[meteorite-list] getting oriented on orientation

[Darryl Pitt]

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, dave at fallingrocks.com 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 <darryl at dof3.com>
> Date: Wed, March 05, 2008 9:27 am
> To: Meteorite List <meteorite-list at 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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