I may be wrong, but I don’t think there is significant limit to how
MUCH atmosphere you could place on the moon. So, I don’t see where this 10 to 12 thousand feet ASL comes from. Now doing it and keeping it there for a long period of time is another thing, but if you wanna really pile it on you could have it as dense/high pressure as you’d like.
This would be one of the biggest problems in terraforming the Moon; even if an atmosphere could be maintained, the day side would bake for 2 weeks and reach a very high temperature. Typical Earth day-night temperature swings (inland) are around 20°F rise/fall over 12 hours, so over 2 weeks you might see a 560°F swing in temperature, which is pretty close to the actual temperature swings (an atmosphere would help slow the rise/fall but with enough time it would reach the same temperature, maybe somewhat less than a simple linear extrapolation would suggest but still pretty extreme). Plus you’d have some pretty wicked winds between the hot and cold sides. Having water on the surface would help a lot, but it would have to be oceans, not just a few lakes.
Evidently there’s some question about whether a planetary magnetic field (like the Earth has) will help keep the atmosphere. The idea is that the magnetic field diverts solar wind particles, which can knock the atmosphere away. But there’s debate about it: How Vital Is a Planet's Magnetic Field? New Debate Rises | Space
Yes; that thought occurred to me; find an inert heavy gas and use it instead of nitrogen.
However, to my surprise, several of the heavier noble gases are very good anaesthetics. Especially xenon
so unless you want to be permanently asleep on the Moon, another solution might be better.
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What’s the heaviest non-toxic gas? Uranium hexafluoride sounds like a very bad thing to breath. Sulfur hexafluoride (M.W. 146) is a little heavier than xenon (131), and it’s fairly inert. Apparently it’s injected into the blood as a contrast agent for ultrasound; so it can’t be too toxic.
I presume an additional feature of adding an atmosphere - essentially terraforming - would be to add a lot of water too. As a result, perhaps clouds might form and moderate the amount of sunlight hitting the ground. Additionally, there’s the question of the climate issues as the moon turns, and convection between sunny and dark sides, plus the moderating influence of atmosphere and large bodies of water (Seaside does not always get as hot as the open desert - nor as cold). Plus, the higher latitudes would also have a moderating influence - cooler breezes from teh temperate zones? I’ve seen discussions about how the climate would behave on an earth tidally locked facing the sun (not good!) but not on the effect of a 14-day day or night.
The 10,000 to 12,000 ASL discussion was about whether we could skimp on the atmosphere to get there sooner. We don’t need exactly 21% O2, 78% N2; IIRC the original Apollo capsures were 7PSI (half Seal Level 14.7PSI) but very rich in O2, enough to create an interesting fire.
Or we could just increase the rotational speed of the moon.
You absolutely do not want heavy gasses in the atmosphere: the lungs won’t be able to expel them. As for the balloon idea, it’d be great until a meteorite punctures it.
It’s going to need a system to patch holes and replace large sections. But it has to be made of something that won’t just rip apart causing it to burst. Lot’s of atmosphere will be lost through the constant penetration of meteorites, but it’s not going to just deflate unless one of the massive ones gets through. And it’s going to lose a lot less atmosphere than any system that doesn’t bring the moon up to a large percentage of earth’s mass.
Small leaks from meteorites would be trivial on a planetary scale, and the system would need to have a system of repair. but over a very long time the atmosphere would leak out; eventually you’d have a thin atmosphere outside the worldhouse which would be gradually lost, as well as a thicker atmosphere inside. Such an arrangement could last many millions of years.
Doesn’t sound hard. Just look at Titan. A very thick atmosphere. With a gravity of 1.534 m/sec^2. The moon’s gravity is 1.62 m/sec^2.
If titan can do it, the moon wouldn’t be a problem.
But Titan is also much colder than Luna, so wouldn’t that slow down the escape of Titan’s atmosphere?
Yes and no.
Breathing something resembling air doesn’t become a serious problem until you start breathing densities in the 10’s of sea level pressures (diver data here). Therefore, if your surface pressure is something like sea level, then the molecular weight of whatever gas you want can be 10’s of times greater than that of say oxygen or nitrogen.
Rough WAG here of course.
Well it should work like any other pump where the difference in density is what matters. There might be a problem if the oxygen is a lot lighter than the heavy gasses and most of it anti-gravitates away from the surface. Also, everyone will talk funny.
I thought gases in the lungs mixed pretty well, and thus heavy gases were expelled quickly.
Here is a link where somebody makes the same claim, and there’s a big discussion about it. But the link to the xenon in the lungs picture shows that heavy gases don’t seem to pool in the lungs.
Hear’s a thought. You surround the Moon with some heavy gas that will escape more slowly than an Earthlike atmosphere. Then you go the world-balloon route; taking advantage of the Moon’s low gravity (and your no doubt really advanced materials science) you cover its surface with towers several miles tall supporting a canopy to keep the breathable atmosphere in. Tall enough so there’s room for a weather system underneath. The outer unbreathable atmosphere serves as anti-meteorite shielding and provides air pressure on the outside of the canopy, so it doesn’t have to be as strong as a canopy holding in the atmosphere against a vacuum. Equal pressure on both sides also means leaks are less dramatic in their effects, and therefore easier to fix.
Maybe another way is to make it smaller, keeping the mass the same. By my calculations, since the Moon is 0.0123 the mass of Earth, to have the same surface gravity as Earth, the ratio ((new moon’s radius)/(Earth’s radius))^2 must be 0.0123, and the Moon needs a radius of 700 km, or 40% of its original.
As far a breathing problems go it isn’t pooling or mixing that is the problem. Its the density of the gas. The denser the gas is due to pressure the “thicker/more vicous” it is and the harder it is to get in and out of your lungs. And if it is really “thick” I suspect the gas in the really tiny parts of your lungs, where the oxygen exchange is going on, is not being changed out very efficiently.
In the old days there were a fair number of bold/crazy divers that do 300 feet on regular air (dangerous as hell due to high partial O2 pressures and nitrogen narcosis). But they didn’t report any significant problems with the breathing part.
With mixed gases, with a high percentage of Helium instead, divers have approached 1000 feet and I believe 2000 in test chambers.
300 feet is 10 atmospheres of pressure. So we know air at 10 atm is breathable in terms of being able to get the denser gas in and out.
Now, I am making the assumption that if molecule X has a molecular weight of 15 and molecule Y has molecular weight of 150 that the breathing difficulty of X at 10 atm and Y at 1 atm are roughly equal (there’s almost got a be a general trend of that sort at least).
So, if you cover the moon in some special very high molecular weight gas, but it is only one atmosphere of pressure I don’t think it is remotely going to be like trying to breath molasses.
Adam Savage (and countless others who have dared to inhale pure sulfur hexafluoride) lived to tell the tale. Doesn’t seem to be an issue.
What’s wrong with domes and tubes? Wouldn’t enveloping the entire moon with an atmosphere cost loads more than filling a dome with air and expanding out when needed? What’s the benefit?