[meteorite-list] THE CARANCAS PERU METEOROID IMPACT CALCULATIONS

From: Sterling K. Webb <sterling_k_webb_at_meteoritecentral.com>
Date: Sun, 7 Oct 2007 15:10:07 -0500
Message-ID: <124601c8091e$0f4db980$b92ee146_at_ATARIENGINE>

Hi, Jan, List,

    I wish email allowed one to scribble little pencil
diagrams with arrows and pointers in the margin!
Then this would be so much easier!

    A heightened rim on one side can result from two
different situations. One would be if the impactor
came in a low angle from the south, say 20 to 30
degrees. The force of initial impact would have a
vector that pushed very much harder on the rim
opposite the direction of flight, raising it higher
than the other rim. This is fairly easy to visualize.

    With a high angle from the north, say 60 degrees,
it's harder to visualize. But imagine a half sphere of
outward force from the initial impact that's oriented
on the direction of the object's travel; it's tilted 30
degrees up on the south and 30 degrees down on
the north. Picture its center as below ground level
at the depth where the impactor stops moving into
the ground and the explosive event peaks in force.

    This results in the south rim getting "blown out"
more easily. For any angle away from the impactor's
direction of travel, the forces on the "south" side have
less material between the center of force and the surface
of the ground, hence it more easily "blows out" to the
surface.

    On the "north" side of the explosion, the side force
vectors are tilted down, are resisted by more material;
it's harder to blow out as much of it out. It "piles up"
and raises the "north" rim. It's a relative weak effect
that would only show up in a cratering event this "small."

    Now, in a really fast (or really big or both) impact,
the impactor penetrates so deeply, so quickly that when
it explodes, it produces a perfectly symmetrical result,
just as if you'd buried a small nuclear device in the dead
center of your planned crater

    This wasn't that powerful an event, and while it seems
to have been an explosive event, I doubt it was a "rock
vaporizing" event, meaning I don't think the impact velocity
was as high as 6000 m/sec.

    I believe that Piper R. W. Hollier's suggestion that it
was "hot" enough to vaporize the troilite in the stone is
correct. The INGEMMET analysis says 5% troilite in the
"survivor" fragments. Since troilite "pools" into inclusions,
the amount in the stone as a whole could be even higher.

    If 5% to 8% of a stone is instantly converted to vapor,
you get a moderately good sized explosive event (and
the smells and the acid-base reactions in the water)! That
amount of energy could be generated by a velocity as low
as perhaps 1200 m/sec (Mach 3.5) or less, depending
on the "efficiency" of the impact. Efficiency?

    In calculating impacts, a complicating factor is the fact
that the impact has so many jobs to do: exploding the
impactor, excavating the crater, producing seismic waves,
producing acoustic waves, and a dozen other tasks! They
all have to draw their energy from the impact -- everybody
wants a piece of the action.

    The truth or folly of all this analysis will become clear
when (and if) the Instituto Astrofisica successfully excavates
the crater, and I will either be dining on crow for a month
(baked crow, crow soup, crow a la King on toast, crow
sandwiches and crowburgers...) or will be fatuously satisfied
for about five minutes.



Sterling K. Webb
----------------------------------------------------------
----- Original Message -----
From: "Jan Hattenbach" <jan.hattenbach at web.de>
To: "Meteorite List" <meteorite-list at meteoritecentral.com>
Sent: Sunday, October 07, 2007 10:45 AM
Subject: Re: [meteorite-list] THE CARANCAS PERU METEOROID IMPACT
CALCULATIONS



> -----Urspr?ngliche Nachricht-----
> Von: "Sterling K. Webb" <sterling_k_webb at sbcglobal.net>
> Gesendet: 07.10.07 09:27:54
> An: "Meteorite List" <meteorite-list at meteoritecentral.com>
> Betreff: [meteorite-list] THE CARANCAS PERU METEOROID IMPACT CALCULATIONS

Hi Sterling,
>
> The north portion of the rim is higher than the south
> portion; the impactor came from the north. The slope
> of the crater wall on the south is less than on the north;
> this argues a steep angle of impact for the object (>60
> degrees), which means that it came more or less from
> the "top" of the sky.

I don't get this. Should it not be the opposite? If the impactor came from
the north, I would expect the south rim to be higher. Are there any pictures
showing the crater, the rim AND the cardinal points?

Best regards,

Jan


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Received on Sun 07 Oct 2007 04:10:07 PM PDT