[meteorite-list] Last on Adamana for a while (I hope)

From: Sterling K. Webb <sterling_k_webb_at_meteoritecentral.com>
Date: Fri, 2 Mar 2007 01:57:14 -0600
Message-ID: <091501c75ca0$64427c30$32ea8c46_at_ATARIENGINE>

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" <dna1 at cableone.net>
To: "Meteorite-list" <meteorite-list at meteoritecentral.com>
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
size....now. 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 brown....much 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 story....the 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 most likely be the same as the
> rest of the fall.
>
> That said, you do seem to acknowledge the fact that it's crust does,
> in general, appear to be much more thick/different in appearance than
> that of Holbrook, to say nothing of the interior...
>
> >There are pictures of original finds
> that have chondrules as much as 5-7 mm in diameter.
>
> I know. Holbrook has much larger chondrules than that of Adamana, at
> least as well as can be seen on the broken surfaces.
>
> >Also, one has to
> keep in mind that it was found in a horse corral. I'm sure acidic horse
> urine and different soil conditions could have some kind of effect on it
> as well...IF it was.
>
> Versus sitting in a watershed plain next to an annually torrential
> wash? Different soil conditions might create a difference in
> weathering (though if it is, as you say, a mere four miles away, I
> doubt there would be any difference at all), but horse urine effects
> would be negligible at best...corrals are used sporadically at best
> anyways, to say nothing of the fact that annual rainfall.
> In fact, while the horse urine would be acidic, it would take
> rain/moisture to disassociate the ions in order to actually create any
> acidic effects - and as we all know, when it rains in Az, it
> pours...and would wash all of the acid downriver and out of the
> soil anyways.
>
> >I'm just saying that I for one, am not quite ready
> to throw the "half-baked" theory in the trash....yet.
>
> Eh, I grant you that there's a small chance Adamana's a part of
> Holbrook...in my opinion, very, very small.
>
> >Actually, the Adamana Meteorite was found 11 miles from Arntz (aka
> Aztec). Not quite all the way to Adamana which is 13 miles "as the
> meteor flies". (I did some remeasuring). And, if the Goodwater theory
> is correct, then you are only talking about 4 miles. According to the
> July 26, 1912 article on the Holbrook Argus: "There was a heavy
> explosion similar to that of a heavy blast followed by a fuscillade of
> smaller explosions which terminated in a thunder-like rumble of
> approximately two minutes in duration." In Warren Foote's Preliminary
> Notes of the July 19, 1912 Meteoric Fall at Aztec, Arizona, he writes:
> "It was heard in Concho, St. Joseph, Woodruff, and Pinedale, some 40
> miles away. One large explosion was quickly followed by several small
> ones in rapid succession."
>
> Firstly, the strewnfield has varying descriptions in almost every
> paper that I've seen. I just read a paper in which Kring stated that
> the strewnfield was ~1.5 sq. miles, a writeup by the DeLanges that
> states that it was ~1 by ~1/2 miles. I'm looking into Farrington - a
> little hard for me while I'm at school ;)
>
> >Now it's more like 3 miles long by 1 mile wide and growing. Even Warren
> Foote mentions this dimension in 1912.
>
> Again, conflicting reports...though by now, erosion could have made
> the field that large even if it hadn't been as big to start out
> with...that would explain the 'growing' aspect of it I guess. In any
> case, I cannot consider myself a judge, seeing as I was not there at
> the time of the fall, as were several well regarded scientific
> figures, who gave conflicting reports.
>
> >Hmmm....I've never heard that before. I'd like to know where you
> read/heard that information as that is interesting to me. According to
> Foote: "The large and small stones, according to all answers received,
> were said to be indiscriminately spread over the ground, without regard
> to size. The violent disruptions near Holbrook might account for the
> lack of such a separation...."
>
> If, as you say, there truly was no separation between sizes of
> fragments, it would almost certainly rule out any possibility of a
> larger mass having continued much farther than the already defined
> strewnfield. Such a chaotic distribution could suggest nothing other
> than a complete and catastrophic, if not instantaneous atmospheric
> breakup. Any classic atmospheric fragmentation would, as you know,
> create an organized strewnfield with larger stones at one end and
> small at the other. If there is no distribution, there must have been
> a very low and complete breakup - if large fragments did not even have
> enough air-time to make it to one end of the strewnfield, how would
> you expect another mass to proceed several miles farther? It would
> have to be part of a much larger (several tens of kilograms at the
> very minimum) fragment.
