XPost: sci.space.policy   
   From: g_d_pusch_remove_underscores@xnet.com   
      
   Hop David  writes:   
      
   > Gordon D. Pusch wrote:   
   >>  wbogen@visteon.com (Bill Bogen) writes:   
   >>   
   >>> Did any of the Apollo astronauts ever drag a magnet across the   
   >>> regolith to see how much, if any, metal particles might be available?   
   >>> I've seen references to the possibility of Apollo astronauts checking   
   >>> on a magnetic foot on a Surveyor probe and a paper or two on regolith   
   >>> composition but not anything on a test of the practicality of easily   
   >>> accumulating significant amounts of high quality iron/titanium/nickel   
   >>> "ore" with a simple process.   
   >>   
   >>  Highly unlikely, since the Moon is as depleted of both iron and   
   >>  "siderophiles" ("iron-loving" elements) as it is of volatiles.   
   >>  Most of the iron near the Moon's surface is likely to be meteoric   
   >>  in origin.   
   >   
   > I can imagine ways for the moon's surface to lose volatiles. How is iron   
   > depleted?   
      
   The mars-sized body that whacked into the proto-Earth to create the cloud of   
   superheated debris that re-condensed into the Moon was already differentiated;   
   most of its iron and siderophiles had already sunk down to its own core.   
   During the "Big Whack," most of the mantle of the impactor and a good bit   
   of the proto-Earth's mantle were vaporized, and the bare core of the   
   impactor merged with the proto-Earth, leaving the result of the merger   
   with the abnormally large iron core the Earth has today. Meanwhile,   
   the cloud of superheated mantle debris re-condensed into a short-lived   
   unstable ring whose particles rapidly coalesced to form the Moon.   
   Hence, the Moon is composed almost entirely of the most refractory   
   fractions of pure "mantle" material, with almost no remaining iron,   
   and at most a minuscule iron core.   
      
   So if you want to know where the Moon's iron went, you need look no further   
   than straight down about 6000 km... :-/   
      
      
   -- Gordon D. Pusch   
      
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