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Re: Exotic meteorites? (was: Origins)

Most experts feel that our current sampling of meteorites comes
from the asteroid belt. It is not a representative sampling of all asteroids,
mostly it is a sampling of types that have wandered into one of the Kirkwood
gaps in the asteroid belt where Jupiter's influence would cause chaotic orbits.

There have been no known meteorites found that come from meteor showers, which
are remnants of comets.

The main problem to be addressed is how would an object that has been in orbit
around the sun for about 4.5 billion years suddenly find it's way to earth?

During the early bombardmant period where there were large body collisions,
what was to be the earth encountered many, but all evident of these have been
obliterated by geological activity since that time.

The process of planetary accretion was quite efficient and left very little
'rubble' behind between planets. There are only a few known bodies or groupings
of object that don't fall in the planetary orbits or asteroid belt. The belt itself
is believed to contain primitive planetary accretional stuff that never
amassed suffient matter to form a full-sized planet - due mostly to
the early formation of Jupiter which cleared out most of the larger
objects near it's orbit.

So, to take each of your questions:
1) how would an object get out of a planetary ring and fall to earth?
If something perturbed the ring, most likely the objects would fall into
a decaying orbit and impact the parent planet - the large ringed planets have
enormous gravity wells.

2) Volcanoes typically do not have sufficient eruptive power for ejecta to
attain escape velocity. There probably is a bit of Io's sulfur dust on nearby
moon, but that dust would have a hard time finding a path to earth and
surviving re-entry.

3) solar ejectas - I can't speak much about this, but most flares 
seem to collapse back onto the sun. The solar wind does reach earth
and we feel it's effect, but these particles are hardly meteorites.

4) Extra-solar meteorites and comets are certainly possible. But
the problem is like a needle in a haystack. Also, an object from
extra-solar space would most likely impact either Jupiter
or the Sun, the Earth is a very small target on these scales.

The closest thing we have in our collection to extra-solar
matter resides in Allende.

I don't think there is any strong evidence that we have a sample
of a comet in any of our collections, but there is a possibility.


> Julien COURTOIS wrote:
> 
> Hello list,
> 
> After weeks of lurking, it's probably time for me to jump in the cold and rather tumultuous waters of the meteorite-list ;-)
> 
> My first question would be: I have seen several explanations from where do the meteorites originate (asteroid belt, moon, mars, comets), but I've never heard or read any of the following explanations:
> 
> - Planetary rings (a piece of Saturn's rings would be sooo cool in my collection)
> - Planetary volcanoes ejectas (Io would be a very good candidate, but there are some more)
> - Solar ejectas
> - Extra-solar meteorites (I know, Allende have some CAl inclusions, but I'm speaking here of a _meteorite_ )
> - ...maybe I've forgotten something...
> 
> Do somebody knows why are these hypothesis not relevant?
> 
> Thanks in advance,
> 
> Julien
>

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