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Re: Carbonates and CI Chondrites
Hello Jim,
Thanks for your reply about Orgueil and the sun. Also, thank you (your
wife, actually) for providing a translation of the Chinese article on the
Juancheng fall. When I read it, I once again thought of the power of this
global communication medium we are all playing with.
One other thing, you have an excellent collection of scanned meteorite
pictures on your site. In a prior posting, you mentioned you scanning
technique. It does provide a clear and (I assume) color-accurate image. The
only problem I notice is that the viewer-perspective is not one often found
in nature. The viewer-perspective is an overhead view or underside view
since you are using a scanner. From a clinical or scientific point of view,
it makes little or no difference, but from an artistic angle, there is
little image perspective since the meteorite is in a position with no up,
down, left, or right, and the shadowing surrounds the specimen since the
light source moves as the image is being made.
On the other hand, your images have gone through far fewer processes before
being digitally imaged, and through each process, the image is degraded
slightly i.e. through camera lens to film, through film through enlarger
lens to paper, from paper through scanner glass to the scanner's imaging
device, to output on a computer screen. The more one can reduce the number
of steps, the better the image.
Oh, I almost forgot, we were on the topic of Orgueil:
RE:
"If one ignores the gases (which we would not expect to find in
chondrites) and then plots the atomic ratios with respect to silicon
[there follows a plot of Ti, K, P, Na, Ni, Ca, Al, Fe, Si, Mg, and S]
there is precise agreement between Orgueil Chondrites and the Sun."
and
"... as long as we restrict the comparison to elements that remain
solid to temperatures of a few hundred degrees Celsius, chondrites in
general and one variety in particular have almost solar compositions."
Before the aqueous metamorphosis of Orgueil, did it ever have chondrules?
In other words, if Orgueil has metamorphosed from a type 3 to a type 1
(according to figure 2.10 in McSween's Meteorites and their Parent
Planets), shouldn't the type 3 chondrites (or their unmetamorphosed
chondrules) represent an even more primitive material?
Allende is a CV3 and is credited with having pre-solar material, or
material from the situation that was present before the formation of our
sun, or the material our sun is made from. Or as Norton (RFS, 1994) puts
it "suggest that some material forming the CAIs [calcium-aluminum
inclusions] came from preexisting interstellar grains that mixed with the
forming solar nebula." Is this pre-solar material in the form of CAIs
related to chondrules? Or did the matrix material capture (or build-up
around) both the chondrules and CAIs found in Allende? Or another
possibility, i.e. asteroid impacts combining materials?
I've read that many of the spectral patterns from asteroids actually match
the fingerprint of carbonaceous chondrites, yet few of the recovered
meteorites are CCs. If this abundance of CC material in space is the case,
then why are there not more CCs falling to earth?
I know I have put several (possibly unrelated) questions together in this
posting, but in order to put together the current known picture of
Orgueil's formation to use as a reference, I need to get its parts and
their relationship under control before moving onto other questions
including those about biological orgainics.
Sincerely curious,
Martin
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