[meteorite-list] Angrites hot under the colar

From: Greg Hupe <gmhupe_at_meteoritecentral.com>
Date: Fri, 31 Oct 2008 13:24:02 -0400
Message-ID: <11416B1CDC0B4187954BE8B538A6AFD5_at_Gregor>

Hi Pete, Darren and List,

Pete states, "You would think then, that there would be more angrite
meteorites found..."

Of the Angrites I have been fortunate to bring to the meteorite world; NWA
2999 (and pairings 3159/4931), NWA 4590 "Tamassint" and NWA 4801, both NWA
4590 and 4801 are extremely friable so they would not have lasted very long
on the earth's surface if it were not for the lucky nomads who found them in
the Sahara.

If half of the Angrite meteors which entered earth's atmosphere were similar
to these, they terrestrialized and disintegrated soon after becoming
'meteorites'. We are fortunate that such pristine examples have been
collected for science and collectors alike! To see what I mean, click here
for some great examples: http://search.ebay.com/_W0QQsassZnaturesvault

Now if another one could land in my Trick-or-Treat bag tonight! ;-)

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



----- Original Message -----
From: "Pete Pete" <rsvp321 at hotmail.com>
To: <cynapse at charter.net>; <meteorite-list at meteoritecentral.com>
Sent: Friday, October 31, 2008 10:15 AM
Subject: Re: [meteorite-list] Angrites hot under the colar



Hi, Darren and List,

You would think then, that there would be more angrite meteorites found, and
chondrules in meteorites would be more rare...?

Cheers,
Pete




> From: cynapse at charter.net
> To: meteorite-list at meteoritecentral.com
> Date: Fri, 31 Oct 2008 09:30:39 -0500
> Subject: [meteorite-list] Angrites hot under the colar
>
> http://www.space.com/scienceastronomy/081030-planet-formation.html
>
> Ancient Meteorites Give Clues to Planet Formation
> By SPACE.com staff
>
> posted: 30 October 2008
> 02:04 pm ET
>
> Meteorites that are among the oldest rocks ever found have provided new
> clues
> about the conditions that existed at the beginning of the solar system,
> solving
> a longstanding mystery and overturning some accepted ideas about the way
> planets
> form.
>
> The ancient meteorites, called angrites, still contain magnetic records
> about
> the very early history of planets, like disk drives salvaged from an
> ancient
> computer, new research by MIT planetary scientist Benjamin P. Weiss
> indicates.
>
> The results of the study, which was by a grant from the National Science
> Foundation's Instrumentation and Facilities Program, are detailed in the
> Oct. 31
> issue of the journal Science.
>
> The analysis showed that surprisingly, during the formation of the solar
> system,
> when dust and rubble in a disk around the sun collided and stuck together
> to
> form ever-larger rocks and eventually the planets we know today, even
> objects
> much smaller than planets ? just 100 miles (160 kilometers) across or so ?
> were
> large enough to melt almost completely.
>
> This total melting of the planet-forming chunks of rock, called
> planetesimals,
> caused their constituents to separate out, with lighter materials
> including
> silicates floating to the surface and eventually forming a crust, while
> heavier
> iron-rich material sank down to the core, where it began swirling around
> to
> produce a magnetic dynamo. The researchers were able to study traces of
> the
> magnetic fields produced by that dynamo, now recorded in the meteorites
> that
> fell to Earth.
>
> "The magnetism in meteorites has been a longstanding mystery," Weiss said,
> and
> the realization that such small bodies could have melted and formed
> magnetic
> dynamos is a major step toward solving that riddle.
>
> Until relatively recently, it was commonly thought that the
> planetesimals ?
> similar to the asteroids seen in the solar system today ? that came
> together to
> build planets were "just homogenous, unmelted rocky material, with no
> large-scale structure," Weiss said. "Now we're realizing that many of the
> things
> that were forming planets were mini-planets themselves, with crusts and
> mantles
> and cores."
>
> That could change theorists' picture of how the planets themselves took
> shape.
>
> If the smaller bodies were already molten as they slammed together to
> build up
> larger planet-sized bodies, that could "significantly change our
> understanding"
> of the processes that took place in the early years of the nascent
> planets, as
> their internal structures were forming, Weiss said. This could have
> implications
> for how different minerals are distributed in the Earth's crust, mantle
> and core
> today, for example.
>
> "Events happened surprisingly fast at the beginning of the solar system,"
> Weiss
> said. Some of the angrite meteorites in this study formed just 3 million
> years
> after the birth of the solar system itself, 4,568 million years ago, and
> show
> signs that their parent body had a magnetic field that was 20 to 40
> percent as
> strong as Earth's today.
>
> "We are used to thinking of dynamo magnetic fields in rocky bodies as
> uncommon
> phenomena today," Weiss said. "But it may be that short-lived planetesimal
> dynamos were widespread in the early solar system."
>
>
>
> http://sciencenow.sciencemag.org/cgi/content/full/2008/1030/2
>
> First Planets Lived Fast and Died Young
>
> By Phil Berardelli
> ScienceNOW Daily News
> 30 October 2008
> Surprising findings from some of the oldest known meteorites suggest that
> our
> solar system was once chock-full of miniature planets, complete with
> metallic
> cores and rocky crusts. The findings could force a rethinking of how the
> solar
> system and its constituent bodies evolved.
>
> Some 4.568 billion years ago, our sun and solar system condensed out of a
> primordial cloud of dust and gas. Within about 3 million years, small,
> rocky
> objects called planetesimals were circulating in the nascent solar system.
> Fragments of these planetesimals remain today as meteorites called
> achondrites,
> which scientists have pored over for clues to how planets formed. Oddly,
> the
> meteorites are magnetic, which is strange because the planetesimals were
> supposed to be just large agglomerations of rubble.
>
> A U.S.-Canadian team took a new approach to the problem, testing samples
> of
> three well-preserved achondrite meteorites with an extremely sensitive
> magnetometer. What they discovered stunned them: The meteorites showed
> evidence
> of ancient magnetic fields similar to those of rocks formed on Earth
> within the
> planet's magnetic field. In other words, the team reports this week in
> Science,
> the 4.565-billion-year-old meteorites once were part of bodies that were
> either
> big enough or hot enough to produce central, molten, metallic cores.
>
> "The meteorites, therefore, are essentially magnetic recording tapes,"
> says
> planetary scientist and lead author Benjamin Weiss of the Massachusetts
> Institute of Technology in Cambridge. The magnetic fields that they
> recorded
> were probably generated by molten metal swirling around inside the
> planet's core
> like a giant, rotating dynamo, as happens on Earth. Although most
> asteroids now
> are rocky through and through, the new findings suggest that back at the
> beginning of the solar system even planetesimals could melt at their cores
> and
> retain a rocky crust. These bodies could be as small as 160 kilometers in
> diameter, the research suggests. The planetesimals, which eventually
> merged to
> form the rocky planets, were more planetlike than previously thought, with
> cores
> that must have formed and melted within just a few million years of the
> formation of the solar system, Weiss says.
>
> The paper "makes a good case," says planetary scientist David Stevenson of
> the
> California Institute of Technology in Pasadena. Although dynamos are
> thought to
> require large planetary cores, it's possible that the
>
>
>
> for those with access to _Science_ full text:
>
> http://www.sciencemag.org/cgi/content/abstract/322/5902/713
>
>
> and here's a related PDF:
>
> http://www.lpi.usra.edu/meetings/lpsc2008/pdf/2143.pdf
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Received on Fri 31 Oct 2008 01:24:02 PM PDT