[meteorite-list] Mercurian Meteorites (was: Rocks from Space Picture of the Day - June 16, 2010)

From: Galactic Stone & Ironworks <meteoritemike_at_meteoritecentral.com>
Date: Fri, 18 Jun 2010 12:58:33 -0400
Message-ID: <AANLkTinrds1HhMNjc4mECRsOIKT7YpaZAKrzsI_2bE4B_at_mail.gmail.com>

Hi Bernd and List,

When people ask me about the possible angrite-Mercury connection, I
generally refer to them to the excellent article written by Melinda
Hutson that appeared in the May 2008 issue of Meteorite Magazine. In
summary, the article casts some serious doubts on Mercury being the
parent body of angrites. Since that time, no research has been
published that supports the connection.

I think what we have here is a case of possibilities - it is
mathematically possible that a meteorite from Mercury could arrive on
Earth. But it's far more likely I will be struck in the head by the
first American lunar fall while I am typing this. ;)

(*whistling noise*)

(*crash*)

(*thud*)


On 18 Jun 2010 16:47:09 UT, bernd.pauli at paulinet.de
<bernd.pauli at paulinet.de> wrote:
> Greg S. inquired:
>
> "I heard that possible meteorites from Mercury should contain very little
> (or no) free iron. Is this true? I think the one pictured here and NWA 2999
> do contain some free iron."
>
>
> Hello Greg and List,
>
> I thought this summary of the "Summary and Conclusions" part of Love's
> article
> might be of interest because it partly answers your question about Mercury's
> iron:
>
> Summary:
>
> - orbital evolution of Mercurian material to Earth-crossing orbits possible
> - efficiency probably < 1% of that computed for Mars
> - a ~ 10% chance that a mercurian rock could exist in current meteorite
> collections
> - may possess an unusual isotopic composition
> - rocks from Mercury probably low in volatiles
> - Mercury bulk composition moderately enriched in refractory oxides of Al,
> Ti, and Ca
> - FeO contents not more than ~ 5%, and possibly much lower
> - Mercurian regolith breccias:
> - rich in micrometeorite craters
> - rich in exogenic chondritic materials
> - rich in agglutinates
> - rich in impact vapor deposits
> - lower solar-wind content than similar lunar soils
> - implanted gas may be fractionated by interaction with Mercury's global
> magnetic field
> - a uniquely high solar-to-galactic cosmic-ray damage track ratio of surfac
> rocks
> - launch-induced shock damage may be comparable to or greater than in
> martian meteorites
> - no match of these predicted properties of mercurian rocks in current
> meteorite groups
> - misclassified mercurian meteorites most likely differentiated, low-FeO
> objects such as
> lunar anorthosites and aubrites
>
> Reference:
>
> LOVE S.G. et al. (1995) Recognizing mercurian meteorites (MAPS 30-3, 1995,
> 269-278).
>
> .........................................................................................
>
> There are some scientists who favor enstatite chondrites but there's a
> problem with that:
> Mercury's mean density is about 5.4 g/cm^3, whereas enstatite chondrites
> have a density
> of about 3.4-3.7 g/cm^3.
>
> In 2002, H. Palme proposed that NWA 011 (and paired material like NWA 4587)
> might be
> a fragment of Mercury but the high FeO content of this meteorite would point
> toward
> a parent body with a small metallic iron core. Mercury, however, is believed
> to have
> a large iron core.
>
> Best wishes,
>
> Bernd
>
>
>
>
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Mike Gilmer - Galactic Stone & Ironworks Meteorites
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Received on Fri 18 Jun 2010 12:58:33 PM PDT