Re: [meteorite-list] Meteorites - warm or hot to the touch?
Eighty-eight years ago today, a 104 kg. L6 was observed to fall on a warm, humid July 4th evening in Colby, WI (celestial fireworks!). When recovered shortly thereafter, the two main mass pieces were found to be covered with frost. Mark - Original Message - From: Sterling K. Webb [EMAIL PROTECTED] To: Chris Peterson [EMAIL PROTECTED]; Meteorite-list@meteoritecentral.com Sent: Monday, July 04, 2005 12:30 AM Subject: Re: [meteorite-list] Meteorites - warm or hot to the touch? Chris, Read: http://six.pairlist.net/pipermail/meteorite-list/2005-January/148342.html for internal ambient temperatures on space. During ablation (which usually removes 90% or more of the rock, leaving the inner core only) surface temperatures are 1800 degrees C and up, depending on angle and initial velocity. Peak temperatures are about 20,000 degrees C. It requires at least 150 gee's (at 45 degrees) to decelerate a meteoroid to Earth's surface at median entry velocities. Tunguska air-burst at 200 gee's calculated. Fragmentation and crushing are far more likely, and the fragments usually vaporize instantly, anyway. Crushing strength of chondrites is a measly 0.1 to 10 bar; achondrites 62 to 2700 bar; irons to 4000 bar, but they're very brittle and come apart way below those lab values. Calculation of crushing in actual observed fireballs, 30 to 50 bars. The smaller the object is, the cooler on arrival, but even the tiniest Pultulsk or Holbrook has crust, or if it's small enough, IS crust. Anything that has or had crust has reached the melting to boiling point of rock. It won't cool if still in hypersonic flight, and anything that is in hypersonic flight when it reaches the ground won't survive impact, a narrow window if crushing strength is less than 10 bar. Impactor vaporizes when impact speed approaches the speed of sound in the impacting body. Measurement of the speed of sound in meteoritic stones (as low as 600 m/sec) much less than in well consolidated Earth rocks. Some are cool, some are warm, but not very cold and not very warm. Sterling K. Webb -- Chris Peterson wrote: Hi Elton- I'm curious about the basis of your assertion that physics suggests a typical meteorite should be hot on the outside and cool on the inside. I would expect a large stone (or iron) to have an internal temperature similar to what it was at in space, which can vary from around -100°C to +60°C depending on the parent's albedo and surface properties. As the object gets smaller, its passage through the atmosphere becomes more important in determining its final temperature. Something fist sized, for instance, will have probably equilibrated its temperature to the atmosphere during most of its fall (-40°C is a good value for this), and then begun warming from the outside during the last minute in warmer air. Depending on the thermal conductivity of the material, I think it will feel somewhere between ambient and slightly cool. I believe that the conditions leading to a warm or hot exterior are not common. Chris * Chris L Peterson Cloudbait Observatory http://www.cloudbait.com - Original Message - From: E. L. Jones [EMAIL PROTECTED] To: Meteorite-list@meteoritecentral.com Cc: AL Mitterling [EMAIL PROTECTED] Sent: Sunday, July 03, 2005 5:42 PM Subject: Re: [meteorite-list] Meteorites - warm or hot to the touch? I personally believe the meteorite surface is very warm slightly hot on most falls while the interior is very cold. That is what the physics say should be. While metal/iron is a good heat conductor, olivine/silicates is/are not, and it should take a longer time for the two temperature extremes to neutralize in a stony fall. Ironically, an iron might actually take longer to cool down than a stone becasue it could theoretically store up more of the ablation heat internally than a stony could. __ Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list __ Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list __ Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list
Re: [meteorite-list] Meteorites - warm or hot to the touch?
