Path: utzoo!attcan!uunet!lll-winken!ames!husc6!purdue!decwrl!jumbo!stolfi
From: stolfi@jumbo.dec.com (Jorge Stolfi)
Newsgroups: sci.space
Subject: Is the moon a 'known quantity'?
Summary: Relatively speaking, yes.
Message-ID: <13531@jumbo.dec.com>
Date: 24 Jan 89 12:35:30 GMT
References: <6145@thorin.cs.unc.edu>
Reply-To: stolfi@src.dec.com (Jorge Stolfi)
Followup-To: sci.space
Organization: DEC Systems Research Center, Palo Alto
Lines: 59

Jonathan Leech writes:
>   
>   We have more samples of asteroidal material than lunar material
>   and closeup photos of Martian moons ... spectroscopic and
>   radar observations ...  

Not exactly.  Yes, we have lots of meteorites, but we only *think* they
are bits asteroids---we do not know for sure.  We DO know that they are
at best a very skewed sample.  For one thing, rocky meteorites are much
harder to recognize than metallic ones, and hence they are highly
under-represented in our collections.  There are probably lots of
meteorites (and perhaps asteroids) made of loose dust or of volatile
materials, but those never reach the ground; and yet those would be the
most interesting ones.  

We also don't know whether the Martian moons are captured asteroids;
this is only a conjecture, plausible but with no hard evidence to
support it.  Even if they are asteroids, we have no idea as to how
typical they are of the whole lot.  (In fact, there probably isn't such
a thing as a "typical" asteroid).  

Spectroscopic and radar observations of solid objects can only give
broad hints as to the average composition---say, "metallic" vs "rock".
Also, radar can't see deeper than a few inches, and spectroscopy can't see 
deeper than a few mm.

>   Landing 6 times on the moon does not make it a 'known quantity'
>   by any stretch of the imagination.

Come on.  We know a *lot* more about the moon than about any other body
outside the Earth.  Certainly there are many unanswered questions about
the moon, but they are nothing compared to our abysmal ignorance about
the rest of the solar system.  

(Quick, how many open questions about the moon can you think of?
How many of those could be resolved by returning there?)

I submit that more than 90% of the scientific value of the Apollo
program came from the first moon landing, and specifically from the
soil samples it brought back. 

It is always nice to have more data, but the last few Apollo landings
added very little to the knowledge we got from the first few.
It would have been foolish to continue spending the limited money
available on additional Apollos instead of on things like Viking and
Voyager.  

                Jorge Stolfi
                stolfi@src.dec.com, ...!decwrl!stolfi

  ``Strange, this lunacy,'' he said to Barbicane after the delegation
  left, ``and it's a type of madness that often hits the best minds.
  One of our most famous scientists, Arago, told me that many perfectly
  sane and respectable people will experience great excitement and behave
  incredibly whenever the moon posesses them. ''
     --Verne, _From the Earth to the Moon_ (1865)
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DISCLAIMER: The above opinions are not the sort of stuff my employer,
my teachers, my friends, or my mother would like to be associated with.