[meteorite-list] Speaking of Mazapil - Vienna Main Mass observations

From: Rob Lenssen <rlenssen_at_meteoritecentral.com>
Date: Thu, 12 Aug 2010 21:23:54 +0200
Message-ID: <632E38473C5445E2B3151FCC1D7143BE_at_EIGENAARNJEQJY>

Dear List,

When visiting Austria's Natural History Museum in Vienna last month, I
noticed a (for me) unexpected feature in Mazapil's Main Mass that was on
display.

http://home.planet.nl/~rlenssen/Mazapil_1.jpg

It reminded me of a feature, sometimes visible in Individuals of the Sikhote
Alin shower. There have been discussions about its origin, but it's
typically considered to be an "impact crater". A crater from an impact that
occurred in a meteorite shower, in time somewhere around the retardation
point.

Here is a photo of Mazapil's crater:
http://home.planet.nl/~rlenssen/Mazapil_2.jpg (I'm referring to the
top-middle depression).

Buchwald's Handbook of Iron Meteorites mentions only one Mazapil mass being
discovered. Of course that is no proof it was the only piece falling down
that evening in Mexico, but I assume the chance for obtaining an impact
crater was significantly less than in the case of Sikhote Alin.

As can be seen in this photo: http://home.planet.nl/~rlenssen/Mazapil_3.jpg
, Mazapil contain many graphite-troilite nodules. The photo with the crater
shows at least one of these nodules peeping out of the crust I think. The
question that came up was: Did the feature I had always assumed to be an
impact crater, really had an impact origin?

I know the nodule peeping out does look somewhat different from the crater,
and we do not know for sure there weren't more masses falling down, but
anyway. wouldn't have expected to see this in Mazapil.

Checking Buchwald's handbook when back home, I found Buchwald stating: "The
metallic fusion crust contains numerous spherical gasholes and globular iron
oxide melts." in a chapter covering shapes and surface characteristics (Page
52, Figure 47). He is talking micro scale here.
The description of the Mazapil iron shows a photograph of the Vienna mass,
also showing the crater. The caption of this photo (Page 809, Figure 1115)
states: ". Regmaglyphts and a few circular depressions from ablated troilite
nodules are visible."

I'm not so sure anymore I saw an "impact crater".
(Remember the Main Mass is assumed to be flying in front in a stream.)



Nothing to do with impact craters, but furthermore striking I found the
account of Mazapil's Fall (Buchwald's Handbook of Iron Meteorites, Pages 809
and 810):

http://home.planet.nl/~rlenssen/Mazapil_4.jpg

Would we have judged this to be a false report without any second thought?
:-)

All the best,
Rob Lenssen


----- Original Message -----
From: "Chris Spratt" <cspratt at islandnet.com>
To: <meteorite-list at meteoritecentral.com>
Sent: Thursday, August 12, 2010 5:59 AM
Subject: [meteorite-list] Meteor shower meteorite dropping events


>I know of one meteor shower (November Andromedids) where an iron meteorite
>fell in Mazapil, Mexico during the shower.
>
> Are there any similar events?
>
> Chris Spratt
> Victoria, BC
> (Via my iPhone)
> ______________________________________________
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Received on Thu 12 Aug 2010 03:23:54 PM PDT