[meteorite-list] Two Questions

star-bits_at_meteoritecentral.com

--
Eric Olson
ELKK Meteorites
http://www.star-bits.com
> Hi Walter, Eric and List,
> Would Martian Tectonic forces ie. subduction, be a possible mechanism to 
> trap and transport atmospheric gases into the bowels of the planet, later to 
> be be contained in a magma chamber?
> Just an odd thought. Jerry
> ----- Original Message ----- 
> From: <star-bits_at_comcast.net>
> To: <meteorite-list_at_meteoritecentral.com>
> Sent: Tuesday, May 24, 2005 1:26 PM
> Subject: Re: [meteorite-list] Two Questions
> 
> 
> > Walter Branch wrote:
> >
> > <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.>
> >
> > Hello Walter
> >
> >    The mechanism for trapping gasses in Martian basalts is not entirely 
> > clear.  One method that has been proven is implanting during shock events, 
> > such as being blasted off Mars.  However there are some problems with this 
> > as well such as sometimes the gasses are fractionated (Kr/Xe ratio changes 
> > for instance).  So although impact is likely part of the answer it isn't a 
> > clear winner.  Another suggestion is fluid (water) transplant, however the 
> > gasses mostly reside in the water unaltered portions so this is likely not 
> > the answer.  Trapping of mantle gasses during cooling has been suggested, 
> > but mantle reservoirs of gasses should have different ratios than 
> > atmospheric.   So the exact mechanism is undetermined.
> >
> > <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?>
> >
> > Yes fragmentation and ablation can affect the results and must be taken 
> > into account.  Cosmic rays generally penetrate 3-10 meters into asteroidal 
> > bodies.  Parts buried more than 10 meters or so receive almost no cosmic 
> > ray exposure so their CRE age is zero.   If depth isn't taken into account 
> > a surface sample would show a older CRE than one at 5 meters.   One method 
> > of determining depth is with Neon isotopes which have been shown to have a 
> > constant relationship with burial depth and cosmic ray exposure.  So the 
> > neon can be used to determine depth and the other elemental isotopes can 
> > then be adusted for depth to give the CRE age.
> >
> >
> > --
> > Eric Olson
> > ELKK Meteorites
> > http://www.star-bits.com
> >
> >
> >> 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
> >>
> >>
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