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Re: Extra-solar material - comets

Hi Walter, Steve, and list,

It is a problem determining if something is coming from ouside our solar
system.  In studying the elements manufactured in outer space may be
where the clue is.  I would suspect that there would be a way to
determine this by measuring the amount of lithium in the sample, whether
it be meteorite or cometary.

Lithium is the third and last primordial element, after hydrogen and
helium, created in the Big Bang from fusion of hydrogen atoms.  The
lesser form (lithium-6, which constituted about 8% of the total) is
created in interstellar space by high speed collisions, when hydrogen
and helium nuclei crash into, and break apart, nuclei of carbon,
nitrogen, and oxygen.  These high speeds are usually produced in
supernovae.

Even though lithium is not significantly manufactured in stars as it is
not the end product of a major energy-generating fusion chain,  it is
used by astronomers to determine the star's age, acting much as a
clock.  Through this medium, it might be possible to determine
extrasolar system origin if the lithium level does not match our sun's.
Furthermore, it might even be possible to determine the age of the star
or planetary solar system from which it originated.

The subject of cosmic chemistry is very complex, and other methods could
very well be available along the same line.
                                                               Best,
                                                               Sarah
Kennedy
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