April 26, 2002
Greetings Meteorite Enthusiasts!
With the startling news announced by European Fireball
researchers in regard to the EN060402 bolide being
linked with the Pribram chondrite, fellow enthusiasts
on the Meteorite-list are likewise trying to make
"connections". However, I must say something that
may not have been considered. When trying to discover
a "meteorite" stream (meteoroid is the better term
here) we should not just consider or try to link
meteorite falls of only one distinct type with each
other. In reality, the composition of such a stream
composed of asteroid matter is quite likely not to be
homogenous! Dr. Pavel Spurny in his history making
e-mail had this little footnote to add:
"Finally, from the perfect similarity of both
heliocentric orbits we can predicate, that both
bodies had also the same composition and therefore we
can expect that meteorites produced by the April 6
fireball are H5 ordinary chondrites."
Astounding! I was intrigued that such a bold
statement was made, especially in such a mysterious
and sparsely understood whelm. However, in this case,
I believe the logic which drew the conclusion should
be revised. Just because the orbital data and/or
fireball information of both meteorite falls are so
similar doesn't mean that they are one in the same
meteorite, petrologic type and all! Asteroids almost
undoubtedly vary in overall composition as one nears
the core, which does of course assume we are talking
about a good sized asteroid body to begin with or a
big fragment from such. With the discovery of so
many asteroid moon systems recently, we again should
not be so certain that the two linked meteorite falls
have almost equal compositions. For all we know these
asteroid moons could form a hefty percentage of a
rocky meteoroid stream, ones with slight petrologic
and composition differences or entirely different
classes! Gravitational pulls by our planet could be
prying them loose from the "mother ship" asteroid
during close encounters. As a result, the behavior of
such a stream could be noticeably different from that
of a normal cometary meteoroid stream. Something else
to keep in mind.
In conclusion, chondrites of different petrologic
types (or possibly even meteorites of different
classes) should not necessarily be excluded when
trying to identify a date(s) that a possible meteoroid
swarm is encountering Earth. Also, EN060402 does not
necessarily have to be an H5 chondrite as is Pribram
when one "digs" more deeply into the compositional
nature of asteroids. Lastly, the behavior of an
asteroid meteoroid stream may involve new methods of
sending material to Earth.
All the above is my personal slant and I am open to
all comments on this matter. Please correct me for
any possible errors.
Long strewn fields!
Mark Fox
Newaygo, MI USA
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