[meteorite-list] Two Questions

[Walter Branch]

Second try at posting this email:

Hello Everyone,
 
I been researching but I can't find the answers to two questions.
 
First, what is the mechanism by which atmospheric gasses
are trapped in the formation of basalts?  I have been doing some 
lit reviews on martian meteorites and I find it interesting that some
were formed in magma chambers deep undergound.  indeed, some are 
thought to have formed several kilometers down.  How does the 
Martian atmosphere get trapped in cooling rock so far underground.
 
Second, when determining Cosmic Ray Exposure ages, can atmospheric
fragmentation and ablation of a meteoroid affect the results from such 
testing and if so, how are fragmentation and ablation taken into
consideration when determiniing CREs?
 
Thanks to anyone who can help me understand these processes.
 
-Walter Branch