Re: [meteorite-list] Last on Adamana for a while (I hope)
Hello All, Firstly, all of your statements rely either on the fact that this was an atmospheric breakup in which larger (or oriented/atmospherically more streamlined) stones falling at one end and the smaller stones falling at the other. This is clearly not the case. As you stated, the Holbrook fall is an anomaly - there is no clear differentiation between the sizes of stones found and opposing ends of the strewnfield - rather, the larger stones have been found in the center of it. The only logical conclusion to draw from this is that the Adamana stone, had it indeed been a large individual of Holbrook, would have done the same as the other large Holbrooks and fallen in this area. The only other possible explanation for its falling so far beyond the boundary of the mapped strewnfield would be a highly abnormal multiple-stage breakup with large distances between fragmentation at a relatively great height (this would be needed to create such a long strewnfield). This, however, is impossible. If this were indeed the case, the initial strewnfield would have a clearly defined strewnfield going from small stones at one end to large at the other - but this does not occur. Assuming that the main portion of the fall was only a fragment of the body that continued and then itself fragmented (at a greater altitude than that of the body that contained the Adamana fragment [because in order for the mapped strewfield to have fallen *before* Adamana, its breaking off of the main part of the fall must have been earlier and thus higher than the fragment which continued on], which must have been much larger than the mass that fragmented to create the majority of the Holbrook fall - for it continued for a much greater distance), there would be a clearly defined strewnfield with large stones at one end and smaller at the other in the already mapped strewnfield. Furthermore, I find the assumption that an oriented stone would travel greater distances interesting, but most likely erroneous. In falls that have been mapped, oriented stones have shown little to no exception to the 'rule' that large stones fall farther from fragmentation point of the body than do smaller stones. If you have some reasoning that might exempt a piece of Holbrook from these tendencies, I'd be open to hearing it, but I see nothing that would cause this to occur. That being said, the possibility still remains that Adamana was a fragment of a much larger fragment of Holbrook that detonated later in flight. However, seeing as no other large stones, or, indeed, any other stones were found between Adamana and the rest of the Holbrook strewnfield, I find this conclusion highly unlikely. The fact that Holbrook in general tends to be very friable also points us away from this conclusion. Regards, Jason On 3/2/07, MexicoDoug <[EMAIL PROTECTED]> wrote: Hi again, like Sterling I will repost my message sent a while ago as it didn't go through instantaneously and Holbrook is hot. Undoubtable the messages will show up sometime in a couple of days so pardon the duplication... Best health, Doug From: "MexicoDoug" To: "DNAndrews"; "Meteorite-list" Sent: Friday, March 02, 2007 12:29 PM CST Subject: Re: [meteorite-list] Last on Adamana for a while (I hope) Hi Dave and Jason, I appreciate the discussion from you both, all the food for thought... Each time I saw your posts, I didn't find any of you referencing the obvious fact of the possible effect on travel distance of the superb orientation of the Adamana specimen with respect to the physics. Sorry if I missed it! I wish I had time to cook up a quantitative story, but the Adamana orientation would contribute to a 75% faster (guess*) velocity over a longer path length as the tumbling stones reached free fall I'm guessing. I am somewhat comparing apples to oranges with free fall velocities and incident velocities, but it illustrates the considerations. I'm not expressing any opinion over this case, but just pointing out that there is a theoretical ways to determine whether the distance traveled is ridiculous or whether intuition can be ridiculous. Note that friction has a direct proportion to velocity, and you can play with the projectile formula on a hand calculator to get a feel for the angles necessary and differences in distance traveled: distance = sin(2*ranging angle)(1-(4/3)*(vi/vt)*sin(ranging angle) which will give you the a feel for the distance traveled by a launched projectile subjected constant atmosphere, where vi is the initial velocity and vt is the terminal velocity - this is the easiest way I think to get some good intuition. So if you can settle on the azimuth of Adamana generally being in line with Holbrook, you might have another argument to cover relating to how quickly the Adamana changed from straight line flight to parabolic and then nosed down into free fall. I am guessing that the right conditions a
