A Terraformed Venus' Future?

[Dollan]

Hi folks...

A question came up in my ArcBuilder mailing list that, I felt, some might be able to offer insight to here.

I know that Venus is a popular subject for terraformed add-ons. Runar has done a spectacular one, and Malefant's Cytherea was one of the first planetary maps that I had ever found on the 'Net, when I started looking into this stuff. In my setting, Venus will eventually become a terraformed world, and at some point in the distant future, it will be self-sustaining.

Which brought up the question: what are the implications for the geology of a wet Venus? I'm not sure if it is still popular or not, but the theory of a complete crustal turnover on Venus every 500 million years or so was not *too* derided the last time I looked. If we make the assumption that this *is* the case for Venus, would all of that water on its surface, seeping down into the crust, act as a lubricant or a catalyst to hasten the next turn-over event? Would water even have an effect on the planet's geology? Or would all that water, in a most optomistic universe, simply kick-start a more typical system of plate tectonics such as we have on Earth?

...John...

[Malenfant]

Actually the global crustal turnover idea is pretty much dead now (it only existed in the first place because the planet was incorrectly mapped and its geological history misinterpreted) - a gradual and continual regional resurfacing over time has been found to be more reasonable and realistic.

I think that water there wouldn't have much effect for at least several thousand years (if not a few million) since it has to seep down into the deep crust, react with mineral, and actually start lowering melting temperatures and so on. Adding water wouldn't suddenly change things overnight (in a literal or geological sense).

[Dollan]

Actually the global crustal turnover idea is pretty much dead now (it only existed in the first place because the planet was incorrectly mapped and its geological history misinterpreted) - a gradual and continual regional resurfacing over time has been found to be more reasonable and realistic.

So there could be active surface volcanism right now? What would this imply for a terraformed Venus? Do we have any idea of the extent of the global surfacing, and what that would mean for a stable biosphere?

I think that water there wouldn't have much effect for at least several thousand years (if not a few million) since it has to seep down into the deep crust, react with mineral, and actually start lowering melting temperatures and so on. Adding water wouldn't suddenly change things overnight (in a literal or geological sense).

That was something along my thoughts, though I simply wasn't certain about it.

Thanks!

...John...

[Don. Edwards]

Dollan,

I think the volcanic activity on Venus is pretty much as it is here on Earth. At any given time you can take a snapshot of Venus or the Earth and see no real volcanic activity. But that doesn't mean it isn't going on. You have to keep in mind that things on the geologic time scale are very different than our human times scales. If you could speed up time and watch all the volcanic activity here on Earth and on Venus I would guess that they would be very similar. Venus' situation is a bit different though. Its atmosphere acts as a thermal blanket insulating its magma allowing it to flow in its liquid state for much longer periods of time and for greater distances than on Earth. Our atmosphere on the other hand does a great job of cooling and hardening magma, so it doesn't travel as far or as fast as it can on Venus.
Of course this makes one then ask about how volcanism works on Mars. Here we see great amounts of magma that has flowed on the surface of what is even a colder planet than the Earth. But the case on Mars is that the there has been little to cover and erode the vast amounts of lava/magma on Mars. So we see almost all it. Venus continually over time covers its older lava fields. Earth does the same or erodes it away by water, wind, and ice.

I think the main issue for any idea of terraforming Venus is in the long run would it be feasible in the long term. I would have to say NO!

The main reason is that by the time we could have a stable biosphere going on Venus, we would only be able to hold on to it for a short time. The reason for this is that as the sun gets older it is getting hotter and brighter. I am not talking about the Red Giant phase. As Yellow dwarf stars age and as the amount of hydrogen decreases they start burning the helium they create along with the hydrogen. This make the star gradually burn hotter and brighter. This pushes the habitable zone further and further away from where it is now. This additional heat would just recreate another overriding greenhouse effect by evaporating any water on the surface and putting back into the atmosphere as clouds and a new thermal blanket. This is what is going to start to happen here on Earth in a several millions of years. The economic costs of terraforming a world that is simply going to revert back to a lead melting hothouse isn't worth it. By that time we will be worrying about keeping the Earth terraformed and eyeing Mars more and more.

