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

[E.L. Jones]

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.