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

[Jörn Koblitz]

Dear Eric,

A good question which I don't have an answer to. In terms of orbital evolution and probabilities to be catched up the larger solar system bodies, I do not se a reason, why iron meteoroids shall survive longer than stony meteoroids. May be, the differences in CRE ages are a result of cosmic-ray shielding effects. Does someone else has a good idea to explain these differences?

Cheers,
Jörn / MetBase

> -----Ursprüngliche Nachricht-----
> Von: star-bits at comcast.net [mailto:star-bits at comcast.net]
> Gesendet: Mittwoch, 20. Oktober 2004 20:06
> An: Jörn Koblitz; almitt; Bernhard Rems
> Cc: Meteorite-list at meteoritecentral.com
> Betreff: Re: AW: [meteorite-list] There are no silly questions? Wait
> until youhaveread that :-)
> 
> 
> <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
> 
> 
> 
>