[meteorite-list] Tektites and Meteorites of Terrestrial Origin

From: MexicoDoug_at_aol.com <MexicoDoug_at_meteoritecentral.com>
Date: Sun Jun 4 19:41:07 2006
Message-ID: <47a.2b9f041.31b4814e_at_aol.com>

Rob M. wrote:

>Considering that there are readily identified
>meteorites from two other large bodies on earth, I
>find it hard to believe that there are none from
>Earth. The higher gravity and thicker atmosphere
>cannot account for it all, surely.
 
Large Bodies, my Lad! Large Bodies, Indeed! On the Moon, the astronauts
jumped tall buildings in a single bound...Granted, Mars, has a higher gravity
and thicker atmosphere, so let's forget about the debilitatively beautiful
Moon by comparison.
 
Question: Where on Earth would one need to be to duplicate the more
favorable Martian conditions at Martian ground-zero for the successful meteorite
ejections observed to have landed on Earth? (Without even considering the
possibility of meteorites from Olympus Mons at over thrice the height of Everest?
 
Answer: 25 km high for atmosphere thickness and 3,950 km high for gravity.
 
At 25 kilometers high on Earth we can match Martian surface pressure with
our exponential drop off in pressure - though the drop off on Earth is somewhat
more pronounced due to its being about 60% our scale height, I'm thinking.
To find the Gravitational point of reference corresponding to Mars' surface
on Earth we note that great Englishman's Universal law of gravitation Mm/r2
dependence. The radius of Mars is: 53% of Earth, and it's mass is 10.7% of
Earth. So (.107)/(.53*.53) is 38% at Mar's surface. To get to 38% earth's
gravity with Earth's mass this changes to 1/(d2)=.38 =>d2=2.63=> thus d=1.62
I.e., 62% of our radius in height above earth's surface. Our planet's radius
is about 6370 km. ===> You need to be 3,950 km high above earth to get to
only 38% of the gravity.
 
In conclusion, you might as well be comparing Jupiter to Earth as well as
Earth to Mars. Most meteorites don't really start to break up until below 25
km, and even then, to make it into the envelope of survival, they need to come
in quite slowly. As far as gravity, to equalize it you'd need to be more
than 10 times higher out into space than the International Space Station!
 
You're right, atmosphere and gravity don't account for everything but they
are pretty important laws for the survival of Earth's finest...not to be
confused with the fining done to glass...
 
Saludos, Doug
 
Received on Sun 04 Jun 2006 02:32:46 PM PDT