Hi Eric, I'll take a stab at a few of your questions:
> How long does the formation of meteoroid bodies and larger asteroids take? This is not an easy question, as there were many processes at work during the early solar system -- some constructive (gravitational/electrostatic clumping), some destructive (high velocity impacts between clumps), and the time it would take to form, say, a 100-km sized body would depend on the initial quantity of dust in the pre-solar nebula. I don't know how long planetary scientists believe it took to form 1-km-sized bodies, but it was at least hundreds of thousands of years, probably longer. But when do you "start the clock"? When what became the solar system was just a molecular cloud, when the protostar formed, or tens of millions of years later when the protostar transitioned from T-Tauri stage to main sequence burning?) Whichever you choose, once you have asteroids a kilometer or so in size, barring collision with other such bodies they would continue to accrete at a rate of centimeters per year. So it would still take more than a million years to grow from 1-km to 100-km size. > 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). > Do all "large" asteroids consist of an iron core surrounded by > lighter materials further towards the asteroids surface? Yes, beyond a certain size nearly all should. One way to create an exception might be to have a large, already-differentiated asteroid get impacted by a smaller one in such a way that its iron core remains intact, but a portion of the outer rocky shell is blown off. Any large fragments of the original differentiated asteroid would then be depleted in iron/nickel. --Rob ______________________________________________ http://www.meteoritecentral.com Meteorite-list mailing list [email protected] http://six.pairlist.net/mailman/listinfo/meteorite-list
