[meteorite-list] Yet more gleanings from the MAPS abstracts -

From: Galactic Stone & Ironworks <meteoritemike_at_meteoritecentral.com>
Date: Mon, 20 Jul 2009 16:06:30 -0400
Message-ID: <e51421550907201306w37b071e7xd663d2ada039d18e_at_mail.gmail.com>

Hi List,

In the July 2009 MAPS supplement, I ran across a few more interesting
abstracts -

"CR54 Isotopic Anomalies in the Tagish Lake and Orgueil Carbonaceous
Chondrites."

In this study, samples of Tagish Lake and Orgueil were examined using
stepwise dissolution. CR was released and then measured. The
results, quoted below say it all -

"We report here the highest CR54 excess found so far in a silicate
fraction of a meteorite. This occurs in Tagish Lake and reinforce the
fact that this meteorite is made up of very pristine material (the
most pristine of all according to this study) and strengthens
suggestions that Tagish Lake may have originated from a comet or a
type-D asteroid in a cold region beyond the asteroid belt, where it's
components could have conserved their pristine signatures."

...

Another fascinating abstract, that left wanting more detailed info, was this -

"Six Models for the Formation of the Earth's Atmosphere"

In studying the source and formation of planetary atmospheres, six
different models were used to simulate the formation of an Earth-type
atmosphere.

Model #1 is the volcanic atmosphere as defined by W.W. Rubey.
Model #2 is the atmosphere released by geysers and fumaroles
contaminated with surface water.
Model #3 is outgassed Hawaiian volcanoes, sourced from a degassed upper mantle.
Model #4 is atmosphere expected by a purely cometary impact.
Model #5 is a "steam" atmosphere from a CI-type asteroid impact.
Model #6 is a pure meteoroid atmosphere from sustained bombardment.

Guess which model came closest to producing Earth's atmosphere?

#6. Only the #6 model fits the measure composition of Earth's
atmosphere. Also of note is that the very low Ne mixing ratio
invalidates the 5th model completely.

So, perhaps we owe the water we drink and the air we breathe to meteorites. :)

That's all for now....more gleanings later....

Best regards and clear skies,

MikeG

-- 
.........................................................
Michael Gilmer (Florida, USA)
Member of the Meteoritical Society.
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Received on Mon 20 Jul 2009 04:06:30 PM PDT