Re: [meteorite-list] Asteroid Or Comet Sutters Mill
Hi List, This is great stuff. Thanks to Alan and Larry for enlightening us on this. There has been some talk of the volatiles content of CM meteorites. So, is it safe to assume that CM meteorites also originate from the darker outer reaches of the asteroid belt where Tagish Lake hails from? Meteorites rich in volatiles presumably come from that region where solar effects are minimized? Best regards, MikeG -- --- Galactic Stone Ironworks - MikeG Web: http://www.galactic-stone.com Facebook: http://www.facebook.com/galacticstone Twitter: http://twitter.com/GalacticStone RSS: http://www.galactic-stone.com/rss/126516 --- On 5/2/12, lebof...@lpl.arizona.edu lebof...@lpl.arizona.edu wrote: Hi Alan: I would agree with you on the consensus that CMs would appear to come from asteroids. Based on spectra and albedo, CM meteorites look like C-class (and possibly several other low-albedo classes) asteroids (very common in the Main Belt). These are asteroid that have surface compositions showing that they have been exposed to liquid water, phyllosilicates. There is no (or little) evidence that comets have had interiors warm enough to melt ice and create the water necessary to form phyllosilicates. Larry I guess I've been goaded into responding. First, at this point we don't know if the meteorite is a CM chondrite or not. No meteorite researcher has completed an analysis of it yet (perhaps tomorrow or Friday) and I have not seen a piece. But, on the more general question of CM chondrites, most researchers believe that the carbonaceous chondrites all are derived from asteroids. There is more or less a continuum in properties across the chondrite groups; it is difficult to imagine that they are from different classes of parent bodies, i.e., asteroids vs. comets. All chondrite groups (except CI) contain chondrules, CAIs, matrix, metal and sulfide although the abundances of these phases can vary a lot among the groups. Even CI chondrites contain a few olivine and pyroxene grains that seem to be chondrule fragments, a few refractory mineral grains that seem to be CAI fragments, and even one reported intact CAI. Furthermore, the isolated olivine and pyroxene grains in CI chondrites have the same olivine Fa vs. CaO distribution as in CM chondrites suggesting that they are from a similar source. I think that the CM chondrites are from an asteroid that was fairly porous and had a fair amount of water, present either as ice or in phyllosilicates. Stochastic impacts on this asteroid caused fracturing in some regions more than others and during subsequent aqueous alteration (probably caused by impact mobilization of water), the more fractured regions retained more water and became more altered. Alan Rubin Institute of Geophysics and Planetary Physics University of California 3845 Slichter Hall 603 Charles Young Dr. E Los Angeles, CA 90095-1567 phone: 310-825-3202 e-mail: aeru...@ucla.edu website: http://cosmochemists.igpp.ucla.edu/Rubin.html - Original Message - From: Matson, Robert D. robert.d.mat...@saic.com To: meteorite-list meteorite-list@meteoritecentral.com Sent: Wednesday, May 02, 2012 2:16 PM Subject: Re: [meteorite-list] Asteroid Or Comet Sutters Mill Hi Paul, Probably not a misquote -- Dr. Jenniskens is interested in deciphering the nature of the original asteroid (meteoroid) body that produced the meteorites. The original body was large enough that it may not have been a monolithic body; as with 2008 TC3 (Almahata Sitta), the pre-encounter body may have been a rubble pile, consisting of more than just CM2 material. In any case, I don't think the parent body (or bodies) for CM2 is cometary. Would be interested in hearing Dr. Rubin's theory on the nature of the CM2 parent. --Rob -Original Message- From: meteorite-list-boun...@meteoritecentral.com [mailto:meteorite-list-boun...@meteoritecentral.com] On Behalf Of Paul Gessler Sent: Wednesday, May 02, 2012 2:08 PM To: meteorite-list Subject: [meteorite-list] Asteroid Or Comet Sutters Mill In the LA times article it reads in part: We want to learn about this asteroid, said Peter Jenniskens, an astronomer and senior research scientist at the Carl Sagan Center at the SETI (Search for Extraterrestrial Intelligence) Institute and the NASA Lunar Science Institute. This is scientific gold. I hope/probably they miss quoted him? I vote comet Paul G __ Visit the Archives at http://www.meteoritecentral.com/mailing-list-archives.html Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list __ Visit the Archives at http://www.meteoritecentral.com/mailing-list-archives.html Meteorite-list
