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The polar caps do not have anywhere near 75 mBar of CO2 unless you count clathrates. (And I've seen no figures on how much CO2 is dissolved in that ice.)
Do we know how much pressure we'd get from just the pure CO2 in the ice caps? Somebody must know this, surely? We know the depth and we have pictures of the extent.
I suppose the hard limit of what we need is 63mb to avoid vacuum effects. If we can get that, we just need some way to oxygenate the blood. I suspect this could be done with a breathing mask and nanotechnology in the form of artificial red blood cells. (maybe)
So in this case, why not split water from the ice caps to release O2. ...
The reason is energy cost. If we have enough energy to do that, it would be cheaper to build perfluorocarbons and heat the planet and let plants split CO2.
Yes, but that would take a very long time (I was suggesting making perfluorocarbons as well as oxygen btw). My point is simply that the only technological advance we need to make oxygen is an advanced form of energy generation. These are in the works e.g. fusion. If we had a vast supply of electricity, it would be "easy" technology.
No one has suggested any reason why Mars would have not started off with its share of N2. However, lightning and cosmic rays create nitrogen compounds (various nitrates) which leach into the soil. (Life recirculates these compounds on Earth.) Some deserts on Earth have extremely concentrated nitrate deposits caused by thousands of years of lightning. I expect Mars will have vast nitrate deposits with a certainty approaching 100%. The question is: if we get a bacteria biosphere going, will the bacteria find these nitrates accessible enough to free a significant amount into the air? No one knows this.
That's good, I think, if it turns out to be true. We don't need nitrogen in the atmosphere. We only really need it in accessible forms in the soil for plants.
Do we know how much CO2 there actually is on Mars?
I have read 75mb or so in the poles and then an unknown amount in the regolith. But what if there's no CO2 in the regolith and this 75mb is it. In this case, we could convert it all to oxygen and it still wouldn't be a breathable atmosphere (although I believe bodily fluids wouldn't boil, so maybe with nanotech it could be).
So in this case, why not split water from the ice caps to release O2. I don't know what we'd do with the hydrogen: ideally not send it into space; it's valuable. I have read on this forum that 100mb O2 and 50mb CO2 is a breathable mixture.
In a sense if we just get enough O2 into the atmosphere for breathing, the planet is already terraformed even without warming. You'd need to wrap up warm, but you need to wrap up warm in Canada. No one wants to "terraform" Canada, do they? Admittedly Antarctica is a better analog.
However, if there is fluorine mineral on Mars, which I imagine there virtually has to be, then we can release this as the correct cocktail of fluorocarbons to warm the planet.
I suspect the lack of nitrogen will prevent much wildlife from growing (unless the soil is really full of nitrates: anyone know?), but we should still be able to get nitrates to grow crops either from geological nitrate deposits (which will probably exist: they do on Earth), or if necessary via e.g. the Haber process from the Martian atmosphere. A lack of wildlife even after "terraformation" could be desirable, in the sense that it will preserve the beauty of the "natural" Mars. So I am not worried about nitrogen either way. It's good if it's there. If not, that's still OK as we can fix what we need ourselves.
The point of this approach is that (other than postulating the presence of fluorine; how can there not be fluorine?) it does not require any particular elements to be present. Just lots and lots of energy, which a future society will have access to, either from very efficient, cheap solar power or (more likely, I think) from fusion.
Actually, I'm assuming there's enough oxygen in the ice of the polar ice caps for this? I have no figures or intuitive grasp at present. That must be correct, though?
I have several quesions regarding ideas for terraforming Venus.
1) I have read that if Venus were bombarded with metallic iron, this would remove CO2 from the atmosphere. Is this correct? If so, how much iron would be needed to leave 200mb of CO2 at the suface (for later conversion into oxygen), and what proportion of the mass of the asteroid belt (where I assume the iron would have to come from?) would that be?
2) If all the C02 in the Venusian atmosphere were converted to C and 02 and the S were removed, would there then be a habitable altitude i.e. one with circa 200 mbar of 02 and human-friendly temperatures?
If so, could we use the graphite and sulfur liberated from the atmosphere to build a mound up to that height? I'm imagining something like a simple truncated cone with a coating of soil to prevent burning. (It may be that there's a happy medium with some C02 remaining, of course, or some other complex situation. I'm hoping someone here can do the math.)
Would the platform produced - if it could reach that far - be the size of a country? I'm imagining something like a small version of Ethiopia: a temperate zone in an otherwise inhospitible desert.
It seems a shame to have a long night. If we put the peak on a polar region, could it be in daylight permanently? Or would it be better to put it (them?) on Maxwell Montes or one of the highland regions to save material?
If there were a hospitable altitude, would it rain at that altitude? Could we concentrate a large proportion of the planet's limited water supply into a crater-like lake on our artificial mountain? I'm not sure we would actually want to, as it would take up the precious real-estate, but could we?
If this is all feasible, how long would it take to convert the atmosphere of Venus if we were able to use, say 0.5% of the solar energy falling on the planet for this purpose and none of the carbon ever burnt up?
3) In fact, could we in any case just build a platform 50km up and then put an equal-pressure dome there right now without doing anything to the atmosphere? If we did this, we could get many of the advantages of a floating city without risking falling onto the surface because of a puncture. It's worth bearing in mind that the Burj Dubai (what will be the tallest building in the world when it is finished) is intended to be 0.8km tall i.e 1.6% of the height we need, and is not guyed, broad-based or made of an exotic material.
4) Would it be desirable to build a solar screen for the planet, giving a 24 hour night-day cycle? I believe this would reduce the incoming radiation to the same levels as on Earth. Basically you would have a terrible dark winter and then a summer with Earth length days. A good idea for some terraforming strategies, or not?
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