So in the end, terraforming Venus just isn?€™t a logical move. Now if in the future we find a Venus like planet in a much cooler habitable orbit around another star, that would be a very different case.

Don. Edwards

[Malenfant]

I think the volcanic activity on Venus is pretty much as it is here on Earth. At any given time you can take a snapshot of Venus or the Earth and see no real volcanic activity. But that doesn't mean it isn't going on. You have to keep in mind that things on the geologic time scale are very different than our human times scales. If you could speed up time and watch all the volcanic activity here on Earth and on Venus I would guess that they would be very similar. Venus' situation is a bit different though. Its atmosphere acts as a thermal blanket insulating its magma allowing it to flow in its liquid state for much longer periods of time and for greater distances than on Earth. Our atmosphere on the other hand does a great job of cooling and hardening magma, so it doesn't travel as far or as fast as it can on Venus.

I'm not sure our planets are so similar actually. I know that Venus has a lot of major volcanoes like Earth but it also has uncountable small shield volcanoes that occur in vast 'shield fields' on the plains. There's circumstantial evidence for continuing eruptive activity too (IIRC one of the old venus orbiters detected a big increase of sulphur dioxide in the atmosphere at one point that was most likely from an eruption). I guess the big question really is whether or not all those small volcanoes and fissures are still active, and we don't know one way or the other yet. I suspect Venus would be more active over time than Earth though.

You're on target with the rest of your points though, no disagreement here!

[eburacum45]

In order to maintain a temperate Venus it would probably be necessary to build a sunshade; I used one in my page about terraforming Venus (the .ssc for the sunshade was written by Grant Hutchinson, as you may remember).
http://www.orionsarm.com/worlds/Venus.html

A similar sunshade has been proposed for Earth, to regulate the climate against global warming and the slow increase in the Sun's luminosity.

As far as volcanic activity goes, there will be many other problems with the surface of Venus wich might be more problematical. Chemical weathering on Venus has probably resulted in a lot of unusual minerals, many of which would probably be soluble. I think that the waters of a newly terraformed Venus would be full of dissoved salts, possibly even excess acids or alkalis. Consider the toxic runoff from mine tailings- the chemical weathering in newly exposed tailings can pollute water supplies on our world.

Every terraformed world will have similar problems, in one form or another. No-one said this would be easy...

[Don. Edwards]

Malenfant,

Yes Venus has many volcanic feature we don't have here one Earth. Or do we? Over 75% of Earths surface is covered by oceans that obscure it surface. Now we have seen what the surface looks like in radar imaging. Of course it looks a great deal different than Venus. But on Earth the water allows and supports vast volcanic mountains with extreme sloping sides that are all but impossible out of the water. So the volcanism we have on Earth is very different than what you will find on Venus. Also you mentioned Venus possibly having constant volcanic activity; we have the same thing here on the Earth. Most of Earth?€™s volcanoes are underwater so when they erupt we just never know about it unless they break the surface, cause earthquakes, or tsunamis. Again that is why I compared Earth and Venus. Many of the unusual volcanic systems viewed on Venus have parallels here on Earth. We seem to have a few Venus doesn?€™t. I am not sure whether they have found vast caldera type volcanic systems on Venus as we have here on Earth. But again, different atmospheres and pressures allow for different kinds of volcanic systems. Or possibly they aren?€™t different but merely look different because of the atmospheres of the two planets. They really are more alike than unalike. In many ways they truly are sister planets. But like most family members they look and act very different.

I am very convinced that if Venus had been in Earths place and Earth in Venus place they would have turned out the same. Meaning Venus would be just like the Earth and visa versa. The number one thing that makes them different is the fact that Earth has vast oceans and Venus doesn?€™t. Move Venus into an Earth orbit and cover it with water and I bet you ten to one it would end up with tectonic plates and surface volcanism just as the Earth. And put Earth in Venus?€™ orbit and Earth wouldn?€™t have the tectonic plates and appearance it has today. Something went very wrong on Venus in the past. It?€™s upside down making it spin retrograde and it spins too slowly.