[meteorite-list] Asteroid Or Comet Sutters Mill
In the LA times article it reads in part: We want to learn about this asteroid, said Peter Jenniskens, an astronomer and senior research scientist at the Carl Sagan Center at the SETI (Search for Extraterrestrial Intelligence) Institute and the NASA Lunar Science Institute. This is scientific gold. I hope/probably they miss quoted him? I vote comet Paul G __ Visit the Archives at http://www.meteoritecentral.com/mailing-list-archives.html Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list
Re: [meteorite-list] Asteroid Or Comet Sutters Mill
Hi Paul, Probably not a misquote -- Dr. Jenniskens is interested in deciphering the nature of the original asteroid (meteoroid) body that produced the meteorites. The original body was large enough that it may not have been a monolithic body; as with 2008 TC3 (Almahata Sitta), the pre-encounter body may have been a rubble pile, consisting of more than just CM2 material. In any case, I don't think the parent body (or bodies) for CM2 is cometary. Would be interested in hearing Dr. Rubin's theory on the nature of the CM2 parent. --Rob -Original Message- From: meteorite-list-boun...@meteoritecentral.com [mailto:meteorite-list-boun...@meteoritecentral.com] On Behalf Of Paul Gessler Sent: Wednesday, May 02, 2012 2:08 PM To: meteorite-list Subject: [meteorite-list] Asteroid Or Comet Sutters Mill In the LA times article it reads in part: We want to learn about this asteroid, said Peter Jenniskens, an astronomer and senior research scientist at the Carl Sagan Center at the SETI (Search for Extraterrestrial Intelligence) Institute and the NASA Lunar Science Institute. This is scientific gold. I hope/probably they miss quoted him? I vote comet Paul G __ Visit the Archives at http://www.meteoritecentral.com/mailing-list-archives.html Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list
Re: [meteorite-list] Asteroid Or Comet Sutters Mill
I guess I've been goaded into responding. First, at this point we don't know if the meteorite is a CM chondrite or not. No meteorite researcher has completed an analysis of it yet (perhaps tomorrow or Friday) and I have not seen a piece. But, on the more general question of CM chondrites, most researchers believe that the carbonaceous chondrites all are derived from asteroids. There is more or less a continuum in properties across the chondrite groups; it is difficult to imagine that they are from different classes of parent bodies, i.e., asteroids vs. comets. All chondrite groups (except CI) contain chondrules, CAIs, matrix, metal and sulfide although the abundances of these phases can vary a lot among the groups. Even CI chondrites contain a few olivine and pyroxene grains that seem to be chondrule fragments, a few refractory mineral grains that seem to be CAI fragments, and even one reported intact CAI. Furthermore, the isolated olivine and pyroxene grains in CI chondrites have the same olivine Fa vs. CaO distribution as in CM chondrites suggesting that they are from a similar source. I think that the CM chondrites are from an asteroid that was fairly porous and had a fair amount of water, present either as ice or in phyllosilicates. Stochastic impacts on this asteroid caused fracturing in some regions more than others and during subsequent aqueous alteration (probably caused by impact mobilization of water), the more fractured regions retained more water and became more altered. Alan Rubin Institute of Geophysics and Planetary Physics University of California 3845 Slichter Hall 603 Charles Young Dr. E Los Angeles, CA 90095-1567 phone: 310-825-3202 e-mail: aeru...@ucla.edu website: http://cosmochemists.igpp.ucla.edu/Rubin.html - Original Message - From: Matson, Robert D. robert.d.mat...@saic.com To: meteorite-list meteorite-list@meteoritecentral.com Sent: Wednesday, May 02, 2012 2:16 PM Subject: Re: [meteorite-list] Asteroid Or Comet Sutters Mill Hi Paul, Probably not a misquote -- Dr. Jenniskens is interested in deciphering the nature of the original asteroid (meteoroid) body that produced the meteorites. The original body was large enough that it may not have been a monolithic body; as with 2008 TC3 (Almahata Sitta), the pre-encounter body may have been a rubble pile, consisting of more than just CM2 material. In any case, I don't think the parent body (or bodies) for CM2 is cometary. Would be interested in hearing Dr. Rubin's theory on the nature of the CM2 parent. --Rob -Original Message- From: meteorite-list-boun...