This is such a fascinating subject for which many theories could hold merit and it's very interesting to hear them all. One thing that would lead me to believe meteorites are 'generally' not HOT is the function of ablation. My rudimentary understanding is that it's not the meteorite itself that gets hot, but rather the super heated/compressed air in front. This in turn heats the surface of the stone which is then immediately ablated away. I would assume that's why meteorite fusion crust is also comparatively so thin. It seems ablation is a very efficient way of removing heat/energy and there really might not be an appreciable rise in temperature throughout the interior. Obviously this would depend a lot on the size of the stone too. And the shape! I bet there would be a significant difference between highly oriented meteorites and a normal shape. Cheers, Jeff - Original Message - From: E. L. Jones To: Meteorite-list@meteoritecentral.com Cc: AL Mitterling Sent: Monday, July 04, 2005 9:42 AM Subject: Re: [meteorite-list] Meteorites - warm or hot to the touch? Hello Guys and Gals, The Mohahans fall was reported by the young finders to be barely hot potato holdable owing to the warmth. As to the Portales Valley and the tarp, I believe there was a bit of debate as to whether or not the tarp was melted or embedded. As an alumni of Ft Hood, Texas I remember putting a black tie rod-end down on a boat cover where a couple of 120°+ days later the tie rod had melted the tarp enough for there to be a bubble/smear of melted plastic under where the tie rod had lain. So I remain slightly unconvinced as to whether the meteorite was reentry hot enough to have done the melting or hot on subsequent days with high solar loading hot! One of the modern falls in Connecticut(Westfield?) was photographed ( if I recall correctly) with a frost rind on the broken face of the stone lying on the dinning room floor. Ms Hodge's account(Sylicaga , 1964?) failed to mention if the stone was hot or cold. I recall from previous discussions that when the Shuttle Orbiter returns, there are some components that are dangerously hot while other components rapidly frost up in the humid Florida air. Navigators know never to touch the mast of the sextant after a reading for it can be cold as -60°c especially over Greenland. Growing up on a TAC fighter base the wings of an F-104 Starfighter were reputedly dangerously hot upon a landing after a supersonic scramble. Over time, the leading edge of the wing was so sharpened via ablation, they had to place rubber strips on them for safety. I also recall that the cockpit temperature of the SR-71 Blackbird could raise to over 400°f during the speed runs. Even the waste/urine could boil and the cockpit was known for it's nasty smell. Pilots of course wore an additional space-certified environmental suit owing to the cockpit conditions mentioned above. All that said, there is no dispute that meteorites (and aircraft) heat up in transit. How specifically hot they are on the surface remains the unknown. I personally believe the meteorite surface is very warm slightly hot on most falls while the interior is very cold. That is what the physics say should be. While metal/iron is a good heat conductor, olivine/silicates is/are not, and it should take a longer time for the two temperature extremes to neutralize in a stony fall. Ironically, an iron might actually take longer to cool down than a stone becasue it could theoretically store up more of the ablation heat internally than a stony could. IF I am ever at the moment of a fall, I've already rehearsed the procedure. I intend to brand myself--hot and/or cold, and see if Al Lang will send me around to shows with Michelle Knapp's Malibu. Regards, Elton AL Mitterling wrote: I believe a tarp melted on the Portales Valley specimen provides un-refutable proof. __ Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list __ Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list
[meteorite-list] Meteorites - warm or hot to the touch? - A Re-post
AL wrote: Years ago on the list we had the hot/cold debate. People have pointed out a number of exceptions of meteorites being hot. 01) The Binningup meteorite was recovered within a few minutes of the fall and was reported to have been warm to the touch. 02) Cabin Creek: Three hours after the fall, Mr. and Mrs. Shandy were able to find the hole and excavate the mass, reportedly still uncomfortably warm. 03) Glatton: was warm, not hot, when first picked up. 04) Gurram Konda: ... but near the tent some small warm stones, which the Sentry has seen falling down. 05) Juromenha: ... The mass was said to have been incandescent when discovered and still warm when recovered next morning ... 06) L'Aigle: Affrighted persons who picked them up found the stones to be very warm and smelling of sulfur. 07) Limerick: It was immediately dug up, and I have been informed by those that were present, and on whom I could rely, that it was then warm and had a sulphurous smell. 08) Middlesbrough: The stone was new-milk warm when found, ... 09) Noblesville: The meteorite was not glowing as it passed the boys and was slightly warm when Spaulding picked it up a few seconds after it fell. 10) Pettiswood: The affrighted horse fell to the Earth, and two boys rushed to him in terror carrying fragments that Bingley found to be warm as milk just from the cow. 11) Pontlyfni: When I picked up the fragment of metal, or whatever it is, it was warm in my hand. 12) Rowton: It is, moreover, stated that when Mr. Brooks found the mass it was quite warm. 13) Tsukuba: Seconds later student Ryutaro Araki stopped to retrieve a still-warm stone that had fallen in front of his car near Tsukuba 14) Wold Cottage: Rushing to the spot he found a large stone, warm and smoking and smelling of sulfur. 15) Crumlin: When dug out the object, which had embedded itself in a straightdownward course for 13 inches, was found to be quite hot, continuing so for about an hour. 16) Eichstädt: The man rushed to the spot but found the black stone too hot to pick up until it cooled in the snow. 17) Hanau: A hot stone the size of a pea was picked up, weight 0.37g. 18) Harrogate: A hot stone, like basalt, fell accompanied by whistling in the air and lightning and thunder ... 