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

From: Jörn Koblitz <koblitz_at_meteoritecentral.com>
Date: Fri Oct 22 09:29:28 2004
Message-ID: <E5E6112EA31FA24CB448E091C6883C0517A5E6_at_server2000.microfab.de>

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,
J?rn / MetBase

> -----Urspr?ngliche Nachricht-----
> Von: star-bits_at_comcast.net [mailto:star-bits@comcast.net]
> Gesendet: Mittwoch, 20. Oktober 2004 20:06
> An: J?rn 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
>
>
>
>
Received on Fri 22 Oct 2004 09:30:49 AM PDT