>
> >In recent years, say the last 40, the larger finds that I know of have
> been about in the center of the known field and on both sides of the
> tracks. I and others have found many smaller ones further north and
> east of these larger stones. I would like to know where the main mass
> was found, but I've never been able to dig that up yet. However, I've
> never read or heard anywhere that it was found at the furthest point of
> the field.
>
> I simply assumed that it was found in such a location based on all of
> the arguments being put forth - if there is indeed no distribution
> based on weight within the strewnfield, I see virtually no possibility
> for Adamana being a part of the Holbrook fall, unless it was
> previously found in the strewnfield and was later transported by
> people. The physics of it simply don't work out.
>
> >With all the numerous explosions, why not another 11 miles? Some parts
> must have still been ablating after the main explosion to have more
> explosions. At say, 7 miles per second (just as an aribitrary figure),
> it wouldn't take long to cover that distance. There is still quite a
> bit of material still missing off of Haag's aerodynamic piece too. But,
> certainly not enough to make it come close to being the main mass.
>
> Because almost every fall has numerous stages of breakup. Because
> even within these falls, there is (to my knowledge) always a single
> strewnfield, with very little deviation from the rule that larger
> stones fall at the far end and small ones at the other.
>
> When you say 'explosions,' you do realize that you are referring to
> sonic booms in most cases, do you not? The multiple 'booms' often
> heard during falls are not due to the physical breakup of the
> meteorite itself, but rather to the stones' breaking of the sound
> barrier. Thus these multiple detonations heard were probably due to
> the existence of a number of number of stones that were large enough
> to retain some of their cosmic velocity for long enough to break the
> sound barrier in an audible manner.
> The initial large explosion heard would explain the initial sound
> effects of the large body either simply passing overhead at a great
> velocity or possibly it's violent fragmentation, whereas the rumbling
> heard afterwards can certainly be attributed to the many fragments
> that must have been large enough just after this explosion to still
> retain the velocity needed to create sound effects of their own, on a
> much smaller scale.
>
> >Huh? In the Holbrook Argus article, it states: "The sky was lightly
> overcast with patches of high floating clouds, but immediately after the
> explosion a smoky trail similar to the smoke of an automobile's exhaust
> was visible. The trail disappeared in a LITTLE NORTH of east in
> direction." Well, Arntz is ENE of Holbrook and Adamana is ENE of
> Arntz. The strewn field and the railroad tracks are in a ENE
> orientation. Drawing a line from Holbrook through Arntz takes you right
> to Adamana....in fact, this line can possibly go a little bit north of
> what is shown as Adamana on a topo map. (next to the railroad tracks
> where the propane plant is).
>
> And I've read other reports stating that it followed a due East
> path...figures. I wasn't there, and see no way how one can decide
> between your sources and mine. This path, even if followed to a
> ridiculous extent (you're going to be hard pressed to find a
> strewnfield for a stony meteorite that's confirmed to be this long),
> takes you quite a distance south of Adamana. But this all depends on
> the accuracy of the reports....who could possibly know.
>
> Regards,
> Jason
>
> On 2/27/07, DNAndrews <dna1 at cableone.net <mailto:dna1 at cableone.net>>
> wrote:
>
>
>
> Jason Utas wrote:
>
> > Hello All,
> > There are a few things that separate Adamana from Holbrook in my
> mind...
> > The texture of the crust alone of Adamana versus that of Holbrook
> > leaves me little doubt that the two could possibly be paired.
>
> Hi Jason,
> I think you meant to say that "the two could NOT possibly be paired?
> Not trying to argue, just think a few points need to be said.
>
> > The fusion crust of Adamana is a matte black, which contrasts
> sharply
> > with the crust of recently found Holbrooks, which exhibit a
> typically
> > blue/black almost shiny crust in most cases, often liberally spread
> > with rust spots.
> > The interior tells the same story - Adamana is a uniform brown, with
> > chondrules poking out here and there. Recently found Holbrooks
> tend
> > to be less weathered internally, if not more externally, and their
> > dark chondrules contrast starkly with the lighter matrix, creating a
> > much more heterogeneous appearance than that of Adamana.
