Hello Eric and Meteorite List,
Robert Matson makes a key point on this question: How does the iron migrate to the core? "Through the combination of porosity, heat and gravity. If you start with a glass of finely crushed ice and let it melt, the water doesn't stay put in the ice matrix -- it settles to the bottom (since water is denser than ice)." This establishes the hole in the dyck. However, at the atomic level of minerals in a spinning motion, accretion is a natural result, as the motion of the bodies pull particles in a spiral 'wake' after them adding either to a larger, grabby neighbor, or themselves if close to a Kirkwood Gap, for example. Several points need consideration: 1. Centripetal force (inward) plays a role since we are dealing with objects in motion, both rotating and revolving....each asteroid in it's own orbit, ( we are dealing with celestial mechanics in a chaotic area of our Solar System), these objects, specifically relating to iron, move in an orbit producing a net force acting towards the center which causes the object to seek the center. 2. The scientific consensus seems to be that the Yarkovsky Effect, by heating the asteroids in the presence of the sun and cooling them in it's absence, accounts for the differentiation and location of the various asteroid types in the belt according to composition. 3 Understanding the 'transcient' nature of minerals due to heat (mentioned by Robert) and pressure, not so much gravity directly. Two minerals can have the exact molecular structure and, based on their respective circumstances, heat, pressure, cooling time, result in two completely different minerals. (Until exposed to other dynamic processes, e. g., simple increase in pressure with accretion of cosmic particles over time, changes in angular momentum, etc. of these unevenly balanced creatures account for some weird dynamics in this wild bunch. Not an expert, Someone please chime in, Thanks for your indulgence, Julie
How does the iron migrate to the core?
----- Original Message ----- From: "Meteorites USA" <e...@meteoritesusa.com>
To: <geo...@aol.com>; <meteorite-list@meteoritecentral.com> Sent: Sunday, April 05, 2009 3:52 PM Subject: Re: [meteorite-list] Questions about accretion.
Thanks for the responses thus far... I've studied lots of material and scientific papers on accretion, but still have some questions. The gravity explanation is great, but it's a little vague. I want to know what causes it I guess at the molecular level. What physical forces and interactions cause the iron to migrate into such a solid mass at the core? If gravity alone were the case, why is it we have H and L chondrites at all? Everything would be one big clump of mixed material. Has the iron not had a chance yet to migrate out of this layer of rock to the center of the asteroid? I know H and L chondrites are meteoroids that have broken off the parent bodies but my question is simply, had they not been blasted off the main body, how long would it take and in what manner would the iron have migrated from these layers of rock to the core? Iron doesn't just move through stone without some sort of catalyst or outside force does it? Gravity itself is not sufficient to move iron through a stone matrix no matter how much time passes is it? If there are no impacts or outside forces acting upon the body how does the iron loose itself from the grasp of the stone matrix to move through toward the core? Impacts? At the beginning of the formation of a meteoroid is it electrostatic attraction that causes it to get larger? At what size does it produce it's own gravity? Or does it? How does and asteroid become so dense? If asteroids are super dense, and comets are loosely bound material and gases, would that mean that asteroids are dead comets? Wow! I know that a lot of questions. sorry... ;) Eric ______________________________________________ http://www.meteoritecentral.com Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list
______________________________________________ http://www.meteoritecentral.com Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list
