Re: Re : [meteorite-list] Chondrule formation mechanism (Info Please)
an early solar system and a present asteroid belt that is very tightly zoned. In other words, the Earthly prevalence of chondrites would just be a coincidence. The evidence is that the asteroid belt is a gumbo, though, full of all sorts of things that don't belong there. The failure to find obvious sources for chondrites in the asteroid belt is one of the great nagging problems that has never been answered well, so he may have something. I'm just not sure what. Sears says one advantage of the theory is that otherwise the energy required to flash melt a solar system full of chondrules is a major fraction of the total energy available. Of course a precursor supernova that melted them would take care of that problem, too. Supernovae have a way of making short work of both problems and non-problems alike! The nearest short-term supernova candidate is HR8210 or IK Pegasi, which is incomfortably close at 150 light years. http://www.eso.org/outreach/eduoff/edu-prog/catchastar/casreports-2004/rep-310/ and http://www.newscientist.com/article.ns?id=dn2311 Of course, it could take millions of years to go super, or it could happen in 10,000 years, or it could start up tomorrow. That's what makes life so interesting. Sterling K. Webb --- - Original Message - From: Rob McCafferty [EMAIL PROTECTED] To: Pete Pete [EMAIL PROTECTED]; meteorite-list@meteoritecentral.com Sent: Wednesday, October 25, 2006 2:52 PM Subject: RE: Re : [meteorite-list] Chondrule formation mechanism (Info Please) I suppose you are correct. I suspect the iron flecks in chondrites must be stellar relics. The iron is formed in the cores of all stars. Nuclearly speaking it is the stablest of all elements (lowest binding energy per neucleon...or is it the highest, can't remember) So as a consequence it is the final fusion product in the cores of all stars which are heavy enough to get that far (red dwarf stars aren't considered massive enough to get beyond the helium burning phase). However, only supernovae spread their innards out at the end so every atom of iron was created by a supernova as indeed was every atom that isn't hydrogen, helium or lithium. All others are created in stars. However, the atoms higher in the periodic table cannot be made in stars as they require a net input of energy to fuse whereas the lighter ones relase energy. Only in a huge energy surplus can you manufacture these higher elements. This is where the supernova comes in. In that brief period where the star aoutshines an entire galaxy, there is enough excess energy to create quantities of elements up to Uranium (and possibly beyond but non of these are stable). This is a most wonderful process which not only creates all the elements needed for life but also seeds the universe with them. And not a crackpot creationist theory involving venting asteroids into space in sight. As for the ages of the iron/nickel. I'm not sure if ages are measured or if they can be. That'd be interesting if they could. It's probable that our sun and solar system are not even second or third generation. The big stars last only a short period and there's been a long time for the cycle to repeat a few times. Rob McC --- Pete Pete [EMAIL PROTECTED] wrote: Hi, all, This discussion about chondrules is fascinating! Hoping not to digress off this topic too much, but a question I have is about the metal flecks (not the later-formed iron meteorites) in any of the stonies. Have they ever been given an estimated age? If the heavy elements, such as nickel and iron, are created by a supernova, and the chondrules are in theory formed much later during the future dynamics of our solar system's nebula, would it be fair to say that the metal flecks would be billions and billions (apologies, Carl) of years OLDER than chondrules? And that they came from a distance much further than our solar system's vicinity? Considering that the supernova is exploding outward and the new elements' density is thinning out very quickly, wouldn't it be more likely that these iron and nickel flecks that eventually found a new home in our solar nebula and meteorites have come from more than one, probably a lot more, supernova? If so, why don't we see any remnants of any supernova explosion in our relative proximity? The Helix Nebula is the closest to us, at 450 light-years! http://images.google.ca/images?q=helix+nebulahl=enlr=sa=Xoi=imagesct=title Not even a wisp left... Are tiny, but very dense, nebulas even possible? I can't imagine dust-bunny nebulae. If not, would it be unreasonable to expect that our planetary nebula could have extended out to Centauri, where our closest star neighbours are? When I dwell on the Pillars of Creation photos (Orion stellar-formation nebula, http://hubblesite.org/newscenter/newsdesk/archive/releases/1995/44/image/a) that describes a small point being comparable to the breadth of our solar
