[meteorite-list] Re: Scientists Find Mars Met. (NWA 1950)

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From: MexicoDoug_at_aol.com <MexicoDoug_at_meteoritecentral.com>
Date: Thu Apr 22 10:31:57 2004
Message-ID: <174.2493e06b.2d29bd7b_at_aol.com>

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I've alway had that exact same question: Where are the Earth meteorites? Th=
e=20
answers I have contemplated are, which only plug the curiosity, and I=20
apologise if this is basic stuff published in some texts, as I have yet to r=
ead and=20
meteorite reference materials except "Find a Falling Star":

Tektites are a form of Earth Meteorites that didn't make escape velocity. =20
And we have plenty of them.

>From a collision with the Earth, by an impacting stone or iron, anything=20
which DID obtain escape velocity from the Earth would do just that: escape.=20=
It=20
would go any direction AWAY from the earth.

The gravity of Earth is much greater than the minimal gravity of the=20
asteroids, and also greater than Mars or the Moon. So a much greater escape=
velocity=20
is required to remove material from Earth.

Additionally, Due to the atmosphere Earth has, at least atmospheric density=20
in the last X millions of years, a hot stone propelled from Earth would have=
to=20
be fairly large to have it not dampened and returned to Earth. Thus, all=20
small stones would be quenched , by the atmosphere, medium stones exploded a=
nd=20
quenched. That leaves very large stones...

All the potential meteorites that have returned to Earth during the=20
provolking impact events timing have degraded and blended in with the surrou=
nding rock,=20
except for some impact glasses, as glass as we all know is nearly=20
indestructable for millions of years. So it would have to be a rock returni=
ng during the=20
last few dozen thousands of years.

If Earth material is ejected in an orbit coincidentally similar to Earths, i=
n=20
a few years the Earth will alter its course and sweep it up.

Thus only very massive rocks sent AWAY from Earth's orbit would be potential=
=20
meteorites.

To actually become a meteorite on Earth, that big body would have to later=20
suffer a collision and be once again propelled towards Earth's orbit. The c=
ase=20
with Mars is different since this material not swept out by Mars may settle=20
into near Earth's orbit over astronomical scales.

Table:
Escape velocity; Atmospheric density vs. Earth

Earth 11.2 km/sec (25,000 mph); 1.00
Venus 10.4 km/sec (23,200 mph); 90
Mars 5.0 km/sec (11,200 mph); 0.01=20
Luna 2.4 km/sec (5,400 mph); 0.00
Vesta 0.39 km/sec (870 mph); none

So you can see why there are no Venusian meteorites found yet -- ther=20
atmosphere is 90 times thicker than Earth's, similar gravity and escape velo=
city (you=20
weigh 90% your Earth weight on Venus) and just as meteorites usually reach=20
free fall velocities when hitting Earth, to escape Earth, its the same in=20
reverse. One must ask, when was the last meteorite we know of that hit Eart=
h at=20
more than free fall velocity? Perhaps Siberia (1908, the largest fall in th=
e=20
last 2000 years, probably 400,000,000 Kg stone, known to have blown a man in=
to a=20
tree forty feet away hundreds of km from impact, who later died of the injur=
y)=20
... no not even that one...it couldn't handle the atmosphere!!! So, the=20
small fragments upon an Earth impact typically would be blown to smitherines=
=20
recaptured and fall immediately due to the atmospheric damping. And if they=
are=20
Earth rocks, unless it is a fresh fall, one will never know as all but tekti=
tes=20
disintegrate rapidly (less than a million years - excepting very special=20
preservation circumstances).

If you look at my table atmospheres, you will see that the moon has none, an=
d=20
Mars only 1% of Earth's. Add that to the fact that Escape velocity is less=20
than half for Mars, and for the Moon, almost down to a fifth, then mix in th=
at=20
within 1,000,000 years, the Earth and Moon will sweep out virtually all of t=
he=20
rocks that pass by its orbit, or change their orbit.

In the case of Mars, the expulsion is more random from our point of view, an=
d=20
although it is still unlikely, it is quite believable that some mass could b=
e=20
orbiting, around, further modified by Jupiter and impacts in the asteroid=20
belt that can find its way to Earth. In the case of the Moon they should be=
much=20
more common, except for the fact of the sweeping, they get cleaned out=20
quickly on an astronomic scale.

If you still don't believe me, ask yourself (if you believe in Tektites):=20
What is the largest known tektite? That should make things clearer as to wh=
at=20
happens to the resulting particles of a big impact, of the type necessary to=
=20
make Earth meteorites, after the secondary shocking of atmospheric passage.=20=
=20
Anyone have a one kilo tektite? And hot SiO2 I would guess is more cohesive=
(=3D=20
larger fragments) than other "typical" Earth rocks.

Those are the arguments I can come up with for the lack of Earth parented=20
meteorites. Of course, they are statistical, and a single rock doesn't foll=
ow=20
statistics, just what happens to it...so don't give up looking for Earth=20
meteorites.

