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[Fwd: 'aerodynamic'tektites (Not related to #800)]

I failed to notice that my browser's reply button had sent this reply directly
to jj rather than to the list. Darn computers!!

Gene

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Hello jj,

To add to Martin's description of tektites, all meteoroids become
aerodynamically shaped as they pass through the atmosphere. It can't help but
happen, being a function of air resistance, friction and the ablation process. 

The degree to which any meteorite specimen shows an aerodynamic shape becomes
a function of whether or not the meteoroid was tumbling as it fell ("oriented"
specimens being an indication of stable flight), whether or not the meteorite
fell intact or fragmented in flight or on impact, and, if it did fragment in
flight, whether or not there was sufficient time for ablation to begin shaping
individual fragments before dark-flight  or impact.

As with tektites, the degree of shaping is an indication of the meteorites
flight history. Sikhote-Alin "shrapnel" are fragments from an explosion of the
meteoroid that took place shortly before or after entering dark-flight or on
impact with the surface depending on the degree of any rounding of the edges
on the specimens. Smooth, rounded pieces of S-A are fragments that that tore
off earlier in flight or might have entered the atmosphere as individuals.

Rounded edges and flow lines (sometimes squiggles) in the fusion crust are
indications of ablation and aerodynamic shaping. Most meteorite specimens will
show it to some degree with the exception of sharp edged, broken fragments.
With stones in particular it is usually possible to find the facing and
trailing surface of the meteorite if there was even slight orientation during
flight. With many of the new Jauncheng specimens it is fairly easy to
determine flight orientation.

Hope this helps you out.

Gene


JJSwaim wrote:
> 
> Hello to everyone,
>      For those of us whose curiosity far exceeds our data base of knowledge,
> I need some help understanding tektites.    One of their characteristics
> seems to be something of an 'aerodynamic' quality.  I have seen many
> different shapes and yet have not seen any that would indicate anything that
> would make them particularly aerodynamic.  (Obviously, most meteorites are
> not necessarily aerodynamically shaped).  Hence, my curiosity as to why or
> what it is about tektites that puts them in this category.  Is it something
> other than shape?  Any assistance would be greatly appreciated.  Best
> regards, jj

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