Venus or Mars for terraforming and colonisation?

[Tvtyrant]

Some major cities (London, New York, Chicago, Venice, Rome, Rio etc.) are due to go under, that's got to be billions or maybe even trillions of pounds or dollars of property flooded (skyscraper offices rather than housing, though the housing will flood too). I think people will start looking at spending millions before that happens.



Vetinari was right when he implied that everyone having tons of gold wouldn't mean everyone would be rich. It's pretty, and its resistance to corrosion is useful, but the main cause of its value is its rarity, the more you bring to Earth, the lower its value will fall, the same applies to anything which is mainly valued for rarity.

There are lots of things you could bring that would be worth it though. Lithium and uranium are both used up by processing and relatively rare; bringing a few tons of lithium to Earth would literally cause a revolution in technology as batteries went from $20K to $2K.

[Nifft]

Some major cities (London, New York, Chicago, Venice, Rome, Rio etc.) are due to go under, that's got to be billions or maybe even trillions of pounds or dollars of property flooded (skyscraper offices rather than housing, though the housing will flood too). I think people will start looking at spending millions before that happens.

Property values are dropping already thanks to COVID-19.

Might be significantly easier than we'd thought to evacuate the immediate coasts in a timely manner.

[InvisibleBison]

bringing a few tons of lithium to Earth would literally cause a revolution in technology as batteries went from $20K to $2K.

Even with the most generous definition of few, it would take more than a few tons of lithium to produce this effect: in 2020, the global lithium production was 58,800 tons.

[halfeye]

Property values are dropping already thanks to COVID-19.

They'll go up again if it ends though, and how much anyway? it would have to be 1% of the pre-covid value before moving out and rebuilding made sense.

Might be significantly easier than we'd thought to evacuate the immediate coasts in a timely manner.

It's not just the coasts, it's anywhere below the new sea level that the water can get to. Some coasts are cliffs, they'll be safe if they're higher than high tide.

[Tvtyrant]

Even with the most generous definition of few, it would take more than a few tons of lithium to produce this effect: in 2020, the global lithium production was 58,800 tons.

Fair enough. It's still the most likely space-mining material. 58,000 tons is a tiny amount, less then the daily amount of iron produced for instance. The demand is also rising faster then the supply; if space can increase production by more then a marginal amount space colonization will be worth it (and also possibly be instrumental in fighting climate change.)

[halfeye]

Fair enough. It's still the most likely space-mining material. 58,000 tons is a tiny amount, less then the daily amount of iron produced for instance. The demand is also rising faster then the supply; if space can increase production by more then a marginal amount space colonization will be worth it (and also possibly be instrumental in fighting climate change.)

It's a tiny amount on Earth. The amount of ore you would need to process to get hold of that will be bigger. According to Wikipedia, it occurs in ores in which 10% Lithium is high. It seems that between sea water and ores there's plenty on Earh, it's just difficult to get it out of the mixtures.

[Yora]

I believe that concentrations in asteroids are assumed to be considerably higher. Metals on Earth generally had billions of years to oxidize, get crushed to powder, and be mixed up with other sediments before being spread over large areas by errosion.
Not really sure about how asteroids form, but there are many cases of meteorites that are really just giant lumps of iron and nickel. Before the iron age and the techniques to extract elemental iron from iron oxides, iron objects in Europe were made from meteorites that landed in oxygen poor swamps where they were safe from rusting into powder.
I think asteroid ores would generally be of considerably higher purity than those in the Earth's crust.

[LibraryOgre]

This conversation has me playing TerraGenesis again. Gonna beat Mars, then try to beat Venus, both as the Gaians.

Beat both. Now, I'm trying to terraform Mercury.

[Fat Rooster]

Vetinari was right when he implied that everyone having tons of gold wouldn't mean everyone would be rich. It's pretty, and its resistance to corrosion is useful, but the main cause of its value is its rarity, the more you bring to Earth, the lower its value will fall, the same applies to anything which is mainly valued for rarity.

