[meteorite-list] Meteorite Questions

[star-bits at tx.rr.com]

Walter branch wrote:

<Traveling over eons to make it to the inner solar system, how can a 
meteoroid stream stay intact enough to cause a tiny strewnfield on the 
Earth? I would not think that the Earth's gravitational field would be 
strong enough to do what Jupiter did.>

     The small strewnfields are caused not by meteoroid streams, but by an asteroid which is gravitationally clumped rocks and not a solid chunk.  Because they are just gravitationally attached to each other the earths gravity probably starts separating them and then the atmosphere easily separates them farther.
 
     <Also, I know I have asked this before but I still don't understand how 
researchers can determine cosmic ray exposure ages for a meteorite which 
ablated a significant portion of the material that absorbed most of the 
cosmic rays and which may have fragmented in flight through the Earth's 
atmosphere. >

     One way of doing this is using Neon isotopes.  I forget the exact details, but the relative abundances of the neon isotopes can be used to determine depths.   This can then be used to make a correction for depth for the other noble gases which are then used for calculating the CRE.

--
Eric Olson
7682 Firethorn Dr
Fayetteville, NC 28311

http://www.star-bits.com