[meteorite-list] Re: Any Meteorites of Earth Origin?

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu Apr 22 09:47:10 2004
Message-ID: <200111122104.NAA07117_at_zagami.jpl.nasa.gov>

>In a personal communication with Paul Warren of UCLA,
>he explained to me the reason that we have Martian and
>lunar meteorites, but not "terrestrial meteorites", is
>because of the larger size/gravity of Earth, and the
>energy necessary to reach escape velocity is more than
>enough to, if not vaporize any ejecta, at least melt
>it all and solidify as a glass (read tektite).

Back in the 1970's, similar arguments were made
for Mars meteorites. It was later discovered that
a large impactor hitting Mars at a shallow angle could
eject Martian material into space without melting it.
Admittedly, it is harder to eject material from Earth's
surface due to its larger size and thicker atmosphere.
But I wouldn't rule out the possibility just yet.

Also, take a close look at the leading theory on how the Moon formed.
The theory says that early in the solar system's history,
an object the size of Mars had impacted Earth. A lot of material
was ejected into space, and a large portion of this material
coalesced to form our Moon. The bulk composition of the Moon is not
vaporized material, so if this theory is correct, then here's one
example where Earth material can be ejected into space without
necessarily being melted down. In fact, the impact event that
created the Moon probably ejected a lot of material that escaped
both the Earth's and Moon's gravity.

Ron Baalke
Received on Mon 12 Nov 2001 04:04:26 PM PST