Re: [meteorite-list] Further thoughts
Hi Chris, Bob, Listees, Just to expand a little on what Chris says (he speaks from a great deal of observational experience), Bob, let's pose a few thoughts for indirect musing... If meteorites had volatiles that were subject to violent expansions, why don't all potential meteorites just turn into powder blasts? It is plausible that this happens to some cometary particles, btw. Think of where and how the meteoroid formed that is responsible for the 'rites in our collections. If it has chondrules, for example, which have metamorphized even slightly due to thermal effects - do you think it has been hotter at some point in its life considering the Earth's atmosphere never alters the matrix (insides) of the meteorites we recover? Not only has it been hotter - but it also was formed at low pressure if it is a chondrite. Why can we say the latter? If it formed hot and relatively low pressure or space, would there be many volitiles? Which are the meteorites represented in our collections that are chondrites and thermally altered? H3.X (X0), H4, H5, H6, H7. L3.X(X0), L4, L5, L6, L7 Feldspar formed from glasses is a common component in these meteorites - at what temperature does this reaction begin to occur? Indeed - they are mostly thought to have formed between 500 and 900 degres CENTIGRADE, a range which which reaches over 1650 F. If they are achondrites, what can we say? How did they get that way? By melting and essentially a process of sedimention + a little crystalization now and then? How hot do we need to be to melt silicates? HOT! Same story, but even hotter for the iron melt that leads to irons. If the silicates separated in this differentiation - do you suspect the gasses mostly did and bubbled out too? So what does that leave? Mostly a few carbonaceous things that carry water, amino acids and boozes. Let's say we instantly dropped a few of them in an oven at 3000 C. They are just rocks. Do you think they would blow up and hurl pieces in all directions and dent the insides of the oven from impacts? Or would they likely just form fissures where any volitile would just slither out of the nooks and cranies and cracks saying p? Jim has written of the blow torch test of a tektite. If something looks like a tektite but he isn't sure, he puts it under a real hot torch. Obsidian turns into Pumice complete with pores and fissures. (tektites usually don't).While safety glasses would be a good idea, the rocks don't turn into firecrackers. (Though I heard certain petrified wood rocks from Texas provide entertainment to pyros and explosive nuts if you like this thought). How far do you think a rock splitting open would hurl all the fragments? Especially if it is going over 10,000 mph forward? If we could really make decent bombs by just heating rocks to 3000 degrees, the military certainly has been wasting a lot of RD money-) All the above hypotheses ignore whay Chris has pointed out. Ablation is a very efficient process. Even in irons which conducrt heat really well, we have quite shallow heat affected zones. I completely agree with Chris, though I would prefer to say that 10,000 mph breath cools down the porridge quickly. How could a hot liquid persist so long on a slippery surface at that speed? Ablation therefore can be seen to be a surface phenomenon in meteorite after meteorite by just looking at the thickness of the fusion rind. Chris' comments are also right on regarding the temperatures of meteoroids in space (and he is assuming they are in Sunlight at about 1 AU). Here's a foolish comment of mine to think about. Did you by chance see an old Star Trek episode called For the World is Hollow and I have Touched the Sky? Do you think a mesosiderite with eucrite inclusions named Yonada at 1 AU would be an mild temperatured world to hollow out and and spend some time in a pinch (but not a nova)? I do...Natira, dear? Best wishes and good health, Doug -Original Message- From: Chris Peterson [EMAIL PROTECTED] To: Meteorite-list@meteoritecentral.com Sent: Wed, 19 Mar 2008 11:53 pm Subject: Re: [meteorite-list] Further thoughts Hi Bob- Even small meteoroids don't heat up inside during their brief meteor phase. Ablation is simply too efficient at carrying away heat. Also, it's doubtful any significant gas pockets exist in meteoroids. There are quite a few videos of meteors breaking up, and they don't seem to show anything like true explosions. I've recorded perhaps 100 events bright enough to show fragmentation, and the fragments always appear to continue along substantially the same path. BTW, the space environment isn't particularly cold. The interior of meteoroids varies from tens of degrees below freezing to tens of degrees above. Chris * Chris L Peterson Cloudbait Observatory http://www.cloudbait.com - Original Message
