[meteorite-list] Its official! NWA 6291 "The King ofAngrites"for sale - AD

From: Sterling K. Webb <sterling_k_webb_at_meteoritecentral.com>
Date: Thu, 22 Jul 2010 16:03:44 -0500
Message-ID: <97F800D050354F5B8B3E1C195325DDC5_at_ATARIENGINE2>

Martin, Jason, Shawn, &c.,

The fly or flaw in the ointment, the paper, and the
responses is an unspoken but apparently universal
assumption that every sizeable body in the solar
system currently resides at the same address where
it accreted originally.

What about a body that accretes in the 0.50 AU block,
then moves 'way up the street and out to the 2.35 AU
neighborhood? Like say, Vesta. Now, I'm not saying
Vesta did that, you know, fled from the 'hood and
moved to the suburbs... I just saying Vesta did not
form where it is.

No Way.

Models that "fit" Vesta propose a iron core of about
http://www.lpi.usra.edu/meetings/lpsc2010/pdf/2129.pdf
300 kilometers out of an original spherical body of
540 km. diameter. Such a body HAS to have accreted
much, much closer to the Sun. I repeat, No Way.

So, isotopic data that tell you where a body accreted
MIGHT tell you everything you need to know about the
place or it MIGHT tell you nothing of any use whatsoever.

Even the old notion about the distribution of iron cores
in the inner solar system is wrong. Decades ago, we
assumed bigger iron cores in close, getting smoothly
smaller as you moved out from the Sun. Then, we
discovered that Venus' core is proportionally much
smaller than the Earth's, and that Mars core is puny.

Then, when we moved to the theory of the Moon being
formed by a giant "impact," or graze, or embrace, all
the models said we had two cores -- our original core
and the core captured from the big proto-Moon. Mercury
too shows evidence of such a collision (although no
moon resulted).

All of a sudden, Venus and Mars have "normal" cores.
The Earth is cheating -- it's packing an extra halfcore
in its hip pocket, and Mercury has two cores-worth of
core. Venus and Mars that are normal respectable planets,
and Earth and Mercury are "core-snatchers."

A simple question like "what should a meteorite from
Mercury be like?" is not a simple question. First, if
Mercury suffered a giant impact early on, then its
present crust (and upper mantle and maybe more)
is derived from the impacting body. And that Big
Whacker accreted... where? Nearby? Faraway?
In-between?

Then, there is the case of a parent body of some
size blasted off the ORIGINAL primordial crust (and
mantle) of Mercury by the giant impact, finding a new
orbit, and providing enigmatic meteorites for the next
billions of years. That original Mercurian crust could
have been quite different from the present crust.

As Jason pointed out, there were a gaggle of large
differentiated bodies in the early system. I go with
the "hundreds" rather than 30-40; see the work by
SwRI that suggests 100+ of them from the inner
solar system ended up in the Asteroid zone. The
Zone is made up of "natives" and a horde of refugees,
which could have accreted pretty much anywhere
and will each have a unique formation history all
their own.

Present arguments are somewhat simple-minded.
It's going to take centuries to sort out the life history
of every body big enough to bother with.

It's going to be fun.


Sterling K. Webb
--------------------------------------------------------------------------------
----- Original Message -----
From: "Martin Altmann" <altmann at meteorite-martin.de>
To: <meteorite-list at meteoritecentral.com>
Sent: Thursday, July 22, 2010 6:00 AM
Subject: Re: [meteorite-list] Its official! NWA 6291 "The King
ofAngrites"for sale - AD


Huh, I found even a paper, which postulates, that the HEDs are from
Mercury
and the angrites from Venus....

http://www.lpi.usra.edu/meetings/otp2004/pdf/3012.pdf



;-)
Martin



-----Urspr?ngliche Nachricht-----
Von: meteorite-list-bounces at meteoritecentral.com
[mailto:meteorite-list-bounces at meteoritecentral.com] Im Auftrag von
Jason
Utas
Gesendet: Donnerstag, 22. Juli 2010 11:27
An: Shawn Alan; Meteorite-list; Adam Hupe
Betreff: Re: [meteorite-list] Its official! NWA 6291 "The King of
Angrites"for sale - AD

Shawn,
Well-said -
But I can't emphasize enough the fact that such large bodies existed
in large numbers in the early solar system. That much is obvious from
the large numbers of ungrouped (and grouped) differentiated
achondrites that we have in our collections here on earth, as well as
from all various types of iron meteorites, which represent the cores
of diffeentiated planetismals. All in all, we have meteorites that
suggest well over 30-40 such bodies in the early solar system, and
computer-run models in some cases suggest hundreds of such bodies.

http://www.ucmp.berkeley.edu/education/events/cowen1d.html

http://en.wikipedia.org/wiki/Formation_and_evolution_of_the_Solar_System#For
mation_of_planets

Note that wikipedia suggests 50-100 such bodies. I wouldn't usually
reference wikipedia for something like this, but see references 35-36
for the article - that's actually a decent estimate that's been backed
up by some serious work done by experts -- it's not just a crap
wikipedia reference.

So, angrites may be from Mercury. If we say that, regardless of their
composition and history, they just needed to be from a large
planetismal capable of some metamorphic activity, then we've got a
1/50 to 1/100 chance that angrites are, in fact, from Mercury.

The trouble is that their chemistry and age suggest that they're not
from Mercury.

I agree. They *might* be from Mercury. And yes, some smart people
have said that they *might* be from Mercury.
But it seems to me that this article is being deemed credible because
of its authors, and not because of what it actually says.

>I do not refute Melinda Hutson's article that was never peer reviewed
>and
contains several errors according to the classifying scientists. I
asked
scientists about the article and they stated, it is obvious that she
didn't
read
the original peer reviewed abstract carefully, even mistaking the type
of
petrology that was discussed using formulas that simply do not apply to
the
texture NWA 2999 exhibits.

I'd like to know what these errors were, and how the error might have
affected her conclusions. Perhaps Adam or someone else would be
willing to explain her errors and how they suggest that angrites are
actually from Mercury.

Seems like this is the perfect sort of topic for the list...

Regards,
Jason




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Received on Thu 22 Jul 2010 05:03:44 PM PDT