19) Holbrook: One piece larger than an orange fell into a tree in a yard at Aztec cutting the limb off slick and clean and falling to the ground, and when picked up was almost red-hot. Von Achen, who saw them fall, reported that they were too hot to pick up. Two accounts state that they became lighter in color after cooling. 20) Lucé: ... several harvesters, startled by sudden thunderclaps and a loud hissing noise, looked up and saw the stone plunge into a field where they found it half-buried and too hot to pick up. 21) Magombedze: A 10-cm stone weighing approximately 600 g survived the impact intact and was hot to touch. 22) Menziswyl: The farmers say that the stone fell with the lightning and shattered when it hit the ground; it was hot when they picked it up. __ Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list
Re: [meteorite-list] Meteorites - warm or hot to the touch? - A Re-post
Warm is one thing- it is quite easy for a mass in space at around 1 AU to be warm- it is sitting in full sunlight, after all, and has no efficient way to get rid of heat. But I'm not buying stories about stones on the ground being incandescent, or even too hot to touch. Obviously, cool is most likely given the several minutes most stones spend exposed to a blast of -40°C air. There is nothing more unreliable than an actual witness to a fall. Chris * Chris L Peterson Cloudbait Observatory http://www.cloudbait.com - Original Message - From: [EMAIL PROTECTED] To: Meteorite-list@meteoritecentral.com Sent: Sunday, July 03, 2005 1:04 PM Subject: [meteorite-list] Meteorites - warm or hot to the touch? - A Re-post AL wrote: Years ago on the list we had the hot/cold debate. People have pointed out a number of exceptions of meteorites being hot. 01) The Binningup meteorite was recovered within a few minutes of the fall and was reported to have been warm to the touch... __ Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list
Re: [meteorite-list] Meteorites - warm or hot to the touch? - A Re-post
Hi Chris and all, I agree with you on the red hot, white hot stories. I don't go along with those. The study of meteorites is the study of un-differentiated material, though various degrees of differentiation can tell the solar system story better. If meteorites were heated to that extreme then isotopes would be reset and information lost. However as I mentioned and as Sterling post so well defined the fall characteristics there ARE exceptions to the rule. Not on the glowing red, glowing white but the fact some meteorites are hot to the touch. I believe a tarp melted on the Portales Valley specimen provides un-refutable proof. Some of Bernd's references are no doubt exaggerations by lay people on the ground. Other references are no doubt good witnessed reports. Noblesville, I believe was warm to the touch as an example. Always a good idea to keep an open mind where science is concern. --AL __ Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list
Re: [meteorite-list] Meteorites - warm or hot to the touch?
Hello Guys and Gals, The Mohahans fall was reported by the young finders to be barely hot potato holdable owing to the warmth. As to the Portales Valley and the tarp, I believe there was a bit of debate as to whether or not the tarp was melted or embedded. As an alumni of Ft Hood, Texas I remember putting a black tie rod-end down on a boat cover where a couple of 120°+ days later the tie rod had melted the tarp enough for there to be a bubble/smear of melted plastic under where the tie rod had lain. So I remain slightly unconvinced as to whether the meteorite was reentry hot enough to have done the melting or hot on subsequent days with high solar loading hot! One of the modern falls in Connecticut(Westfield?) was photographed ( if I recall correctly) with a frost rind on the broken face of the stone lying on the dinning room floor. Ms Hodge's account(Sylicaga , 1964?) failed to mention if the stone was hot or cold. I recall from previous discussions that when the Shuttle Orbiter returns, there are some components that are dangerously hot while other components rapidly frost up in the humid Florida air. Navigators know never to touch the mast of the sextant after a reading for it can be cold as -60°c especially over Greenland. Growing up on a TAC fighter base the wings of an F-104 Starfighter were reputedly dangerously hot upon a landing after a supersonic scramble. Over time, the leading edge of the wing was so sharpened via ablation, they had to place rubber strips on them for safety. I also recall that the cockpit temperature of the SR-71 Blackbird could raise to over 400°f during the speed runs. Even the waste/urine could boil and the cockpit was known for it's nasty smell. Pilots of course wore an additional space-certified environmental suit owing to the cockpit conditions mentioned above. All that said, there is no dispute that meteorites (and aircraft) heat up in transit. How specifically hot they are on the surface remains the unknown. I personally believe the meteorite surface is very warm slightly hot on most falls while the interior is very cold. That is what the physics say should be. While metal/iron is a good heat conductor, olivine/silicates is/are not, and it should take a longer time for the two temperature extremes to neutralize in a stony fall. Ironically, an iron might actually take longer to cool down than a stone becasue it could theoretically store up more of the ablation heat internally than a stony could. IF I am ever at the moment of a fall, I've already rehearsed the procedure. I intend to brand myself--hot and/or cold, and see if Al Lang will send me around to shows with Michelle Knapp's Malibu. Regards, Elton AL Mitterling wrote: I believe a tarp melted on the Portales Valley specimen provides un-refutable proof. __ Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list
Re: [meteorite-list] Meteorites - warm or hot to the touch?
