all that different on a sufficiently terraformed Venus. Assuming a 24-hour day/night cycle, and we haven't played Spin the Planet very much, the trade winds and jet stream would likely be extremely weak, and cyclonic storms probably wouldn't be able to form very well (tornadoes being an exception). If we have spun up Venus, and thus don't need the mirrors, it would be much like Earth, except the Sun would rise in the West and set in the East.

Thank you for your entire post. It is quite informative, and answers my questions to the limit that I would expect. Honestly, the technical stuff isn't totally important to me, but having a general understanding of how it would be done is probably worthwhile. I'm actually more concerned with what the oceans and landmasses would probably look like. I have this map which is quite convieniently coloured in blue and green.

In Solar Storms I throw a dwarf planet the size of Mars at it.

I do not have that luxury this time round.

[Darth Raptor]

Two continents, Ishtar Terra in the northern hemisphere and Aphrodite Terra just south of the equator. Approximately the size of Austrailia and South America, respectively.

How so? The introduction of large amounts of water shouldn't do much to start the mantle convection currents necessary for plate tectonics, unless my rudimentary geophysical intuition is far off base.

The whole problem of starting plate tectonics is starting the mantle convection; generating core convection is probably required for this, and coincidentally is required to produce the strong magnetic field we want. I don't see any way to do either, unless oceans really are that significant to a planet's internal processes.

As I understand it, Venus already has convection currents, but its crust is too viscous. Too much of the mostly-solid lithosphere and not enough (if any) of the ductile aesthenosphere we have on Earth. IOW, oceans would foster the development of shear zones to break up the crust into plates, and form a low-viscosity aesthenosphere for those plates to "float" on. This would be an extremely long-term process, but the resurfacing events aren't exactly frequent, so you'd have plenty of time.

[Ford Prefect]

Two continents, Ishtar Terra in the northern hemisphere and Aphrodite Terra just south of the equator. Approximately the size of Austrailia and South America, respectively.

There's actually more land than just the two 'continents', as I understand it; there are other areas of which are of sufficient elevation to act as landmasses.

[Sikon]

Although optionally able to be created artificially, such as with giant superconductor loops, a magnetic field isn't too much of an issue.

On earth, ten tons per square meter of atmosphere serving as radiation shielding is what primarily stops space radiation, which is like having about a meter thick lead plate over one's head or better. The importance of earth's magnetic field is often vastly overrated. It reverses every fraction of a million years anyway, in the process temporarily declining towards zero strength shielding an area, and everything survives fine, not that such has more than on the order of a few percent effect on overall ground-level radiation exposure after the effect of the atmosphere. A good discussion is here.

A reflector diverting a lot of sunlight away from Venus might be some fraction as much as the ~ 0.2 billion ton mass of a micron-thick reflector of as much area as the 1.15E8 km^2 cone of sunlight intercepting Venus. (Up to several hundred thousand terawatts of sunlight gets redirected; for perspective, earth electricity usage is 2 terawatts today). In contrast, trying to adjust the planet's rotation would mean accelerating its 4.9 trillion billion ton mass, such as up to 400 m/s at the outer surface for a 24-hour day.

The former figure for reflector mass is literally *trillions* of times less than the astronomical mass of the planet having to be accelerated if trying to change the planet's rotation. As a result, having a network of mirrors create a day/night cycle is far more logical and practical than trying to get the planet rotating like earth.

Even after the initial cooling, usage of reflectors can be needed constantly since Venus receives 190% as much sunlight per square meter as earth due to its closer orbit.

A problem is the extra atmosphere mass. Long ago, Venus was too short on water and lost out on oceans. Venus didn't have sufficient water dissolving CO2 and the conversion of it plus calcium oxides into carbonate rock. The result is a planet with almost no water but a 92-atm massive atmosphere such as to be the mass equivalent of a thousand meters of water covering the planet. That's a lot of mass to get rid off, 480 million billion tons.

It's one thing to build thin reflectors massing a fraction of a billion tons to cool the planet, but it is quite another to deal with handling so many millions of times as much for the atmospheric mass. Trying to ship 500000 trillion tons of atmosphere offplanet would be astronomically resource intensive, as would be most means of processing, storing, or converting it if kept on the planet. (It wouldn't be only a matter of adding oceans either, since 1000 tons per square meter of CO2 is not something that can be absorbed or dealt with quickly, to say the least).

