Hi Jason, all - What we know about the composition of the centers of comets is near zero.
If Tunguska can be associated with Comet Encke, then the spherules there might be some indication, but only of what's left of that particular comet. If I remember correctly, Moss Lake is also associated with Comet Encke. Aside from that, there is the "KT fossil" meteorite. There are several large circular holes in the surface of the Earth, surrounded by impactites, which have not been fully examined yet and which are likely to also contain comet samples. In any case, we're likely soon to learn a whole lot more about Comet Schwassmann Wachmann 3, with very large (and very fast) samples possible in 2022. E.P. Grondine Man and Impact in the Americas --- On Tue, 11/23/10, Jason Utas <[email protected]> wrote: > From: Jason Utas <[email protected]> > Subject: Re: [meteorite-list] Cometary meteorites > To: "E.P. Grondine" <[email protected]>, "Meteorite-list" > <[email protected]> > Date: Tuesday, November 23, 2010, 7:17 PM > Hello E.P. All, > We do not have examples of anything that even remotely > resembles what > actually constitutes cometary material. > What follows is an excerpt from an email that I posted to > the list on > August 11th of this year that addresses the same subject. > --- > The simple answer is no. No meteorites have ever been > found that > match all criteria for what we believe cometary material > should look > like. > > http://www.lpi.usra.edu/meetings/LPSC98/pdf/1004.pdf > > This is also the sort of topic that has been brought up > again and > again on the list. While I couldn't find any direct > references for > some reason, I was able to turn these up: > > http://www.mail-archive.com/[email protected]/msg84604.html > > http://six.pairlist.net/pipermail/meteorite-list/2004-May/000683.html > > To condense: a few meteorites, namely the CI's, come close > to what we > think cometary material might look like. But those > meteorites weren't/aren't > associated with any known meteor showers, and are likely > just > fragments of D-class asteroids, which may or may not be > remnants of > "burned-out" comets (comets that got trapped in the > inner solar system > and stripped of most of their volatiles). > But, based on the above paper, even the CI's are probably > not actual > "cometary" material, though they fit the bill better than > most other > meteorites, for sure. > ... > Some more basic reading: > http://www.amsmeteors.org/faqm.html#11 > > Scroll to section before bottom: "Meteorites > from Comets?" > > http://www.pibburns.com/catastro/meteors.htm > --- > > The assertion that CI meteorites are cometary in origin > goes against > practically every detail of cometary composition that we > have learned > over the past several decades, and the even more general > assertion > that cometary meteorites have been found and recognized is > thus simply > untrue. > > We may or may not have samples of the other asteroid > classes; that is > a completely different issue, and if you'd like to start a > new thread, > by all means do so. > > Regards, > Jason > > Jason Utas > University of California, Berkeley 2012 > College of Letters and Science > Psychology, Geology > > > On Tue, Nov 23, 2010 at 4:46 PM, E.P. Grondine <[email protected]> > wrote: > > > > Hi Larry - > > > > And when I started on this list there were no major > differentiated parent bodies for other meteorites (following > McSween), and now we have what, at least five? > > > > I suppose that if we knew what comets were, then there > wouldn't be any need to spend any money finding out what > they are. And then there is that tricky problem of the > source for C, B, G (and maybe D) asteroids. > > > > E.P. > > > > --- On Tue, 11/23/10, [email protected] > <[email protected]> > wrote: > > > > > From: [email protected] > <[email protected]> > > > Subject: Re: [meteorite-list] Cometary > meteorites > > > To: "E.P. Grondine" <[email protected]> > > > Cc: [email protected], > [email protected] > > > Date: Tuesday, November 23, 2010, 3:48 PM > > > Hi: > > > > > > I have said this to you before that there is > about zero > > > evidence that > > > carbonaceous chondrites are from comets. There is > only > > > minimal evidence > > > that there are hydrated silicates in comets and > at least > > > the CI and CM CCs > > > very much aqueously altered and are consistent > with an > > > origin from C, B, > > > and G (and maybe D) asteroids. > > > > > > Larry > > > > > > > Hello Elizabeth, all - > > > > > > > > The general informal consensus within the > meteorite > > > community has been > > > > that carbonaceous meteorites are cometary in > origin. > > > That being the case, > > > > a few questions: > > > > 1) At what compression/temperature will CO2 > dissociate > > > into Carbon and > > > > Oxygen? > > > > 2) Will Epoxi provide fine spectra data for > trace > > > elements such as calcium > > > > and aluminum? Platinum Group Elements? > > > > > > > > E.P. Grondine > > > > Man and Impact in the Americas > > > > > > > > > > > > > > > > > > > > > > > > > ______________________________________________ > > > > 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
