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: <[EMAIL PROTECTED]>
To: <meteorite-list@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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