PS I would expect the Moon to have conserved some Earth meteorites, and=20
perhaps some of the fresh Howardites contain ancient Earth meteorites.

Saludos,
Doug Dawn
Mexico

En un mensaje con fecha 01/04/2004 8:04:48 AM Mexico Standard Time,=20
cviau_at_beld.net escribe:

>=20
> Really, can you imagine making an announcement like that and typo such=20
> important dating?
>=20
> =20
>=20
> Your question is really a good one, and I have always thought that there=20
> MUST be some terrestrial =E2=80=98meteorites=E2=80=99 misclassified as bei=
ng of=20
> extraterrestrial origin.
>=20
> I also would like to hear a good reason why they are missing from the fin=
d=20
> records.
>=20
> =20
>=20
> Regards,
>=20
> CharlyV
>=20
> =20
>=20
> -----Original Message-----
> From: meteorite-list-admin_at_meteoritecentral.com=20
> [mailto:meteorite-list-admin_at_meteoritecentral.com] On Behalf Of Fredmeteor=
hall_at_aol.com
> Sent: Sunday, January 04, 2004 4:29 AM
> To: baalke_at_zagami.jpl.nasa.gov; meteorite-list@meteoritecentral.com
> Subject: [meteorite-list] Re: Scientists Find Mars Met. (NWA 1950)
>=20
> =20
>=20
> "SNC meteorites are extremely rare - fewer than 20 confirmed examples=20
> have been discovered - and are believed to all come from the same body of=20=
rock.=20
> They are distinguished by their relative youth, being at most 1.3 million=20
> years old, compared to 4.5 million for other meteorites." From "Scientists=
find=20
> Mars meteorite" "From Gerard Sevestre in Paris" January 04, 2004.
> Hum, 1.3 million, 4.5 million? Not 1.3 billion and 4.5 billion? "fewer=
=20
> than 20 confirmed examples"???=20
> Regards, Fred Hall
> What was Earth's atmosphere like 1.3 Billion years ago? I'm sure Earth=
=20
> had hydrated basaltic rocks then, right? Is there any possibility that som=
e of=20
> the SNC's (lava meteorites) are not from Mars, but Earth? Isn't there an=20
> Earth meteor crater that formed around 1.3 billion years ago? I have yet=20=
to=20
> hear a good reason as to why we have not found an "Earth meteorite". Some=20
> scientist out there, please set me straight as to why we have found some 2=
5+ Mars=20
> meteorites and not one Earth meteorite.
> Thanks
>=20
>=20
>=20

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<HTML><HTML>I've alway had that exact same ques=
tion: Where are the Earth meteorites?  The answers I have contemplated=20=
are, which only plug the curiosity, and I apologise if this is basic stuff p=
ublished in some texts, as I have yet to read and meteorite reference materi=
als except "Find a Falling Star": 
 
Tektites are a form of Earth Meteorites that didn't make escape velocity.&nb=
sp; And we have plenty of them. 
 
>From a collision with the Earth, by an impacting stone or iron, anything whi=
ch DID obtain escape velocity from the Earth would do just that: escape. It=20=
would go any direction AWAY from the earth. 
 
The gravity of Earth is much greater than the minimal gravity of the asteroi=
ds, and also greater than Mars or the Moon.  So a much greater escape v=
elocity is required to remove material from Earth. 
 
Additionally, Due to the atmosphere Earth has, at least atmospheric density=20=
in the last X millions of years, a hot stone propelled from Earth would have=
to be fairly large to have it not dampened and returned to Earth.  Thu=
s, all small stones would be quenched , by the atmosphere, medium stones exp=
loded and quenched.  That leaves very large stones... 
 
All the potential meteorites that have returned to Earth during the provolki=
ng impact events timing have degraded and blended in with the surrounding ro=
ck, except for some impact glasses, as glass as we all know is nearly indest=
ructable for millions of years.  So it would have to be a rock returnin=
g during the last few dozen thousands of years. 
 
If Earth material is ejected in an orbit coincidentally similar to Earths, i=
n a few years the Earth will alter its course and sweep it up. 
 
Thus only very massive rocks sent AWAY from Earth's orbit would be potential=
meteorites. 
 
To actually become a meteorite on Earth, that big body would have to later s=
uffer a collision and be once again propelled towards Earth's orbit.  T=
he case with Mars is different since this material not swept out by Mars may=
settle into near Earth's orbit over astronomical scales. 
 
