The Moon is not capable of keeping an Earth like atmosphere, nor is it practical to keep satellites in lunar orbit. Which means all transportation and communication would need to be ground based. No airplanes, no satellites, no GPS, decreased radio communication, etc.

Xenon is a heavy, colorless, dense, odorless noble gas. You would not be able to breath it, but if you inhaled some it would not kill you. It is heavy enough to make a fairly stable atmosphere on the moon. If you had enough of it you could fly a kite, fly a plane, or float a balloon. It is rare on Earth, but assuming you found an asteroid or other source of significant amounts of Xenon, how much would you need to make atmospheric plane and/or balloon operations possible?

Note: The boiling point of Xenon is 165K and the asteroid belt seems to have a temperature of around 200K, so finding a frozen ball of Xenon seems unlike, but if we did, how much would we need?

  • $\begingroup$ Your question might benefit from not being restricted to merely xenon. Rather you might simply want to ask what kind of feasible transportation and exploration methods would work on the moon (with or without humans). $\endgroup$
    – spacer
    Nov 6 '15 at 12:28
  • $\begingroup$ @spacer if you have a better choice gas I would encourage you to post it as an answer. I picked Xenon for the question because other than availability it would probably be the best choice. But if you can make a good argument for another gas, go for it. $\endgroup$ Nov 6 '15 at 12:31
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    $\begingroup$ Creating Moon atmosphere with xenon, just to make flight-based transportation available? What about developing genetic engineering to create dinosaurs, then a time travel system, breed dinosaurs, kill them, move them a good few million years back to their time and bury them, thus creating new oil fields to resolve the fossil fuel crisis? $\endgroup$
    – SF.
    Nov 6 '15 at 12:39
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    $\begingroup$ @JamesJenkins: Solid at the collection point but gaseous on the Moon, where the conditions aren't that vastly different if the cargo is to be delivered in a reasonable timeframe (asteroid orbit approaching Earth orbit)... $\endgroup$
    – SF.
    Nov 6 '15 at 15:17
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    $\begingroup$ Inhaling Xenon will make you loose conscious, it is used as a general anaesthetic, see Wikipedia. If there is no anaesthetist present, inhaling Xenon might kill you. $\endgroup$
    – Uwe
    Dec 3 '17 at 11:25

First of all, while Xenon would be the most stable due to it's molecular weight being the largest non-radioactive gas, there are other gases that would work as well. Sulfur Hexafloride would be a particularly interesting choice, and that should be easier than Xenon to find.

Okay, that notwithstanding, how well would it work to fly in an atmosphere of Xenon or similarly heavy gas? As a source, I am going to use XKCD's interplanetary Cessna flying chart, and Bernoulli's Principal from Wikipedia. Of particular note are a few things. One is that the ability to fly largely depends on the pressure, not on the weight of the gas. So you would need a whole lot of gas, making the atmosphere quite heavy (Ideal gas law). You would then be able to fly, but only rocket powered items, which would probably be easier to do without the atmosphere anyways, although precision landing would be easier.

The other advantage of an atmosphere would be the protection against small micro-meteors, which is one of the major obstacles of Lunar colonies. The temperature would also be somewhat regulated, etc. However, I still wouldn't recommend this.

Bottom line, I'd invest in some kind of high speed train, which should be much cheaper and easier to manage than filling the atmosphere with Xenon.

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    $\begingroup$ If the gas was flammable, you could still fly on jet engines; you'd just load up on oxidizer instead of fuel. $\endgroup$
    – SF.
    Nov 6 '15 at 13:37
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    $\begingroup$ True enough. The two best gases (Xenon and Sulfur hexafluoride) are not flammable, but I suppose a heavy hydrocarbon gas could be used. But that heavy gas would tend to be more susceptible to solar wind ionization, not to mention burning the gas would make it smaller and thus more susceptible to leaving the atmosphere. $\endgroup$
    – PearsonArtPhoto
    Nov 6 '15 at 13:55
  • $\begingroup$ I wouldn't worry about the last part though considering volume present:burnt ratio. $\endgroup$
    – SF.
    Nov 6 '15 at 13:57
  • $\begingroup$ If we are worried about using Xenon to keep the atmosphere around, I would think the burnt ratio would be an influencer as well. $\endgroup$
    – PearsonArtPhoto
    Nov 6 '15 at 13:59
  • $\begingroup$ Surprisingly, sucking in inert gas is more efficient than not doing so. Halving a jet engine's ISP (effect of equal load of oxidizer) is still better than a kerosene rocket engine's ISP. $\endgroup$
    – Joshua
    Jan 27 '16 at 0:11

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