mmhhmm...
quick stab
as a result of a lack of tumbling and corkscrewing through the
atmosphere (the result of the object's mass, distribution of mass and
angle of entry), the object maintains a somewhat stable horizontal
and vertical axis during its plunge through the atmosphere, resulting
markedly different characterics on its obverse and reverse.
On Mar 5, 2008, at 9:52 AM, [EMAIL PROTECTED] wrote:
Darryl & List,
I'd add a point for consideration, and that is the question "what
are we talking about when we say a meteorite is oriented?" By this
I mean that, at least from one perspective, the fundamental
definition of an oriented meteorite is that it made it's violent
passage through out atmosphere in a fixed (non-tumbling) position.
As I mentioned somewhere in the series of yesterdays discussion on
orientation, we're talking a few second of flight in the "shaping
environment" (i.e. the atomsphere). "Perfect orientation" is often
taken to mean that a perfect nose cone with a flat trailing face
was created in the process. But it could also be taken to mean
that the meteoroid never tumbled at all, and the original shape of
the object as well as its composition, it often seems, has a
significant impact on the resultant shape (in other words, in
flight the meteoroid was "perfectly oriented" but perhaps the
resultant shape is not "perfect"). It is a great thing that you've
started this process by virtue of yesterday's dialogue, and
hopefully we can emerge with something quantifiable through the
process...
Thanks,
Dave
-------- Original Message --------
Subject: [meteorite-list] getting oriented on orientation
From: Darryl Pitt <[EMAIL PROTECTED]>
Date: Wed, March 05, 2008 9:27 am
To: Meteorite List <meteorite-list@meteoritecentral.com>
topic: grading system for orientation
just trying to get things started off here.
i don't believe there should be 10-grades of orientation, as was
suggested, as it seems too broad and results in a situation that is
similar to the one before us: the too-liberal invocation of the
term. might i suggest a scale of O1-O4 or perhaps to O5 at the most.
it would seem the determination of the extent of orientation should
be based on the presence of a number of specific characteristics and
the extent to which such characteristics are manifest. i beseech the
input of scientists who are expert in eliminating the ambiguities in
such a grading system.
let's start with some characteristics of orientation that come to
mind....
evidence of ablation
presence of flow lines/rivulets
flow lines radiating in all directions off a single coordinate
elongated parallel regmaglypts radiating off a single coordinate
distinctly different morphologies of the obverse and reverse
evidence of bubbling in the low-pressure zone (reverse)
parabolic curvature of lead face (including small parabolas at tip of
oriented "bullets")
"lipped" edges and evidence of molten material having ablated over
the edge of such lips
please add or subtract to the list. maybe some characteristics
should be weighted more than others and then there is the quandary of
quantifying the extent of such characteristics.
i hope this helps to start things off. and i hope we're able to get
this resolved and get....oriented on orientation.
all best / d,
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