[meteorite-list] Re: Iron meteorite & Mars Water articles

From: meteoriteplaya_at_comcast.net <meteoriteplaya_at_meteoritecentral.com>
Date: Thu Jun 29 20:08:00 2006
Message-ID: <062920062319.10955.44A4600D0004931100002ACB22135396530E970E049F0A9B079D010A9B0A03_at_comcast.net>

Hi All
There are a couple of interesting articles in the June 15, 2006 issue of Geochimica et Cosmochimica Acta. Unfortunately only the abstracts are viewable on the website.
Enjoy

1) Silica and pyroxene in IVA irons; possible formation of the IVA magma by impact melting and reduction of L-LL-chondrite materials followed by crystallization and cooling John T. Wasson, Yoshiyuki Matsunami and Alan E. Rubin

Abstract (Too long to put in this post)
http://makeashorterlink.com/?C1762395D


2) Metallographic cooling rates of the IIIAB iron meteorites
Jijin Yang and Joseph I. Goldstein

Link to abstract http://makeashorterlink.com/?H5A62395D

Abstract
An improved computer simulation program has been developed and used to re-measure the metallographic cooling rates of the IIIAB irons, the largest iron meteorite chemical group. The formation of this chemical group is attributed to fractional crystallization of a single molten metallic core during solidification. Group IIIAB irons cooling rates vary by a factor of 6 from 56 to 338 °C/My. The cooling rate variation for each meteorite is much smaller than in previous studies and the uncertainty in the measured cooling rate for each meteorite is greatly reduced. The lack of correction for the orientation of the kamacite–taenite interface in the cooling rate measurement of a given meteorite in previous studies not only leads to large cooling rate variations but also to inaccurate and low cooling rates. The cooling rate variation with Ni content in the IIIAB chemical group measured in this study is attributable, in part, to the variation in nucleation temperature of the Widmanstat
 ten pa
ttern with Ni content and nucleation mechanism. However, the factor of 6 variation in cooling rate of the IIIAB irons is hard to explain unless the IIIAB asteroidal core was exposed or partially exposed in the temperature range in which the Widmanstatten pattern formed. Measurements of the size of the island phase in the cloudy zone of the taenite phase and Re–Os data from the IIIAB irons and the pallasites make it hard to reconcile the idea that pallasites are located at the boundary of the IIIAB asteroid core.


Here is some interesting information on water on Mars from Elements magazine. Two of the articles mention Martian meteorites role in the research.

1) Water on Mars Harry Y. McSween Jr
2) Aqueous Processes Recorded by Martian Meteorites: Analyzing Martian Water on Earth Laurie A. Leshin and Edward Vicenzi

Unfortunately full text of the articles will not be available of a couple of months (probably in August). Just keep checking back at this url http://www.elementsmagazine.org/

Mike

--
Mike Jensen
Jensen Meteorites
16730 E Ada PL
Aurora, CO 80017-3137
303-337-4361
IMCA 4264
website: www.jensenmeteorites.com

Received on Thu 29 Jun 2006 07:19:41 PM PDT