Re: [meteorite-list] Further thoughts-Observations
I have to respectfully disagree Doug. I'd agree more with you had I not witnessed it myself. I believe there might be an unconsidered chemical source to drive an explosion. The Maryville Bolide(1983), which I was lucky to observe may have been an aberration from the norm on several levels( e.g. calculations indicate it was still incandescent between 3-4 miles when conventional wisdom places the max altitude for incandescence at 5 miles above sea level)but none-the-less it expanded explosively in all directions formaing a slightly squat turnip-shapped fire/smoke ball. This meteorite was likely still traveling 1-2 or more kilos per second when it first appeared in front of me. When it bolided, there was a visible smoke trail of a fragment that was ejected up and out at 45-60° leaving 3 distinct doglegs of smoke trails as it went up, out, then started down. An area of secondary crust was found on the only recovered mass suggesting that may have been the source of the wayward fragment. Many questions remained about this fall. Owing to an early morning entry with both cosmic velocity and meeting Earth's 15kps(?) orbital velocity combined, it was screaming fast. The size of the bolide/smoke sphere was estimated between 400-1200 ft in diameter. This seems rather large for the approx. 1kg stone which was recovered. The fall was very close to a large lake so we could never be confidant if the recovered stone was truly the surviving/main mass or if it was the fragment observed ejected from the upper hemisphere of the bolide. In that we know factually little and only weakly theoretically-- about the actual expansion mechanism aka explosive disruption, I believe that there is a case to be made for an explosion--i.e. rapidly expanding, gas-driven, wave front which is moving at or near shock wave velocities of chemical explosives or propellant burn speeds-- even if we are unsure of the mechanism that expands the fireball to many diameters of the original smoke/incandescent trail. Be it recalled that when air suspended, combustible particles such as coal dust or wheat flour are ignited, they act as explosives and can collapse large structures or mine shafts. The nano-gram sized particles of a extensive disruption when suddenly exposed to oxygen might be a sufficient chemical explosive mechanism. For example, metallic iron, shearing at apart at plasma temperatures, might be literally burned in the higher oxygen levels of the lower atmosphere and the rapid expansion of the fireball could be driven by a burning iron fog--meeting the definition of explosive. Regards, Elton --- [EMAIL PROTECTED] wrote: Pete wrote: Some will be blown up and some will be blown down. I believe this is a common misconception for many in the meteorite community and common thought. I don't think anything is blowing up. Simply fragmenting. Each part of the original whole maintains its portion of momentum upon fragmentation. The direction of the momentum is along the angle of entry. There is no blowing up in that sense of a bomb which propells fragments in all directions as there is no internal source of energy (like in a chemical explosive). __ http://www.meteoritecentral.com Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list
Re: [meteorite-list] Further thoughts-Observations
Hi Elton- I don't see that any sort of explosion- especially not chemical- is required to explain what you saw. There is a significant difference between sending material in all directions relative to the point of breakup, and imparting some lateral velocity. The former requires more energy than can be reasonably explained- at least several times the parent body mass in TNT. But it's certainly possible that with the right sort of breakup (especially at low altitude), aerodynamics could produce components that fly off the original path somewhat (but still with much of the original forward velocity component). Combine that with an expanding smoke cloud (where all forward momentum has been lost), and I imaging a striking explosion effect. I see nothing about your description of the Maryville fireball that contradicts this explanation. In fact, videos of fragmenting meteors and of decaying space junk do show components with some lateral velocity component. It's just not common for that amount to be very much. Of course, if a fireball has a large motion component towards the observer, the terminal explosion may appear to radiate outwards in all directions even though all the material is still traveling along substantially the same path. We should also take care to distinguish between what might be possible in exotic cases from what is typical. We all know that small meteors don't reach the ground with hypersonic velocity. Well, except for one. While we can't say for certain that there isn't a set of