Re: Re : [meteorite-list] Chondrule formation mechanism (Info Please)
supernova. Lots of theories to choose from (limit three to a customer). I think Derek Sears' theory is clever and well-thought-out and ingenious and probably wrong. He supposes that the resonant orbits from which the Earth receives its many chondrites are wall-to-wall with condrite parent bodies, that these bodies are the ONLY chondrite bodies there are, that they are few and rare, that Earth's meteorite population is specific and unique, that chondrules and their accreted chondrites were a rare and unique by-product of the early solar system and not representative of early solar materials at all. In other words, aren't we special...? Very narrow zones of unique chondrite parent bodies implies both an early solar system and a present asteroid belt that is very tightly zoned. In other words, the Earthly prevalence of chondrites would just be a coincidence. The evidence is that the asteroid belt is a gumbo, though, full of all sorts of things that don't belong there. The failure to find obvious sources for chondrites in the asteroid belt is one of the great nagging problems that has never been answered well, so he may have something. I'm just not sure what. Sears says one advantage of the theory is that otherwise the energy required to flash melt a solar system full of chondrules is a major fraction of the total energy available. Of course a precursor supernova that melted them would take care of that problem, too. Supernovae have a way of making short work of both problems and non-problems alike! The nearest short-term supernova candidate is HR8210 or IK Pegasi, which is incomfortably close at 150 light years. http://www.eso.org/outreach/eduoff/edu-prog/catchastar/casreports-2004/rep-310/ and http://www.newscientist.com/article.ns?id=dn2311 Of course, it could take millions of years to go super, or it could happen in 10,000 years, or it could start up tomorrow. That's what makes life so interesting. Sterling K. Webb --- - Original Message - From: Rob McCafferty [EMAIL PROTECTED] To: Pete Pete [EMAIL PROTECTED]; meteorite-list@meteoritecentral.com Sent: Wednesday, October 25, 2006 2:52 PM Subject: RE: Re : [meteorite-list] Chondrule formation mechanism (Info Please) I suppose you are correct. I suspect the iron flecks in chondrites must be stellar relics. The iron is formed in the cores of all stars. Nuclearly speaking it is the stablest of all elements (lowest binding energy per neucleon...or is it the highest, can't remember) So as a consequence it is the final fusion product in the cores of all stars which are heavy enough to get that far (red dwarf stars aren't considered massive enough to get beyond the helium burning phase). However, only supernovae spread their innards out at the end so every atom of iron was created by a supernova as indeed was every atom that isn't hydrogen, helium or lithium. All others are created in stars. However, the atoms higher in the periodic table cannot be made in stars as they require a net input of energy to fuse whereas the lighter ones relase energy. Only in a huge energy surplus can you manufacture these higher elements. This is where the supernova comes in. In that brief period where the star aoutshines an entire galaxy, there is enough excess energy to create quantities of elements up to Uranium (and possibly beyond but non of these are stable). This is a most wonderful process which not only creates all the elements needed for life but also seeds the universe with them. And not a crackpot creationist theory involving venting asteroids into space in sight. As for the ages of the iron/nickel. I'm not sure if ages are measured or if they can be. That'd be interesting if they could. It's probable that our sun and solar system are not even second or third generation. The big stars last only a short period and there's been a long time for the cycle to repeat a few times. Rob McC --- Pete Pete [EMAIL PROTECTED] wrote: Hi, all, This discussion about chondrules is fascinating! Hoping not to digress off this topic too much, but a question I have is about the metal flecks (not the later-formed iron meteorites) in any of the stonies. Have they ever been given an estimated age? If the heavy elements, such as nickel and iron, are created by a supernova, and the chondrules are in theory formed much later during the future dynamics of our solar system's nebula, would it be fair to say that the metal flecks would be billions and billions (apologies, Carl) of years OLDER than chondrules? And that they came from a distance much further than our solar system's vicinity? Considering that the supernova is exploding outward and the new elements