Re: [meteorite-list] Last on Adamana for a while (I hope)
Hi Dave and Jason, I appreciate the discussion from you both, all the food for thought... Each time I saw your posts, I didn't find any of you referencing the obvious fact of the possible effect on travel distance of the superb orientation of the Adamana specimen with respect to the physics. Sorry if I missed it! I wish I had time to cook up a quantitative story, but the Adamana orientation would contribute to a 75% faster (guess*) velocity over a longer path length as the tumbling stones reached free fall I'm guessing. I am somewhat comparing apples to oranges with free fall velocities and incident velocities, but it illustrates the considerations. I'm not expressing any opinion over this case, but just pointing out that there is a theoretical ways to determine whether the distance traveled is ridiculous or whether intuition can be ridiculous. Note that friction has a direct proportion to velocity, and you can play with the projectile formula on a hand calculator to get a feel for the angles necessary and differences in distance traveled: distance = sin(2*ranging angle)(1-(4/3)*(vi/vt)*sin(ranging angle) which will give you the a feel for the distance traveled by a launched projectile subjected constant atmosphere, where vi is the initial velocity and vt is the terminal velocity - this is the easiest way I think to get some good intuition. So if you can settle on the azimuth of Adamana generally being in line with Holbrook, you might have another argument to cover relating to how quickly the Adamana changed from straight line flight to parabolic and then nosed down into free fall. I am guessing that the right conditions are theoretically there to keep the possibility open from a strewn field perspective given the nosecone sculpted orientation of the piece and its generally higher momentum. This would be a very interesting thing to do given all the data on Holbrook out there and if any larger oriented specimens were collected in known points. One of my own Holbrooks is loaded with chondrules on the surface and looks old and worn and another tiny one is complete and asphalt black, but that's all I can say other than having the fun with mechanics and the effect of friction on projectile angles... I don't see the benefit searching the 'Adamana' locality on the supposition it is another Holbrook piece unless you expect to find another equally oriented and sized stone there (though the line that connects Adamana to Aztec is another story)...but if you believe they are not the same fall, and have reliable coordinates, happy hunting! Best wishes and Health, Doug *from my post on this day in history of 2004: http://www.mail-archive.com/meteorite-list@meteoritecentral.com/msg20269.html "Also for fun, an oriented bowling ball that fractures in exactly two hemispherical pieces traveling terminally at 150 mph will leave the two fragments at a terminal rate of ... 106 mph a piece. That's probably why "explosions" seem to brighten fireballs. Suddenly the greater surface area for the same total mass steps up the overall frictional energy released and the meteors slow down from an instantly greater potential." . - Original Message - From: "DNAndrews" <[EMAIL PROTECTED]> To: "Meteorite-list" Sent: Thursday, March 01, 2007 11:09 PM Subject: [meteorite-list] Last on Adamana for a while (I hope) > Hi again, Jason, > > I've been researching the Holbrook field and it's history for about 9 > years now. Talking to old timers and listening to their stories passed > down from their ancestors, etc. I've found 100's of the stones and the > people I've hunted with, at least a hundred more. I think I/we have a > pretty good idea now as to the orientation of the elipse and the size of > the known field. From all of this, I can pretty much now tell what > direction the bolide came from and which way it was headed. I can tell > you now, from personal experience, it's now 3-1/2 x 1-1/2 miles. You > can quote Norton, Kring, Farrington, Google all you want, but that's the > sizenow. It's not growing from erosion. Now that's "ridiculous" > (as you keep saying). Those stones didn't blow in the wind on top and > sides of those dunes, nor did they go down some torential wash and end > up there either. I'm sure the modern day King of Holbrook, Steve > Schoner, will agree with me on this as will a few others. In fact, it > was years I ago I got the approx. dimensions from him off this very list. > > The only reason I mentioned large chondrules in some of the original > finds, is to point out the Holbrook meteorite was not homogenous in > structure. There is even a picture I have of an original Foote stone > that has an 11mm hole where a chondrule fell out of it's crust. > Howe
Re: [meteorite-list] Last on Adamana for a while (I hope)
