[meteorite-list] Meteorite Questions

[Walter Branch]

Hello Everyone,

I have had plenty of time recently to ponder things such as meteorites.  I 
am also alone at home at present and am bored.  Would some kind, 
more-knowledgeable-than-me soul help me with some meteoritical questions.

For example, why does the rim of meteor crater appear "squared" in some 
photos, while in others it appears very round?  Perspective?  Lighting? 
Extremely highly localized tectonic shifting (back and forth)?

Also, why is Tatahouine so green? Olivine? Krylon?

I am looking at a slice of NWA 4664 right now (thank you Eric Olson) and I 
don't see any much green.  Maybe that one is a bad example because NWA 4664 
doesn't even look like at Diogenite!

Also, I have read that some meteoroids travel through space in streams and 
impact the Earth simultaneously (i.e., they have already broken up before 
they hit the Earth's atmosphere).  How can this be?  I would think that once 
a meteoroid has broken in space (most likely due to impact), minute 
deviations of the individual pieces in the initial trajectory would 
translate into ever increasing deviations in the individual piece's 
trajectory, over time.  Unless two pieces were traveling in EXACTLY parallel 
lines, over time the pieces would be widely dispersed in space.

Remember comet Shoemaker-Levy 9?  It was broken apart by gravitational 
forces from Jupiter only a year prior to impact, yet by the time it had 
encountered the Jovian atmosphere the separation between the pieces was 
wider than the diameter of the Earth!  After only a year.

Traveling over eons to make it to the inner solar system, how can a 
meteoroid stream stay intact enough to cause a tiny strewnfield on the 
Earth? I would not think that the Earth's gravitational field would be 
strong enough to do what Jupiter did.

Also, I know I have asked this before but I still don't understand how 
researchers can determine cosmic ray exposure ages for a meteorite which 
ablated a significant portion of the material that absorbed most of the 
cosmic rays and which may have fragmented in flight through the Earth's 
atmosphere.

Anyone?

-Walter Branch
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