[meteorite-list] Re: Sikhote Question, Impact Pits, Oriented Campo

From: E.L. Jones <jonee_at_meteoritecentral.com>
Date: Sun Nov 6 23:34:10 2005
Message-ID: <436ED92E.8050409_at_epix.net>

Actually, Geoff-- ALL parts start out as "shrapnel shapes" once
disruption began: when deceleration stresses sheered the meteor body(s)
apart from front to rear. We know from eye witnesses that there were
several explosive disruptions(8+) and at each disruption there were more
shrapnel surfaces exposed to ablation. The parts that we treasure are
those that had enough velocity to go through ablation and regmglypthing,
etc. I surmise that those sharing both characteristics of smoothies and
shrapnel were those that ran out of speed towards the end of
incandescent flight and ablation ceased to sculpt them. As to impact
pits, these are a bit harder to explain. One thought is that the larger
surfaces-- with more air resistance, were slowing faster than smaller
bodies that entered the sheltered slip stream of the larger and caught
up to them with still enough energy as a bullet. Even this theory
likely doesn't account for all the physics. If someone knows the
Rockwell grade of SA, given the diameter of the pit, one might be able
to compute the relative size of the impactor plus energy involved
gouging the pit. it might give insight in how the pits were formed.

Regards,
Elton

Notkin wrote:

> When I started collecting Sikhotes seven or eight years ago, I was
> under the impression that all individuals had come through the
> atmosphere on their own, and all shrapnel pieces were the result of
> explosive fragmentation around the craters (this view supported, I
> believe, by the fact that only shrapnel is found in the craters?).
> Over time, I've seen a few pieces that exhibit characteristics of both
> individuals *and* shrapnel, and I'm sure some of you have too. An
> example would be, say, a ~1kg otherwise completely regmaglypted
> individual that has one sheared, shrapnel-like face. I expect this is
> the result of a larger individual fragmenting in the air shortly
> before impact.
Received on Sun 06 Nov 2005 11:33:50 PM PST