Re: Re : [meteorite-list] Chondrule formation mechanism (Info Please)
I shall be forever grateful that I saved this post. Having read an exerpt of it in Ed G's reply, I returned to the original and am forced to reiterate a previous effusive, unabashed compliment of Sterling's effective translation into laymans terms of the most simple of processes in the universe. Simple in the sense of elemental. Sterling, I hope that you can make time in your life to preserve and collect these posts. I for one, and I realize, I may be in the minority, find such threads more than words like facinating can describe. Meteorites are the glue which keeps this group together but ultimate meaning motivates some of us to touch these sublime sources of understanding and imagine our origins among the stars. Who are we? Where did we come from? Where are we going? Astrophysics, Cosmology, Chemistry, Petrology, Relativity, Sp. relativity! Holy Cow! Hindu Metaphysics. Jerry Flaherty - Original Message - From: Sterling K. Webb [EMAIL PROTECTED] To: meteorite-list@meteoritecentral.com Cc: E.P. Grondine [EMAIL PROTECTED] Sent: Friday, October 27, 2006 2:30 AM Subject: Re: Re : [meteorite-list] Chondrule formation mechanism (Info Please) Hi, Rob, Pete, Ed, List, Rob wrote: The iron is formed in the cores of all stars. Nuclearly speaking it is the stablest of all elements (lowest binding energy per neucleon...or is it the highest, can't remember) I hate it when I have to dive into thick books more suited for anchors than reading but here goes... Not all stars form iron. The one thing that determines the entire life of a star is how fat it is. An anorexic star is just another Jupiter or Super-Jupiter. At somewhere around 12-13 times the mass of Jupiter, a star starts to burn deuterium and we can really call it a star. Stars burn hydrogen. Deuterium is just regular hydrogen toting a neutron in its backpack. Slap two of them together and you get helium (and a lot of excess energy). All stars, regardless of size, start out as hydrogen burners. The D-D chain is the easiest reaction to get started but there are lots of routes from hydrogen to helium that use other elements for their intermediate stages (called proton-proton reactions) and I'm not going to type them all out. So there. Fast forward a few billion years. A star will use up all of its hydrogen. About the time it's running on fumes, the helium ash left over from burning up all your hydrogen like there was no tomorrow has sunk to the core and is getting hotter and denser. Eventually, that helium in the core starts to burn. Now, the star is a helium-burner. This nuclear heat generated in the helium-burning core causes the star to expand and expand and expand into a big gasball many times its original size: a red giant. A star has to be at least half the mass of our Sun to do this. Our Sun will do this... in another 4-5 billion years. Goodbye, Solar System. A helium burner this big will evolve carbon12-burning. Again there are many possible reactions, but most of the carbon is turned directly into oxygen16. As things get hotter, we get neon20, magnesium24, silicon28, each one is produced by slapping (fusing) a helium nucleus into the last one, hence the jump by 4, 4, 4, 4... Now, a nice little star like our Sun will just end up as a bright superdense carbon12 diamond a few thousand miles across, called a white dwarf. But if the mass of a star is 1.4 times the mass of the Sun or greater, it will just go crazy with this fusion stuff. The end result is a star with an onion structure: an outer shell of hydrogen burning surrounding a shell of helium burning, surrounding a shell of carbon burning, surrounding a shell of neon burning, surrounding a shell of oxygen burning, surrounding a shell of silicon burning, surrounding a core where the really weird stuff goes on. Silicon burning should proceed until iron is built, but it doesn't happen. By this time the heat, pressure and energies involved are so great that the LIGHT produced by the fusion becomes more powerful and energetic than all the other players! As soon as a nuclei heavier than silicon is produced, a photon on steroids knocks it apart, slaps it down, and kicks it around until it gives up those extra nucleons