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 <[email protected]>
To: [email protected]
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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