[meteorite-list] NWA 5400: Earth-Related Meteorite

From: Sterling K. Webb <sterling_k_webb_at_meteoritecentral.com>
Date: Thu, 10 Jun 2010 01:16:11 -0500
Message-ID: <379558B9AFBB4F1EBC1CDCC6AD5E9A1E_at_ATARIENGINE2>

Hi, List,

The theoretically possible origins of NWA are specific:
http://www.lpi.usra.edu/meetings/lpsc2009/pdf/2332.pdf
   "Alternative possibilities are that the new specimen
is (a) a terrene meteorite, (b) a Theian meteorite, or
(c) a meteorite related to another former differentiated
body accreted near Earth... The very different Fe/Mn
ratios in olivine and pyroxenes set NWA 5400 apart
from any known lunar rock, as well as any modern
terrestrial rock from Earth's crust or shallow mantle
(especially given the presence of accessory FeNi metal).
In texture, mineralogy and mineral compositions, NWA
5400 resembles some brachinites, but those ancient
achondrites have very different oxygen isotope compositions...
The giant collision of Theia with proto-Earth (or collisions
involving other Earth-like bodies) may have resulted in
the ejection of some asteroid-sized fragments of one or
both colliding bodies into orbits that precluded their
reaccretion to Earth or Moon. Some such spalled
fragments could have been (1) accreted to or captured
as satellites by other extant planets, (2) captured by
the Sun, or (3) trapped within the main asteroid belt.
In the last case, such bodies could be targets for very
recent impacts and collisions, and delivery of material
as meteorites to Earth."

    Specific in that it could only be a "terrene" meteorite
if it came from the Earth BEFORE it collided with Theia
(the Mars-sized future Moon). It's not a chip of Earth
from the last 4.4 billion years.

    Or it could be a "Theian" meteorite from BEFORE Theia
collided with the Pre-Moon Earth. That would make it
OLDER than the collision.

    Or it could be from a third (or fourth or fifth...) body
that accreted in the Earth-Theia orbit BEFORE the
Pre-Moon Earth - Theia collision and was ejected from
the Earth orbit by the new more-massive Earth.

    Or it could be from an asteroidal fragment OF that
collision which was batted out into the Belt (I call this
the "long fly ball" theory) from which this is a chip
that got here the way most meteorites do.

    Or it could be from a large asteroid fragment of that
collision that was captured by Venus as a retrograde
moon which spiraled in and broke up but this piece
is from a fragment that escaped re-entry to Venus and
was cast onto an asteroidal orbit that supplies a meteorite
rarely.

    It has NOT wandered around until now when it landed
on the modern Earth.

    Or...

    Please, I'm getting dizzy.

    Can it be made simple? OK, every other non-lunar,
non-planetary meteorite we know of has been shown to
be or is presumed to come from a smallish body whose orbit
takes it through or places it in the Asteroid Belt. The odds
are pretty good that this one did too. It got here the way
almost all meteorites do.

    Dump the thought that this one stone wandered around
for 4.4 billion years and then hit the Earth. The odds against
that simple story are colossally high. "Astronomical" is too
small to describe the odds against that notion.

    On the other hand, we have 100,000 meteorites AND
this one. There must be something unusual about its
life story, worthy of an interview by Oprah or Ted Koppel.

    It could have come from a very small asteroid
that does not often send a rock to Earth, or an asteroid
that is placed in an unusual orbit with characteristics
that make Earth-delivery difficult and hence rare.

    Another thing to bear in mind. Our sample of
100,000 meteorites is NOT a sample of 4.5 billion
years of time. It is a sample of the meteorites that
have made it to Earth in the last 100,000 years
or less (except for a small handful of Antarctic ones
that might be 370,000 years on Earth or more).

    Yes, we have "fossil meteorites" and traces that are
too terrestrialized to tell us much except that meteorites
(and asteroids) have always fallen to Earth and always will.
But our present collection is a thin slice of time, of the
present parent-body supply, a supply which almost
certainly changes over long periods of time.

    Thousands of NWA 5400-type meteorites could have
fallen to Earth over millions (and billions) of years and
we would never know it unless one fell in the last fifty
or a hundred thousand years.

    ONE did.

    The problem is identified nicely by the authors of the
second LPI paper Greg mentioned -- they called it the
"storage" problem. Where have you been hiding, little
felllah, for all this time?

    My money's on the Asteroid Belt.