Putting Mars back on the table; they have recently discovered through magnetic field scanning that Mars in its ancient past has signs of the very early stages of seduction zones and rifting. If Mars history would have been a bit different, if it would have had a bit more mass, had more iron in its core, and would have held onto its magnetic field longer who knows what would be orbiting in its place today.

Just a few more things to think over.

Don. Edwards

[PlutonianEmpire]

Personally, I think that by the time the sun gets too hot for venus, we might have the technology to move venus into a new, farther orbit.

Really, 7 million years is a long time for a technically advanced civilization.

[Malenfant]

Yes Venus has many volcanic feature we don't have here one Earth. Or do we? Over 75% of Earths surface is covered by oceans that obscure it surface. Now we have seen what the surface looks like in radar imaging. Of course it looks a great deal different than Venus. But on Earth the water allows and supports vast volcanic mountains with extreme sloping sides that are all but impossible out of the water. So the volcanism we have on Earth is very different than what you will find on Venus. Also you mentioned Venus possibly having constant volcanic activity; we have the same thing here on the Earth. Most of Earth?€™s volcanoes are underwater so when they erupt we just never know about it unless they break the surface, cause earthquakes, or tsunamis. Again that is why I compared Earth and Venus. Many of the unusual volcanic systems viewed on Venus have parallels here on Earth. We seem to have a few Venus doesn?€™t. I am not sure whether they have found vast caldera type volcanic systems on Venus as we have here on Earth. But again, different atmospheres and pressures allow for different kinds of volcanic systems. Or possibly they aren?€™t different but merely look different because of the atmospheres of the two planets. They really are more alike than unalike. In many ways they truly are sister planets. But like most family members they look and act very different.

I guess if you put it that way, you have a point . I didn't think of the midocean ridges...

I am very convinced that if Venus had been in Earths place and Earth in Venus place they would have turned out the same. Meaning Venus would be just like the Earth and visa versa. The number one thing that makes them different is the fact that Earth has vast oceans and Venus doesn?€™t. Move Venus into an Earth orbit and cover it with water and I bet you ten to one it would end up with tectonic plates and surface volcanism just as the Earth. And put Earth in Venus?€™ orbit and Earth wouldn?€™t have the tectonic plates and appearance it has today. Something went very wrong on Venus in the past. It?€™s upside down making it spin retrograde and it spins too slowly.

Well, I think the point remains that if you add water then Venus isn't suddenly going to sprout earthlike plate tectonics overnight. Venus does actually have tectonism - the problem is that its plates don't subduct under eachother, and you don't get MOR-like areas where new crust is created (though Artemis Chasma might be a subduction-like feature). Instead the crust is just 'broken' - you get these big plates bordered by huge rift zones that just jiggle around on the surface within tight constraints.

"Wrong" is very 'terracentric' of you . Venus is probably a more ideal candidate for a terrestrial planet than Earth is - at least you're looking at a bona fide, untainted planet with Venus. Earth however is this mishmash of whatever was here first and a mars-sized impactor. Its chemistry, density and future evolution were irrevocably changed when that body slammed into it to melt its entire surface and ultimately create the very unusual moon we have today.

I think arguably WE are on the planet that turned out "wrong". It just happens that this very "wrongness" is a large part of the reason why we're here, because if that hadn't happened we'd probably still have our thick primordial atmosphere and our planet would be absolutely nothing like what it is today.

Putting Mars back on the table; they have recently discovered through magnetic field scanning that Mars in its ancient past has signs of the very early stages of seduction zones and rifting. If Mars history would have been a bit different, if it would have had a bit more mass, had more iron in its core, and would have held onto its magnetic field longer who knows what would be orbiting in its place today.

