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The physics of a 'double helix' meteor

List,

I have been pondering what could be the cause of the look of the
before mentioned 'double helix' meteor observed by me on the 17th of
November last year.
I am as I said, quite convinced it was a Leonid (of the reasons 
mentioned).
I also said I thought that the pieces were driven by their own propulsion,
because of the violent boiling and outgassing of its volatile
compouds suddenly being extremly rapidly heated by the shock
in meeting the earth atmosphere.

It could however be that the very thight spiraling smoke trains also
could be explained by spin (without moving about) as suggested by others.
As I did, assuming 100 revolutions/sec. and _moving_ 300 m in
diameter, would mean a (sideways) speed of about 360 000 km/hr - which I
imagine is too fast for some small centimeters large pieces of comet stuff to
produce. (Maybe some rocket scientist would know better ?)

So I now think that very fast spin could possibly have tossed smoke and glowing 
debris out in a helix, creating an illusion that the pieces was spiraling
themselves. Certainly a combination of spin and spiraling movement is possible,
although I now lean towards the spin as being the most important cause
of the phenomena. It could also be that two pieces was the reason
for the two distinct trails to be created. An explosion could have ripped 
one original piece into two, thus creating freshly exposed surface areas with a 
softer and not hardened surface, thus much more easily exposed to the erosive
forces of the byrushing air moluceles.

Certainly I also think that high energy is the most important prerequisite 
to bring about the phenomena. We know that the Leonids is the fastest of the
important meteor showers, so this is another reason to connect this meteor to
the Leonids. I would believe that the phenomena has a strong tendency to 
(almost only) be connected to the meteor showers of the highest velocity. 
Therefore, in the future, I would recommend all to watch for such
behavior in connection with high velocity meteor showers...

Phil suggest that 'it was probably something more substantial [than the 
friable Leonids]'. As I said I don't know how the parameters of friability
have come about (would be really interesting to know), but one important
fact tells us that the meteors observed at the time mentioned, was _not_
the ordinary variety of the Leonids. 
As most may know, the early maximum of the Leonids of 98' was not expected.
It had a characteristically high proportion of bright fireballs.  This was
later interpreted in this way: The debris had not been produced by the 
lastest orbits of the mother comet Temple-Tuttle, rather it was believed
to be old and 'weathered out' fragments, They were thought to have been moving
through the inner solar system since - was it the 14th century? The lighter 
compounds had been removed, only to leave the harder compounds - rock
fragments??
So you are probably right Phil - it was something more substantial..!

Looking forward to next Leonids,
Bjørn Sørheim




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