and crawls off in all its silicon shabbiness. Iron may get formed but it doesn't last. And, yes, iron has the HIGHEST binding energy per nucleon and a high electric charge barrier, but the real problem is that the photons produced by creating it are energetic enough to rip it apart. If you want to picture the true violence of a stellar interior, try imagining a beam of light powerful enough to smash atoms... OK, they're super-gamma rays, but they're still just light. The iron (and nickel) core forms inside the silicon burning shell as some of the iron continually being formed escapes from the cycle of birth and instant photo-death by dripping down out of sight in the core as it forms. But the iron core is doomed. Eventually
RE: Re : [meteorite-list] Chondrule formation mechanism (Info Please)
Hi, all, This discussion about chondrules is fascinating! Hoping not to digress off this topic too much, but a question I have is about the metal flecks (not the later-formed iron meteorites) in any of the stonies. Have they ever been given an estimated age? If the heavy elements, such as nickel and iron, are created by a supernova, and the chondrules are in theory formed much later during the future dynamics of our solar system's nebula, would it be fair to say that the metal flecks would be billions and billions (apologies, Carl) of years OLDER than chondrules? And that they came from a distance much further than our solar system's vicinity? Considering that the supernova is exploding outward and the new elements' density is thinning out very quickly, wouldn't it be more likely that these iron and nickel flecks that eventually found a new home in our solar nebula and meteorites have come from more than one, probably a lot more, supernova? If so, why don't we see any remnants of any supernova explosion in our relative proximity? The Helix Nebula is the closest to us, at 450 light-years! http://images.google.ca/images?q=helix+nebulahl=enlr=sa=Xoi=imagesct=title Not even a wisp left... Are tiny, but very dense, nebulas even possible? I can't imagine dust-bunny nebulae. If not, would it be unreasonable to expect that our planetary nebula could have extended out to Centauri, where our closest star neighbours are? When I dwell on the Pillars of Creation photos (Orion stellar-formation nebula, http://hubblesite.org/newscenter/newsdesk/archive/releases/1995/44/image/a) that describes a small point being comparable to the breadth of our solar system, ~4.3 light-years to Centauri isn't that far... Maybe the seldom-discussed/appreciated metal flecks are the real gems in the meteorites? Or, is the nebula in my head too dense that am I just missing something obvious? How is my logic flawed? Cheers, Pete From: Warin Roger [EMAIL PROTECTED] To: Sterling K. Webb [EMAIL PROTECTED],meteorite-list@meteoritecentral.com CC: E.P. Grondine [EMAIL PROTECTED] Subject: Re : [meteorite-list] Chondrule formation mechanism (Info Please) Date: Tue, 24 Oct 2006 16:15:53 + (GMT) Hi, all, I am surprised that nobody evoked the theory following which chondrules were formed in relatively very few privileged zones of space. They would then form through one or more impacts of relatively large asteroids, onto the parent body covered with regoliths (and even with megaregoliths). The excellent book of Derek Sears, entitled The origin of chondrules and chondrites (Cambridge Planetary Science, 2004) supports this hypothesis. In corollary, ordinary chondrites (85% on Earth) would be quite rare in cosmos, and only few parent bodies would produce chondrites. Glad to hear some comments on the above assumptions. Thanks, Roger Warin - Message d'origine De : Sterling K. Webb [EMAIL PROTECTED] À : meteorite-list@meteoritecentral.com Cc : E.P. Grondine [EMAIL PROTECTED] Envoyé le : Dimanche, 22 Octobre 2006, 20h38mn 55s Objet : Re: [meteorite-list] Chondrule formation mechanism (Info Please) Hi, Ed, Rob, This scenario (Ed's) would require that we would find a chondrule with a formation age of 3.9 Gya, I think. As far as I know, that has never happened. All chondrites (so called because they contain chondrules) are the same age: about 4.555 Gya. Chondrules are the same age (2 to 5 million years variation among chondrules) as the chondrites they occur in. The about is because the dating methods have a limit to how precisely they can resolve small age differences. Dating by lead isotopes says the solar system is 4.560 +/- 0.005 Gya old. Other systems of isotope measurements (like 147Sm/143Nd) give 4.553 +/- 0.003, and so forth. Within the limits of measurement, all chondrites are the same age, a hair younger than the solar