[meteorite-list] NEW Plutonic Angrite - NWA 4590 "Tamassint"

From: Sterling K. Webb <sterling_k_webb_at_meteoritecentral.com>
Date: Fri, 13 Apr 2007 03:38:26 -0500
Message-ID: <011201c77da7$1b85ea40$862e4842_at_ATARIENGINE>

Hi, Adam, List,

    The real "clincher" for the Mars rocks actually
being Mars rocks is the isotope ratios of incorporated
atmospheric gases. It's a clincher because we have
the data from our probes to Mars, data produced
by direct contact and from measurements made on
the planet. Those ratios provide a unique "fingerprint"
of Mars. Nowhere else in the solar system has those
isotopes in those ratios. You find a rock with those
fingerprints all over it, so to speak, you know that
such a rock is a Mars rock. It's a QED, a Slam Dunk,
turn it over and it has "Made on Mars" stamped on
its bottom.

    Likewise, even though we've had much less science
produced by contact with Venus, its argon isotope
ratios are startling and unlike anywhere else. If you
or anybody finds a rock with argon ratios similar to,
or even close to, those odd proportions, you can slap
it down and say "Venus rock," and we will all nod our
heads and start wondering if we can afford the $42,000
per gram...

    But, as Rob pointed out, the crying shame is that
we only flew by Mercury with one probe, decades
ago, never went back, never followed up, never even
photographed the entire surface, and know little more
now than we did 40 years ago when we did that. No
one will ever demonstrate Mercurian origin of anything
without having some data from Mercury with which to
compare the putative stone. Nor should they.

    We simply don't know enough about Mercury to
be able to identify any rock as having come from there,
or not. We don't even know enough about Mercury to
be able to say whether they serve beer. If they do, I
guess that it will be, like Britain, warm beer, or maybe,
considering the 0.37 AU orbit, hot beer.

Sterling K. Webb
----- Original Message -----
From: "Adam Hupe" <raremeteorites at yahoo.com>
To: <meteorite-list at meteoritecentral.com>
Sent: Friday, April 13, 2007 2:48 AM
Subject: Re: [meteorite-list] NEW Plutonic Angrite - NWA 4590 "Tamassint"

Dear List,

I just want to express my views on this subject and
then tend to more pressing issues.

It is interesting to note that similar arguments were
presented when discussing SNCs. A lot of groups had a
hard time believing that these series of rocks
actually came from Mars. Now, you would be hard
pressed to find somebody that would argue that they
came from anywhere else.

As far as I know, a single argument discounting
Mercury as the origin for NWA 2999 was presented. This
argument makes assumptions based on NWA2999 being an
igneous rock. NWA 2999 was determined without a doubt
to be a metamorphic rock(interlocking grains with
triple junctions). Furthermore, formulas used to
describe igneous processes here on Earth were used to
describe a plutonic rock from a different planetary
body as far as I can surmise. I guess this would be
alright if the other planetary body was just like
Earth with the same gravity, atmospheric pressure,
water and so on. It would have been nice if the
authors of this paper actually took the time to
examine a piece NWA 2999. I don't think they have
ever seen a piece of this meteorite. All that would
have been required is to merely ask for a piece and
they would have been supplied.

As for it being too metal-rich, the metal was found to
be introduced by the impactor.

A great number of scientific heavyweights are listed
as authors and coauthors representing 100s of year of
combined experience so for now, they have my
attention. A List debate will not suffice to sway my
opinion one way or another. I think it best to keep
an open mind in regards to Mercury being the PB for
Angrites. Look what open minds did for the SNCs!

Save the Earth, It is the only planet that serves


--- David Weir <dgweir at earthlink.net> wrote:

> Hello Sterling and hopeful Hermean collectors,
> The angrites have FeO contents in the general range
> of ~25 wt%, so if
> they are from Mercury this does not conform to your
> inverse iron core
> ordering, unless the core of Mercury was not fully
> differentiated before
> the impact-related dissemination occurred. Some
> angrites like NWA 2999
> do contain too much iron to be consistent with
> representing a completely
> differentiated body. As for the stable orbit, the
> iron cores of early
> differentiated bodies which formed near Mercury and
> now stored in the
> inner asteroid belt is a good point, although I was
> thinking about
> possible Lagrange-like regions. Storage in the the
> inner asteroid belt
> is definitely more reasonable.
> For Rob, here is some CRE age info:
> The results of CRE age studies (Eugster et al.,
> 2002) utilizing
> cosmogenic nuclide data indicate that the CRE age of
> D'Orbigny (12.3
> +/-0.9 m.y.) is significantly different from that of
> other angrites
> studied: Sah 99555 (6.6 +/-0.8 m.y.), Asuka 881371
> (5.4 +/-0.7 m.y.),
> Angra dos Reis (55.5 +/-1.2 m.y.), LEW 86010 (17.6
> +/-1.0 m.y.), and LEW
> 87051 (~0.2 m.y.). All or most of these angrites
> represent unique
> ejection events on the angrite parent body. I don't
> have CRE data yet
> for the latest finds.
> David
> ______________________________________________
> Meteorite-list mailing list
> Meteorite-list at meteoritecentral.com

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Received on Fri 13 Apr 2007 04:38:26 AM PDT

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