Gold should not be more abundant on Mars than Earth (largely unproven assumption, but I can argue why I believe it if required) and Mars is much smaller than Earth. There is no reason to believe that Mars has enough gold reserves to crash the price. Assuming we can recover a couple of hundred tons that would mean returns in the billions range. That may be enough for a viable colony if the Starship works out as hoped. That wouldn't need any 'hopes of humanity' type blue sky thinking; it would just work as far as investors are concerned. That's what we need for a colony to be really viable. It is much harder to charge people for their impact on Earth when there is no alternative (which may make going to Mars the lesser of two negative options), but if a colony can be built based on things people will pay for, it works.

The other platinum group metals fall into this thinking too, and are arguably more useful.

There are lots of things you could bring that would be worth it though. Lithium and uranium are both used up by processing and not relatively rare; bringing a few tons of lithium to Earth would literally cause a revolution in technology as batteries went from $20K to $2K.

Both lithium and uranium are processing bound, rather than deposit bound. Good lithium deposits do exist, but even without them the price is capped by the price to recover it from sea water. Uranium is also not particularly expensive, relative to it's processing. Even if we used up all the uranium on earth, thorium is a viable substitute, and far more abundant. We would invest in thorium tech before bringing in more raw uranium from elsewhere.

I believe that concentrations in asteroids are assumed to be considerably higher. Metals on Earth generally had billions of years to oxidize, get crushed to powder, and be mixed up with other sediments before being spread over large areas by errosion.
Not really sure about how asteroids form, but there are many cases of meteorites that are really just giant lumps of iron and nickel. Before the iron age and the techniques to extract elemental iron from iron oxides, iron objects in Europe were made from meteorites that landed in oxygen poor swamps where they were safe from rusting into powder.
I think asteroid ores would generally be of considerably higher purity than those in the Earth's crust.

Initially, asteroids form from stuff coalescing. They would largely reflect the abundances cosmically, with a bias based on volatility depending on formation region. Then they form into planetoids, which are molten, and differentiate. Then those planetoids hit each other hard enough to break, or at least pass close enough to break up. M type asteroids are believed to be the remains of the core of planetoids.
Basically, we do not assume that asteroids formed in different compositions than planets. For late asteroids the difference is that the interior minerals may be present, or other concentrating mechanisms may have occurred in it's history. Lithium is not expected to concentrate anywhere other than salt flats.
Either way, are we expecting 1kg of asteroid lithium to be easier to access than 2,000 tons of sea water? Even if we find native lithium (highly unlikely, given it would react before anything else), we might be best ignoring it!

Ironically, we mostly consider oxidation state of elements with regard to how it affects volatility. Hydrogen is only accessible because it is usually oxidised to water. Even carbon is limited by it's volatility with oxygen (after hydrogen fails to make it volatile). Changing oxidation state is just a question of energy, and that is usually not your limiting resource, given how much energy it costs to transport materials between planets. Rusted to powder in a good place is far better than a pile of ingots in a bad one. It just takes that much energy to move stuff between planets.


I would love to say that it was worthwhile going looking for a whole host of different resources, but it actually isn't. Gold and the platinum group metals are the only ones that make economic sense with the current setup (and I'm glad they at least do). Unless we really put our money where our mouth is with regard to saving earth and pay to move people off it (they will not be willing; bankrupt people generally aren't), we will destroy it until it is worth moving. I do not like that outcome.

[halfeye]

Gold should not be more abundant on Mars than Earth (largely unproven assumption, but I can argue why I believe it if required) and Mars is much smaller than Earth. There is no reason to believe that Mars has enough gold reserves to crash the price.

I'm told that 99.9% of Earth's gold is in its molten core, the core of Mars is frozen, so maybe it could be mined.

The other platinum group metals fall into this thinking too, and are arguably more useful.

They would have to be found, there was a gold rush in California, because this stuff isn't spread thinly everywhere.