@meteoritecentral.com [mailto:meteorite-list-boun...@meteoritecentral.com] On Behalf Of Paul Gessler Sent: Wednesday, May 02, 2012 2:08 PM To: meteorite-list Subject: [meteorite-list] Asteroid Or Comet Sutters Mill In the LA times article it reads in part: We want to learn about this asteroid, said Peter Jenniskens, an astronomer and senior research scientist at the Carl Sagan Center at the SETI (Search for Extraterrestrial Intelligence) Institute and the NASA Lunar Science Institute. This is scientific gold. I hope/probably they miss quoted him? I vote comet Paul G __ Visit the Archives at http://www.meteoritecentral.com/mailing-list-archives.html Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list __ Visit the Archives at http://www.meteoritecentral.com/mailing-list-archives.html Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list
Re: [meteorite-list] Asteroid Or Comet Sutters Mill
I hope/probably they miss quoted him? I vote comet I'd think if the parent body was cometary, it would had a faster entry velocity and thus likely to explode at a higher elevation than the approximate 5 miles I've been hearing. For it to not explode higher up, I'd be surprised that the fragile material it was made up of survived to the lower reaches of the atmosphere. GeoZay __ Visit the Archives at http://www.meteoritecentral.com/mailing-list-archives.html Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list
Re: [meteorite-list] Asteroid Or Comet Sutters Mill
Hi Alan: I would agree with you on the consensus that CMs would appear to come from asteroids. Based on spectra and albedo, CM meteorites look like C-class (and possibly several other low-albedo classes) asteroids (very common in the Main Belt). These are asteroid that have surface compositions showing that they have been exposed to liquid water, phyllosilicates. There is no (or little) evidence that comets have had interiors warm enough to melt ice and create the water necessary to form phyllosilicates. Larry I guess I've been goaded into responding. First, at this point we don't know if the meteorite is a CM chondrite or not. No meteorite researcher has completed an analysis of it yet (perhaps tomorrow or Friday) and I have not seen a piece. But, on the more general question of CM chondrites, most researchers believe that the carbonaceous chondrites all are derived from asteroids. There is more or less a continuum in properties across the chondrite groups; it is difficult to imagine that they are from different classes of parent bodies, i.e., asteroids vs. comets. All chondrite groups (except CI) contain chondrules, CAIs, matrix, metal and sulfide although the abundances of these phases can vary a lot among the groups. Even CI chondrites contain a few olivine and pyroxene grains that seem to be chondrule fragments, a few refractory mineral grains that seem to be CAI fragments, and even one reported intact CAI. Furthermore, the isolated olivine and pyroxene grains in CI chondrites have the same olivine Fa vs. CaO distribution as in CM chondrites suggesting that they are from a similar source. I think that the CM chondrites are from an asteroid that was fairly porous and had a fair amount of water, present either as ice or in phyllosilicates. Stochastic impacts on this asteroid caused fracturing in some regions more than others and during subsequent aqueous alteration (probably caused by impact mobilization of water), the more fractured regions retained more water and became more altered. Alan Rubin Institute of Geophysics and Planetary Physics University of California 3845 Slichter Hall 603 Charles Young Dr. E Los Angeles, CA 90095-1567 phone: 310-825-3202 e-mail: aeru...@ucla.edu website: http://cosmochemists.igpp.ucla.edu/Rubin.html - Original Message - From: Matson, Robert D. robert.d.mat...@saic.com To: meteorite-list meteorite-list@meteoritecentral.com Sent: Wednesday, May 02, 2012 2:16 PM Subject: Re: [meteorite-list] Asteroid Or Comet Sutters Mill Hi Paul, Probably not a misquote -- Dr. Jenniskens is interested in deciphering the nature of the original asteroid (meteoroid) body that produced the meteorites. The original body was large enough that it may not have been a monolithic body; as with 2008 TC3 (Almahata Sitta), the pre-encounter body may have been a rubble pile, consisting of more than just CM2 material. In any case, I don't think the parent body (or bodies) for CM2 is cometary. Would be interested in hearing Dr. Rubin's theory on the nature of the CM2 parent. --Rob -Original Message- From: meteorite-list-boun...