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
geo...@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
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