Dave, It was good to talk to you on the phone the other day. Thanks for the update and your always appreciated opinion. I hope to get up there and do a little scouting around with you before Summer. And, as far as I'm concerned, you and Schoner are the experts when it comes to Holbrook. Best, JKG At 10:09 PM 3/1/2007, DNAndrews wrote: >Hi again, Jason, > >I've been researching the Holbrook field and it's history for about 9 >years now. Talking to old timers and listening to their stories passed >down from their ancestors, etc. I've found 100's of the stones and the >people I've hunted with, at least a hundred more. I think I/we have a >pretty good idea now as to the orientation of the elipse and the size of >the known field. From all of this, I can pretty much now tell what >direction the bolide came from and which way it was headed. I can tell >you now, from personal experience, it's now 3-1/2 x 1-1/2 miles. You >can quote Norton, Kring, Farrington, Google all you want, but that's the >sizenow. It's not growing from erosion. Now that's "ridiculous" >(as you keep saying). Those stones didn't blow in the wind on top and >sides of those dunes, nor did they go down some torential wash and end >up there either. I'm sure the modern day King of Holbrook, Steve >Schoner, will agree with me on this as will a few others. In fact, it >was years I ago I got the approx. dimensions from him off this very list. > >The only reason I mentioned large chondrules in some of the original >finds, is to point out the Holbrook meteorite was not homogenous in >structure. There is even a picture I have of an original Foote stone >that has an 11mm hole where a chondrule fell out of it's crust. >However, of all my finds, I only see a size of 1mm or maybe a very few >2mm (as the largest) chondrules in the matrix. I found one stone of >~140 gms in weight, that was in fragments. It's non-crusted, exposed >surfaces were brownmuch like the sides of the Adamana stone. I have >a cast of the Adamana, and it's of such quality that I can see some of >the chondrules. They look just like the size of the typical chondrules >in the Holbrook finds to me. > >I appreciate all your textbook explanations as to why I'm a kook, but I >really don't think the Holbrook was a "textbook" fall. Yes, I thought >of sonic booms as the rapid succession explosions. As far as all the >pressure and stress on the front of the bolide, what effect does that >have on the trailing portion of the body? It appears that the Adamana >nose cone made it through it's flight in the atmosphere to it's strewn >field. Did I say strewn field? Sorry, my mistake. And the back side >of the stone? Looks quite cracked and friable to me. The only thing >about it that bothers me is the top-side crust. > >Now, I'm not going to tell everything I know to you or hundreds of other >people. That would be cutting my own throat like I've probably already >said too much already. However, I will share that I talked to the >original finders of the Adamana stone last night on the phone. It was >found in their horse corral and then they used it as a door stop on >their barn. They know nothing of any Railroad bed filler in the >corral. So, out goes the fence post storythe cowboy with the .22 ( >who will remain nameless as well).the Goodwater story, etc. The >good news is I have my permission to hunt on their property. I expect >to come up empty-handed, but who knows? Might get lucky like Larry >did. ;-) > >Anyway Jason, you are entitled to your opinion and I'm entitled my >kooky, half-baked theory. As you said, you weren't here at the time of >the fall, neither was I. But, I'm here now...that's the difference. > >Cheers, >Dave (who is running late to work) > >Jason Utas wrote: > > > Hello Dave, All, > > > > >If indeed the Adamana meteorite is the front piece of the Holbrook, and > > I'm NOT saying it is > > > > The idea of a 'front piece' of the Holbrook mass is something that I > > find completely ridiculous. Stress mechanics alone state that > > anything at the front of the object would be subjected to much greater > > stress than the remainder of the stone and would therefore be the > > first part of the stone to fragment. There's simply no reason > > whatsoever for the trailing remainder of the meteorite to so violently > > explode, seeing as it must have been subjected to much lesser forces. > > If, however, it were simply a small portion of a larger 'main mass' of > > Holbrook that one hypothesizes must have traveled an additional number > > of miles past the known termination of the strewnfield, you might have > > the basis for some sort of multiple-fragmentation, the likes of which > > has *never* been seen before, with at least two distribution ellipses > > separated my miles of 'barren' land. I, however, find this about > > equally unlikely as the previously mentioned possibility, if not more > > so. > > > > >then it would have the th
Re: [meteorite-list] Last on Adamana for a while (I hope)
Hi,
At the risk of stepping into a private argument
and collecting a wild punch, I just wanted to point
out something about meteoric entry.
