The question was raised if chondrules occur in achondrites or moon rocks.
If you look back at papers from 1970 - 1972, there are reports of "lunar
chondrules" found in the first returned Apollo samples. These "chondrules,"
as nearly everyone acknowledges, are millimeter-size impact-melt spherules
produced after collisions of meteorites with the lunar surface. Some folks
think that chondrules in chondrites also formed this way, but most chondrule
researchers believe that chondrules were formed as isolated droplets in the
solar nebula. If this is correct, then after being melted, they would have
cooled quickly because there was little or no insulating material around
them. Only later would these chondrules accrete along with CAIs, matrix,
metal and sulfide assemblages, etc. to form planetesimals which later
accreted into larger bodies. If chondrules indeed formed as isolated
droplets in the nebula, then if the planetesimals into which they
subsequently accreted ever melted, then the chondrules would also melt and
the textural evidence for them would be forever erased.
Alan Rubin
----- Original Message -----
From: "Greg Stanley" <[email protected]>
To: <[email protected]>; <[email protected]>
Sent: Friday, October 02, 2009 1:51 PM
Subject: Re: [meteorite-list] Chondrule formation
Hello All:
I had a thought:
It seems to me that chondrules are prevalent in meteorites blasted from
asteroidal bodies and not from planetary bodies. For example, do chondrules
exist (or have been found) on any meteorites from the moon, mars or maybe
from Mercury (Angrites?)? Now I understand that these are called
achondrites, and thus they do not have chondrules, but it seems that
chondrites are only from asteroidal bodies (or perhaps comets). With that
said, maybe there is a relationship between formation of rock without
gravity (or a very small amount of gravity); chondrules form initially
during the formation of the solar system, and then later over millions of
years are altered on planetary bodies under a gravitational force.
Just my two cents worth.
Greg S.
----------------------------------------
Date: Fri, 2 Oct 2009 11:58:02 -0700
From: [email protected]
To: [email protected]
Subject: Re: [meteorite-list] Chondrule formation
Hi all -
"We don't know crap..." Hey!, who stole my line?
But that's okay, I can come up with another one:
We don't know crap about the impact hazard,
and NASA senior managers know less than that.
E.P. Grondine
Man and Impact in the Americas
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