Hello Graham, All, Krinov concluded that all of these features we call "craters" are in fact small pits caused by the vaporization of more volatile inclusions under the fusion crust of the iron.
In other words, you have a heat-affected zone under the surface of the iron, and if you get a more volatile inclusion, it can be heated to the point that it vaporizes/expands, creating a small explosion...."crater" in the overlying soft/molten metal. This would explain the vast number of such "craters" seen on Franconia irons -- since those specimens contain large amounts of disseminated stony particles and troilite, it makes sense that they would contain a greater number of inclusions that might create such features (versus a relatively homogeneous Sikhote-Alin). The exception to this rule would be craters formed on shrapnel, but most of those supposed craters I've seen appeared to be exposures of where round (troilite) inclusions had been. The "raised rims" appeared to form from the shear/fracture propagating towards the weak point in the meteorite (the inclusion), creating a surface that gently sloped upwards to a smooth, round cavity. I've seen a few exceptions, but not many. Regards, Jason > ---------- Original Message ---------- > From: Graham Ensor <[email protected]> > Date: Sun, Jun 10, 2012 at 6:28 PM > Subject: Re: [meteorite-list] NEW FALL > To: MICHAEL JOHNSON <[email protected]> > Cc: "[email protected]" > <[email protected]> > > > Wow! where is that from Michael/Mike? Strange that it has so many > small impacts on the oriented ablated leading edge and weird chisel > marks too? Looks like some satellite debris I've seen before but the > stoney and pyroxene inclusions plus the entry speed it would have had > seem to rule that out. > Curious. > > Graham > > On Mon, Jun 11, 2012 at 1:30 AM, MICHAEL JOHNSON <[email protected]> wrote: >> http://www.rocksfromspace.org/new-fall-2012.html >> ______________________________________________ >> >> Visit the Archives at >> http://www.meteoritecentral.com/mailing-list-archives.html >> Meteorite-list mailing list >> [email protected] >> http://six.pairlist.net/mailman/listinfo/meteorite-list > ______________________________________________ > > Visit the Archives at > http://www.meteoritecentral.com/mailing-list-archives.html > Meteorite-list mailing list > [email protected] > http://six.pairlist.net/mailman/listinfo/meteorite-list ______________________________________________ Visit the Archives at http://www.meteoritecentral.com/mailing-list-archives.html Meteorite-list mailing list [email protected] http://six.pairlist.net/mailman/listinfo/meteorite-list