The "stone" is most likely to fragment at the
point of maximum dynamic pressure from the
atmosphere (or Max Q). The dynamic pressure
equals (density) x (velocity)^2 / 2. Now, the square
of the object's velocity decreases exponentially, that is
to say very rapidly, from the drag created by that
rising pressure. A good chunk of rock is going to
be slowing down at anywhere from 50 gees to perhaps
200 gees. We can measure the actual deceleration of
meteors and we can test existing meteorites to determine
their crushing strength, and that is the range we find.
The density of the atmosphere increases linearly in
proportion to altitude, so the pressure builds up
mostly in the later stages of the entry.
The three factors (rapid slowdown, weak stones,
and atmospheric density) combine to USUALLY result
in a low altitude fragmentation. If the stone is unusually
weak ("friable") it will fragment at a higher altitude.
Stones that fragment into a very large number of pieces
(like Holbrook) seem to do so because they are very
weak. Thus, Holbrook could be considered atypically
weak and that could produce some odd behavior.
While Jason is correct that the maximum pressure
is exerted on the "nose" of a "nose cone," that point
is also the most stable and the least subject to vibration.
The external shock waves in hypersonic flight could have
folded smoothly over the ablating cone-shaped portion
of the mass and then become turbulent further back along
the more irregular and less ablated main body of the object,
producing buffeting and vibration that caused the main
portion of the mass to shatter and break in half (or at least
into two pieces because the stone was very weak), while the
"nose" managed to transition the hypersonic-subsonic
boundary more or less intact, leaving the "second" stone
to re-fragment and re-fragment, ablating until they too could
also drop to subsonic velocities. It's an unusual scenario,
not the "normal" breakup (if there is such a thing as a
normal meteoric breakup).
This could all be a wild fantasy but, interestingly,
there is this paper that claims that a mathematical analysis
of the distribution of sizes of fragments found in a meteorite
fall can reveal such details as the number of breakups the
object went through or if the shape of the original body
deviated from the spherical:
http://www.iop.org/EJ/article/0295-5075/43/5/598/node4.html
by L. Oddershede (Technical University of Denmark ), A. Meibom
(University of Odense, Denmark ) and J. Bohr (Hawai'i Institute of
Geophysics and Planetology, University of Hawai'i at Manoa)
The authors say: "A known example is the Holbrook
shower, where the presence of different thicknesses of
the fusion crust shows that the meteoroid was subject
to at least two fragmentation processes. The mass
distribution of fragments from the Holbrook shower...
seems S-shaped which might be consistent with a
superposition of two power laws with different cut-off
masses... The mass distributions could equally well or
better be a result of three (or more) fragmentations."
They are talking about the fragments called "Holbrook"
only, but it is clear that the statistics suggest a "stepped"
process in which a big rock breaks into two rocks, one of
which breaks into multiple fragments, the largest of which
could in turn break into smaller multiple fragments...
They studied a number of "showers" and found some
to be the result of a single fragmentation event and some
to be the result of multiple fragmentations. Quite incidentally,
the equations also imply the volumetric coefficient of the
original shape. The Mbale Object was almost spherical
(with Vc=3) while the original Sikhote-Aline meteoroid
was a long cylinder (Vc=1.8). Hey, no wonder it had such
a bumpy ride! A big iron splinter.