Sterling K. Webb
--------------------------------------------------------------------------
----- Original Message -----
From: "Richard Kowalski" <damoclid at yahoo.com>
To: "Greg Hupe" <gmhupe at htn.net>; <meteorite-list at meteoritecentral.com>;
"Stuart McDaniel - Action Shooting Supply"
<actionshooting at carolina.rr.com>
Sent: Wednesday, June 09, 2010 10:34 PM
Subject: Re: [meteorite-list] NWA 5400: Earth-Related Meteorite


>I don't want to speak for Greg, but yes, that is one possible origin.
> It could be from the proto-Earth, the Mars sized impactor that stuck
> the proto-Earth, (this is the impact that formed the moon) or the
> remnants of that event.
>
> No matter which, it is an awesomely exciting meteorite!
>
> --
> Richard Kowalski
> Full Moon Photography
> IMCA #1081
>
>
> --- On Wed, 6/9/10, Stuart McDaniel - Action Shooting Supply
> <actionshooting at carolina.rr.com> wrote:
>
>> From: Stuart McDaniel - Action Shooting Supply
>> <actionshooting at carolina.rr.com>
>> Subject: Re: [meteorite-list] NWA 5400: Earth-Related Meteorite
>> To: "Greg Hupe" <gmhupe at htn.net>, meteorite-list at meteoritecentral.com
>> Date: Wednesday, June 9, 2010, 5:30 PM
>> So this could be a piece of Earth
>> before Earth was Earth??
>>
>>
>> Stuart McDaniel
>> Lawndale, NC
>> Secr., CCAS
>> ----- Original Message ----- From: "Greg Hupe" <gmhupe at htn.net>
>> To: <meteorite-list at meteoritecentral.com>
>> Sent: Tuesday, June 08, 2010 7:31 PM
>> Subject: [meteorite-list] NWA 5400: Earth-Related
>> Meteorite
>>
>>
>> > Dear List Members,
>> >
>> > I would like to announce an important new meteorite
>> that has been under intense analysis over the last two years
>> by a select group of scientists from around the world...
>> >
>> > NWA 5400: Earth-Related Ungrouped Meteorite
>> >
>> >
>> > Northwest Africa 5400 may be a sample from a large
>> asteroid or dwarf planet, which accreted in the early solar
>> nebula in the vicinity of proto-Earth or Theia. NWA 5400 has
>> oxygen isotope ratios indistinguishable from those of rocks
>> from the Earth and the Moon, which plot on the TFL
>> (Terrestrial Fractionation Line). A precise formation age
>> has not yet been measured, but it cannot be older than 4.54
>> billion years, which likely makes NWA 5400 anomalously young
>> among primitive achondritic objects from the early Solar
>> System. It is generally accepted that the Earth-Moon system
>> was created when Theia collided with proto-Earth about 4.3
>> billion years ago. Is it possible that NWA 5400 is somehow
>> related to this phenomenal event?
>> >
>> >
>> >
>> > NWA 5400 adds valuable understanding of events that
>> took place in the early evolution period of the Solar
>> System. After two years of intense analysis, scientists at
>> prominent institutions from around the world continue to
>> diligently study this 'stand-alone' meteorite, which will
>> add to the already incredible information NWA 5400 has to
>> offer.
>> >
>> >
>> >
>> > Link to 2009 LPSC abstract on NWA 5400:
>> >
>> > http://www.lpi.usra.edu/meetings/lpsc2009/pdf/2332.pdf
>> >
>> >
>> >
>> > Link to 2010 LPSC abstract on NWA 5400:
>> >
>> > http://www.lpi.usra.edu/meetings/lpsc2010/pdf/1492.pdf
>> >
>> >
>> >
>> > NWA 5400 has a Total Known Weight of 4.818 kg in a
>> single stone that was discovered in Northwest Africa in
>> 2008. The chocolate-brown mottled matrix takes an extremely
>> nice polish, which reveals the dazzling olivine crystals
>> exhibited in this scientifically important new meteorite!
>> >
>> >
>> >
>> > Cross-polarized light optical thin section image of
>> NWA 5400 (width of field = 1.2mm):
>> >
>> > http://www.lunarrock.com/NWA5400/nwa5400xpl.jpg
>> >
>> >
>> >
>> > Image of 58.9-gram complete slice with hologram-like
>> olivine crystals that dance across the polished surface when
>> tilted from side to side:
>> >
>> > http://www.lunarrock.com/NWA5400/nwa5400slice.jpg
>> >
>> >
>> > Best regards,
>> > Greg
>> >
>> > ====================
>> > Greg Hupe
>> > The Hupe Collection
>> > NaturesVault (eBay)
>> > gmhupe at htn.net
>> > www.LunarRock.com
>> > IMCA 3163
>> > ====================
>> > Click here for my current eBay auctions:
>> > http://search.ebay.com/_W0QQsassZnaturesvault
>> >
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>> >
>>
>>
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Received on Thu 10 Jun 2010 02:16:11 AM PDT