[meteorite-list] Chondrule formation mechanism (Info Please)

From: Rob McCafferty <rob_mccafferty_at_meteoritecentral.com>
Date: Tue Oct 24 15:32:21 2006
Message-ID: <20061024192446.10391.qmail_at_web50905.mail.yahoo.com>

--- "E.P. Grondine" <epgrondine_at_yahoo.com> wrote:

> Hi Rob -
>
> "molecules of a feather flock together"? why?
>

This is the most blatant speculation on my part and I
have not looked it up to check this (though to be
fair, I didn't make the comment above, I just like it)
but this is what I think and no more...

Supernova are responsible for the synthesis of all the
heavier elements. I suspect that large quantities of
single elements are likely to be formed at the same
place in the catastrophic destruction. I base this
soley on the shell model of Supergiant stars and that
the explosion is likely to apply the same temperature
and energy to these regions making it likely that many
fusion events in one place produce the same daughter
element. These will inevitably spread in the explosion
but are still going to travel in similar directions.
This is obviously an off the cuff description and I've
probably no justification for suggesting they head off
in the same direction into space.

This debris will eventually come together to form a
protodisk. I am not sure that it is necessarily the
case that elements or molecules of a feather -as it
was put- may necessarily flock together. How
homogenous the disk is I don't know but I cannot see
any reason why it shouldn't be. Jupiter is essentially
the same composition as the sun, after all but the sun
also contains all the same elements as the earth, as
observed spectrally.
The structure of gas giants have rocky interiors and
probably similar to terrestrial planets bulk
composition.
What it may be is that the minerals/elements which
formed the chondrules condensed first. I believe this
is what is currently believed. This being the case, it
makes sense that they are mostly made of similar stuff
as this is all there was to make them.

I appreciate that different chondrules have different
minerals, even in the same meteorite. I suppose this
is where your question is most valid, why did they
group together like that and why aren't they all a
general mish-mash of all the available minerals?

I suppose an answer to this is the chondrules may have
initially formed at different distances. They can come
together to form parent bodies interspersed by matrix
at a later period. We've seen on this list in the last
few months that planetary orbits are not nearly as
fixed as we tend to think (the dancing rings video of
the inner solar system and Neptune's migration spring
immediately to mind). My difficulty with this is why
would minerals form at different distances? Under
gravity they'd all fall inward at the same rate during
the earliest period of the disk formation. I need to
have a bit of a think about it. It may be due to
temperature in the protdisk at different distances.
Not convinced I can bull**** my answer to that.

Another contentious rambling I have is that the reason
for the clumping of similar molecules is normal. If
you think how crystals form in liquids, you need a
nucleation point but once you begin to build up a
structure there is a tendency for them to stick to
their own type. This is true for liquid drops as well.
I don't know if this is Van der Waal's forces or
something else. VdW is a tiny force as I recal but in
a low density environmet with a few thousand years, it
may be enough. Dunno. I hope to one day have the
mathematical ability and the time to work this out
before someone else does...If only to prove I'm wrong.

Sorry for the lengthy mail. I felt it needed it, even
if it is all unsubstantiated. I just hope it's not
twaddle.

Rob McC

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Received on Tue 24 Oct 2006 03:24:45 PM PDT