conditions that might cause meteor components to be propelled from the parent at radical angles and high velocities, we can say with absolute confidence that any such event is very rare, and certainly doesn't represent a typical fireball/meteorite fall. Chris * Chris L Peterson Cloudbait Observatory http://www.cloudbait.com - Original Message - From: Mr EMan [EMAIL PROTECTED] To: [EMAIL PROTECTED]; [EMAIL PROTECTED]; Meteorite-list@meteoritecentral.com Sent: Thursday, March 20, 2008 4:16 PM Subject: Re: [meteorite-list] Further thoughts-Observations I have to respectfully disagree Doug. I'd agree more with you had I not witnessed it myself. I believe there might be an unconsidered chemical source to drive an explosion. The Maryville Bolide(1983), which I was lucky to observe may have been an aberration from the norm on several levels( e.g. calculations indicate it was still incandescent between 3-4 miles when conventional wisdom places the max altitude for incandescence at 5 miles above sea level)but none-the-less it expanded explosively in all directions formaing a slightly squat turnip-shapped fire/smoke ball. This meteorite was likely still traveling 1-2 or more kilos per second when it first appeared in front of me. When it bolided, there was a visible smoke trail of a fragment that was ejected up and out at 45-60° leaving 3 distinct doglegs of smoke trails as it went up, out, then started down. An area of secondary crust was found on the only recovered mass suggesting that may have been the source of the wayward fragment. Many questions remained about this fall. Owing to an early morning entry with both cosmic velocity and meeting Earth's 15kps(?) orbital velocity combined, it was screaming fast. The size of the bolide/smoke sphere was estimated between 400-1200 ft in diameter. This seems rather large for the approx. 1kg stone which was recovered. The fall was very close to a large lake so we could never be confidant if the recovered stone was truly the surviving/main mass or if it was the fragment observed ejected from the upper hemisphere of the bolide. In that we know factually little and only weakly theoretically-- about the actual expansion mechanism aka explosive disruption, I believe that there is a case to be made for an explosion--i.e. rapidly expanding, gas-driven, wave front which is moving at or near shock wave velocities of chemical explosives or propellant burn speeds-- even if we are unsure of the mechanism that expands the fireball to many diameters of the original smoke/incandescent trail. Be it recalled that when air suspended, combustible particles such as coal dust or wheat flour are ignited, they act as explosives and can collapse large structures or mine shafts. The nano-gram sized particles of a extensive disruption when suddenly exposed to oxygen might be a sufficient chemical explosive mechanism. For example, metallic iron, shearing at apart at plasma temperatures, might be literally burned in the higher oxygen levels of the lower atmosphere and the rapid expansion of the fireball could be driven by a burning iron fog--meeting the definition of explosive. Regards, Elton __ http://www.meteoritecentral.com Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list
[meteorite-list] Further thoughts
Consider the Fireball. When the (soon to be) meteorite explodes into a fireball, the pieces are blown in every direction, Those blown in the direction that the meteor came from which should give them a negative speed and as such will start to drop first. Those in the direction of travel give the furtherest reach from the above mentioned pieces. This will define the outside distance of the strewnfield. Some will be blown up and some will be blown down. I would suspect that those that are blown downward would be the first to reach ground as these will be accelarated and those that are blown upward must go up before they can come down, so they should be the last to reach the ground. This means that the middle of the strewnfield is the first to be populated as well as the last to be populated. The two ends fill up in between the first and last parts of the fall. Anyone care to check? I don't think I missed anything, but I'm not an EXPERT, just using deductive reasoning. Pete __ http://www.meteoritecentral.com Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list
Re: [meteorite-list] Further thoughts
