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Unclassified   contributed by Paladino Vincenzino, IMCA 4223   MetBul Link
 


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180.4 grams.   Chondrite



Paladino writes:
Oriented chondrite with exceptional escape lines from the back of the meteorite, certainly due to a suction effect during the passage of the body in the atmosphere


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Paladino vincenzino
 10/25/2020 12:55:01 PM
Thanks jason
Jason Utas
 10/19/2020 3:32:17 PM
@ John I think these back-face flow lines form due to air flowing from the outside edge in, to the center of the specimen, but I have never seen accumulations of melt due to these flow lines at either the edge or center of a specimen, so I am not certain. Studies have shown that you can get similar lamellar / non-turbulent airflow effects behind projectiles in the right conditions: www[dot]researchgate.net/profile/Hazim_Moria/publication/228812404/figure/fig2/AS:393803300130822@1470901431966/Airflow-structure-of-football-with-smoke-flow-visualization_W640[dot]jpg Replace both [dot]s with .s
John Divelbiss
 10/8/2020 7:00:29 PM
I am assuming the so-called stove piping implies a vertical point of flow away from the radiating centering point on the back. Sounds made up...but then again I am not a young meteortist...just an old mechanical engineer :) BTW...upside down comma shaped airfoils tend to want to tumble when flown that way. That I do know.
Paladino vincenzino
 10/8/2020 3:11:17 PM
maybe i am wrong, but i think the lines go from outside to inside, jason can surely give us more precise information
John Divelbiss
 10/8/2020 3:02:29 PM
Palladino/Jason...which direction does the flow go on the back side? From the edge inward or from the centering point outwards? The piece itself I mean...not the stove pipe theory. If inward then a vacuum effect with the outflow away the stone being the "stove pipe". If so...pretty cool.
Paladino vincenzino
 10/8/2020 2:21:39 PM
and this vacuum effect could also modify the visual aspect of the generally V-shaped light trail as the body passes through the atmosphere?
Paladino vincenzino
 10/8/2020 2:17:39 PM
thanks jason for the very thorough explanation.
Jason Utas
 10/8/2020 2:08:08 PM
From other specimens I have seen, this is not *double orientation* or due to tumbling / flipping in flight. Flow lines like these, on the rear faces of oriented stones, have a different morphology than ones on the front of stones. They are thinner, taller, and often perfectly straight, unlike flow lines on the front of stones that are deflected around obstacles by ram pressure / air flow. And there is also no corresponding lipping or other evidence of the stone flipping over, on this stone or others I have seen. Note the thin lip on the left-hand edge of photo #3 here: that should have been ~the first feature removed by ablation if the stone had flipped over. These flowlines have previously been attributed to *stovepiping,* which is analogous to a *vacuum effect* as mentioned here: fluid air flow over the side and back of the stone. That explanation is consistent with all observed surface features.
John Divelbiss
 10/8/2020 1:58:58 PM
A "vacuum point" could cause radiating lines on the backside that would be wrap-around flow from the front around to the back to the low pressure point in theorym moving IN from the edges...which is hard to imagine in principle because where does the material go once it gets there? If the lines radiate OUT from the upper centering point then I think it flipped over...at least once if not many time. IMHO :/
Paladino vincenzino
 10/8/2020 1:18:20 PM
could it possibly be a vacuum effect?
Steve Brittenham
 10/8/2020 11:01:06 AM
Stunning specimen! Love those radial flowlines. Congratulations!!
John Divelbiss
 10/8/2020 10:35:21 AM
Does this occur when the ablated-shaped stone becomes like an upside airfoil (which it is) that would eventually tumble with a change in the center of gravity to put the final touches on the two surfaces?
Paladino vincenzino
 10/8/2020 9:27:56 AM
thanks Mendy, for your precious explanations
Mendy M Ouzillou
 10/8/2020 9:05:39 AM
This specimen is, I believe, double oriented. The nose cone is one orientation and the second is indicated by the radial flowlines emanating from the peak on the "back". No matter the process, this stone is really beautiful.
Don Cracraft 2650
 10/8/2020 9:03:21 AM
Pictures showed everything qyite well! Thanks!
Dave Smith
 10/8/2020 8:42:48 AM
Absolutely gorgeous!
Paladino vincenzino
 10/8/2020 6:58:37 AM
thanks to all, this phenomenon is called double orientation. but what exactly is the dynamics that this meteorite has undergone? how is it possible to have the escape lines in the back of the meteorite?
Twink Monrad
 10/8/2020 6:28:00 AM
Wow super interesting and beautiful. It will make me get out one of my larger Gold Basin finds with the fine lines radiating from a center point on one side and study it again.
Kally Wombacher
 10/8/2020 4:33:47 AM
Very nice oriented piece!
Bernd Pauli
 10/8/2020 3:49:56 AM
Both flight-marked and flight-oriented. Beautiful!
 

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