system itself, the Class of Zero, and so are their chondrules. Meteorites that do not (never did) contain chondrules have varying ages. Lunaites are the age of that portion of the lunar crust they came from, generally quite old compared to Martians which have the formation age of the basalt flow they were chipped off of for the long haul to Earth. Irons, which formed inside a differentiating body, have younger ages; some very much younger if the differentiation took a long time (Weekeroo Station IIe is 4.340 Gya, Kodaikanal IIe 3.800 Gya, many IAB irons the same). I'm thinking that before you need to develop a theory to explain a 3.9 Gya chondrule, you'd have to actually have a 3.9 Gya chondrule. As far as I know, none with discordant ages have ever been found. In certain solar circles it would be Big News. Oddly, if you Google for oldest chondrule, you get the oldest chondrules, and if you Google for youngest chondrule, you get the oldest chondrules... on the grounds that it is young as the solar system. If you Google for
Re: RE: Re : [meteorite-list] Chondrule formation mechanism (Info Please)
On Wed, 25 Oct 2006 11:52:23 -0400, you wrote: If the heavy elements, such as nickel and iron, are created by a supernova, and the chondrules are in theory formed much later during the future dynamics of our solar system's nebula, would it be fair to say that the metal flecks would be billions and billions (apologies, Carl) of years OLDER than chondrules? Of course the individual atoms in chondrules are much older than the chondrules themselves (but know knows exactly how many stellar generations ago) but as for the actual flecks of metal themselves, I think that they are concentrated by whatever mechanism it is that melts the chondrules-- like oil seperating from water, the iron/nickel seperated from the silicates (and that is more apparent in armored chondrules). Recently there has been news of studies on the decay products of short-lived supernova produced elements that show that there were supernovas very close (both in space and time) to the proto-solar system. (This article was posted 22 minutes ago as I'm finding it) http://www.cnn.com/2006/TECH/space/10/25/sun.sisters/ I believe (though I haven't googled up the articles related to it) that recent studies of elements and isotopes in certain meteorites suggest that components from at least 3 seperate supernovas contributed to the materials in the early solar system. If so, why don't we see any remnants of any supernova explosion in our relative proximity? The Helix Nebula is the closest to us, at 450 light-years! In our current position, it takes around 225 million years for one orbit of the center of the galaxy, or about 20 orbits since the birh of the sun. That's plenty of time and distance for a whole lot more than 450 light-years of drift between the sun and the nursery. __ Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list
Re: RE: Re : [meteorite-list] Chondrule formation mechanism (Info Please)
Thanks, Darren, Much clearer to me, now. And now I can get some sleep ;) The link you provided http://www.cnn.com/2006/TECH/space/10/25/sun.sisters/ is almost a complete answer to my post. *Note that my post was about a half hour before the news break. The odds of such a directly related news topic being released at such timing must beastronomical! I think that they are concentrated by whatever mechanism it is that melts the chondrules-- like oil separating from water, the iron/nickel separated from the silicates (and that is more apparent in armored chondrules). If they were separated and the flecks were formed then, (I see that silica, iron and nickel all melt at close to the same temp: ~1500 C) what mechanism could have brought them back together into a relatively consistent mixture of chondrule/metal flecks? Maybe simply time, gravity, and the start of the rotation of the new solar system swirling the soup? That would be the most obvious, eh? I would appreciate a reference, if anyone has one. Cheers, Pete From: Darren Garrison [EMAIL PROTECTED] Reply-To: [EMAIL PROTECTED] To: Pete Pete [EMAIL PROTECTED] CC: meteorite-list@meteoritecentral.com Subject: Re: RE: Re : [meteorite-list] Chondrule formation mechanism (Info Please) Date: Wed, 25 Oct 2006 12:55:53 -0400 On Wed, 25 Oct 2006 11:52:23 -0400, you wrote: If the heavy elements, such as nickel and iron, are created by a supernova, and the chondrules are in theory formed much later during the future dynamics of our solar system's nebula, would it be fair to say that the metal flecks would be billions and billions (apologies, Carl) of years OLDER than