[meteorite-list] Iranian Fireball Was Of Geophysical Origin

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From: MexicoDoug_at_aol.com <MexicoDoug_at_meteoritecentral.com>
Date: Thu Apr 22 10:31:22 2004
Message-ID: <c0.5202343.2d5e5171_at_aol.com>

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This topic was discussed a few weeks ago on the list, and it seems pretty=20
convincing that Earth parented meteorites are elusive for good scientific=20
reasoning - it seems that if conditions to produce them happened, that the m=
aterial=20
would be glass or a split planet Earth (a la did the moon come from Earth=20
question we had recently).=A0=20

While it may be possible (though statistically highly improbable), it is=20
important not to say it is "a bit of a stretch", "just like we have Martian=20
meteorites here".

Those statements taken together are misleading, to say the least.

It is important to recognize that Earth and Mars are so different regarding=20
atmospheric density (over 100X) / viscosity and to a much lesser degree=20
gravity, that such an analogy is not based on astronomy and physics, but rat=
her=20
wishful thinking, with a general ignoring of scientific principles - i.e. a=20
solution (Earth parented meteorites exist because I can think it and there a=
re=20
Martian meteorites here) looking for a problem (Why no one has ever confirme=
d an=20
Earth parented meteorite).

Extending that logic, I would ask where the Solar parented meteorites are at=
,=20
and while we are at it the Jovian parented=A0 and Venusian parented meteorit=
es=20
as well.=A0 The conditions on Mars simply do not lend themselves for compari=
son=20
to Earth.=A0 Venus is a better comparison for Earth.=A0 Perhaps someone coul=
d work=20
out the physics to show what sort of impactor on Earth is capable of causing=
s=20
something besides glass and giving it escape velocity.

Without doing the physics, it is clear it would have to be a kilometer plus=20
sized impactor imparting in an instant to a kilometer plus sized Earth rock=20
escape velocity plus frictional loss velocity, which further does not explod=
e=20
with that velocity at sea level as it makes its way through the exponiential=
ly=20
most dense part of the atmosphere (i.e. a "reverse meteorite") at a right or=
=20
obtuse angle to the impact (which tends to create a velocity vector landing=20=
back=20
on Earth).=A0 While this might sound "plausible", for an impactor to produce=
a=20
kilometer plus sized rock with such a velocity seems nearly impossible, know=
ing=20
the characteristics of Earth surface features.

To actually achieve the above, either ground zero has to become liquid or=20
plasma eventually producing glasses, for which there is some evidence in=20
tektites, or Earth must be split like a nut, for which the Moon was presente=
d as=20
evidence in such a hypothethised impact around 4.5 billion years ago....

So that would leave a scenario of a gigantic impactor hitting near the base=20
of a Mount Everest made of solid iron or other high tensile type structure,=20
incoming at a low entry angle, and propelling the peak into outer space.

In the case of Mars objects over 10 meters (but probably in the realm 500 km=
)=20
can impact whole much more readily and produce "reverse meteorites" with the=
=20
initial velocities potentially conducive to this event which can escape more=
=20
readily as gravity (and hence resulting escape velocities) is less than 40%=20
Earth's.=A0 Furthermore Mars is closer to the Asteroid belt and is expected=20=
to have=20
more flux of such potential impacts.

Saludos
Doug Dawn
Mexico

En un mensaje con fecha 02/13/2004 8:21:52 AM Mexico Standard Time,=20
cviau_at_beld.net escribe:

> and bit of a stretch.. but plausible:=A0 Just like we have
> Martian meteorites here on earth, so would we not have some of the
> ejecta from our terrestrial impacts also in orbit around the Sun

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<HTML><HTML>This topic was discussed a few week=
s ago on the list, and it seems pretty convincing that Earth parented meteor=
ites are elusive for good scientific reasoning - it seems that if conditions=
to produce them happened, that the material would be glass or a split plane=
t Earth (a la did the moon come from Earth question we had recently).=A0 <BR=
>
 
While it may be possible (though statistically highly improbable), it is imp=
ortant not to say it is "a bit of a stretch", "just like we have Martian met=
eorites here". 
 
Those statements taken together are misleading, to say the least. 
 
It is important to recognize that Earth and Mars are so different regarding=20=
atmospheric density (over 100X) / viscosity and to a much lesser degree grav=
ity, that such an analogy is not based on astronomy and physics, but rather=20=
wishful thinking, with a general ignoring of scientific principles - i.e. a=20=
solution (Earth parented meteorites exist because I can think it and there a=
re Martian meteorites here) looking for a problem (Why no one has ever confi=
rmed an Earth parented meteorite). 
 
Extending that logic, I would ask where the Solar parented meteorites are at=
, and while we are at it the Jovian parented=A0 and Venusian parented meteor=
ites as well.=A0 The conditions on Mars simply do not lend themselves for co=
mparison to Earth.=A0 Venus is a better comparison for Earth.=A0 Perhaps som=
eone could work out the physics to show what sort of impactor on Earth is ca=
pable of causings something besides glass and giving it escape velocity. 
 
Without doing the physics, it is clear it would have to be a kilometer plus=20=
sized impactor imparting in an instant to a kilometer plus sized Earth rock=20=
escape velocity plus frictional loss velocity, which further does not explod=
e with that velocity at sea level as it makes its way through the exponienti=
ally most dense part of the atmosphere (i.e. a "reverse meteorite") at a rig=
ht or obtuse angle to the impact (which tends to create a velocity vector la=
nding back on Earth).=A0 While this might sound "plausible", for an impactor=
to produce a kilometer plus sized rock with such a velocity seems nearly im=
possible, knowing the characteristics of Earth surface features. 
 
To actually achieve the above, either ground zero has to become liquid or pl=
asma eventually producing glasses, for which there is some evidence in tekti=
tes, or Earth must be split like a nut, for which the Moon was presented as=20=
evidence in such a hypothethised impact around 4.5 billion years ago.... 
 
So that would leave a scenario of a gigantic impactor hitting near the base=20=
of a Mount Everest made of solid iron or other high tensile type structure,=20=
incoming at a low entry angle, and propelling the peak into outer space. 
 
In the case of Mars objects over 10 meters (but probably in the realm 500 km=
) can impact whole much more readily and produce "reverse meteorites" with t=
he initial velocities potentially conducive to this event which can escape m=
ore readily as gravity (and hence resulting escape velocities) is less than=20=
40% Earth's.=A0 Furthermore Mars is closer to the Asteroid belt and is expec=
ted to have more flux of such potential impacts. 
 
Saludos 
Doug Dawn 
Mexico 
 
En un mensaje con fecha 02/13/2004 8:21:52 AM Mexico Standard Time, cviau_at_be=
ld.net escribe: 
 
<BLOCKQUOTE TYPE=3DCITE style=3D"BORDER-LEFT: #0000ff 2px solid; MARGIN-LEFT=
: 5px; MARGIN-RIGHT: 0px; PADDING-LEFT: 5px">and bit of a stretch.. but plau=
sible:=A0 Just like we have 
Martian meteorites here on earth, so would we not have some of the 
ejecta from our terrestrial impacts also in orbit around the Sun</BLOCKQUOTE=
> 
</HTML>
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Received on Fri 13 Feb 2004 11:12:33 AM PST

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