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Re: Cometary meteoroids landing on sea?

Hello again,

Well as you might have assumed, the description in my first post
was not pure fantasy or a theoretical example.

Actually this spring there was a fall of an 'object' here in my country,
which has been much discussed in the media, including TV - mostly locally.
All kinds of theories of what it could have been have surfaced, from UFOs!,
falling satellites, defense missiles, amateur rockets, fireworks and then
lastly also meteorites.

The object fell on a early March evening at 21:30 hours (locally).
The witnesses seem to give descriptions of a phenomena which could be 
'a run of the mill' fireball:

- 'A fireball, exploding at several kilometers height,
slightly oblong shape, burning colour, great speed,
it rotated - like a flashlight rotating,
coming pretty steep down, it split into smaller pieces
and a bigger ball, no sound was heard'.

But what sets this apart from the ordinary fireballs is what was 
observed thereafter:
An object 4-5 meters long have been observed by several credible witnesses 
to fall into the sea and subsequently be floating 7-800 m ashore 
glowing/burning in '2-3 minutes time'.

The spot was searched from boat and police divers some days afterwards,
but nothing was found. The case seems to be dismissed as 'unexplainable'
by all parties, the most likely theory (of the police) seems to be an
amateur rocket...

What must have put off the meteor theory is the fact that it was _floating
and glowing afterwards in a period of 2-3 minutes_. Hardly the average 
behaviour of a chondrite or iron :)

(I hope this doesn't sound as 'a run of the mill' UFO-report! :-( All 
witnesses seems credible and can be contacted.)

...
About the speed of a possible cometary object of this size.
Remember that ice (if we mean water) has a weight of 0.9 tons/m^3
(or 0.9 kg/dm^3). That means that it is over 3 times lighter than
a stone and 7 times lighter than iron. The ice block will be much
more affected by air resistance. This relation is not linear,
but I really don't know how to calculate it (for the time being). 
The obtained speed from the retardation must be lower than 200 mph.
Does anyone have a possible surface speed value for a block of ice of
5 m length, being dropped from let's say 2 km height?
 
I would certainly think that a deep frozen core of a comet is not
brittle! It would be hard as stone (depending upon what kind of
strain it has experienced during the entry). 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. Remember also that the temperature inside
the surface is hardly affected by the melting on the surface as the
surface material is stripped off immedeatly!

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..?!

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.

Regards,
Bjørn Sørheim


At 11:18 11.07.98 EDT, you wrote:
>In a message dated 98-07-11 10:23:06 EDT, you write:
>
>bjorn<< 
> Comet surfaces are frosen gasses and liquids (water) - 'the dirty snowball'.
> If this material survives to the sea surface, what will happen?
> Let's also assume it is one of the smaller fireballs, so that it has achieved
>a
> terminal velocity of a free fall ~200 km/h. (Perhaps also somewhat slower 
> because of the light material in this case.) This means that the meeting with
> the water will not be too hard. <<
>
>Perhaps? But an object hitting water at 200 mph is quite violent...violent
>enough to kill people.  But when this very fragile object of cometary material
>meets the atmosphere at a high velocity prior to slowing down to terminal
>velocity....it will be quite traumatic I would think? I don't think it would
>be strong enough to withstnd the stresses involved...Most likely it will
>terminal burst if it reaches the lower atmosphere.
>
> bjorn>>Let's also assume that the material 'is on fire' in the later stage of
>the
> flight,
> Not necessarily all of the fire will be extinguished because of the meeting 
> with the water body.<<
>
>Okay...the object is at terminal velocity near 200 mph...too slow for friction
>to cause it to heat up and glow. There will be no "fire" to be extinguished by
>the water.
>
>bjorn>>If it is the dark part of the day, is it possible to
> have a floating 
> glowing/burning object on the sea surface for some time - until the waves and
> melting eventually will turn out the warmth and the remains will sink and
> disappear.
>  >>
>
>I think it has three chances for this to occur...Slim, Fat and None.    :o)
>George Zay
>
>

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