[meteorite-list] Mesosiderites= Vestan?

From: E.P. Grondine <epgrondine_at_meteoritecentral.com>
Date: Fri Sep 22 13:08:05 2006
Message-ID: <20060922170800.90536.qmail_at_web36914.mail.mud.yahoo.com>

Hi Sterling, list -

Perhaps a key to this problem is to sort out the
parent bodies first, and contra McSween, perhaps
Artemis and the LPBE(s?) indicate one of the keys'
shape.

Crater counts and crater spectra are important in
sorting this out, and here NASA has not been doing its
job. An amateur working alone is not going to be able
to solve these problems, nor for that matter is a
professional working alone going to be able to do it.

Accretion is not entirely a theoretical problem, and
as "going there" runs say a hundred million dollars
per visit, the accretion problem is not going to be
even partially solved until we get someone qualified's
hand on the NASA space sciences faucet...

IMO, the NASA bureaucracy and constituency even appear
to be doing their best to ignore an act of Congress...

Money makes the world go around, the world go around,
the world go around...

good hunting everyone,
Ed

--- "Sterling K. Webb" <sterling_k_webb_at_sbcglobal.net>
wrote:

> Hi,
>
> Identifying the parent bodies of meteorite types
> has been
> disappointing. Early optimism suggested that if
> could just
> get enough spectra of enough bodies, we could match
> most
> everything up and untangle a lot of early solar
> system history.
> Didn't work out that way. Matches were few.
>
> That was a puzzle until the discovery of "space
> weathering."
> The surface of asteroids are altered by long
> exposure and no
> longer always resemble in spectra the meteorites
> that might
> have come from them.
>
> There some fairly certain matches: Vesta (and
> the Vestoids)
> for the Howardites, Eucrites and Diogenites, Mars
> and the Moon
> (of course), and a batch of tentative argued-over
> proposed
> matches...
>
> The biggest mystery is the parent body of the L
> types.
> We have one good match for H chondrites (and the IIE
> irons), 6 Hebe (~200 km), but can it alone account
> for 40% of
> all the meteorites that fall to Earth? These folks
> say "yes."
>
http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1998M%26PS...33.1281G&db_key=AST&data_type=HTML&format=&high=438c93072f28336
>
> 16 Psyche (254 km) has been suggested for the
> mesosiderite
> parent body, but it's far from certain.
>
> Mesosiderites:
> "The silicates are heavily-brecciated
> (smashed-up), evolved
> igneous rocks similar to those found in members of
> the HED
> group. Evidently, these silicates came from the
> crust of an
> achondritic parent body. The iron-nickel in
> mesosiderites,
> on the other hand, looks like the metal in group
> IIIAB iron
> meteorites, and shows every sign of having derived
> from
> the core of a completely different asteroid than
> that which
> spawned the silicates. One possible explanation of
> the origin
> of mesosiderites is that a collision took place
> between two
> differentiated asteroids in which the still-liquid
> core of one
> asteroid mixed with the solidified crust of the
> other.
> Subsequently, at least one of the asteroids
> reassembled
> from the collision fragments and became the
> mesosiderite
> parent body. It remains uncertain whether the HED
> parent
> body, Vesta, is one of the asteroids involved."
>
> Pallasites:
> "Pallasites are believed to have come from the
> core/mantle
> boundary of differentiated asteroids that were
> broken apart
> by impact. In most cases, they have chemical,
> elemental,
> and isotopic features that link them to specific
> chemical
> groups of iron meteorites, suggesting that they come
> from
> the same parent bodies as these irons."
> While we type iron meteorite into gross classes,
> the
> complicated distribution of trace metals shows that
> iron
> meteorites can be grouped into 80-some parent bodies
> (with a dozen or so unique irons making almost 100).
> So,
> there were originally 100 (or hundreds) of
> differentiated
> parent bodies of which they were the cores.
>
> Imagine that we were the recipients of 50,000
> samples
> returned from Venus, but that the collectors didn't
> tag them,
> didn't record their point of origin on the planet,
> mixed the
> entire batch in a giant rock tumbler, fried their
> exteriors with
> hyperblowtorches, and said, "Hey, you sort it out!"
> Could
> we deduce the geological history of Venus from that?
> We
> would be long on generalizations and short on
> specifics,
> a situation similar to trying to identify
> meteorites' parent
> bodies.
>
> There's no substitute for going there.
>
>
> Sterling K. Webb
> -------------------------------------------------
> ----- Original Message -----
> From: "Rob McCafferty" <rob_mccafferty_at_yahoo.com>
> To: <cynapse_at_charter.net>;
> <meteorite-list_at_meteoritecentral.com>
> Sent: Friday, September 22, 2006 8:39 AM
> Subject: Re: [meteorite-list] Mesosiderites= Vestan?
>
>
> >> Main-group
> >> pallasites represent intermixed core-mantle
> material
> >> from a single disrupted
> >> asteroid and have no known equivalents among the
> >> basaltic meteorites.
> >
> > Is that right? They all come from the same parent?
> >
> > What are the other groups of pallasite. Sorry, my
> > knowledge on these rocks is thin. (Can't afford to
> buy
> > them so I only read up the basics)
> >
> > Rob McC
> >
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Received on Fri 22 Sep 2006 01:08:00 PM PDT