[meteorite-list] Tunguska Questions

[Meteorites USA]

In response to your question...

"...A couple small asteroids per year do themselves in without leaving 
ground fragments seems natural, why not a somewhat bigger asteroid once 
every 50 or 100 years doing the same thing?..."

OK, I'll go along with that "if" you can answer this question 
definitively with an absolution and no doubt.

How do we know for sure we're looking in the right place? (in regards to 
any fireball not just the Tunguska event)

The quick and dirty answer is obviously we don't know for sure until we 
give up the search or find a meteorite. We are basing the assumption of 
disintegration on fruitless searches for meteorites from other fireballs 
throughout history. Of all fireballs and meteoroid/asteroid air-bursts 
how many of those fireballs actually get chased? And of those that do 
get chased how many of those searches are looking in the right area?

Oh yeah... Of all historical "witnessed" meteorite falls, how many were 
found by using trajectory calculations by scientists or meteorite 
hunters? Most meteorites that come from witnessed falls I've researched 
have been found by farmers, villagers, or residents of towns and cities 
in or near where the meteorites fell, relatively easily locatable, and 
usually only because they saw it hit the ground, heard it hit, or 
noticed the "odd rock" on the ground. In some cases meteorites actually 
struck people or objects.

LIST OF WITNESSED METEORITE FALLS:
http://en.wikipedia.org/wiki/Meteorite_falls

Locating a meteorite strewnfield when one witnesses a distant fireball 
is difficult on a small asteroid or meteoroid. So without conclusive 
data or studies on a number of witnessed fireballs that resulted in 
meteorites being recovered one can only assume that when no meteorites 
are found that it burned up completely.

My suggestion is very simple. Did anyone ever consider that this 
disintegration theory might be incorrect because we might just simply be 
looking in the wrong place? In Tunguska we're assuming that any 
meteorite fragments would be directly beneath the epicenter.

So my big question still stands... How do we know for sure EVERYTHING 
disintegrates, burns up, or vaporizes, without going to each witnessed 
location and compiling solid data?

If there is solid data on this (meteorite dropping fireball expeditions 
in general) I'd like to know where it is... I've searched for the data, 
but maybe I'm just looking in the wrong place too...

In the case of Tunguska the first successful expedition made it to the 
epicenter 19 years after the fact.

Regards,
Eric




GeoZay at aol.com wrote:
>>> I agree... If the Tunguska event was  caused by a comet and not a 
>>>       
> meteoroid or asteroid there truly may not be any  material left from the 
> blast. However, if I remember correctly, the cometary  theory is based 
> not just on the fact no meteorites were found near the  epicenter, but 
> somewhat on the presence of high levels of carbon in the  samples taken 
> from peat and tree bark drill core samples near the epicenter.  A 
> carbonaceous meteoroid/asteroid could have left those same levels of  
> carbon.<<
>
> I personally think that Tunguska was an asteroid. For no  better reason 
> that to me it represents a little larger object than what hits our  atmosphere 
> a few times each year. Why not a similar object somewhat bigger with  
> similar characteristics on occasions? Tunguska was a big wallop and so were two  
> others in the 1930's over the Amazon basin, though somewhat smaller than  
> Tunguska, but it still knocked over trees for a few miles with no meteorite  
> fragments that I know of. A couple small asteroids per year do themselves in  
> without leaving ground fragments seems natural, why not a somewhat bigger  
> asteroid once every 50 or 100 years doing the same thing? 
> GeoZay  
>
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-- 
Regards,
Eric Wichman
Meteorites USA
http://www.meteoritesusa.com
904-236-5394