I don't think that fireballs explode that way. What happens is that pressure builds up until the material strength of the meteoroid is exceeded, and it fragments. There isn't an explosion as such (the appearance of an explosion is largely the result of energy released when lots of additional surface is suddenly exposed to ablation). The fragmented components continue traveling forward with approximately equal velocities. There's little lateral movement, and nothing ends up traveling in the opposite direction. In the case of a single terminal explosion, the shape and direction of the strewn field may have more to do with upper atmosphere winds than with the original direction of the meteor, or with the dynamics of the breakup. Chris * Chris L Peterson Cloudbait Observatory http://www.cloudbait.com - Original Message - From: Pete Shugar [EMAIL PROTECTED] To: Meteorite-list@meteoritecentral.com Sent: Wednesday, March 19, 2008 10:45 AM Subject: [meteorite-list] Further thoughts Consider the Fireball. When the (soon to be) meteorite explodes into a fireball, the pieces are blown in every direction, Those blown in the direction that the meteor came from which should give them a negative speed and as such will start to drop first. Those in the direction of travel give the furtherest reach from the above mentioned pieces. This will define the outside distance of the strewnfield. Some will be blown up and some will be blown down. I would suspect that those that are blown downward would be the first to reach ground as these will be accelarated and those that are blown upward must go up before they can come down, so they should be the last to reach the ground. This means that the middle of the strewnfield is the first to be populated as well as the last to be populated. The two ends fill up in between the first and last parts of the fall. Anyone care to check? I don't think I missed anything, but I'm not an EXPERT, just using deductive reasoning. Pete __ http://www.meteoritecentral.com Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list
Re: [meteorite-list] Further thoughts
Pete wrote: Some will be blown up and some will be blown down. I believe this is a common misconception for many in the meteorite community and common thought. I don't think anything is blowing up. Simply fragmenting. Each part of the original whole maintains its portion of momentum upon fragmentation. The direction of the momentum is along the angle of entry. There is no blowing up in that sense of a bomb which propells fragments in all directions as there is no internal source of energy (like in a chemical explosive). The only dispersion will be caused by different frictional (aerodynamic effects) deviations like sticking your hand out the car window and using yourwrist as an aileron. If your fingers fell off your hand, there would be no explosion, and nothing being blown forward either :-) Best health, Doug sorry - now caught up with the good replies on this topic, we just got electricity internet, etc. back after the nuclear winter our city experienced yesterday where we couldn't see the Sun on a clear day -Original Message- From: Pete Shugar [EMAIL PROTECTED] To: Meteorite-list@meteoritecentral.com Sent: Wed, 19 Mar 2008 10:45 am Subject: [meteorite-list] Further thoughts Consider the Fireball. When the (soon to be) meteorite explodes into a fireball, the pieces are blown in every direction, Those blown in the direction that the meteor came from which should give them a negative speed and as such will start to drop first. Those in the direction of travel give the furtherest reach from the above mentioned pieces. This will define the outside distance of the strewnfield. Some will be blown up and some will be blown down. I would suspect that those that are blown downward would be the first to reach ground as these will be accelarated and those that are blown upward must go up before they can come down, so they should be the last to reach the ground. This means that the middle of the strewnfield is the first to be populated as well as the last to be populated. The two ends fill up in between the first and last parts of the fall. Anyone care to check? I don't think I missed anything, but I'm not an EXPERT, just using deductive reasoning. Pete __ http://www.meteoritecentral.com Meteorite-list mailing list [EMAIL PROTECTED] http://six.pairlist.net/mailman/listinfo/meteorite-list __ http://www.meteoritecentral.com Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list
Re: [meteorite-list] Further thoughts
Hi mexicodoug, et al, Does anyone have evidence of what really happens (i.e. explode or fragment) with meteors/meteoroids that pass through the atmosphere? I'm a newbie and therefore not pretending to know what I'm talking about, but it would seem to me that there are some meteors/meteroids that COULD have gases trapped in their molecular structure that COULD heat up and actually explode during their fiery passage through our atmosphere. Large meteors wouldn't do this because their internal temperatures never increase at all (they are still as cold as the space environment where they have been traveling for eons), but small friable meteors like Carancas could possibly have gases in them that could heat up and therefore explode in our atmosphere. That is