chondrules? Of course the individual atoms in chondrules are much older than the chondrules themselves (but know knows exactly how many stellar generations ago) but as for the actual flecks of metal themselves, I think that they are concentrated by whatever mechanism it is that melts the chondrules-- like oil seperating from water, the iron/nickel seperated from the silicates (and that is more apparent in armored chondrules). Recently there has been news of studies on the decay products of short-lived supernova produced elements that show that there were supernovas very close (both in space and time) to the proto-solar system. (This article was posted 22 minutes ago as I'm finding it) http://www.cnn.com/2006/TECH/space/10/25/sun.sisters/ I believe (though I haven't googled up the articles related to it) that recent studies of elements and isotopes in certain meteorites suggest that components from at least 3 seperate supernovas contributed to the materials in the early solar system. If so, why don't we see any remnants of any supernova explosion in our relative proximity? The Helix Nebula is the closest to us, at 450 light-years! In our current position, it takes around 225 million years for one orbit of the center of the galaxy, or about 20 orbits since the birh of the sun. That's plenty of time and distance for a whole lot more than 450 light-years of drift between the sun and the nursery. _ Experience Live Search from your PC or mobile device today. http://www.live.com/?mkt=en-ca __ Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list
Re: RE: Re : [meteorite-list] Chondrule formation mechanism (Info Please)
I think I may have misinterpreted this, Darren: as for the actual flecks of metal themselves, I think that they are concentrated by whatever mechanism it is that melts the chondrules-- like oil seperating from water, the iron/nickel seperated from the silicates (and that is more apparent in armored chondrules). You meant that they were separated at a minute scale - chondrule-and-fleck-size, right? Not on a vast measure, as in kilometers plus. Disregard my remix question. Cheers, Pete From: Darren Garrison [EMAIL PROTECTED] Reply-To: [EMAIL PROTECTED] To: Pete Pete [EMAIL PROTECTED] CC: meteorite-list@meteoritecentral.com Subject: Re: RE: Re : [meteorite-list] Chondrule formation mechanism (Info Please) Date: Wed, 25 Oct 2006 12:55:53 -0400 On Wed, 25 Oct 2006 11:52:23 -0400, you wrote: If the heavy elements, such as nickel and iron, are created by a supernova, and the chondrules are in theory formed much later during the future dynamics of our solar system's nebula, would it be fair to say that the metal flecks would be billions and billions (apologies, Carl) of years OLDER than chondrules? Of course the individual atoms in chondrules are much older than the chondrules themselves (but know knows exactly how many stellar generations ago) but as for the actual flecks of metal themselves, I think that they are concentrated by whatever mechanism it is that melts the chondrules-- like oil seperating from water, the iron/nickel seperated from the silicates (and that is more apparent in armored chondrules). Recently there has been news of studies on the decay products of short-lived supernova produced elements that show that there were supernovas very close (both in space and time) to the proto-solar system. (This article was posted 22 minutes ago as I'm finding it) http://www.cnn.com/2006/TECH/space/10/25/sun.sisters/ I believe (though I haven't googled up the articles related to it) that recent studies of elements and isotopes in certain meteorites suggest that components from at least 3 seperate supernovas contributed to the materials in the early solar system. If so, why don't we see any remnants of any supernova explosion in our relative proximity? The Helix Nebula is the closest to us, at 450 light-years! In our current position, it takes around 225 million years for one orbit of the center of the galaxy, or about 20 orbits since the birh of the sun. That's plenty of time and distance for a whole lot more than 450 light-years of drift between the sun and the nursery. _ Ready for the world's first international mobile film festival celebrating the creative potential of today's youth? Check out Mobile Jam Fest for your a chance to WIN $10,000! www.mobilejamfest.com __ Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list
RE: Re : [meteorite-list] Chondrule formation mechanism (Info Please)