Hi Elton- I'm curious about the basis of your assertion that physics suggests a typical meteorite should be hot on the outside and cool on the inside. I would expect a large stone (or iron) to have an internal temperature similar to what it was at in space, which can vary from around -100°C to +60°C depending on the parent's albedo and surface properties. As the object gets smaller, its passage through the atmosphere becomes more important in determining its final temperature. Something fist sized, for instance, will have probably equilibrated its temperature to the atmosphere during most of its fall (-40°C is a good value for this), and then begun warming from the outside during the last minute in warmer air. Depending on the thermal conductivity of the material, I think it will feel somewhere between ambient and slightly cool. I believe that the conditions leading to a warm or hot exterior are not common. Chris * Chris L Peterson Cloudbait Observatory http://www.cloudbait.com - Original Message - From: E. L. Jones [EMAIL PROTECTED] To: Meteorite-list@meteoritecentral.com Cc: AL Mitterling [EMAIL PROTECTED] Sent: Sunday, July 03, 2005 5:42 PM Subject: Re: [meteorite-list] Meteorites - warm or hot to the touch? I personally believe the meteorite surface is very warm slightly hot on most falls while the interior is very cold. That is what the physics say should be. While metal/iron is a good heat conductor, olivine/silicates is/are not, and it should take a longer time for the two temperature extremes to neutralize in a stony fall. Ironically, an iron might actually take longer to cool down than a stone becasue it could theoretically store up more of the ablation heat internally than a stony could. __ Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list
Re: [meteorite-list] Meteorites - warm or hot to the touch?
Chris, Read: http://six.pairlist.net/pipermail/meteorite-list/2005-January/148342.html for internal ambient temperatures on space. During ablation (which usually removes 90% or more of the rock, leaving the inner core only) surface temperatures are 1800 degrees C and up, depending on angle and initial velocity. Peak temperatures are about 20,000 degrees C. It requires at least 150 gee's (at 45 degrees) to decelerate a meteoroid to Earth's surface at median entry velocities. Tunguska air-burst at 200 gee's calculated. Fragmentation and crushing are far more likely, and the fragments usually vaporize instantly, anyway. Crushing strength of chondrites is a measly 0.1 to 10 bar; achondrites 62 to 2700 bar; irons to 4000 bar, but they're very brittle and come apart way below those lab values. Calculation of crushing in actual observed fireballs, 30 to 50 bars. The smaller the object is, the cooler on arrival, but even the tiniest Pultulsk or Holbrook has crust, or if it's small enough, IS crust. Anything that has or had crust has reached the melting to boiling point of rock. It won't cool if still in hypersonic flight, and anything that is in hypersonic flight when it reaches the ground won't survive impact, a narrow window if crushing strength is less than 10 bar. Impactor vaporizes when impact speed approaches the speed of sound in the impacting body. Measurement of the speed of sound in meteoritic stones (as low as 600 m/sec) much less than in well consolidated Earth rocks. Some are cool, some are warm, but not very cold and not very warm. Sterling K. Webb -- Chris Peterson wrote: Hi Elton- I'm curious about the basis of your assertion that physics suggests a typical meteorite should be hot on the outside and cool on the inside. I would expect a large stone (or iron) to have an internal temperature similar to what it was at in space, which can vary from around -100°C to +60°C depending on the parent's albedo and surface properties. As the object gets smaller, its passage through the atmosphere becomes more important in determining its final temperature. Something fist sized, for instance, will have probably equilibrated its temperature to the atmosphere during most of its fall (-40°C is a good value for this), and then begun warming from the outside during the last minute in warmer air. Depending on the thermal conductivity of the material, I think it will feel somewhere between ambient and slightly cool. I believe that the conditions leading to a warm or hot exterior are not common. Chris * Chris L Peterson Cloudbait Observatory http://www.cloudbait.com - Original Message - From: E. L. Jones [EMAIL PROTECTED] To: Meteorite-list@meteoritecentral.com Cc: AL Mitterling [EMAIL PROTECTED] Sent: Sunday, July 03, 2005 5:42 PM Subject: Re: [meteorite-list] Meteorites - warm or hot to the touch? I personally believe the meteorite surface is very warm slightly hot on most falls while the interior is very cold. That is what the physics say should be. While metal/iron is a good heat conductor, olivine/silicates is/are not, and it should take a longer time for the two temperature extremes to neutralize in a stony fall. Ironically, an iron might actually take longer to cool down than a stone becasue it could theoretically store up more of the ablation heat internally than a stony could. __ Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list __ Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list
