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The atmospheric mass of Venus is 4.8 × 10^20 kg, turns out that its 96.5% carbon-dioxide with Nitrogen making up the remaining 3.5%. On Earth the percentage of carbon dioxide is 0.04%. To make Venus' atmosphere more like Earth, we could add 9.370 x 10^23 kg of nitrogen and 2.51352 x 10^23 kg of oxygen, then we'd saturate the atmosphere with water so we get clouds, that continually rain out and evaporate. This would of course make the surface inaccessible. The required nitrogen and oxygen would probably come from the outer Solar System, the Kuiper belt perhaps, the result would be a gas giant with a breathable atmosphere, the resulting air pressure at the surface would be 10,000 bar, which would make that surface as inaccessible as Jupiter's. the Mass of Earth by comparison is around 6 x 10^24 kg, so this new atmosphere which is 1.1 x 10^24 kg would have just over one sixth of the mass of Earth. We could imhabit this upper atmosphere and forget about the ground, not worry about the rotation rate of the planet, we might bring the super rotation of the upper atmosphere close to that of Earth, we would get plenty of Earth like weather, lots of rain clouds, but no surface, the rain would just fall and reevaporate. It might be easier to add more atmosphere to Venus than to remove what it has. What do you think?
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Tom, that's a ridiculous waste of resources and energy. What's the point? Even removing the atmosphere of Venus doesn't require that much energy input. Why sequester 10,000 atmospheres of N2 & O2 in such a fashion?
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Actually its not sequestered, its added to Venus to dilute its mostly carbon dioxide atmosphere t make it breathable for humans and other animal life, to get the right percentages, you have to add an air mass to Venus that is one sixth the mass of Earth, this would make Venus into a sort of gas giant, its atmosphere would be opaque, cloud cover would be 100% with this thick an atmosphere, and Venus would appear as a featureless white orb to human eyes as it does today, only this time it would be water clouds, not sulfuric acid! One advantage is if you do your atmospheric right, you can get a "day length" at a certain altitude that is nearly equal to Earth, without having to physically change the actual rotation of Venus. The surface would probably be molten, the extra thick atmosphere would take the place of the planet's crust. People living in the atmosphere would live in floating habitats, only in this case they can breath the atmosphere. How much energy would be required to give Venus a 24-hour day, versus dumping extra nitrogen and oxygen on Venus in he necessary amounts?
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You wouldn't give Venus a 24hr day, you need a slow rotation to keep it habitable.
Use what is abundant and build to last
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Actually its not sequestered, its added to Venus to dilute its mostly carbon dioxide atmosphere t make it breathable for humans and other animal life, to get the right percentages, you have to add an air mass to Venus that is one sixth the mass of Earth, this would make Venus into a sort of gas giant, its atmosphere would be opaque, cloud cover would be 100% with this thick an atmosphere, and Venus would appear as a featureless white orb to human eyes as it does today, only this time it would be water clouds, not sulfuric acid! One advantage is if you do your atmospheric right, you can get a "day length" at a certain altitude that is nearly equal to Earth, without having to physically change the actual rotation of Venus. The surface would probably be molten, the extra thick atmosphere would take the place of the planet's crust. People living in the atmosphere would live in floating habitats, only in this case they can breath the atmosphere. How much energy would be required to give Venus a 24-hour day, versus dumping extra nitrogen and oxygen on Venus in he necessary amounts?
1/6th of Earth mass of O2 is about as much as is available in every other solid world in the solar system. Even if we ignore the practicalities of canibilising that much material, the result would not justify the unimaginable energy requirements.
Maybe the opposite approach would be more workable. Place a solar sail on Venus orbit, ~10,000km ahead. Lower a carbon nanotube pipe into the upper atmosphere, liquify and suck off the atmosphere. The sunlight pressure on the sail, might just balance the weight of the device in Venus gravity. The collected gases could then be frozen, packaged in aluminium foil and shipped out to other terraforming projects, such as Mars and the Jovian moons, using ion propulsion, solar sail, or whatever. We are still in mega-fantasy world of course.
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Problem is, you put all that carbon dioxide into space and some of it will fall on Earth, if you simply add gases to Venus, you don't have that problem. The volume of gases that are one sixth the Earth's would more than double the diameter of Venus, I've calculated that I you add one sixth of an Earth Mass to Venus, you get a planet with a mass equal to Earth, problem is if you double the diameter, you get a gravity one quarter that at Earth's surface. Flying would be very easy in an atmosphere such as this. So this gas giant would end up with a diameter twice that of Earth, as the planetary diameters of gas giants are measured. So due to the lower gravity, I think the planet would end up being 3 times the diameter of Earth, or about 72,000 km in diameter, 36,000 km in radius, the gravity at the fringes of this atmosphere would be one ninth that of Earth, this is all with one Earth mass, of sixth of it in breathable gases.
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Bzzt... Wrong. Compression would make it maybe 500 km deeper than the 1 bar level.
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Why not just pick up all the CO2 and launch it into the sun? I'm sure it would take less energy than extracting 1/30 Earth's mass in Oxygen from water...
Or even better, just work the crust over to lock all that CO2 up as carbonates, then import water. If you insist, break up about a bar of CO2 (lock the carbon away as diamond, or even just soggy dust at the bottom of oceans) to get a breathable atmosphere at the 1bar point (you still have 3 bars of Nitrogen to deal with - then again, if you're that rich, you might as well sell it to the rest of the solar system).
If you really want to build gas dwarfs, go out into the Kuiper belt. Plenty of Nitrogen there. Crash together a few planetoids, and you'll probably get a 100+ bar atmosphere at the surface...
Use what is abundant and build to last
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Easier to drop something than pick it up. Venus is smaller than Earth, so we can add mass to it. If we wanted we could add enough mass to Venus to make it a second Earth. one sixth an Earth mass brings Venus up to one Earth Mass, the Kuiper Belt may have that much mass in it.
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At the energy use you're talking about, removing the atmosphere and launching it into the sun is trivial...
Use what is abundant and build to last
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but why waste mass? If you got enough mass to bring the mass of Venus closer to Earth, why not use it? How much energy would it take to spin up Venus to a 24 hour rotational period? Spinning the planet is a bit difficult when it is wrapped up in its atmosphere, but you could always add more atmosphere to it. The more atmosphere you add to it, the more the upper atmosphere can spin at a different rate from the planet below. Perhaps we can convert some of the Carbon dioxide to a solid carbon and oxygen. Change the atmosphere from 97% carbon-dioxide to 40% carbon dioxide and 60% oxygen, then add five times as much nitrogen as oxygen resulting in an atmosphere that is 80% nitrogen, 4% carbon-dioxide, 16% oxygen.
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