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bjorn>>I would certainly think that a deep frozen core of a comet is not
brittle! <<
I doubt it would be pliable.
bjorn>>It would be hard as stone (depending upon what kind of
strain it has experienced during the entry). <<
It would be as fragile as a piece of ice being slammed against the sidewalk.
This is what it will meet when a piece of cometary material encounters the
dense atmosphere. Stone has a better chance of surviving this encounter. Iron
would have an even better chance.
bjorn>>Remember that a cometary
fragment must have a tremendously larger melting rate than a stone
or a iron. So one would get in the end the absolute inner core which
would be the coldest part. <<
The bottom line is that cometary material is quite fragile from the
differences in pressure from the front and back...enough so that it's not
strong enough to resist from being obliterated.
bjorn>>About the fire: Of course there would be 'fire'!
The 'fire' will be left from the violent reentry face. There
will at least be ice/water steaming. And as it is a probable dirty
snowball, 'the dirt' would burn and glow, I would imagine..?!<<
No there wouldn't be fire...particularly if it's only traveling at terminal
velocity. If it was over around 10 tons in size, it would just barely be going
about 2 percent of it's original cosmic velocity...but not fast enough to
glow...thus no fire. At best it would be somewhat warm upon hitting the
ground.
bjorn>>To sum up, I think there are at least _two factors_ that would make it
survive, contrary to what one would assume:
- It is stone hard frozen in the surviving core.
- It will fall a lot slower than a stone or iron from the
retardation point, becuse of its lower density.
>>
Being stone hard frozen wouldn't matter. An object after reaching it's
retardation point should fall slower than it's original cosmic velocity...but
it's the initial encounter having this cosmic velocity with the atmosphere
that's gonna obliterate it long before it will have to deal with a terminal
velocity.
George Zay
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