Table: 
Escape velocity; Atmospheric density vs. Earth 
 
Earth 11.2 km/sec (25,000 mph); 1.00 
Venus 10.4 km/sec (23,200 mph); 90 
Mars 5.0 km/sec (11,200 mph); 0.01 
Luna 2.4 km/sec (5,400 mph); 0.00 
Vesta 0.39 km/sec (870 mph); none 
 
So you can see why there are no Venusian meteorites found yet -- ther atmosp=
here is 90 times thicker than Earth's, similar gravity and escape velocity (=
you weigh 90% your Earth weight on Venus) and just as meteorites usually rea=
ch free fall velocities when hitting Earth, to escape Earth, its the same in=
reverse.  One must ask, when was the last meteorite we know of that hi=
t Earth at more than free fall velocity?  Perhaps Siberia (1908, the la=
rgest fall in the last 2000 years, probably 400,000,000 Kg stone, known to h=
ave blown a man into a tree forty feet away hundreds of km from impact, who=20=
later died of the injury) ... no not even that one...it couldn't handle the=20=
atmosphere!!!  So, the small fragments upon an Earth impact typically w=
ould be blown to smitherines recaptured and fall immediately due to the atmo=
spheric damping.  And if they are Earth rocks, unless it is a fresh fal=
l, one will never know as all but tektites disintegrate rapidly (less than a=
million years - excepting very special preservation circumstances). 
 
If you look at my table atmospheres, you will see that the moon has none, an=
d Mars only 1% of Earth's.  Add that to the fact that Escape velocity i=
s less than half for Mars, and for the Moon, almost down to a fifth, then mi=
x in that within 1,000,000 years, the Earth and Moon will sweep out virtuall=
y all of the rocks that pass by its orbit, or change their orbit. 
 
In the case of Mars, the expulsion is more random from our point of view, an=
d although it is still unlikely, it is quite believable that some mass could=
be orbiting, around, further modified by Jupiter and impacts in the asteroi=
d belt that can find its way to Earth.  In the case of the Moon they sh=
ould be much more common, except for the fact of the sweeping, they get clea=
ned out quickly on an astronomic scale. 
 
If you still don't believe me, ask yourself (if you believe in Tektites): Wh=
at is the largest known tektite?  That should make things clearer as to=
what happens to the resulting particles of a big impact, of the type necess=
ary to make Earth meteorites, after the secondary shocking of atmospheric pa=
ssage.  Anyone have a one kilo tektite?  And hot SiO2 I would gues=
s is more cohesive (=3D larger fragments) than other "typical" Earth rocks.<=
BR>
 
Those are the arguments I can come up with for the lack of Earth parented me=
teorites.  Of course, they are statistical, and a single rock doesn't f=
ollow statistics, just what happens to it...so don't give up looking for Ear=
th meteorites. 
 
PS I would expect the Moon to have conserved some Earth meteorites, and perh=
aps some of the fresh Howardites contain ancient Earth meteorites. 
 
Saludos, 
Doug Dawn 
Mexico 
 
 
En un mensaje con fecha 01/04/2004 8:04:48 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"> 
Really, can you imagine making an announcement like that and typo such impo=
rtant dating? 
 
  
 
Your question is really a good one, and I have always thought that there MU=
ST be some terrestrial =E2=80=98meteorites=E2=80=99 misclassified as being o=
f extraterrestrial origin. 
 
I also would like to hear a good reason why they are missing from the find=
records. 
 
  
 
Regards, 
 
=
CharlyV 
 
  
 
-----Original Message----- 
From: meteorite-list-admin_at_meteoritecentral.com [mailto:meteorite-lis=
t-admin_at_meteoritecentral.com] On Behalf Of Fredmeteorhall@aol.com 
Sent: Sunday, January 04, 2004 4:29 AM 
To: baalke_at_zagami.jpl.nasa.gov; meteorite-list@meteoritecentral.com<B=
R>
Subject: [meteorite-list] Re: Scientists Find Mars Met. (NWA 1950)</F=
ONT><B=
R>
 
  
 
&=
nbsp;   "SNC meteorites are extremely rare - fewer than 20 confirm=
ed examples have been discovered - and are believed to all come from the sam=
e body of rock. They are distinguished by their relative youth, being at mos=
t 1.3 million years old, compared to 4.5 million for other meteorites." From=
"Scientists find Mars meteorite" "From Gerard Sevestre in Paris" January 04=
, 2004. 
    Hum, 1.3 million, 4.5 million? Not 1.3 billion and 4.5 bi=
llion? "fewer than 20 confirmed examples"??? 
Regards, Fred Hall 
    What was Earth's atmosphere like 1.3 Billion years ago? I=
'm sure Earth had hydrated basaltic rocks then, right? Is there any possibil=
ity that some of the SNC's (lava meteorites) are not from Mars, but Earth? I=
sn't there an Earth meteor crater that  formed around 1.3 billion years=
ago? I have yet to hear a good reason as to why we have not found an "Earth=
meteorite". Some scientist out there, please set me straight as to why we h=
ave found some 25+ Mars meteorites and not one Earth meteorite. 
Thanks 
 
 
</BLOCKQUOTE> 
 
</HTML>
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Received on Sun 04 Jan 2004 02:03:23 PM PST

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