Observations from looking at a CO2 phase diagram:

If the planet was cooled to a little below the freezing point of water, atmospheric pressure would drop to such as 20 or 30 atm, while most of the former atmosphere pooled into CO2 liquid under those conditions, forming seas with a typical depth of a few hundred meters or more. In principle, domed cities could be built on high ground then, with strong shells keeping out most of the remaining atmospheric pressure while people breathed a primarily helium-oxygen mixture like deep-sea divers inside at perhaps some intermediate pressure, heated to room temperature for the people and vegetation inside.

Or drop the atmospheric pressure to around 1 atm by shading the planet enough to lower temperature to -80 degrees Celsius, almost as cold as Antarctica as its very coldest, letting most of the planet get covered in a kilometer-thick sheet of dry ice, building settlements on mountains.

The easiest way to live on Venus if desired would be to have floating cities in its atmosphere suspended from or made into giant balloons since at a suitable altitude the pressure becomes habitable. (That could even be optionally done without the solar reflectors since the temperature drops to moderate levels at high altitude even now, although the reflectors are the relatively easy part here). There's not a clear purpose for such, but it skips handling 500000 trillion tons.

Terraforming is impractical compared to just making asteroids into 100+ times Venus's surface area in space habitats of meters or lesser wall thickness, for less mass handling requirements then dealing with the atmospheric mass equivalence of a 1000-meter deep ocean over Venus's surface.

However, if Venus was terraformed regardless for some reason, that implies such massive capabilities as to do almost anything desired to the planet's surface.

How different would weather be, for example?

It would be more or less whatever you want, for weather control would surely be a technological ability acquired long before since such requires a number of orders of magnitude less capabilities than getting rid of the extra atmosphere did. For example, create or destroy storms with redirected beams of concentrated sunlight heating the surface and air.

What effect would a slow rotation and lack of tectonic activity have on the livable Venusian environment?

A day / night cycle could be created with adjusting orbital mirrors if desired.

Historically, a standard hypothesis has been that Venus had resurfacing events of widespread lava over most of its area a fraction of a billion years ago. However, actually, further recent research suggests otherwise, that much of Venus's surface has survived intact for more than the past billion years, with a gradual decline in volcanic activity over the past 2 billion years, like a discussion here.

[Dooey Jo]

If you use mirrors to fake a 24-hour day, be prepared for radically different weather, due to the lack of Coriolis and centrifugal forces. For example, the fancy spiralling winds around low pressure areas, that we have here, will pretty much not exist at all (that means no cyclones), and you probably won't see much in the way of jet streams or ocean currents either.

[starslayer]

As I understand it, Venus already has convection currents, but its crust is too viscous. Too much of the mostly-solid lithosphere and not enough (if any) of the ductile aesthenosphere we have on Earth. IOW, oceans would foster the development of shear zones to break up the crust into plates, and form a low-viscosity aesthenosphere for those plates to "float" on. This would be an extremely long-term process, but the resurfacing events aren't exactly frequent, so you'd have plenty of time.

But how would the oceans do that? Again, they're basically enormous masses of water and heat reservoirs, not tectonically active regions (yes, I know about the mid-ocean ridge). Pangea did not require Panthlassa to split, neither does the West African Rift Valley. If Venus has convection, but not enough asthenosphere, and Sikon is also right that Venusian volcanism has been decreasing for the past 2 billion years, then the problem is likely not enough internal heat, and inserting more radioactive elements to provide the long-term source necessary would be almost impossible.

On earth, ten tons per square meter of atmosphere serving as radiation shielding is what primarily stops space radiation, which is like having about a meter thick lead plate over one's head or better. The importance of earth's magnetic field is often vastly overrated. It reverses every fraction of a million years anyway, in the process temporarily declining towards zero strength shielding an area, and everything survives fine, not that such has more than on the order of a few percent effect on overall ground-level radiation exposure after the effect of the atmosphere. A good discussion is here.

The problem with no magnetic field is not that the surface will be bombarded with deadly radiation/particles, it's that the atmosphere will be stripped away over time, most especially the ozone layer. This is in fact how Mars probably lost most of its atmosphere. Obviously, this process is a very long one, but if we're to the point of terraforming Venus, and looking at the time scales required, it could be significant.

And Sikon, not saying your volcanism article is wrong, but do you have a better source than New Scientist?

[Sikon]

Obviously, this process is a very long one, but if we're to the point of terraforming Venus, and looking at the time scales required, it could be significant.

Although other parts of terraforming like getting rid of the bulk of the extra atmospheric mass are hard to do at all, the cooling the atmosphere part could occur in a timeframe of centuries if sunlight was mostly prevented from reaching it during that time, though even that is pretty long for a human project. You're apparently worrying more about timeframes of millions to billions of years.

And Sikon, not saying your volcanism article is wrong, but do you have a better source than New Scientist?

One illustration is this.