[meteorite-list] Eucrites are from
From: almitt <almitt_at_meteoritecentral.com>
Date: Thu Apr 22 09:44:38 2004
There are a number of good reason that the HED's and the lunar material are NOT
related. Fist and foremost the Oxygen isotopes don't match up in the mass-fractionation
lines comparing lunar and Howardites,Eucrites and Diogenites. The aubrites actually
match up better with the lunar lines there but can be shown to be different elsewhere.
This was done at the University of Chicago by Robert Clayton and Toshika Mayeda. This
shows distinct parent bodies as achondrites can't move from one fractionation line to
another by melting or crystallization. It does show that more than one parent body can
have the same oxygen isotopic composition but be unique.
Second, Spectra matches of the HED parent body and the HED's are a fingerprint match
and and show a very close correlation. The HED's and the moon Do not match at all.
Clark Chapman (Southwest Research Institute)
Third, the moon contains mineral compositions that distinguish it from other parent
bodies. Mainly the magnesium and iron in olivine or pyroxene with the calcium content
of coexisting plagioclase. Clasts in the lunar meteorites from the highlands plot
almost exclusively within the ferroan anorthosite field, suggesting that this plot
dominates the highlands, possibly on both sides of the moon. We are more sure of the
lunar meteorites (100%) than of any other parent body.
So you see were talking two different families here. I recommend (as I have before)
that people interested in parent bodies read McSween "Meteorites and their Parent
Planets" He does a great job of breaking it down so one can understand rather than
speculate. Best regards to all.
Received on Sat 10 Mar 2001 09:04:54 PM PST