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

From: Rob McCafferty <rob_mccafferty_at_meteoritecentral.com>
Date: Sun Oct 22 10:25:19 2006
Message-ID: <20061022142516.32929.qmail_at_web50911.mail.yahoo.com>

Ed

Thanks for the reply. I'd really like to take a look
at any data but to help be more specific on my
requirements I'll give you an outline on my idea.

The appearance of the unaltered chondrites seems to
show that the outer rim of the chondrules are of a
significantly diferent structure to the interior.
Petrographic slides seem to show this as a dark
boundary between the matrix and the chondrul and
generally, the lower the petrographic type, the
clearer this boundary is. 3.x it is impossible not to
spot it.
Now my understanding of this is that this is evidence
of a rapid quenching period and the good internal
structure is due to a much longer cooling period and
this is where the current literature seems to stop.

I do not believe that it need necessarily be evidence
for rapid quenching and is instead a natural phenomena
which occurs in true microgravity.

A few months ago I was discussing Einstein's theories
on Brownian Motion (as you do) with Canadian
Astronaut, Bjarni Tryggvasson and he said that a few
years ago he noticed Einstein missed a term for
external energy and wanted to know what may happen if
you removed external enegy sources (vibrations).

Even on Mir and The Space Shuttle, the environment was
not true microgravity (it's milligravity) you get
minor accelerations due to vibrations in the
spacecraft.
So he developed a device to remove these vibrations
and the environment in his equipment is of the order
of 10^-6 g.
He found that brownian motion is altered hugely by the
lack of vibrations from an external source. Mixing is
reduced by a factor of 3. A lot of what he was talking
about was too abstract to fully comprehend at the time
but it was fascinating so I read his paper and was
astounded.

Amazingly the temperature gradient at the surface of a
liquid in microgravity is much steeper than on earth.
Liquids are cooler at the surface because they lose
heat outwards but by losing most of your brownian
motion which would otherwise mix the outer and inner
layers it increases the temp gradiaent massively.
(convection is eliminated by microgravity and other
forms of convection due to surface tension are removed
in the experiment. These do not occur in small enough
droplets anyway)
Then I came accross one of his images of a glass bead
forming in microgravity. It's about 0.5mm across
(sound familiar?) and in thin section it has this
beautiful outer rim that I instantly thought "hmm!
I've seen that before".
I'm pretty convinced that nobody else has made this
connection. Meteoritics and brownian motion in
microgravity are pretty far apart in the library of
knowledge I'd have thought. I wondered if I could be
right.

Over the last couple of months I've tried to contact
this guy again with no sucess to ask for more details
of his experiments.
This is why I'm asking you lot for help on the
chondrule issue. I'd like to see some proper analysis
of the structure of the chondrule boundary. It's
likely that the similarity is coincidental but I'd
like to check anyway.
It's why I want to know the theory on the solar nebula
conditions. Too great a density would produce
vibrations which prevent this happening but I suspect
interplanetary vibrations, even that early on, at the
distances these things formed at from a protostar is
going to be unlikely to prevent chondritic glasses
forming the boundary they exhibit.

I personally think this is an elegant idea which does
away with a lot of the messy heating, cooling stuff.
The outer layer would form a nice insulating layer
which would then allow the interior of chondrules to
cool slowly and exhibit the structures we see. It
neatly requires chondrules to form first. Other stuff
would disrupt the pattern we see. The way I see it
they needn't take too long to form either.
But then, I'm probably not seeing it correctly. That's
why I need information.

I don't know enough yet about the birth of solar
systems to even guess at the implications of my idea
if it ever proved correct. I'd like to work on it and
prove SOMETHING, anything.

My mum always had aspirations of me becoming a
doctor...ahem.

Rob McCafferty

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

> jeez Bob,
>
> and all I was trying to do was to come up with a
> good
> excuse to personally examine that Krasnojarsk RSPOD
> Oct 15.
>
> You're just about ready to handle some of my
> asteroid
> and comet impact correspondence.
>
> Ed
>
> --- Rob McCafferty <rob_mccafferty_at_yahoo.com> wrote:
>
> > Hi list
> >
> > What I have ben able to find personally on
> chondrule
> > formation is rather sketchy.
> >
> > Even the otherwise comprehensive Encyclopedia of
> > Meteorites by O. Richard Norton seems to skim over
> > the
> > mechanism in a paragraph. It's almost as if there
> is
> > something which defies explanation and scientists
> > abhor that more than nature abhors a vacuum.
> >
> > The "slow cooling followed by a rapid quenching"
> > period is that which interests me most.
> >
> > I would dearly like to know where to find the most
> > up-to-date theories on chondrul formation. I know
> > about the R-R Lyrae heating, timescales and
> > frequecies
> > for newly forming stars. I need theory of
> > protostellar
> > nebula. Maybe Nebula density/stellar distance
> > formula.
> > The conditions in which and the timescale in which
> > these 0.1- 3mm chondules formed.
> >
> > Contact off list if you wish. I need this
> > information
> > to assist me with a theory I have, the information
> > for
> > which comes from branches of science so diverse,
> > that
> > their relevance has not been realised. It is only
> by
> > serendipity that I make the connection.
> > My thoughts will appear here first (though I will
> > ruthlessly hunt down and murder anyone who tries
> to
> > plagarise my theory, hehe)
> >
> > Rob McCafferty
> >
> >
> > --- Darren Garrison <cynapse_at_charter.net> wrote:
> >
> > > On Sat, 21 Oct 2006 16:41:48 -0700 (PDT), you
> > wrote:
> > >
> > > >> Chondrule textures depend on the extent of
> > > melting
> > > >> of the chondrule precursor- material when
> > cooling
> > >
> > > >> starts.
> > > >
> > > >Kind of begs the question - chodrules formed by
> > > >collision, which causes melt - consider if one
> > > started
> > > >from a steady molten state
> > > >
> > > >>If "viable nuclei"
> > > >
> > > >I wonder what these "viable nuclei" are? viable
> > > cystal
> > > >nuclei=Chondrules?
> > >
> > > How things appear to be (without trying to refer
> > to
> > > chemical/minerological
> > > details that are beyond my level of knowledge)
> is
> > > that what became chondrules
> > > started out as "fluff" that slowly accumulated
> > from
> > > the solar nebula, like you
> > > mentioned earlier. I imagine something like
> > > snowflakes, or dust-bunnies.
> > > Something fragile and irregular filled with
> empty
> > > spaces. Then, something (and
> > > there is no consensus on what that "something"
> > was)
> > > heated those
> > > dust-bunnies/snowflakes up to the point where
> they
> > > melted-- and in a
> > > microgravity environment surface tension pulled
> > them
> > > into little spheres. The
> > > "viable nuclei" means parts of that original
> fluff
> > > that didn't fully melt and
> > > became seeds for the new minerals to grow on.
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Received on Sun 22 Oct 2006 10:25:16 AM PDT