Rusted to powder in a good place is far better than a pile of ingots in a bad one. It just takes that much energy to move stuff between planets.

This is exactly what I'm saying about gold.

Unless we really put our money where our mouth is with regard to saving earth and pay to move people off it (they will not be willing; bankrupt people generally aren't), we will destroy it until it is worth moving. I do not like that outcome.

Moving people off Earth is generally speaking not going to happen. I think that there will be more people off Earth than on it in 10,000 years, possibly as little as 1,000 years, but the number of people who will have left Earth for space in that time will be millions at most, probably only single digit thousands (supposing we don't discover free anti-gravity, which we almost certainly won't). There are much cheaper but much worse ways to get rid of excess people.

[factotum]

I'm told that 99.9% of Earth's gold is in its molten core, the core of Mars is frozen, so maybe it could be mined.

Even if that's true (I have no idea if it is or not), digging a hole more than 3000km deep is a ridiculously major undertaking even with no geological issues to worry about. For comparison, the deepest hole we've ever dug here on Earth is a mere 12km deep or so. Not to mention, to dig this pit on Mars we have to build a bunch of construction equipment that can't rely on combustion engines, ship them forty million kilometres, land them softly enough on the planet to not break them and only then can you start work.

Gold is valuable, no question about that, but it's nowhere near valuable enough to make an operation like that financially viable. Especially since, once you've found your mother lode of gold in the Martian core, the price of gold suddenly nosedives because the availability of it has gone *way* up.

[Nifft]

Even if that's true (I have no idea if it is or not), digging a hole more than 3000km deep is a ridiculously major undertaking even with no geological issues to worry about. For comparison, the deepest hole we've ever dug here on Earth is a mere 12km deep or so. Not to mention, to dig this pit on Mars we have to build a bunch of construction equipment that can't rely on combustion engines, ship them forty million kilometres, land them softly enough on the planet to not break them and only then can you start work.

Gold is valuable, no question about that, but it's nowhere near valuable enough to make an operation like that financially viable. Especially since, once you've found your mother lode of gold in the Martian core, the price of gold suddenly nosedives because the availability of it has gone *way* up.

What you do is you land something on Mars at sufficient velocity to disperse the huge gravity-sink into smaller, more easily managed chunks.

Then you could even get aspirational space-habitat dwellers like myself to "colonize" the place.

[Yora]

When the Earth was completely molten, all the heavier elements would have sunken to the bottom and all the lighter elements to the top. Which is why the rock on the surface is mostly silicon oxide and aluminium oxide. The core is only "mostly iron" because iron is extremely abundant in the universe. The center of the iron core should have a smaller core of heavy metals.
All the metal we have on the surface now are from asteroid impacts after the crust had solidified, preventing them from sinking down.

The same should be true for all planets, but even when they are tectonically inactive, the pressures at the core would be tremendous. Even if you could bore a drill that far down, it would be impossible to keep the hole from getting squeezed shut immediately. Elements in the cores of planets are inaccessible in any plausible way.

[Fat Rooster]

I'm told that 99.9% of Earth's gold is in its molten core, the core of Mars is frozen, so maybe it could be mined.

That would... Wait... (Frantically googles martian core temperature)... 1500K. That would be extremely difficult, but might just be possible.

Even if that's true (I have no idea if it is or not), digging a hole more than 3000km deep is a ridiculously major undertaking even with no geological issues to worry about. For comparison, the deepest hole we've ever dug here on Earth is a mere 12km deep or so. Not to mention, to dig this pit on Mars we have to build a bunch of construction equipment that can't rely on combustion engines, ship them forty million kilometres, land them softly enough on the planet to not break them and only then can you start work.

Gold is valuable, no question about that, but it's nowhere near valuable enough to make an operation like that financially viable. Especially since, once you've found your mother lode of gold in the Martian core, the price of gold suddenly nosedives because the availability of it has gone *way* up.

