From: baalke@kelvin.jpl.nasa.gov (Ron Baalke)
Newsgroups: sci.space,sci.astro,alt.sci.planetary
Subject: Re: Cheap Mars Rocks (was Re: Moon Dust For Sale)
Date: 9 Jan 1993 08:30 UT
Organization: Jet Propulsion Laboratory
Distribution: world
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In article <1993Jan9.041013.27969@siemens.com>, aad@siemens.com (Anthony Datri) writes...
> 
>>To get the Mars rock I'm talking of down to earth didn't cost a single cent,
>>by the way. The 18kg SNC-meteorit simply fell out of the sky in October, 1962
>>near Zagami rock in Nigeria.
> 
>I must admit some skepticism wrt meteorites that are claimed to have been
>ejected from Luna and Mars.

Most of the lunar meteorites have been recovered from the Antarctic and
have been compared with the Apollo moon rocks, and they match up very well.
Correlating the SNC meteorites from Mars is on weaker ground, but there
is still evidence that they may very well have come from there.  Last year,
analysis of water from the SNC meteorites provided a stronger case on to
their origin:

RELEASE:  92-35

METEORITES' WATER PROVIDES CLUE TO RED PLANET'S PAST
March 13, 1992

	A single drop of water rarely causes excitement in the scientific
community, but a few milligrams of liquid extracted from a meteorite may
have started to answer one of the great mysteries of planetary science.

	Dr. Everett Gibson of NASA's Johnson Space Center (JSC), Houston,
Planetary Sciences Branch; Dr. Haraldur Karlsson, formerly a National
Research Council postdoctoral fellow at JSC; and scientists at the University
of Chicago have analyzed drops of water extracted from several meteorites
believed to have come from Mars and have concluded that the oxygen
isotopes in the water were extraterrestrial.

	Photographs returned to Earth from the Mariner 9 and Viking
spacecraft show features that suggest Mars once may have had a water-rich
atmosphere and flowing water on its surface.  Sometime in its history,
however, most of the water apparently disappeared, leaving only minute
amounts of vapor in the atmosphere.

	Through the years, several meteorites have been collected on Earth
that scientists have identified as Martian by comparing them to information
gleaned by the Viking spacecraft.  Six of these meteorites were used in the
water extraction procedure.

	Gibson said the meteorites were heated in steps in a small vacuum
system at JSC to extract trace amounts of water.  The water samples were
hand-carried to the University of Chicago for analysis of oxygen isotopes.
Although the water droplets were less than 1/64ths of an inch in diameter,
it was enough to do the analysis.

	The analysis determined that the oxygen isotopes in the water were
different from the oxygen isotopes in the silicate portion of the meteorites.
In other words, the water had a different parent source than the oxygen in
the silicate minerals in the meteorites.  That parent source could have been
the Martian atmosphere, an ancient Martian ocean or even a comet that
impacted the planet, Gibson said.

	The lack of homogeneous oxygen isotopes on Mars supports the theory
that Mars does not have plate tectonics.  If such a process had been active
on Mars, the oxygen isotopes would have been homogenized as they are on
Earth.
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    /_ /|  /____/ \  /_ /|     Ron Baalke         | baalke@kelvin.jpl.nasa.gov
    | | | |  __ \ /| | | |     Jet Propulsion Lab |
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