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

From: Jason Utas <meteoritekid_at_meteoritecentral.com>
Date: Mon, 5 Mar 2007 18:19:11 -0800
Message-ID: <93aaac890703051819x49fa8e8bqbe998322a3689f24_at_mail.gmail.com>

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 <MexicoDoug at aim.com> 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 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 at 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."
>
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Received on Mon 05 Mar 2007 09:19:11 PM PST