[meteorite-list] Earth Rocks Could Have Taken Life to Titan (doubts)

[Mike Fowler]

> He says only boulders at least 3 metres across could punch out through
> the Earth's atmosphere and escape the planet's gravity, and that only
> extremely powerful impacts could achieve this. The cause of such  
> impacts
> would be comets or asteroids between 10 and 50 kilometres wide,  
> Gladman
> told New Scientist: "The kind of thing that killed the dinosaurs."

I have my doubts.  (again)  Someone please correct me if I err in my  
numbers or logic.

A rock being ejected into space is somewhat like a meteorite falling  
to Earth, but in reverse.
To be ejected into space the rock must leave Earth's atmosphere with  
escape velocity.  That means, it must have been accelerated to a  
velocity GREATER than escape velocity to account for the velocity  
lost punching thru Earths atmosphere.

Question #1  Can an impact accelerate rocks greater than 3 meters in  
diameter  to 15 kilometers per second,or more, without shock melting  
them, or pulverizing them?

Meteorites entering the Earth's atmosphere push ahead of them a  
column of air until the pressure on the meteorite exceeds the  
crushing strength of the meteorite, at which point it explodes and  
the surviving pieces fall under the influence of gravity.

Question #2  If a whole rock, 3 meters or more in diameter, could be  
accelerated to 15 kps intact, wouldn't the back pressure of the  
atmosphere exceed the strength of the rock resulting in fragmentation  
into pieces, just as happens to virtually all stony meteorites  
passing thru the Earth's atmosphere with similar velocity?  Such  
pieces will not coast into space, on the contrary they will be  
retarded by the remaining atmosphere, and quickly loose escape velocity.

I would never say something is impossible.

But I have my doubts about hundreds of millions of Earth Boulders  
being ejected thru the atmosphere unless you can overcome the above 2  
objections.

Any comments Sterling or others?

Mike Fowler
Chicago