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

From: Frank Prochaska <fprochas_at_meteoritecentral.com>
Date: Tue Oct 19 20:00:38 2004
Message-ID: <200410200000.RAA18981_at_spok.premier1.net>

Bernhard Rems wrote:
>
> Or let me put the question like this: what is the minimum size
> for a body to be able to create a metal core?

Bernhard,

Eric gave an answer of the average size I believe. I only recently read
a paper by Kunihiro, Rubin, McKeegan, and Wasson that addressed this.
They implied that bodies below about 3 km are too small to retain enough
heat from 26Al decay to melt, which of course is necessary to produce
differentiation and subsequent core formation. So now you have your
theoretical minimum size, though maybe the actual size is somewhat
larger.

David




Bernhard, David, and list,


This gives us an estimate for the minimum size for a body to differentiate
due to 26Al heating, but not other methods. Did some bodies differentiate
in the inner solar system during the Sun's t-tauri stage? Can't
differentiation occur due to melting from large asteroids colliding and
impacting each other? There are clearly other possibilities than strictly
internal heat sources. Then you get into the whole issue of the "onion
skin" vs. "raisin bread" model of differentiated bodies. While we might all
like a neat, simple model that we can plug all the asteroids and our
meteorites into, I doubt the early solar system could be described that
neatly and simply. It is nice to get constraints on the ways the various
"iron cores" may have formed, but I can't believe that there was only one
way.



Frank Prochaska
Received on Tue 19 Oct 2004 08:00:32 PM PDT