The difficulty with deep drilling is temperature. With a well designed drilling fluid you don't have pressure differential problems, but it is still pretty hot. We are not going to be mining the core any time soon, but it is surprisingly feasible without breaking physics (though closer to oil drilling than normal mining). That is a completely different question than whether we can make a Martian colony viable in the near term though.

As for a colony being financially viable, you can run the numbers. An extra 100 tons of gold would not crash the price, and even if it drops a bit you would still be talking ~$5billion. The question is whether you can set up a colony that can recover that much gold for $5billion. Don't get me wrong, that is 2 orders of magnitude better value than current space projects expect, but the starship may be able to deliver that level of performance. To crash the price you would need to be bringing back comparable amounts to what we have recovered from Earth, and there is simply not that much easily accessable gold on Mars. Mars will have had to have found something else to do in the mean time, but given it has everything required to be self sustaining, trade is only required for 'beer money'. We just need to justify the setting up of a self sustaining colony. It does not need to be reliant on gold money for ever, unlike asteroid mining.

The phrase 'motherload' is from gold prospecting because large deposits near the surface that are extremely easy to recover do exist. A gold recovery effort can literally consist of a guy with a shovel and a pan, and even on Mars you would not need vastly more complicated equipment. That is an ideal industry for a fledgling colony (and why it drove migrations historically). Gold is not currently valuable enough to justify it, but beats out the alternatives by a mile and is not nearly as far off being economic as you seem to think.

Edit: Oh, right. You were talking about core mining with regards to gold justifying it. Got to agree, I don't see why we would ever need that much gold. If you are even considering it though you are probably more interested in the catalytic elements though, and will already have the infrastructure set up to deal with them. Gold is only really relevant as the fastest return on investment from colonisation requiring very little infrastructure (and hence a small colony) to make work.

When the Earth was completely molten, all the heavier elements would have sunken to the bottom and all the lighter elements to the top. Which is why the rock on the surface is mostly silicon oxide and aluminium oxide. The core is only "mostly iron" because iron is extremely abundant in the universe. The center of the iron core should have a smaller core of heavy metals.
All the metal we have on the surface now are from asteroid impacts after the crust had solidified, preventing them from sinking down.

The same should be true for all planets, but even when they are tectonically inactive, the pressures at the core would be tremendous. Even if you could bore a drill that far down, it would be impossible to keep the hole from getting squeezed shut immediately. Elements in the cores of planets are inaccessible in any plausible way.

Not quite. There is quite a lot of chemistry that means elements do not differentiate like that. See the Goldschmidt classification. There is no lump of gold at the middle of the iron, it is spread fairly evenly throughout it. Nearer the surface there are many interesting mechanisms that separate different elements, but I am unaware of any suggestion that there are such processes going on in the core. If there had been we should be some highly enriched meteorites that we just don't see.


Frankly if we are going to be doing any core drilling, Mercury would be much more tempting. The core is closer (half to one third the distance) and cooler, and the gravity is slightly weaker. Surviving there might be more challenging, as you would be reliant on imported carbon and nitrogen, but the energy availability might help with viability.

[factotum]

Frankly if we are going to be doing any core drilling, Mercury would be much more tempting. The core is closer (half to one third the distance) and cooler, and the gravity is slightly weaker. Surviving there might be more challenging, as you would be reliant on imported carbon and nitrogen, but the energy availability might help with viability.

Wouldn't we be better off just finding an asteroid that used to be from somewhere in the deep levels of a planet and mining that instead? Far easier than any sort of planetary core extraction.

[Fat Rooster]

Wouldn't we be better off just finding an asteroid that used to be from somewhere in the deep levels of a planet and mining that instead? Far easier than any sort of planetary core extraction.

Oh yeah. I was sort of taking it as a given that we have exhausted all the even remotely easily accessible supplies in the solar system before moving on to breaking up the planets*. You don't start core harvesting if you just need a little of something. This is type ~1.3 civilisation type stuff. Much higher and we would just be stripping off the entire mantle before using all the core (far simpler than working underneath a collapsing mantle. Much lower and there is no point. I was just amazed that the physics of it works at all (the Martian core is cool enough that a drill could be created without resorting to unobtanium, though it is obviously extremely difficult)!

