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Re: Moonquakes

Subject: Re: Moonquakes
From: "George"
Date: Thu, 16 Mar 2006 17:22:15 GMT
Newsgroups: sci.astro, alt.sci.planetary, sci.geo.earthquakes
"Aidan Karley" <doIlookDAFTenoughTOpost@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx> 
wrote in message 
news:VA.00000d34.26f89ee6@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
> In article <dvabte$8r6$1@xxxxxxxxxxxxxxxxxxx>, Al wrote:
>> I thought that the density of the moon was less than the Earth? Like 
>> iron?
>> How can he tell that the moon is dry subsurface?
>       By doing analyses of the rocks returned by the Apollo missions. The
> rocks returned are *very* dry. Extrememly dry. In comparisons, most
> earth-formed rocks contain a percent or so of water, as both patent water
> (which can be evaporated from the powder by drying at around 120deg C) 
> and
> as chemically-bound water within silicates. For example, most amphibole
> minerals will contain the equivalent of around one percent of water as
> hydroxyl entities, which can be freed from the rest of the components by
> fusion under (earth) atmospheric pressure (may take a while). Moon rocks, 
> by
> contrast, don't contain the free water, and are made from minerals that
> don't contain much of the components of water. The lack of water 
> components
> *within* mineral grains *within* rocks indicates that the Moon was very 
> dry
> at the time that the mineral were formed, typically 4½ gigayears ago.

Which is why moon rocks contain pyroxenes, but no amphiboles.  If there had 
been significant water on the moon, we would see evidence of this in the 
form of amphiboles and other hydrated minerals in the rocks.  There is 
plenty of oxygen bound up in the rocks, but little to no hydrogen.  That 
indicates that the moon never had any significant water or atmosphere.

>> This brings us back to the deep hole drilling - the running water was a
>> surprise.
>       Speaking as someone who drills holes for a living, and who spent
> Monday writing up the "formation pressures" and "formation fluids" part 
> of a
> client's report on (approximately) my 115th well ... which "running 
> water"
> was a "surprise"?
>
>> If we don't know what's under our feet how can we know what's
>> beneath the moon's surface? Conjecture.
>>
>       The texture of many of the "moon rocks" indicates that they've been
> violently excavated from depth, then welded together by further less 
> intense
> shocks and heat. This suggests a model for the lunar surface with quite
> thorough mixing to considerable depth, forming a "regolith" (`shattered
> rock') layer something like 50km thick. The dryness of the mineralogy in
> those mixed rocks indicates that the large majority of this layer is dry.
>       It's "conjecture" based on considerable evidence. Not a solid fact,
> but there are very good reasons for believing it to be true.
>
> -- 
> Aidan Karley FGS
> Aberdeen, Scotland,
> Location: 57°10'11" N,  02°08'43"  W (sub-tropical Aberdeen), 0.021233

That has been my take as well.

George 



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