Well yeah, and if it was many times bigger and had accreted a huge hydrogen atmosphere, it'd be a gas giant . All the planets are unique - personally I have little doubt that if you moved Venus into Earth's orbit, you'd have something that looks nothing like the Earth at all. They've all got their own different chemistries, masses, gravities, compositions, thermal histories... tweak one thing in a tiny way and you'll probably end up with something vastly different to what you expected.

[Don. Edwards]

I don't think we can assume Venus is pristine by any account. Something hit it millions if not billions of years ago and flipped it over on its axis. The impactor simply didn't hit at the right angle to create a moon, or it was too small, but large enough to the damage it did. It is looking more and more like each and every inner planet has had at least one or more very big impacts.

Also what I meant by switching Venus and Earth, still would hold true. If you could play god and change there places, given billions of years as I said I am sure Venus would have full plate tectonics as Earth does. I don?€™t think by pouring oceans water on Venus as it is now you would get instant plate tectonics. You and I know all to well it just doesn?€™t work that way. It would take millions of years to get kick started and there still is no guarantee that it would happen even then. But if done earlier in its life I think it would. I still think if you could exchange the planets before the impactor that hit Earth and made the moon you could still get a planet much the same as Earth is now moon and all. It?€™s what they are made of that would determine this in the long run. Venus and Earth are made of the same stuff basically and in the same proportions. Although there seems to be some reason Venus?€™ core isn?€™t generating a magnetic field. Maybe that ancient impactor had something to do with it. We may never know.

What I meant by "Wrong" is that something hit and turned Venus over on itself. It?€™s just like Uranus this case. Something went horribly wrong there as well. These planets didn't just form this way. They formed much like all the others did. But they are now in there present form due to interactions with other shall we say rouge bodies that moved in our early solar system. It even looks like tiny Pluto gets to join this club as well.

Yes we often think in Terran terms. How else are we to think, we are Terrans. We aren't Venusians or Martians for that matter, although there are some on the fringe that think we are.

At this point in time all we have to compare are really three terrestrial worlds in our own system. I don't count Mercury as it doesn't really show any sign of being truly geologically active as the other are and it doesn?€™t have an atmosphere at the present time.

It?€™s really too bad we can't see back in time and see all the planets that formed in the early solar system. We know there were more planets then there are now. There was an additions Mars size planet orbiting close to the Earth. How many others were there? It would be great if maybe a few of them managed to stay in the outer solar system and weren?€™t fully ejected. Maybe we can find an inner solar system time capsule out there waiting to answer many questions.

All of this is really just conjecture at this point anyway. We need to see a vast number of terrestrial planets around other stars before we can really know any of this for sure. Unfortunately we have a very long wait on our hands. I just hope that before I die we find our first truly Earth like planet. But I am not holding my breath.

Don. Edwards

[Malenfant]

I don't think we can assume Venus is pristine by any account. Something hit it millions if not billions of years ago and flipped it over on its axis. The impactor simply didn't hit at the right angle to create a moon, or it was too small, but large enough to the damage it did. It is looking more and more like each and every inner planet has had at least one or more very big impacts.

Apparently not. Believe it or not, it turns out the 'upsidedownness' is most likely caused by solar tides acting on the dense atmosphere. (don't ask how, it's pretty complicated and I only understand the general gist of it. But I've seen some papers on it though and the analysis did seem fairly convincing).

I still think if you could exchange the planets before the impactor that hit Earth and made the moon you could still get a planet much the same as Earth is now moon and all. It?€™s what they are made of that would determine this in the long run. Venus and Earth are made of the same stuff basically and in the same proportions.

I disagree. You'd have a planet with less metal in its core for starters, since most of the impactor's is down there too. And it'd have more volatiles too, since a good chunk of them wouldn't have been vapourised when the planet melted in the impact. And you'd have a less massive world too, obviously. Any one of those changes - particularly that early on - would result in a totally different environment today. The atmosphere would be massively different too. Sure, it'd still be a rocky planet about 6000 km in radius, but that's about where the similarity would end.

Although there seems to be some reason Venus?€™ core isn?€™t generating a magnetic field. Maybe that ancient impactor had something to do with it. We may never know.