Interestingly, you run into a similar 'why colonise?' problem again around that time. What will push us to leave our nice cushty solar system while we can still dismantle Mercury? Will the paltry resources that sit on the surfaces on planets and asteroids be able to justify colonisation while the Mercury core drill can recover the same stuff (no way you can send a 'full' rig to a fledgling colony, and it would take too long to bring returns anyway)?

* Removing any significant portion of the core while it is still inside is probably going to cause issues. You would have to go quite far before things go full Krypton, and the risk is that the Mantle gets destabilised and suddenly turns over, flooding the crust with fresh lava, rather than exploding, but it might get messy if you are doing it at scale. The energies we are talking about are relevant even when talking about the temperature of the bulk of a planet, and only having a single point at the surface for cooling limits things. Far easier to strip mine if you want that much material, and only harvest the core when you get there. That gives you the whole planet surface area for cooling, avoiding energy concentration.


Edit: Oh, and I just thought of a reason a type 1.3 civilisation might want quite so much gold: It has great x-ray properties, which might make it an important dopant in drive propellant and fuel. Let's say you have a 100 million degree plasma core, and you need to transfer that energy into your reaction mass in a way that gets it's temperature up to the million degrees range. You could do that by harvesting the energy and then putting it in with other equipment, but any inefficiencies would mean you would need to get rid of a vast amount of waste heat, and you are not putting enough propellant through to dump it into that. You would be limited to low thrust or efficiency by cooling considerations. An alternative is to rely on direct x-ray heat transfer, and gold is great for boosting the absorption and emission. Gold would help a lot with that.

[Lord Torath]

The difficulty with deep drilling is temperature. With a well designed drilling fluid you don't have pressure differential problems, but it is still pretty hot. We are not going to be mining the core any time soon, but it is surprisingly feasible without breaking physics (though closer to oil drilling than normal mining). That is a completely different question than whether we can make a Martian colony viable in the near term though.

The problem with deep drilling on Earth is temperature. On other similarly-sized planets with frozen cores, the plasticity of the planet is the problem. You know how we can't build a space elevator from the surface because all the materials we currently have will collapse under their own weight? The extreme pressures as you approach the core of Mars will make it impossible to keep your bore hole open.

[Fat Rooster]

The problem with deep drilling on Earth is temperature. On other similarly-sized planets with frozen cores, the plasticity of the planet is the problem. You know how we can't build a space elevator from the surface because all the materials we currently have will collapse under their own weight? The extreme pressures as you approach the core of Mars will make it impossible to keep your bore hole open.

I reiterate: With a well designed drilling fluid hydrostatic pressure can be eliminated as a problem. You tailor the fluid to be similar density to the surrounding material and have pressure bulkheads with pumping stations periodically. You will need them anyway to keep flow up, but they can also correct the differences that will build up as you go deeper. At each point the pressure within the borehole can be maintained at the same level as outside, up to a tolerance that does not depend on depth, say a couple of dozen bar. That is not enough to make rock behave plastically, and can go either direction anyway.

Potentially you could put positive pressure inside the borehole to the point that you are actually using it to expand your borehole, relying on that plasticity to cause material to move out of the way, rather than be cleared out the top. If your drilling fluid is 30kg per cubic meter denser than the surrounding material, every kilometre would add 1 bar to the overpressure inside the borehole. Put a spike on the front and 'apply percussive pressure spikes' (hit it with a hammer), and the internal pressure can do most of the work. Essentially your borehole is sinking on it's own, with a little help to overcome the remaining rigidity.


What might be a problem is any remaining movement in the mantle, deflecting your borehole and breaking it over time. Mars and Mercury are pretty much done with their convection I think though, so that shouldn't be a problem there.