@meteoritecentral.com [mailto:meteorite-list-boun...@meteoritecentral.com] On Behalf Of Paul Gessler Sent: Wednesday, May 02, 2012 2:08 PM To: meteorite-list Subject: [meteorite-list] Asteroid Or Comet Sutters Mill In the LA times article it reads in part: We want to learn about this asteroid, said Peter Jenniskens, an astronomer and senior research scientist at the Carl Sagan Center at the SETI (Search for Extraterrestrial Intelligence) Institute and the NASA Lunar Science Institute. This is scientific gold. I hope/probably they miss quoted him? I vote comet Paul G __ Visit the Archives at http://www.meteoritecentral.com/mailing-list-archives.html Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list __ Visit the Archives at http://www.meteoritecentral.com/mailing-list-archives.html Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list __ Visit the Archives at http://www.meteoritecentral.com/mailing-list-archives.html Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list
Re: [meteorite-list] Asteroid Or Comet Sutters Mill
CM chondrites are also ubiquitous. The most abundant foreign component of the lunar soil is chemically similar to CM chondrites. If i recall, many fireballs also seem to be CM like, although other list members would be better able to address this point. More CM chondrites would be in our meteorite collections if they weren't so friable. There are also many CM clasts in meteorite breccias, both ordinary chondrite regolith breccias like Abbott, Plainview, Dimmitt and Fayetteville, and howardites such as Kapoeta. This ubiquity mandates a reliable local source, i.e., not a comet but an asteroid. Some of the clasts in ordinary chondrites are unshocked, meaning that they came in at low relative velocities, also very un-comet like. As the asteroid guys say, the CM chondrites are probably from some types of C asteroids located at the outer reaches of the main belt; at those places ambient temperatures are low and volatiles are more likely to remain on the parent body. That is why CMs contain about 9 wt.% water (within phyllosilicates) and CI chondrites contain appreciably more. Quoting Michael Gilmer meteoritem...@gmail.com: Hi List, This is great stuff. Thanks to Alan and Larry for enlightening us on this. There has been some talk of the volatiles content of CM meteorites. So, is it safe to assume that CM meteorites also originate from the darker outer reaches of the asteroid belt where Tagish Lake hails from? Meteorites rich in volatiles presumably come from that region where solar effects are minimized? Best regards, MikeG -- --- Galactic Stone Ironworks - MikeG Web: http://www.galactic-stone.com Facebook: http://www.facebook.com/galacticstone Twitter: http://twitter.com/GalacticStone RSS: http://www.galactic-stone.com/rss/126516 --- On 5/2/12, lebof...@lpl.arizona.edu lebof...@lpl.arizona.edu wrote: Hi Alan: I would agree with you on the consensus that CMs would appear to come from asteroids. Based on spectra and albedo, CM meteorites look like C-class (and possibly several other low-albedo classes) asteroids (very common in the Main Belt). These are asteroid that have surface compositions showing that they have been exposed to liquid water, phyllosilicates. There is no (or little) evidence that comets have had interiors warm enough to melt ice and create the water necessary to form phyllosilicates. Larry I guess I've been goaded into responding. First, at this point we don't know if the meteorite is a CM chondrite or not. No meteorite researcher has completed an analysis of it yet (perhaps tomorrow or Friday) and I have not seen a piece. But, on the more general question of CM chondrites, most researchers believe that the carbonaceous chondrites all are derived from asteroids. There is more or less a continuum in properties across the chondrite groups; it is difficult to imagine that they are from different classes of parent bodies, i.e., asteroids vs. comets. All chondrite groups (except CI) contain chondrules, CAIs, matrix, metal and sulfide although the abundances of these phases can vary