Date: Wed, 21 Oct 1992 21:02:12 GMT
From: Henry Spencer <henry@zoo.toronto.edu>
Subject: Bootstrap hardware for LunaBase
Newsgroups: sci.space

In article <2274@grivel.une.edu.au> bsercomb@neumann.une.edu.au writes:
>There is no way that the moon has had sufficient surficial water to develop
>erosional enrichment deposits, and no way that there has ever been enough
>water around for "crustal" hydrothermal processes when the moon was still
>relatively molten inside. So, all that remains is aolean differentiation..

Okay, another myth surfaces yet again...  People who are going to propose
this one should look at some of the literature on the subject before
spouting off on it.  A particularly good source is S.L. Gillett, "Economic
Geology of the Moon:  Some Considerations", in the Lunar Resource Assessment
Technologies Workshop held in April (unfortunately, I don't know if or when
proceedings will be published -- all I have are the abstracts; anybody?).

First:  You do *not* need water or air for ore formation.  Even on Earth,
there is some exploitation of deposits formed through processes like
fractional crystallization of molten magma.  Such ores are rare, by
comparison, on Earth, but they do occur.  "Examples... include Cu-Ni
sulfide ores from sulfide liquid immiscibility, chromite from cumulate
settling, and magnetite ores crystallized from late-stage magmatic fluids
extremely enriched in Fe [6]..."  (Reference 6 is to Guilbert&Park, The
Geology of Ore Deposits, Freeman 1986.)

Second:  There is no shortage of unexplained phenomena even in the limited
lunar samples collected to date.  We do *not* understand lunar geology all
that well yet.

Third:  The Moon was definitely very geologically active in its early days,
and it's a much more heterogeneous body than was once thought.  Extrapolation
from limited information is risky.

Fourth:  Very little has been done in the way of economic assessment of the
Moon.  Almost all activity in lunar geology has concentrated on the broad
outlines rather than the useful details.

Fifth, and most significant, given some of those earlier points:  ores are,
almost by definition, rare deposits, the result of one or more processes
going to extremes.  Even if most of the Moon is totally useless as a source
of minerals, so what?  So is most of the Earth.  For mineral exploitation,
what we care about are the freaks, the coincidences, the one-in-a-million
long shots.  Ore bodies don't have to be huge to be useful; a deposit (say)
100m on a side contains megatons of material, not a lot by Earth standards
but a treasure trove for any sort of lunar activity.
-- 
MS-DOS is the OS/360 of the 1980s.      | Henry Spencer @ U of Toronto Zoology
              -Hal W. Hardenbergh (1985)|  henry@zoo.toronto.edu  utzoo!henry

From: henry@spsystems.net (Henry Spencer)
Newsgroups: sci.space.tech
Subject: Re: Nuke on the Moon?
Date: Tue, 21 Mar 2000 15:34:49 GMT

In article <8b68f8$501$1@spock.usc.edu>,
John Schilling <schillin@spock.usc.edu> wrote:
}If your orbital X-ray analysis tells you that a given 100m x 100m x 100m
}volume of the lunar surface contains two and a half tons of resource X,
}is it worth going after?  Depends an awful lot on whether that two and
}a half tons is distributed evenly...

Also, one problem with X-ray analysis is that it doesn't tell you about
100m x 100m x 100m volumes.  It tells you about 100m x 100m x 0.0001m
surface layers.  (I wouldn't swear to the exact depth, might even be
shallower, but that's the right general idea.)  The X-rays that are most
useful for this sort of thing are not very penetrating.

Gamma-ray data can tell you somewhat more, to depths of meters at least.
See the gamma-ray-spectrometer maps from Lunar Prospector.

}What you need are geologists on the ground taking samples.  Orbital data
}comes into play when you have enough field experience to say that certain
}combinations of surface morphology, elemental abundance, and so forth are
}strongly correlated with the sorts of ore deposits you are looking for,
}and we aren't nearly there yet.

I agree, with one added comment:  not only do we need geologists on the
ground taking samples, but we need a better understanding of the processes
of lunar geology.  Without theoretical understanding, field experience is
just groping in the dark, and you'll need to do a *whole lot* of rock
gathering, and digging, and drilling, more or less at random to learn what
correlates with what.  (One thing we know already is that the regolith is
sometimes layered, so what you see on the very surface isn't a direct sign
of what's underneath.)  Theoretical understanding of the geology can
greatly speed that up; "the purpose of theory is insight, not theorems".
But we don't understand the details of lunar geology well enough to have
much insight yet.  We have some grasp of the overall large-scale history,
but ore bodies are very localized things, almost by definition extreme
and unusual cases.
--
Computer disaster in February?  Oh, you |  Henry Spencer   henry@spsystems.net
must mean the release of Windows 2000.  |      (aka henry@zoo.toronto.edu)

From: henry@spsystems.net (Henry Spencer)
Newsgroups: sci.space.tech
Subject: Re: Nuke on the Moon?
Date: Fri, 17 Mar 2000 12:57:44 GMT

In article <Pine.GSO.4.10.10003161102520.27537-100000@ux11.cso.uiuc.edu>,
Robert G. Shimmin <shimmin@students.uiuc.edu> wrote:
>Would it be at all feasible for a team of satellites in lunar orbits to
>act as a long distance x-ray spec, gaining an elemental composition
>reading on the moon's entire surface?

We're already got elemental-composition maps, from Lunar Prospector's
gamma-ray spectrometer.  Doing it in X-rays as well would be good,
although it's not clear why you'd need multiple satellites (the Sun
supplies the X-ray illumination for you).
--
Computer disaster in February?  Oh, you |  Henry Spencer   henry@spsystems.net
must mean the release of Windows 2000.  |      (aka henry@zoo.toronto.edu)