>
> If indeed the Adamana meteorite is the front piece of the
> Holbrook, and
> I'm NOT saying it is, then it would have the thickest primary
> crust out
> of any other portion of the fall. There are pictures of original
> finds
> that have chondrules as much as 5-7 mm in diameter. Also, one has to
> keep in mind that it was found in a horse corral. I'm sure acidic
> horse
> urine and different soil conditions could have some kind of effect
> on it
> as well...IF it was. I'm just saying that I for one, am not quite
> ready
> to throw the "half-baked" theory in the trash....yet.
>
> > The location of the find....
> > Fifteen miles is simply impossible, unless it was artificially
> > transported.
>
> Actually, the Adamana Meteorite was found 11 miles from Arntz (aka
> Aztec). Not quite all the way to Adamana which is 13 miles "as the
> meteor flies". (I did some remeasuring). And, if the Goodwater
> theory
> is correct, then you are only talking about 4 miles. According to the
> July 26, 1912 article on the Holbrook Argus: "There was a heavy
> explosion similar to that of a heavy blast followed by a fuscillade of
> smaller explosions which terminated in a thunder-like rumble of
> approximately two minutes in duration." In Warren Foote's Preliminary
> Notes of the July 19, 1912 Meteoric Fall at Aztec, Arizona, he writes:
> "It was heard in Concho, St. Joseph, Woodruff, and Pinedale, some 40
> miles away. One large explosion was quickly followed by several small
> ones in rapid succession."
>
> > The mapped strewnfield was roughly one mile long by a half
> mile wide.
>
> Now it's more like 3 miles long by 1 mile wide and growing. Even
> Warren
> Foote mentions this dimension in 1912.
>
> > The largest stone recovered, weighing in at ~14.5 lbs, was
> found at
> > the end of this ellipse.
>
> Hmmm....I've never heard that before. I'd like to know where you
> read/heard that information as that is interesting to
> me. According to
> Foote: "The large and small stones, according to all answers
> received,
> were said to be indiscriminately spread over the ground, without
> regard
> to size. The violent disruptions near Holbrook might account for the
> lack of such a separation...."
>
> > The possibility that anything made it farther than this stone
> is great -
>
> In recent years, say the last 40, the larger finds that I know of have
> been about in the center of the known field and on both sides of the
> tracks. I and others have found many smaller ones further north and
> east of these larger stones. I would like to know where the main mass
> was found, but I've never been able to dig that up yet. However, I've
> never read or heard anywhere that it was found at the furthest
> point of
> the field.
>
> > it wouldn't surprise me too greatly if a 20lber was found another
> > quarter of a mile on (it could've buried itself on impact, etc), but
> > to say that a smaller stone continued another fifteen miles
> beyond the
> > known end of the strewnfield is simply ridiculous,
>
> With all the numerous explosions, why not another 11 miles? Some
> parts
> must have still been ablating after the main explosion to have more
> explosions. At say, 7 miles per second (just as an aribitrary
> figure),
> it wouldn't take long to cover that distance. There is still quite a
> bit of material still missing off of Haag's aerodynamic piece
> too. But,
> certainly not enough to make it come close to being the main mass.
>
> > to say nothing of the fact that it is much too far north to even
> > be near the same path as the body that created the Holbrook
> strewnfield.
>
> Huh? In the Holbrook Argus article, it states: "The sky was lightly
> overcast with patches of high floating clouds, but immediately
> after the
> explosion a smoky trail similar to the smoke of an automobile's
> exhaust
> was visible. The trail disappeared in a LITTLE NORTH of east in
> direction." Well, Arntz is ENE of Holbrook and Adamana is ENE of
> Arntz. The strewn field and the railroad tracks are in a ENE
> orientation. Drawing a line from Holbrook through Arntz takes you
> right
> to Adamana....in fact, this line can possibly go a little bit
> north of
> what is shown as Adamana on a topo map. (next to the railroad tracks
> where the propane plant is).
>
> Anyway, I just feel more investigating needs to be done to make a
> decision whether "yea" or "nay" on the subject. Maybe Bob will
> someday
> have a little crumb analyzed for curiousities sake or someone will
> make
> another find well outside of the known strewn field.
>
> Respectfully,
> Dave
>
>
Received on Fri 02 Mar 2007 02:57:14 AM PST


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