[meteorite-list] Is 3He a cometary marker?

[Mexicodoug]

Hi Ed, Dr. Bunch,

Not quite sure I follow what you mean by a long period comet becoming a 
short period comet and apparently circulating for millions of years. I 
thought such comet lifetimes are significantly less than that and if 
the literature I saw is to be believed, along the P-Tr unconformity, a 
two million year interval was hypothesized based on 3-He findings, and 
more recently geologically . Farley, posthumous Shoemaker, et al also 
found about 2 million years of a hypothetical comet swarm at the Eocene 
Chesapeake Bay crater time period.

It is hard for me to imagine a comet accumulating much of anything from 
the Sun as you conjecture, since it is losing mass very quickly with 
each orbit, though perhaps meteoroid streams could. I think 3-He is 
certainly considered an ET marker, especially for small particles of a 
cometary nature, bucky balls and the like ... In any case, I think your 
questions would be excellent to pose to Dr. Ted Bunch if he has a 
moment, a list member who has quite a a bit more experience than me in 
this subject ;-), and probably knows the authors you are question about 
personally...

Best wishes,
Doug




-----Original Message-----
From: E.P. Grondine <epgrondine at yahoo.com>
To: meteorite-list at meteoritecentral.com
Sent: Tue, 26 May 2009 10:04 pm
Subject: [meteorite-list] Is 3He a cometary marker?



Hi Doug, all -

Becker and Poreda's work with 3He in fullerenes at the PT boundary has 
never
been duplicated in any lab. I don't know why this is, but I have a 
question: Is
3He a cometary marker?

This should be an easy question to answer, simply by grabbing dust 
samples
during any meteor shower and analyzing them.

I also wonder about 3He capture when a Long Period Comet becomes a 
Short Period
Comet. It would seem to me that if it were in the inner solar system 
long enough
before accreting with another body (say 6 or 7 million years or so), 
then the
comet would accumulate 3He from the Sun, particularly on close passes 
near to
it.

E.P. Grondine
Man and Impact in the Americas



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