[meteorite-list] There are no silly questions? Wait until youhave read that :-)

From: Tom AKA James Knudson <peregrineflier_at_meteoritecentral.com>
Date: Tue Oct 19 16:41:53 2004
Message-ID: <006301c4b61c$0845ace0$2d107918_at_Michelle>

I have a question,
" There were many smaller planetoids. How
big an asteroid needs to be to form a core depends on its composition with
radioactive decay playing a major role in heating it up, but generally it
needs
to be 400 miles diameter plus or minus."

  We had plenty of iron meteorites hit the earth and only a tiny fraction of
the iron in space would have hit the earth, so is all the iron coming from
the same source or is there many sources?

Thanks, Tom
peregrineflier <><
IMCA 6168
http://www.frontiernet.net/~peregrineflier/Peregrineflier.htm
----- Original Message -----
From: <star-bits_at_comcast.net>
To: "Bernhard Rems" <rendelius_at_rpgdot.com>;
<Meteorite-list_at_meteoritecentral.com>
Sent: Tuesday, October 19, 2004 1:27 PM
Subject: Re: [meteorite-list] There are no silly questions? Wait until
youhave read that :-)


> <1) HEDs are from Vesta.
>
> Fine. All of them? How comes that with 50.000+ known asteroids, all HEDs
> come from a single one? As far as I know, spectroscopic evidence points
> to Vesta, yes - but how large is the chance that HEDs do NOT come from
> Vesta.>
>
> ----No they don't all come from Vesta. The spectroscopic evidence is an
indicator, not a
> pedigree. It is a possibility they come from Vesta or a vesta type
asteroid, but there
> is no guarantee.
>
>
> <2) Meteorites have been ejected towards earth by collisions between
> asteroids.
>
> Fine again. But does this mean that all meteorites result from high
> speed collisions of asteroids? Isn't there a chance that some have been
> sent on a trajectory towards earth simply by perturbations and chaos?>
>
> ----Probably very few are a direct result of impact. Most spend hundreds
of
> thousands to millions of years floating around after the impact which is a
lot
> of time for Jupiter, other asteroids or planets to redirect the orbit.
>
> <3) Carbonaceous chondrites are much older than ordinary chondrites.
>
> Ok. Once again: fine. So they must be "leftovers" from the accretion
> disk, matter that hasn't formed into larger bodies. So at least they
> aren't asteroid material, right?>
>
> ----What is your defination of asteroid material? A one meter diameter
carbonaceous
> chondrite is an asteroid just like its larger cousins. If you mean they
didn't get
> large enough to become altered that is not true either because there are
CK
> chondrites throught at least CK6.
>
> <4) Iron meteorites originate from the core of a large and destroyed
> planetoid.
>
> Mhm. How large must this thing have been? Or let me put the question
> like this: what is the minimum size for a body to be able to create a
> metal core? And are those main belt asteroids the remnants of the
> "planetary crust" of this planetoid?
>
> Furthermore - there must have been at least two bodies of that size
> (because planetoids do not explode, they have to collide to eject core
> material into the solar system. Is this assumption right or wrong?>
>
> ----Analysis of iron meteorites show there were at least 30+ (maybe
somebody
> has the exact number) different differentiated bodies that produced iron
> meteroites. There was not a planet that formed in the asterorid region
because
> gravity from Jupiter prevented it. There were many smaller planetoids.
How
> big an asteroid needs to be to form a core depends on its composition with
> radioactive decay playing a major role in heating it up, but generally it
needs
> to be 400 miles diameter plus or minus.
>
> <5) Pallasites
>
> How did the olivine get into the nickel/iron? >
>
> ----One theory is that there is a boundrey layer at the mantle (olivine)
and core (iron)
> and an impact forces some of the iron up into and between the olivine
crystals where
> it remains until the metal cools and crystalizes. This would explain
the appearance
> of fragmented olivines in some pallasites.
> Another theoriy is that as the metal migrates through the mantle to
the core as it
> reaches the core mantle boundry it solidifies before it joins the core.
>
> <6) Seymchan
>
> >From pictures I have seen on the net, There are pieces of Seymchan which
> are just iron, some with very sparse olivine inclusions and some with
> lots of olivine. How can it be that such a variety of compositions can
> be within one fall? Is the Seymchan iron in the Seymchan iron meteorites
> the same iron as in the pallasites?>
>
> ----Glorieta Mountain is the same way. If you imagine a semi-merged core
mantle boundry
> the closer to the core the more metal you would find and the closer to the
mantle the
> more olivine you would find. So you have 1. all iron, 2. lots of metal
some olivine,
> Seymchan and Glorieta, 3. Little metal and lots of olivine, Molong
and
> 4. No iron just large pallasitic type olivine crystals, of which there
are no examples.
>
> --
> Eric Olson
> ELKK Meteorites
> http://www.star-bits.com
>
>
>
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Received on Tue 19 Oct 2004 04:41:37 PM PDT