[meteorite-list] Carancas meteorite crater

From: Rob McCafferty <rob_mccafferty_at_meteoritecentral.com>
Date: Fri, 5 Oct 2007 08:24:39 -0700 (PDT)
Message-ID: <7129.64500.qm_at_web51010.mail.re2.yahoo.com>

I remember doing calculations at university to
estimate the size of an impact crater and for a rock
maintaining it's cosmic velocity, it tends to be
around 20:1.

The conditions for surviving to the surface are quite
exacting and with chondrite craters such a rarity, are
we looking at an absolute ideal angle and speed for
this not to disintegrate or slow down completely on
its descent.
And I apologise if this answer has already been given,
but what mass/dimensions was the impactor likely to
have had? I suspect a 1m diameter rock is consistent
with a proper crater of this size. While this may be a
3tonne rock most of it would be destroyed by the
impact if it retained much of its cosmic velocity.
This seems consistent with the few fragments though
backward spallation. While I find the prospect of
ablation right to the surface unappealing, I don't
believe it could have made a crater rather than a
tunnel had it not been going at several km/s when it
hit that wet ground.
It's just it seems such a rare occurence, I wonder if
we're looking at a special case for incoming bolides
here, with very narrow limits on angle, speed and
meteor structure.
If this crater, the fragments and the witness reports
are properly studied, this fall has the potential to
improve our understanding of the dynamics involved.
Very interesting stuff
Rob McC
--- Michael Farmer <meteoriteguy at yahoo.com> wrote:

>
>
> http://www.star-bits.com/impact-craters.htm
>
> Hi everyone, Eric Olson is at my house to see the
> Carancas meteorites, and he asked me to post this
> link.
>
> It is a list of every known impact crater of more
> than
> 10 meters in diameter, from which meteorites had
> been
> found. Of all of those craters, not one, ZERO is
> associated with a chondrite. Jilin and Norton
> County,
> both masses well over a ton, had craters less than
> 50%
> the size of the Carancas meteorite. This is very
> interesting and proves how rare such a chondrite
> fall
> is!
>
> Michael Farmer
>
> I am ready to forget and ignore the controversy and
> focus on the science of this spectaclar event at
> this
> time, I have had my say and told my story.
>
> ______________________________________________
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> Meteorite-list at meteoritecentral.com
>
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>



       
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Received on Fri 05 Oct 2007 11:24:39 AM PDT