[Radar]

Putting the reasonability of colonizing Mars, I want to drop an article concerning the sustainability of a colony. As it turns out, bacteria could grow in Mars-like conditions if the proportion between N2 and CO2 could be changed. Since the total pressure could still be equal to the typical Mars atmosphere, this is not that big of a technical problem. The article in question.

[Fat Rooster]

Putting the reasonability of colonizing Mars, I want to drop an article concerning the sustainability of a colony. As it turns out, bacteria could grow in Mars-like conditions if the proportion between N2 and CO2 could be changed. Since the total pressure could still be equal to the typical Mars atmosphere, this is not that big of a technical problem. The article in question.

Nice, though you should note they are not talking about Martian pressures, just low pressures. We would still need a pressure vessel for this. Still a big deal, as a 1/10th atmosphere requires 1/10th of the structural strength that a full atmosphere does, but you are still 20x away from Martian pressure. Party balloon material can hold about 1 bar for reference, meaning you could inflate a dome 3m across using the same material that would give us a 30cm balloon (though obviously a 100x more of it). Being able to bring a 3m dome for the mass of a bag of party balloons would be a big deal. That is probably the pressure range you would want to use anyway, as it gives you inflatable structures that are entirely tensile without being very heavy. It might make more sense to use .3 bar, as that would allow people to operate with just breathing gear, but if it is not requiring frequent work and needs an EVA to get to anyway why let people be a consideration. Probably safer not to let people in without a suit anyway, as it would also allow us much better safety margins, and better protections. If something goes wrong you can vent the gas, rather than risk the structure getting damaged. Can't do that if there might be a person in there.

One of the early production facilities probably wants to be polythene, for building new facilities (probably polytunnels, rather than domes. Avoids needing to fabricate double curves to a large extent). They would probably need to import dopants for quite a long time, but if you are just importing additives rather than bulk material you can expand much more cheaply than bringing everything in.

Incidentally, I lol-ed at the section talking about the viability of feeding other micro-organisms the mass produced. It jumped out at me as one of those translation things where they compare what is in the paper to what actually happened:

"We then tested the viability of feeding other micro-organisms" = "Our sample then went mouldy"

With more reading it sounds like this was more deliberate than that, but made me laugh anyway.

[halfeye]

For mining I would go to the asteroids, there are enough small ones that anything we want is probably within reach without a silly gravity well to climb out of afterwards, though I still think it probably isn't worth it to bring stuff back to Earth, but it will be worth it not to have to lift stuff (particularly metals) to Earth orbit.

I still think it's going to be easier in the long run to get Venus to Earth standard than Mars. For a start the mass is nearly perfect as it is. Plants love CO2. There would need to be water, but there's hydrogen in H2SO4, and we have sulphur loving bacteria.

The current temperature is a problem, but the pressure really isn't, it's that high about 3000 ft below the surface of the sea, and we know there's all sorts of life down there, the Marianas Trench is over ten times that deep and there's life there. When the plants have eaten most of the CO2, most of that pressure will be gone and we can live there ourselves if we want, but finding plants that could live there now, if the temperature was right, won't be difficult.

The pressure of seawater at a depth of 33 feet equals one atmosphere. The absolute pressure at 33 feet depth in sea water is the sum of atmospheric and hydrostatic pressure for that depth, and is 66 fsw, or two atmospheres absolute. For every additional 33 feet of depth, another atmosphere of pressure accumulates.

https://en.wikipedia.org/wiki/Metre_sea_water

[factotum]

It's getting green plants to live in the 500C hellhole that is Venus' surface that's the real problem there, as you acknowledge. Unless we can devise some sort of algal bloom that can float in the upper atmosphere, where temperatures and pressures are more bearable--although then you have the issue that CO2 is a fairly dense gas and will tend to stay low down even as you convert the upper atmosphere, so you'd probably still have the surface level hellhole to contend with even once your magic algae had done their job.