I suppose you are correct. I suspect the iron flecks in chondrites must be stellar relics. The iron is formed in the cores of all stars. Nuclearly speaking it is the stablest of all elements (lowest binding energy per neucleon...or is it the highest, can't remember) So as a consequence it is the final fusion product in the cores of all stars which are heavy enough to get that far (red dwarf stars aren't considered massive enough to get beyond the helium burning phase). However, only supernovae spread their innards out at the end so every atom of iron was created by a supernova as indeed was every atom that isn't hydrogen, helium or lithium. All others are created in stars. However, the atoms higher in the periodic table cannot be made in stars as they require a net input of energy to fuse whereas the lighter ones relase energy. Only in a huge energy surplus can you manufacture these higher elements. This is where the supernova comes in. In that brief period where the star aoutshines an entire galaxy, there is enough excess energy to create quantities of elements up to Uranium (and possibly beyond but non of these are stable). This is a most wonderful process which not only creates all the elements needed for life but also seeds the universe with them. And not a crackpot creationist theory involving venting asteroids into space in sight. As for the ages of the iron/nickel. I'm not sure if ages are measured or if they can be. That'd be interesting if they could. It's probable that our sun and solar system are not even second or third generation. The big stars last only a short period and there's been a long time for the cycle to repeat a few times. Rob McC --- Pete Pete [EMAIL PROTECTED] wrote: Hi, all, This discussion about chondrules is fascinating! Hoping not to digress off this topic too much, but a question I have is about the metal flecks (not the later-formed iron meteorites) in any of the stonies. Have they ever been given an estimated age? If the heavy elements, such as nickel and iron, are created by a supernova, and the chondrules are in theory formed much later during the future dynamics of our solar system's nebula, would it be fair to say that the metal flecks would be billions and billions (apologies, Carl) of years OLDER than chondrules? And that they came from a distance much further than our solar system's vicinity? Considering that the supernova is exploding outward and the new elements' density is thinning out very quickly, wouldn't it be more likely that these iron and nickel flecks that eventually found a new home in our solar nebula and meteorites have come from more than one, probably a lot more, supernova? If so, why don't we see any remnants of any supernova explosion in our relative proximity? The Helix Nebula is the closest to us, at 450 light-years! http://images.google.ca/images?q=helix+nebulahl=enlr=sa=Xoi=imagesct=title Not even a wisp left... Are tiny, but very dense, nebulas even possible? I can't imagine dust-bunny nebulae. If not, would it be unreasonable to expect that our planetary nebula could have extended out to Centauri, where our closest star neighbours are? When I dwell on the Pillars of Creation photos (Orion stellar-formation nebula, http://hubblesite.org/newscenter/newsdesk/archive/releases/1995/44/image/a) that describes a small point being comparable to the breadth of our solar system, ~4.3 light-years to Centauri isn't that far... Maybe the seldom-discussed/appreciated metal flecks are the real gems in the meteorites? Or, is the nebula in my head too dense that am I just missing something obvious? How is my logic flawed? Cheers, Pete From: Warin Roger [EMAIL PROTECTED] To: Sterling K. Webb [EMAIL PROTECTED],meteorite-list@meteoritecentral.com CC: E.P. Grondine [EMAIL PROTECTED] Subject: Re : [meteorite-list] Chondrule formation mechanism (Info Please) Date: Tue, 24 Oct 2006 16:15:53 + (GMT) Hi, all, I am surprised that nobody evoked the theory following which chondrules were formed in relatively very few privileged zones of space. They would then form through one or more impacts of relatively large asteroids, onto the parent body covered with regoliths (and even with megaregoliths). The excellent book of Derek Sears, entitled The origin of chondrules and chondrites (Cambridge Planetary Science, 2004) supports this hypothesis. In corollary, ordinary chondrites (85% on Earth) would be quite rare in cosmos, and only few parent bodies would produce chondrites. Glad to hear some comments on the above assumptions. Thanks, Roger Warin - Message d'origine De : Sterling K. Webb [EMAIL PROTECTED] À : meteorite-list@meteoritecentral.com Cc : E.P. Grondine [EMAIL PROTECTED] Envoyé le : Dimanche, 22 Octobre 2006, 20h38mn 55s Objet : Re: [meteorite-list] Chondrule formation mechanism