Actually we do have a pretty good idea why it doesn't have one. It's largely down to the slow rotation - there's just not enough rotational energy to make a dynamo. And also, the core is most likely completely molten and stably stratified, which means there's no inner core forming to make convection currents in there.

What I meant by "Wrong" is that something hit and turned Venus over on itself.

I think the "wrong" part is the idea that something hit Venus. That simply isn't supported by the evidence, which is that the solar tides on the atmosphere are what tilted the planet (I'd throw a scientific paper reference at you, but all my papers are in boxes and I have no idea where that one is. If you're really interested I'll see if I can dig it up).

It?€™s just like Uranus this case. Something went horribly wrong there as well. These planets didn't just form this way. They formed much like all the others did. But they are now in there present form due to interactions with other shall we say rouge bodies that moved in our early solar system. It even looks like tiny Pluto gets to join this club as well.

Well, the 'standard way' that planets would form is exactly along the plane of the sun's rotational equator, with no tilt at all. But we all know that no planet is like that, so saying that's the 'right way' is misleading. The fact is that the protoplanets got whacked around by impactors large and small, tipped over by tides, realigned by moons, and whathaveyou. It's pretty meaningless to talk about "normal" in this or any other solar system, beyond talking about how things generally orbit the same way around the sun. The point is that each planet is unique - despite their common origins. You can't just pick one and say "that's what a "normal" or "right" planet is supposed to be" because that's a totally arbitrary definition.

Yes we often think in Terran terms. How else are we to think, we are Terrans. We aren't Venusians or Martians for that matter, although there are some on the fringe that think we are.

Just because we're Terrans doesn't mean we have to be limited to thinking that we're the norm. If there's anything I learned from all my years of learning geology and astronomy and planetary science, it's that our planet is most definitely NOT the norm.

The challenge is to climb outside that mental box and see each planet as a unique world, and that our world isn't really any more or less unique than the others.

At this point in time all we have to compare are really three terrestrial worlds in our own system. I don't count Mercury as it doesn't really show any sign of being truly geologically active as the other are and it doesn?€™t have an atmosphere at the present time.

But that's a completely arbitrary definition. Why should you ignore a bona fide planet just because it doesn't have a thick atmosphere (actually it has a trace atmosphere of trapped helium and sodium ions)? I'd say we have a LOT of terrestrial worlds in our system - I'd count all the inner planets, our moon, Jupiter's Galileans, Titan, Enceladus, all of Saturn's other classical moons, Uranus' five main moons, Triton, Pluto, Charon, Ceres, and a bunch of the big KBOs. They're all worlds with their own character and individuality, and all bring something unique to the table. Mercury has its contraction scarps, Venus has its atmosphere and 'jiggly' geology, Earth has its MORs and tectonism and life, Mars has its hemispherical dichotomy and huge volcanoes and rift valleys, the Moon has it's origin and maria, Io has its permanent volcanism, Europa it's cracks and oceans, Ganymede it's sulci, and so on. We've got a hell of a lot to compare and examine here, and all of those worlds - even our own - have things that continue to baffle us.

It?€™s really too bad we can't see back in time and see all the planets that formed in the early solar system. We know there were more planets then there are now. There was an additions Mars size planet orbiting close to the Earth. How many others were there? It would be great if maybe a few of them managed to stay in the outer solar system and weren?€™t fully ejected. Maybe we can find an inner solar system time capsule out there waiting to answer many questions.

Well, we're looking at the survivors of the process in the inner system. I'm sure Mars itself was probably just another mars-sized body wandering around the inner system at some point, it just happens to be the one that survived.

All of this is really just conjecture at this point anyway. We need to see a vast number of terrestrial planets around other stars before we can really know any of this for sure. Unfortunately we have a very long wait on our hands. I just hope that before I die we find our first truly Earth like planet. But I am not holding my breath.

I think we'll find another habitable planet in the next 10-20 years. It'll probably be very far away though. But I think we have a lot more terrestrial variety in our own system than you give credit for.