[Yora]

To make Venus habitable, the first step is to create a giant system of pipes and pumps that siphons off 99% of the atmosphere and blows it into the sun or somewhere else where it's not going to just be pulled back to Venus.
Once air pressure at the surface is down to 1 or 2 bars, we can start thinking about regulating temperature and making the air breathable.

[Forum Explorer]

To make Venus habitable, the first step is to create a giant system of pipes and pumps that siphons off 99% of the atmosphere and blows it into the sun or somewhere else where it's not going to just be pulled back to Venus.
Once air pressure at the surface is down to 1 or 2 bars, we can start thinking about regulating temperature and making the air breathable.

I remember reading somewhere that it's possible to strip or change Venus' atmosphere by bombarding it with asteroids of sufficient size. Of course, that involves moving an asteroid the size of the moon around which has it's own problems. Like I think you need to have invented some sort of anti-matter engine to get enough energy to move objects that size.

[Nifft]

I remember reading somewhere that it's possible to strip or change Venus' atmosphere by bombarding it with asteroids of sufficient size. Of course, that involves moving an asteroid the size of the moon around which has it's own problems. Like I think you need to have invented some sort of anti-matter engine to get enough energy to move objects that size.

If the asteroid is made of rocket-fuel -- for example, water -- then you wouldn't need anti-matter to accelerate it sufficiently.

I remember reading a proposal to dump half the water of Europa on Venus, and the other half (along with all the non-water mass) onto Mars, minus whatever water would be used as fuel.

[halfeye]

To make Venus habitable, the first step is to create a giant system of pipes and pumps that siphons off 99% of the atmosphere and blows it into the sun or somewhere else where it's not going to just be pulled back to Venus.
Once air pressure at the surface is down to 1 or 2 bars, we can start thinking about regulating temperature and making the air breathable.

I strongly disagree. Most of the pressure is due to CO2. Plants convert CO2 to sugars.

In my view, the main problem is the temperature. We need to check there isn't anybody alive down there, but if there isn't, blocking all the sunlight ought to do the job inside a couple of hundred years or maybe much less.

[Radar]

To make Venus habitable, the first step is to create a giant system of pipes and pumps that siphons off 99% of the atmosphere and blows it into the sun or somewhere else where it's not going to just be pulled back to Venus.
Once air pressure at the surface is down to 1 or 2 bars, we can start thinking about regulating temperature and making the air breathable.

Those things are interconnected as lower temperature would also result in a condensation of a lot of the heavy substances. Since Venus conditions are a result of a runaway greenhouse effect, tipping the scales in the other direction could potentially have an inverse effect, but it would require action on a properly massive scale. If we can go wild, I would ponder on obscuring the Sun with a miniature Dyson swarm. It would not even have to completely cut off the light to give results. It is still more fiction than science though.

[Forum Explorer]

If the asteroid is made of rocket-fuel -- for example, water -- then you wouldn't need anti-matter to accelerate it sufficiently.

I remember reading a proposal to dump half the water of Europa on Venus, and the other half (along with all the non-water mass) onto Mars, minus whatever water would be used as fuel.

Or just frozen hydrongen. That would react with the Carbon Dioxide to create water and lower the amount of CO2 that way. So basically throwing a giant frozen moon at Venus would be a good first step. The blast would simultaneously remove some atmosphere while also providing a source of hydrogen needed to convert even more of the atmosphere into something else.

[Lord Torath]

Or just frozen hydrongen. That would react with the Carbon Dioxide to create water and lower the amount of CO2 that way. So basically throwing a giant frozen moon at Venus would be a good first step. The blast would simultaneously remove some atmosphere while also providing a source of hydrogen needed to convert even more of the atmosphere into something else.

It will also dump a truly staggering amount of kinetic energy at the planet, which will relatively rapidly be converted to heat.

[Forum Explorer]

It will also dump a truly staggering amount of kinetic energy at the planet, which will relatively rapidly be converted to heat.

I'm pretty sure that'll be small potatoes compared to the heat we have to shed in the first place.