a lot among the groups. Even CI chondrites contain a few olivine and pyroxene grains that seem to be chondrule fragments, a few refractory mineral grains that seem to be CAI fragments, and even one reported intact CAI. Furthermore, the isolated olivine and pyroxene grains in CI chondrites have the same olivine Fa vs. CaO distribution as in CM chondrites suggesting that they are from a similar source. I think that the CM chondrites are from an asteroid that was fairly porous and had a fair amount of water, present either as ice or in phyllosilicates. Stochastic impacts on this asteroid caused fracturing in some regions more than others and during subsequent aqueous alteration (probably caused by impact mobilization of water), the more fractured regions retained more water and became more altered. Alan Rubin Institute of Geophysics and Planetary Physics University of California 3845 Slichter Hall 603 Charles Young Dr. E Los Angeles, CA 90095-1567 phone: 310-825-3202 e-mail: aeru...@ucla.edu website: http://cosmochemists.igpp.ucla.edu/Rubin.html - Original Message - From: Matson, Robert D. robert.d.mat...@saic.com To: meteorite-list meteorite-list@meteoritecentral.com Sent: Wednesday, May 02, 2012 2:16 PM Subject: Re: [meteorite-list] Asteroid Or Comet Sutters Mill Hi Paul, Probably not a misquote -- Dr. Jenniskens is interested in deciphering the nature of the original asteroid (meteoroid) body that produced the meteorites. The original body was large enough that it may not have been a monolithic body; as with 2008 TC3 (Almahata Sitta), the pre-encounter body may have been a rubble pile, consisting of more than just CM2 material. In any case, I don't think the parent body (or bodies) for CM2 is cometary. Would be interested
Re: [meteorite-list] Asteroid Or Comet Sutters Mill
fractured regions retained more water and became more altered. Alan Rubin Institute of Geophysics and Planetary Physics University of California 3845 Slichter Hall 603 Charles Young Dr. E Los Angeles, CA 90095-1567 phone: 310-825-3202 e-mail: aeru...@ucla.edu website: http://cosmochemists.igpp.ucla.edu/Rubin.html - Original Message - From: Matson, Robert D. robert.d.mat...@saic.com To: meteorite-list meteorite-list@meteoritecentral.com Sent: Wednesday, May 02, 2012 2:16 PM Subject: Re: [meteorite-list] Asteroid Or Comet Sutters Mill Hi Paul, Probably not a misquote -- Dr. Jenniskens is interested in deciphering the nature of the original asteroid (meteoroid) body that produced the meteorites. The original body was large enough that it may not have been a monolithic body; as with 2008 TC3 (Almahata Sitta), the pre-encounter body may have been a rubble pile, consisting of more than just CM2 material. In any case, I don't think the parent body (or bodies) for CM2 is cometary. Would be interested in hearing Dr. Rubin's theory on the nature of the CM2 parent. --Rob -Original Message- From: meteorite-list-boun...@meteoritecentral.com [mailto:meteorite-list-boun...@meteoritecentral.com] On Behalf Of Paul Gessler Sent: Wednesday, May 02, 2012 2:08 PM To: meteorite-list Subject: [meteorite-list] Asteroid Or Comet Sutters Mill In the LA times article it reads in part: We want to learn about this asteroid, said Peter Jenniskens, an astronomer and senior research scientist at the Carl Sagan Center at the SETI (Search for Extraterrestrial Intelligence) Institute and the NASA Lunar Science Institute. This is scientific gold. I hope/probably they miss quoted him? I vote comet Paul G __ Visit the Archives at http://www.meteoritecentral.com/mailing-list-archives.html Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list __ Visit the Archives at http://www.meteoritecentral.com/mailing-list-archives.html Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list __ Visit the Archives at http://www.meteoritecentral.com/mailing-list-archives.html Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list __ Visit the Archives at http://www.meteoritecentral.com/mailing-list-archives.html Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list
Re: [meteorite-list] Asteroid Or Comet Sutters Mill