Jason would be "right" in that it is counter-intuitive
and does not follow the "usual" course of events for the
many Holbrooks and the Venus Stone to be part of the
same mass, but there are many indications that this may
be an unusual fragmentation event, in which case all the
usual bets are off.
Theory is one thing, but the proof is always on the
ground (or in it, sometimes). Keep hunting!
Sterling K. Webb
--
- Original Message -----
From: "DNAndrews" <[EMAIL PROTECTED]>
To: "Meteorite-list"
Sent: Thursday, March 01, 2007 11:09 PM
Subject: [meteorite-list] Last on Adamana for a while (I hope)
Hi again, Jason,
I've been researching the Holbrook field and it's history for about 9
years now. Talking to old timers and listening to their stories passed
down
Re: [meteorite-list] Last on Adamana for a while (I hope)
Hi again, like Sterling I will repost my message sent a while ago as it didn't go through instantaneously and Holbrook is hot. Undoubtable the messages will show up sometime in a couple of days so pardon the duplication... Best health, Doug From: "MexicoDoug" To: "DNAndrews"; "Meteorite-list" Sent: Friday, March 02, 2007 12:29 PM CST Subject: Re: [meteorite-list] Last on Adamana for a while (I hope) Hi Dave and Jason, I appreciate the discussion from you both, all the food for thought... Each time I saw your posts, I didn't find any of you referencing the obvious fact of the possible effect on travel distance of the superb orientation of the Adamana specimen with respect to the physics. Sorry if I missed it! I wish I had time to cook up a quantitative story, but the Adamana orientation would contribute to a 75% faster (guess*) velocity over a longer path length as the tumbling stones reached free fall I'm guessing. I am somewhat comparing apples to oranges with free fall velocities and incident velocities, but it illustrates the considerations. I'm not expressing any opinion over this case, but just pointing out that there is a theoretical ways to determine whether the distance traveled is ridiculous or whether intuition can be ridiculous. Note that friction has a direct proportion to velocity, and you can play with the projectile formula on a hand calculator to get a feel for the angles necessary and differences in distance traveled: distance = sin(2*ranging angle)(1-(4/3)*(vi/vt)*sin(ranging angle) which will give you the a feel for the distance traveled by a launched projectile subjected constant atmosphere, where vi is the initial velocity and vt is the terminal velocity - this is the easiest way I think to get some good intuition. So if you can settle on the azimuth of Adamana generally being in line with Holbrook, you might have another argument to cover relating to how quickly the Adamana changed from straight line flight to parabolic and then nosed down into free fall. I am guessing that the right conditions are theoretically there to keep the possibility open from a strewn field perspective given the nosecone sculpted orientation of the piece and its generally higher momentum. This would be a very interesting thing to do given all the data on Holbrook out there and if any larger oriented specimens were collected in known points. One of my own Holbrooks is loaded with chondrules on the surface and looks old and worn and another tiny one is complete and asphalt black, but that's all I can say other than having the fun with mechanics and the effect of friction on projectile angles... I don't see the benefit searching the 'Adamana' locality on the supposition it is another Holbrook piece unless you expect to find another equally oriented and sized stone there (though the line that connects Adamana to Aztec is another story)...but if you believe they are not the same fall, and have reliable coordinates, happy hunting! Best wishes and Health, Doug *from my post on this day in history of 2004: http://www.mail-archive.com/meteorite-list@meteoritecentral.com/msg20269.html "Also for fun, an oriented bowling ball that fractures in exactly two hemispherical pieces traveling terminally at 150 mph will leave the two fragments at a terminal rate of ... 106 mph a piece. That's probably why "explosions" seem to brighten fireballs. Suddenly the greater surface area for the same total mass steps up the overall frictional energy released and the meteors slow down from an instantly greater potential." __ Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list
[meteorite-list] Last on Adamana for a while (I hope)
