[meteorite-list] Fwd: Peter's Stunning New Eucrite NWA 5230 paired with the Hupés' NWA 4883

From: mexicodoug at aim.com <mexicodoug_at_meteoritecentral.com>
Date: Fri, 15 Aug 2008 01:24:28 -0400
Message-ID: <8CACCAE5064E174-C00-6F4_at_WEBMAIL-MC04.sysops.aol.com>

Jason wrote:

"And one can't forget meteorites like Vaca Muerta, which is full of
Eucritic clasts (to a much higher degree than would suggest mere
impact-injected fragments)...."

Hi Jason,

At one point Nakhla was a Eucrite. Dho 007 is another can of worms,
that is quite young in a CRE sense. Unless I don't follow your
argument, putting Vaca Muerta in the "mix" is just confusing the issue
along with voicing the genetic "eucritic" POTENTIAL misnomer. Oxygen
isotopes are one convenient measurement, as were consistent
measurements of Iron isotopes. -but are ALL other indicators as
convincing?

If you would like to include these Vaca Muerta "eucritic" inclusions to
try to refute Mike's statements, which you further attempt to cast
doubt in unrelated comments saying:

"Thus, I think it's rather safe to say that 4 Vesta *could* be the
parent body for both types of meteorites...not to
say that it is, but it could be."

(The word both bothers me in this statement, though if you had said
"either" I personally wouldn't object as strongly)

I ca rest if we first rub in and quack (1993) a little about the
landmark result that is often quoted of 133 million years exposure for
the 'Vaca Muerta' meteoroid. If we excavate from the same crater you
reference generously - allowing for the possibility it be the source of
the HED's: we have a group of less than 60 million years exposure
br
eaking loose 70 million years after the ground below it ... kindly
help me connect the dots as your general logic seems ok but somewhat
all over the map.

That said, I definitely agree that the dynamics of how this actually
shook out can be much more complicated than Mike's strawman. But - to
be very fair, his strawman just seems to be still very alive and
kicking to me to be this critical without giving it a more serious
candidacy. We can always do a little arm waving referencing the
problems of deconvoluting a complex past, but it would all be a bigger,
more complicated conjecture, perhaps on equal footing in plausibility
with Mike's general thoughts, but by definition more complex. There is
a lot of great science waiting to be done here. Hopefully, DAWN will
arrive and not send the remarkable Vesta story back to the drawing
board.
Best wishes,
Doug






-----Original Message-----
From: Jason Utas <meteoritekid at gmail.com>
To: Michael Fowler <mqfowler at mac.com>; Meteorite-list
<meteorite-list at meteoritecentral.com>
Sent: Thu, 14 Aug 2008 6:14 pm
Subject: Re: [meteorite-list] Fwd: Peter's Stunning New Eucrite NWA
5230 paired with the Hup?s' NWA 4883



Hola Mike, All,

>As for the logic, I've never heard anyone say that finding a
carbonaceous clast
in an L class meteorite means that the the two parent bodies are
related. It
just means that at some point a fragment20of one parent body collided
with
another. If such clasts were common, then one might infer that the two
bodies
at some point in space and time were in relative proximity to each
other.

Fair enough, but when one looks at the entire picture - especially
meteorites like Dhofar 007 which are structurally Eucritic, but
isotopically (oxygen isotopes) identical to Mesosiderites...the
evidence mounts. And one can't forget meteorites like Vaca Muerta,
which is full of Eucritic clasts (to a much higher degree than would
suggest mere impact-injected fragments)....well, a few small clasts is
one thing, but there's something bigger than sporadic collisions going
on.

>As far as the meso's and HED's having a common parent body, that is
nearly
impossible, especially if you believe that Vesta is the Parent Body of
the
HED's.

Asteroid 4 Vesta is a spectroscopic match for the HED's. That said, I
don't know if there are any other spectroscopic matches
around...anyone have a better idea?
Even so, 4 Vesta's link to HED's hasn't been proven beyond a doubt
yet, so your point is moot. The possibility exists that the parent
body for HED's has simply been completely destroyed, and that's very
possible...

>Consider that Vesta appears to be an intact body, with a core, mantle
and
crust. The HED's sample different depths of the crust. Where is there
room for
the Meso Parent Body? The MPB (Meso Parent Body) was completely=2
0
destroyed by
the collision that mixed the iron core with the basaltic crust. Vesta
is
intact, the MPB has been destroyed. Therefore they can't be the same
Parent
Body.

Hmmm....take a look at this article:

http://www.planetary.org/explore/topics/asteroids_and_comets/vesta.html

"At some point in its past, Vesta suffered a huge impact which left a
crater nearly as large as the asteroid itself (at 460 kilometers or
290 miles in diameter, it is 80 percent the width of Vesta). The
crater is so deep that it exposes materials from deep in Vesta's
mantle."

Deep mantle material could be potentially very rich in iron,
especially with such a gravitationally weak body (less gravity means
less consolidated core). Thus, I think it's rather safe to say that 4
Vesta *could* be the parent body for both types of meteorites...not to
say that it is, but it could be.

Jason



On Thu, Aug 14, 2008 at 1:51 PM, Michael Fowler <mqfowler at mac.com>
wrote:
>
>
>
> Resent, don't think this went through the first time.
>
> Mike
>
>
>> http://www.marmet-meteorites.com/id41.html
>>
>> Peter writes:
>>
>> "It's NWA 5230, a maskelynite rich polymict eucrite breccia! Analized
>> by Tony Irwing, who writes: We made a discovery of a small
mesodiderite
>> clast in it. This is an important observation that adds to the
growing
>> evidence
>> for a common parent body for HEDDO and MESO meteorites! NWA 52300D
>> is paired with NWA 4883. TKW is 909 g."
>
>
> I must disagree both with the above logic, and the rush to join the
> mesosiderite and HED parent bodies.
>
> As for the logic, I've never heard anyone say that finding a
carbonaceous
> clast in an L class meteorite means that the the two parent bodies are
> related. It just means that at some point a fragment of one parent
body
> collided with another. If such clasts were common, then one might
infer
> that the two bodies at some point in space and time were in relative
> proximity to each other.
>
> As far as the meso's and HED's having a common parent body, that is
nearly
> impossible, especially if you believe that Vesta is the Parent Body
of the
> HED's. Consider that Vesta appears to be an intact body, with a core,
> mantle and crust. The HED's sample different depths of the crust.
Where is
> there room for the Meso Parent Body? The MPB (Meso Parent Body) was
> completely destroyed by the collision that mixed the iron core with
the
> basaltic crust.
>
> Vesta is intact, the MPB has been destroyed. Therefore they can't be
the
> same Parent Body.
>
> Mike Fowler
> Chicago
>
>
> ______________________________________________
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> Meteorite-list at meteoritecentral.com
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Received on Fri 15 Aug 2008 01:24:28 AM PDT