just a guess, not a fact, so please no flames. ;-) I'm just trying to get these ideas out of my head and get some explanations for them. Alcohol doesn't stop the voices, it just s l o w s t h e md o w n . . . :-) Regards, Bob -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of [EMAIL PROTECTED] Sent: Wednesday, March 19, 2008 10:08 AM To: [EMAIL PROTECTED]; Meteorite-list@meteoritecentral.com Subject: Re: [meteorite-list] Further thoughts Pete wrote: Some will be blown up and some will be blown down. I believe this is a common misconception for many in the meteorite community and common thought. I don't think anything is blowing up. Simply fragmenting. Each part of the original whole maintains its portion of momentum upon fragmentation. The direction of the momentum is along the angle of entry. There is no blowing up in that sense of a bomb which propells fragments in all directions as there is no internal source of energy (like in a chemical explosive). The only dispersion will be caused by different frictional (aerodynamic effects) deviations like sticking your hand out the car window and using yourwrist as an aileron. If your fingers fell off your hand, there would be no explosion, and nothing being blown forward either :-) Best health, Doug sorry - now caught up with the good replies on this topic, we just got electricity internet, etc. back after the nuclear winter our city experienced yesterday where we couldn't see the Sun on a clear day -Original Message- From: Pete Shugar [EMAIL PROTECTED] To: Meteorite-list@meteoritecentral.com Sent: Wed, 19 Mar 2008 10:45 am Subject: [meteorite-list] Further thoughts Consider the Fireball. When the (soon to be) meteorite explodes into a fireball, the pieces are blown in every direction, Those blown in the direction that the meteor came from which should give them a negative speed and as such will start to drop first. Those in the direction of travel give the furtherest reach from the above mentioned pieces. This will define the outside distance of the strewnfield. Some will be blown up and some will be blown down. I would suspect that those that are blown downward would be the first to reach ground as these will be accelarated and those that are blown upward must go up before they can come down, so they should be the last to reach the ground. This means that the middle of the strewnfield is the first to be populated as well as the last to be populated. The two ends fill up in between the first and last parts of the fall. Anyone care to check? I don't think I missed anything, but I'm not an EXPERT, just using deductive reasoning. Pete __ http://www.meteoritecentral.com Meteorite-list mailing list [EMAIL PROTECTED] http://six.pairlist.net/mailman/listinfo/meteorite-list __ http://www.meteoritecentral.com Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list __ http://www.meteoritecentral.com Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list
Re: [meteorite-list] Further thoughts
Hi Bob- Even small meteoroids don't heat up inside during their brief meteor phase. Ablation is simply too efficient at carrying away heat. Also, it's doubtful any significant gas pockets exist in meteoroids. There are quite a few videos of meteors breaking up, and they don't seem to show anything like true explosions. I've recorded perhaps 100 events bright enough to show fragmentation, and the fragments always appear to continue along substantially the same path. BTW, the space environment isn't particularly cold. The interior of meteoroids varies from tens of degrees below freezing to tens of degrees above. Chris * Chris L Peterson Cloudbait Observatory http://www.cloudbait.com - Original Message - From: Bob Loeffler [EMAIL PROTECTED] To: Meteorite-list@meteoritecentral.com Sent: Wednesday, March 19, 2008 11:42 PM Subject: Re: [meteorite-list] Further thoughts Hi mexicodoug, et al, Does anyone have evidence of what really happens (i.e. explode or fragment) with meteors/meteoroids that pass through the atmosphere? I'm a newbie and therefore not pretending to know what I'm talking about, but it would seem to me that there are some meteors/meteroids that COULD have gases trapped in their molecular structure that COULD heat up and actually explode during their fiery passage through our atmosphere. Large meteors wouldn't do this because their internal temperatures never increase at all (they are still as cold as the space environment where they have been traveling for eons), but small friable meteors like Carancas could possibly have gases in them that could heat up and therefore explode in our atmosphere. That is just a guess, not a fact, so please no flames. ;-) I'm just trying to get these ideas out of my head and get some explanations for them. __ http://www.meteoritecentral.com Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list