Hi again, Jason, I've been researching the Holbrook field and it's history for about 9 years now. Talking to old timers and listening to their stories passed down from their ancestors, etc. I've found 100's of the stones and the people I've hunted with, at least a hundred more. I think I/we have a pretty good idea now as to the orientation of the elipse and the size of the known field. From all of this, I can pretty much now tell what direction the bolide came from and which way it was headed. I can tell you now, from personal experience, it's now 3-1/2 x 1-1/2 miles. You can quote Norton, Kring, Farrington, Google all you want, but that's the sizenow. It's not growing from erosion. Now that's "ridiculous" (as you keep saying). Those stones didn't blow in the wind on top and sides of those dunes, nor did they go down some torential wash and end up there either. I'm sure the modern day King of Holbrook, Steve Schoner, will agree with me on this as will a few others. In fact, it was years I ago I got the approx. dimensions from him off this very list. The only reason I mentioned large chondrules in some of the original finds, is to point out the Holbrook meteorite was not homogenous in structure. There is even a picture I have of an original Foote stone that has an 11mm hole where a chondrule fell out of it's crust. However, of all my finds, I only see a size of 1mm or maybe a very few 2mm (as the largest) chondrules in the matrix. I found one stone of ~140 gms in weight, that was in fragments. It's non-crusted, exposed surfaces were brownmuch like the sides of the Adamana stone. I have a cast of the Adamana, and it's of such quality that I can see some of the chondrules. They look just like the size of the typical chondrules in the Holbrook finds to me. I appreciate all your textbook explanations as to why I'm a kook, but I really don't think the Holbrook was a "textbook" fall. Yes, I thought of sonic booms as the rapid succession explosions. As far as all the pressure and stress on the front of the bolide, what effect does that have on the trailing portion of the body? It appears that the Adamana nose cone made it through it's flight in the atmosphere to it's strewn field. Did I say strewn field? Sorry, my mistake. And the back side of the stone? Looks quite cracked and friable to me. The only thing about it that bothers me is the top-side crust. Now, I'm not going to tell everything I know to you or hundreds of other people. That would be cutting my own throat like I've probably already said too much already. However, I will share that I talked to the original finders of the Adamana stone last night on the phone. It was found in their horse corral and then they used it as a door stop on their barn. They know nothing of any Railroad bed filler in the corral. So, out goes the fence post storythe cowboy with the .22 ( who will remain nameless as well).the Goodwater story, etc. The good news is I have my permission to hunt on their property. I expect to come up empty-handed, but who knows? Might get lucky like Larry did. ;-) Anyway Jason, you are entitled to your opinion and I'm entitled my kooky, half-baked theory. As you said, you weren't here at the time of the fall, neither was I. But, I'm here now...that's the difference. Cheers, Dave (who is running late to work) Jason Utas wrote: > Hello Dave, All, > > >If indeed the Adamana meteorite is the front piece of the Holbrook, and > I'm NOT saying it is > > The idea of a 'front piece' of the Holbrook mass is something that I > find completely ridiculous. Stress mechanics alone state that > anything at the front of the object would be subjected to much greater > stress than the remainder of the stone and would therefore be the > first part of the stone to fragment. There's simply no reason > whatsoever for the trailing remainder of the meteorite to so violently > explode, seeing as it must have been subjected to much lesser forces. > If, however, it were simply a small portion of a larger 'main mass' of > Holbrook that one hypothesizes must have traveled an additional number > of miles past the known termination of the strewnfield, you might have > the basis for some sort of multiple-fragmentation, the likes of which > has *never* been seen before, with at least two distribution ellipses > separated my miles of 'barren' land. I, however, find this about > equally unlikely as the previously mentioned possibility, if not more > so. > > >then it would have the thickest primary crust out > of any other portion of the fall. > > Why? There's no reason for such a 'front piece,' even supposing it > could exist, to not fragment later into multiple pieces just as the > remainder of the fall had. In all probability, if such a 'front > piece' existed, this would most likely be a portion that broke off > of it, and as such, its crust would
