[meteorite-list] Meteorite Questions

From: Sterling K. Webb <sterling_k_webb_at_meteoritecentral.com>
Date: Thu, 30 Aug 2007 00:43:00 -0500
Message-ID: <052201c7eac8$a0f8d7d0$2850e146_at_ATARIENGINE>

Hi, All,

    This is the notion of "meteoroid streams" (as opposed
to the "meteor streams" of a comet. Meteoroid streams would
have an asteroidal origin. This idea was a big back-and-forth
controversy in the XIXth century. One problem is that the term
"meteoroid streams" is now being used for both cometary
AND asteroidal streams. Sloppy usage.

    There ARE asteroidal non-cometary meteoroid streams:
http://www.lpi.usra.edu/meetings/lpsc2007/pdf/2038.pdf
and of course there could be many more if they are composed
of objects too small to be easily detected (yet).

    Venus has a convergence of both kind of streams, so
apparently Venus gets plenty of meteorites (if they can survive
the hellacious trip through its atmosphere... I don't think so.)
http://www.ingentaconnect.com/content/bsc/mnr/1998/00000294/00000002/art00009

    There are nine "cometary" meteoroid streams that are
actually associated with an asteroid instead of a comet,
unless of course, that asteroid is a "dead" comet... The
best known of the nine is the Geminids and the asteroid
3200 Phaethon.
http://www.ingentaconnect.com/content/klu/moon/2005/00000095/F0040001/00002243

    A chemical argument that H chondrites come from "meteoroid
streams" and that they can be grouped by what "stream" they
come from and that the composition of streams changes only
very slowly over time:
http://www.agu.org/pubs/crossref/1997/97JE00137.shtml

    Obviously, no gravitational influence great enough to separate
two adjacent rocks in a short period of time could exist for a
"meteoroid stream," or pretty soon --- No Stream! The key to
having meteoroid streams at all is that the Universe leaves them
alone and does not mess with them...


Sterling K. Webb
------------------------------------------------------------------------
----- Original Message -----
From: "Maria Haas" <dragonsoup at msn.com>
To: "TheMeteorite-list" <meteorite-list at meteoritecentral.com>
Cc: "Walter Branch" <waltbranch at bellsouth.net>
Sent: Thursday, August 30, 2007 2:53 AM
Subject: Re: [meteorite-list] Meteorite Questions


Walter asked:

> 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.


>From Robert Haag's 2003 Collection of Meteorites, Page 89:
"Saint Severin (large at top) 3.1 kilos, and Ensisheim (small, bottom) 85
grams.
Amphoterite chondrites (LL6) 20% total iron. These meteorites are both
historically and scientifically important - while they fell over 500 years
apart, they landed within 100 miles of one another and are chemically and
visually identical. In fact, when placed side by side, they appear to be
from one contiguous piece. Saint Severin fell June 6, 1966 and Ensisheim
fell November 16, 1492. Obviously they come from the same asteroid parent
body."


To expand on Walter's question -- whether they travel in streams or rubble
piles, any idea how these two could fall so many years apart and within such
a close proximity of each other?

Are there others that have fallen "together" like Saint Severin and
Ensisheim?

Maria

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Received on Thu 30 Aug 2007 01:43:00 AM PDT