(meteorobs) Why do some meteors appear to zig-zag?

[Marco Langbroek]

> I am still confused on one point, and that is:
> Of the over 1000 photo's you've mentioned, none
> of which I have had a pleasure to see, not a single
> one was recovered, according to your comments.
> Is it possible you and I are discussing apples and oranges?
> You do mention that some are expected to have
> produced meteorites.  But that is a conjecture ...

Hello Doug,

Yes and no: the 46 MORP fireballs in question were photometrically analysed,
and dynamic masses calculated. All cases in question had calculated
endmasses of 150 grams or (sometimes much) larger (in fact, from 150 grams
to 40 kilo's). But almost all of these occurred over very remote parts of
Canada, hence their non-recovery, except for Innisfree, which was recovered.
Now, those calculated endmasses are something of an estimate, but still
these are suggestive cases. Most of these had end velocities below 10 km/s,
which means they crossed into the range where ablation  largely stops and
illumination is almost entirely due to deceleration, not ablation. Most have
suggestive low end altitudes too. If you search for literature on them: look
up papers by Halliday et al. in the NASA ADS (http://adswww.harvard.edu/).

The number of some 1000 meteors with initial speeds <27 km/s just shows that
these kind of meteors are not particularly rare. Not all of these would be
asteroidal, there's a part contributable to some short period comets as
well. And not all of the asteroidal objects will have been meteorite
droppers too.

> I do not dispute your frequencies you imply,
> as I am not sure if the supposed slower speeds
> at the end of the incandescent train can be I wonder,
> for example, if the Allende meteor(ite) appeared to zigzag.
> It heavily sloughed (fragmented) and probably did not go
> out in a single explosion I believe.  Some pieces have
> primary fusion crust, others secondary, others tertiary,
>  and others none.  Do you really think Allende came in
> a nice arc like the meteor photos you have?

Fragmentation is something different from zig-zagging. Fragmentation is
something that is well know for larger meteoroids. Fragments will usually go
at slightly divergent trajectories, yes. But that is not one fragment making
zig-zags, and that is waht we were discussing.

> still wondering if you really believe in the objections for Pasamonte
> (motion, dust train only)

Yes, I do believe in them. First, the picture really does not look like a
meteor picture to me. It shows something diffuse, not a trail of a meteor,
certainly not a bright one. And it does quite look like a somewhat motion
blurred picture of a persistent train to me. The twists shown in the train,
are the typical twists that quickly form in persistent trains. The kind of
blobs as shown at the end of the trail, is what you get when the meteor
flares, resulting in a bright and thicker  'knot' in the remaining
persistent train. Note that our group photographed quite some bright
meteors, and persistent trains. I do not understand at all why people keep
insisting that the Pasamonte picture is a good photograph of an actual
meteor. To me it is quite obvious, it is not. This apart from the way the
photograph was taken.

For some nice, and in-focus and not motion-blurred photographs of persistent
trains and the twist they get from high altitude winds, see these pages by
our DMS team Delphinus member Robert Haas (note that the pages take some
time to load):
http://delpsurf.www.cistron.nl/photons.htm
and:
http://delpsurf.www.cistron.nl/leo2001/photo7.htm
For a very interesting example showing the meteor itself too:
http://delpsurf.www.cistron.nl/leo2001/photo3.htm (here the first pic shows
the meteor itself, which is straight, and then shows the persitent train,
which twists)
http://delpsurf.www.cistron.nl/leo2001/photo4.htm is another example of
this.

These examples nicely illustrate how the meteor moves straight, but its
bright persistent train starts to twist. While the meteor is gone in a few
seconds and catches the casual observer unaware, such trains persist for
minutes, and I think it is the twisting character of the latter, which the
obsever can see at leisure, that fools casual observers in thinking that the
meteor itself, which they could not view at leisure, was twisted too.

- Marco

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Marco Langbroek
Dutch Meteor Society (DMS)
Leiden, the Netherlands
52.15896 N, 4.48884 E (WGS 84)

e-mail: meteorites at dmsweb.org
DMS website: http://www.dmsweb.org
priv. website: http://home.wanadoo.nl/marco.langbroek
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