Author Topic: An atmosphere for the moon?  (Read 1381 times)

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Offline MarcAFK

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An atmosphere for the moon?
« on: October 03, 2013, 09:03:12 AM »
A post in the Aurora academy about terraforming the moon or mercury got me thinking about whether a body with such low gravity would even be able to hold onto a thicker atmosphere for long, I found a small yet interesting article by N.M.Hoekzema about the subject, which I'll link here: http://www.mps.mpg.de/homes/hoekzema/katman/nick/work/moonat.htm.
 Basically the solar wind would cause most of the atmospheric loss, however if significant quantities of water was present iron in the lunar surface would rust away the oxygen rather easily.

Also I found a paper published by an N.M.Hoekzema Titled "Small-scale topology of solar atmospheric dynamics" which includes the following in it's abstract : "We find that the largest-flux sites in the granulation have appreciably larger than random probability to co-locate with exceptionally bright chromospheric internetwork grains, at an average delay of about two minutes which is likely to represent sound travel time to the chromosphere. This finding strengthens the case for acoustic grain excitation. "
So I'm willing to believe that he may know something about these subjects.
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Offline TallTroll

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Re: An atmosphere for the moon?
« Reply #1 on: October 24, 2013, 04:38:20 AM »
Also, surface gravity has quite an effect on the weight of the largest particle that a body can retain as part of its atmosphere. H and He are light enough that just about any body with measurable gravity could retain some sort of atmosphere (in absence of external factors, like the solar wind), but getting an appreciable partial pressure of O2 to stick around is going to require a decent fraction of G, and hence a certain minimum mass / density.

Partly as a workaround for this in the context of Mars, it has been proposed that one way of terraforming Mars would be to use existing geological features like canyons, and essentially just roof them over, to retain an Earthlike atmosphere. Generating a thicker atmosphere over the whole planet would be a likely longterm goal, and maybe one day it will be possible to walk on the surface of Mars (albeit probably always wrapped up in Arctic gear, even at noon on Misummers Day whilst on the equator, but with minimal or no breathing support).
 

Offline xeryon

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Re: An atmosphere for the moon?
« Reply #2 on: October 24, 2013, 08:13:41 AM »
I am not knowledgeable enough to comment on the atmosphere discussion but I do know that Curiosity did measure daily high temperatures on Mars reaching 70 F on a regular basis.  That temperature was being reached with the minimal atmosphere that Mars currently has.  It is not a far stretch to think that with an appreciable atmosphere that a generous portion of the planet would be habitable without the need for arctic gear, at least during the summer daytimes.
 

Offline TallTroll

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Re: An atmosphere for the moon?
« Reply #3 on: October 24, 2013, 11:41:18 AM »
>> a generous portion of the planet would be habitable without the need for arctic gear, at least during the summer daytimes.

During the day, quite possibly, but the atmosphere would also be terrible at retaining heat out of direct sunlight, so night time temperatures would drop a lot further than you'd expect from an Earth dwellers experience, even on a summers night. You see a similar effect here in settlements at great altitude. It can be blazing hot in the day, and well below freezing at might. I wouldn't like to go out without a jumper or 2. We lose more tourists that way...

Just to further complicate things, "temperature" is a tricky word. It only really means the degree of (mostly) translational and rotational excitation of a molecule. At 50km, Earths atmosphere has a temperature of a relatively balmy 260K. Even if you brought your own oxygen supply and *really good* sunblock, you would freeze quickly enough.
 

Offline xeryon

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Re: An atmosphere for the moon?
« Reply #4 on: October 25, 2013, 05:14:22 AM »
It would not be without limitations.  I hold no false hope of running around on the surface in my bathing suit.  Merely pointing out that surface temperature on the planet was considerably warmer than what scientists were originally expecting.

To what the original poster was referring to: it is very sad news to find out that the moon may never harbor a functional atmosphere on many levels.  The implications of it are depressing.  For one, it is sad to know that our closest celestial body will never be much more than a tourist curiosity and/or commercial mining operation.  The thought of their being a substantial population on the Moon was far fetched at best but still something I always thought would be an intriguing future to imagine.  Second, it brings into doubt the possible habitation of moons universe-wide.  Moons and bodies of this size number in the hundreds in our system alone.  So much real estate unusable without substantial infrastructure for life support.  :(
 

Offline TallTroll

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Re: An atmosphere for the moon?
« Reply #5 on: October 26, 2013, 09:39:43 AM »
>> For one, it is sad to know that our closest celestial body will never be much more than a tourist curiosity and/or commercial mining operation

Well, hold on there. A free surface atmosphere is not necessarily an absolute requirement for even quite large scale settlement of the Moon. Because it is so close, we may be able to ultimately have millions of people living there. It's so easy to get to, cosmically speaking, that it remains quite a good candidate for becoming a decent colony. We would have to put lots of enclosed structures up, either on or buried into the surface, but the list of possible productive activities available on the Moon is probably bigger than you think.

For a start, the lack of atmosphere makes the Moon an attractive place to build observatories. Not as good as deep space, but vastly better than Earth, with its' thick soupy, light-polluted gunk. Low gravity may well lead to novel manufacturing processes, especially for pharmaceuticals and materials. No doubt several branches of the sciences will want to take advantage of the unique research opportunities the Moon will present. It is possible that facilities on the Moons surface could become the major manufacturing centres for spaceship production (once we've actually gone unequivocally into space), although that would probably require a Beanstalk on the Moon for getting raw materials down, and finished components up to space-based construction yards.

Anywhere else in the Universe, such an unprepossessing lump of airless rock would be of little interest to us, but right there...
 

Offline alex_brunius

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Re: An atmosphere for the moon?
« Reply #6 on: October 27, 2013, 10:05:17 AM »
Well, hold on there. A free surface atmosphere is not necessarily an absolute requirement for even quite large scale settlement of the Moon. Because it is so close, we may be able to ultimately have millions of people living there. It's so easy to get to, cosmically speaking, that it remains quite a good candidate for becoming a decent colony.

...

Anywhere else in the Universe, such an unprepossessing lump of airless rock would be of little interest to us, but right there...

Distances and costs don't work at all like on Earth though. On earth twice as far away means twice as expensive to send materials too generally speaking.
That is not true for Space at all.

Actually it is cheaper to send 1 ton of equipment to mars surface from Low Earth orbit (3.6 km/s Delta V) then to the lunar surface (5.67 km/s Delta V) today since Mars has an atmosphere that allows for aerobreaking.

In fact when you add up the numbers you could almost get stuff into Jupiter orbit for the same price as landing it on the moon (even if it of-course will take longer time to do so).

http://i.imgur.com/SqdzxzF.png



Distances do apply in space only when you are transporting humans (that require extra food/energy to survive on longer journeys), but for a serious colony in such hostile environments the absolute majority of cargo transported will not be of human nature.
 

Offline TallTroll

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Re: An atmosphere for the moon?
« Reply #7 on: October 28, 2013, 06:35:51 AM »
In this specific case, I think human psychology will mean more than physics. It might require less actual energy to get to Mars, but the Moon is RIGHT THERE. You can see it from Earth with the naked eye, and vice versa. People will want to live on the Moon more than they do on Mars, and if we can't solve easily solve the problems of maintaining health under low grav, a semi-permanent settlement on the Moon is still feasible, with transport to and from Luna being a matter of days rather than months. It would be little more than a rather exotic "overseas posting". In no other case would that be true
 

 

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