AW: [meteorite-list] There are no silly questions? Wait until youhaveread that :-)

star-bits_at_meteoritecentral.com

--
Eric Olson
ELKK Meteorites
http://www.star-bits.com
> <If all ungrouped iron meteorites are derived from the cores of differentiated 
> bodies, the question is: 
> where is all the crust gone? Why don't we have many more (at least 92) different 
> types of achondrites in our meteorite collections?>
> 
> >From Mittlefehldt et al, chapter 4 p4-15  "Planetary Materials" Reviews in 
> Mineralogy Vol 36
> 
> "cosmic ray exposure ages of iron meteorites are typically in the range of 200 
> to 1000 Ma, some 5 to 50 times longer than typical for stony meteorites.  Tight 
> clusters in exposure ages for groups IIIAB and IVA suggest discrete breakup 
> events for their parent bodies 650 +/- 75 and 420 +/- 70 Ma ago, respectively 
> (Voshage and Feldmann 1979).  No other clusters have been observed.  The highest 
> 41K/40K exposure age measured for an iron meteorite is 2.3 Ga, or half the age 
> of the solar system, for the ungrouped Deep Springs iron."
> 
>     The longest CRE exposure age I know of for a non-iron is Soko-Banja at 71.1 
> Ma although there may be others I don't know of.   This does exclude lunars 
> which do have CRE ages of up to a billion years.  
>     So if the non-irons are swept clean in 100,000 years or less and the irons 
> hang around for a up to a billion or more that would explain why we see more 
> variety in iron parent bodies.
> 
> --
> Eric Olson
> ELKK Meteorites
> http://www.star-bits.com
> 
> 
> 
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