[meteorite-list] Re: Earth originating meteorites

From: Robert Verish <bolidechaser_at_meteoritecentral.com>
Date: Thu Apr 22 09:42:02 2004
Message-ID: <20010122202455.63657.qmail_at_web10412.mail.yahoo.com>

Kelly,

You have made a good point. A fusion crusted rock
with "no radioactivity" may actually be evidence for
an Earth meteorite. (This is where this discussion
dove-tails with the Takysie Lake thread.)

Here's the problem. The energy necessary to launch an
Earth rock (during an impact) into space - far enough
so that it can stay in space over 10,000 years before
Earth's gravity sweeps it back up - is more than
enough to either melt it or vaporize it completely.
Those Earth rocks which survive ejection without
melting will be the first to be "swept up" by Earth's
gravity, and consequently, have little or no cosmic
ray exposure.

Another problem, there are very few impact events
younger than 10,000-20,000 years that were large
enough to eject Earth rock into space, so we're
probably not going to find any freshly crusted earth
meteorites. If we do find one, it will probably be
re-terrestrialized (hey, I think I just invented a new
word;-).

This may be why we haven't found/recognized one, yet.

Would appreciate reading your comments or opinions,
Bob V.

--__--__--

Message: 3
Date: Sun, 21 Jan 2001 22:30:44 -0600
From: Kelly Webb <kelly_at_bhil.com>
To: v-nord_at_excite.com

Subject: Re: [meteorite-list] Concerning Eath
originating meteorites


v-nord_at_excite.com wrote:

> I was down with the Antarctic Search for Meteorites
team. The team always picks up any unusual rock, even
if they aren't sure it is a meteorite. A terrestrial
meteorite would be collected as long as there was some

unusual property associated with it, such as fusion
crust or visible shock damage.
> Indeed, two years age they returned two samples that
turned out to be just unusual mudstones. Counting in
a low-level gamma-ray counting facility showed that
these samples contained no radioactivity caused by
exposure to cosmic-rays in space, and thus the rocks
were never in space.
>

Kelly Webb <kelly_at_bhil.com> wrote:
    The extent of evidence of cosmic ray exposure
would depend on the duration of the extraterrestrial
exposure time. Times of less than perhaps ten thousand
years would be essentially undetectable.

Kelly Webb






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Received on Mon 22 Jan 2001 03:24:55 PM PST