Hi Guys, great contributions; Could we possibly be talking a 944 Hidalgo or something closer to an (old friend of Larry) 733 Irmintraud ? Hidalgo specifically, Iis any possible path from it that leads to an intersection with Earth ... Hidalgo being historically a unicorn of a cometary/asteroid object with low albedo Kindest wishes Doug -Original Message- From: lebofsky lebof...@lpl.arizona.edu To: aerubin aeru...@ucla.edu Cc: meteorite-list meteorite-list@meteoritecentral.com Sent: Wed, May 2, 2012 11:47 pm Subject: Re: [meteorite-list] Asteroid Or Comet Sutters Mill Hi Again: One other place that seems to have abundant CM-like material, the surface of Vesta. There are dark areas on Vesta that seem to be composed of carbonaceous chondritic material (based again on albedo and spectrum). I do not know all of the details (missed some of the papers at the Lunar and Planetary Science Conference), but my impression is that the dark material did have the spectral signature of material altered by water, implying that Vesta has been hit over time by C-class asteroids. This is consistent with what Alan is saying about clasts in howardites (which a thought to come from Vesta). To answer your question, Mike, once you alter (hydrate) the silicate material and make a phyllosilicate, it is not that easy to get rid of the water (need temperatures that are in the hundreds of degrees centigrade. You just needed temperatures low enough when the asteroids formed for water to condense out, probably the middle of the present asteroid belt. Larry CM chondrites are also ubiquitous. The most abundant foreign component of the lunar soil is chemically similar to CM chondrites. If i recall, many fireballs also seem to be CM like, although other list members would be better able to address this point. More CM chondrites would be in our meteorite collections if they weren't so friable. There are also many CM clasts in meteorite breccias, both ordinary chondrite regolith breccias like Abbott, Plainview, Dimmitt and Fayetteville, and howardites such as Kapoeta. This ubiquity mandates a reliable local source, i.e., not a comet but an asteroid. Some of the clasts in ordinary chondrites are unshocked, meaning that they came in at low relative velocities, also very un-comet like. As the asteroid guys say, the CM chondrites are probably from some types of C asteroids located at the outer reaches of the main belt; at those places ambient temperatures are low and volatiles are more likely to remain on the parent body. That is why CMs contain about 9 wt.% water (within phyllosilicates) and CI chondrites contain appreciably more. Quoting Michael Gilmer meteoritem...@gmail.com: Hi List, This is great stuff. Thanks to Alan and Larry for enlightening us on this. There has been some talk of the volatiles content of CM meteorites. So, is it safe to assume that CM meteorites also originate from the darker outer reaches of the asteroid belt where Tagish Lake hails from? Meteorites rich in volatiles presumably come from that region where solar effects are minimized? Best regards, MikeG -- --- Galactic Stone Ironworks - MikeG Web: http://www.galactic-stone.com Facebook: http://www.facebook.com/galacticstone Twitter: http://twitter.com/GalacticStone RSS: http://www.galactic-stone.com/rss/126516 --- On 5/2/12, lebof...@lpl.arizona.edu lebof...@lpl.arizona.edu wrote: Hi Alan: I would agree with you on the consensus that CMs would appear to come from asteroids. Based on spectra and albedo, CM meteorites look like C-class (and possibly several other low-albedo classes) asteroids (very common in the Main Belt). These are asteroid that have surface compositions showing that they have been exposed to liquid water, phyllosilicates. There is no (or little) evidence that comets have had interiors warm enough to melt ice and create the water necessary to form phyllosilicates. Larry I guess I've been goaded into responding. First, at this point we don't know if the meteorite is a CM chondrite or not. No meteorite researcher has completed an analysis of it yet (perhaps tomorrow or Friday) and I have not seen a piece. But, on the more general question of CM chondrites, most researchers believe that the carbonaceous chondrites all are derived from asteroids. There is more or less a continuum in properties across the chondrite groups; it is difficult to imagine that they are from different classes of parent bodies, i.e., asteroids vs. comets. All chondrite groups (except CI) contain chondrules, CAIs, matrix, metal and sulfide although the abundances of these phases can vary a lot among the groups. Even CI chondrites contain a few olivine and pyroxene grains that seem to be chondrule fragments, a few refractory mineral grains that seem to be CAI fragments, and even one
