[meteorite-list] Just Another Question

From: mexicodoug at aim.com <mexicodoug_at_meteoritecentral.com>
Date: Sat, 31 May 2008 14:28:56 -0400
Message-ID: <8CA916352256D33-C8C-372F_at_webmail-mf03.sysops.aol.com>

Just going backwards in this and noticed Dr. Grossman said:

Alan Rubin and I grappled with this issue in our article in Meteorite!
10 years ago ... definition that would exclude things like tektites
 from being called meteorites ... we would say that a terrestrial
meteorite would be an object ejected from earth by natural causes
(i.e., by impact), which entered an orbit around the sun and later was
re-accreted by the earth. ... Nothing like this has ever been found.
Its distinguishing properties might be a fusion crust ...

I liked that useage of the word, "might" regarding fusion crust, and
the exclusion of tektites. Personally, I'd be looking for things that
look just like tektites but with cosmic ray evidence. Tektites do not
have an easily identifyable fusion crust, but in the case of something
that condensed in its own orbit around the Sun, procedent from a very
recent impact on Earth, they might re-melt on the surfaces years later
on re-entry and sculpt an interesting layer we "might" call fusion
crust by a stretch of the definition of fusion crust. While there is a
lot to be said for the Peruvian event, I still think a Terrestrial
meteorite would more likely look a lot like a tektite. Comment?

Best wishes,
Doug



-----Original Message-----
From: Jeff Grossman <jgrossman at usgs.gov>
To: Meteorite-list at meteoritecentral.com
Sent: Fri, 30 May 2008 5:29 am
Subject: Re: [meteorite-list] Just Another Question


Alan Rubin and I grappled with this issue in our article in Meteorite!
10 years ago, "What is a meteorite? The pursuit of a comprehensive
definition." We wanted a definition that would exclude things like
tektites from being called meteorites. Our definition then said that,
to be called a meteorite, an object had to escape the dominant
gravitational influence of its parent body. In this case, we would say
that a terrestrial meteorite would be an object ejected from earth by
natural causes (i.e., by impact), which entered an orbit around the sun
and later was re-accreted by the earth.?
?
Nothing like this has ever been found. Its distinguishing properties
might be a fusion crust, evidence for cosmic-ray exposure in space, and
lithology that is completely exotic for its find location. Without an
exposure history (or being an observed fall) it would be a very tough
sell... a Wingstar.?
?
Jeff?
?
At 12:24 AM 5/30/2008, Pete Shugar wrote:?
>Hello list,?
>I've given this more than just a passing thought as I think this is >a
very intreguing question.?
>If an impactor smacks into the moon with enough energy, objects will
>be dislodged.?
>If they make it to earth intact, we have a luner meteorite.?
>Same goes for Mars and Astroid 4Vesta.?
>So,.....suppose we have a very high speed impactor that hits earth,
>and dislodges material that is now in orbit. If the material crosses
>Earth's orbit again, and survives to the surface of earth, would it
>be modified in it's appearance to the extent that it would be seen >as
a meteorite and not just another rock??
>Has anything ever been found that might be in this class of material??
>Would there be anything that would set it apart as a different
rock/meteorite??
>?
>Pete?
>______________________________________________?
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?
Dr. Jeffrey N. Grossman phone: (703) 648-6184?
US Geological Survey fax: (703) 648-6383?
954 National Center?
Reston, VA 20192, USA?
?
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Received on Sat 31 May 2008 02:28:56 PM PDT