(urth) Green is Urth Redux

[David Stockhoff]

On 1/12/2011 10:03 PM, David Duffy wrote:
> On Wed, 12 Jan 2011, Jeff Wilson wrote:
>
>> On 1/12/2011 6:03 PM, David Duffy wrote:
>>> The moon can keep an atmosphere, once provided, for 10000-20000 years
>>> per top-up IIRC. Those Barsoomian air plants would do the trick nicely.
>>>
>>> http://www.terraformers.ca/Terraforming-the-Moon.html
>>
>> I've heard this before, but I have yet to see how the figure was 
>> obtained. I cannot find it on the cited website, if that was your 
>> intention.
>>
>
> No.  But I presume you can google as well as me ;)  Geoffrey Landis gives
>
> http://www.geoffreylandis.com/moonair.html
>
> Could we manufacture the oxygen? We would need something like two 
> hundred trillion tons. The chemical composition of lunar rock is about 
> half oxygen; all we have to do is reduce the amount of rock equivalent 
> to a cube about fifty kilometers on an edge. That's a lot of rock. On 
> the other hand, it's a small volume compared to the size of the moon. 
> Such a chunk of rock reduced to oxygen would give the moon an 
> atmosphere that would last three thousand years--longer than any 
> civilization on Earth has ever lasted, and when it leaks away, we 
> could keep replacing it every few thousand years for a long, long time 
> before we even begin to use up the moon.
>
> There doesn't seem to be a complete text for
>
> H.W. Renn, "Terraforming the Moon: A Viable Step in the Colonization 
> of the Solar System?" IAC-02-IAA.13.2.08, 53rd International 
> Astronautical Congress, Houston, TX (2002).
>
> I get the impression the 3000 year number is a little arbitrary (it 
> does for example assume the sun to be as hot as it at present ;)).  
> This writer (a professor of astronomy) claims 10-fold differences in 
> retention time depending on who did the calculations: 
> http://cseligman.com/text/planets/retention.htm
>
> The ratio of escape velocity to thermal velocity for H2O and O2 for 
> the moon is 5-6, which gives ~100 My.  This assumes a T of 300K.  
> However, the T at the base of Earth's exosphere is more like 1000K, 
> and that for the moon in a thick atmosphere is given at 800K in the 
> Willett et al presentation "Above the Moon".
>
> Williams et al Nature 1997; 385:234-236 state further
>
> Loss of O is not necessarily fatal to habitability because O2 can be 
> replaced by photosynthesis.
>
> Anyway, I don't know if Wolfe necessarily went through all these 
> calculations ;)
>
> Cheers, David Duffy.
As unlikely as the success of this process might appear from a technical 
standpoint, it is much closer to my own reading. I think the possibility 
that the trees---especially having run wild---might sustain an 
atmosphere fits well with the textual emphasis on a totally green, wild, 
forested moon. Which I think is Wolfe's main descriptive point about Lune.


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