[meteorite-list] Meteor Crater Shape and Entry Angle

[Chris Peterson]

Not at all logically. Meteor Crater was round after the impact. Its current 
shape is produced by the non-isotropic nature of the local geology. In 
essence, it has eroded into its current shape. This process is well 
understood. There is no evidence at all that the impactor arrived at a 
shallow enough angle to actually produce an oval crater.

With our current crater analysis skills, I'd say any suggestion of a 
specific impact angle or direction is scarcely better than a pure guess. And 
even the reports estimating mass and velocity I view with a high degree of 
skepticism.

Chris

*****************************************
Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com


----- Original Message ----- 
From: "Meteorites USA" <eric at meteoritesusa.com>
To: <meteorite-list at meteoritecentral.com>
Sent: Friday, September 10, 2010 11:37 AM
Subject: Re: [meteorite-list] Meteor Crater Shape and Entry Angle


> Hi John, Thanks for the details. It's interesting to note that the angle 
> of descent is not known, though there are educated guesses or 
> calculations. What can probably be agreed is that an impactor with an 
> entry angle of 45* degrees could produce a round crater. Meaning of course 
> that Meteor Crater, since it's not perfectly round as evidenced by the 
> "bulges" in the NW and SE corners, must have been produced by an impactor 
> with a trajectory much shallower than 45 degrees. Logically.
>
> Here's another question. Which direction was it traveling SE to NW or NW 
> to SE?
>
> According to the Shoemaker paper here: 
> http://arrowsmith410-598.asu.edu/Lectures/Lecture16/i0-8137-5402-X-2-0-399Shoemaker.pdf
>
> "...Somewhat greater energy was
> required if the projectile struck at an oblique angle, as suggested
> by the presence of faults with underthrust displacement on the
> north and west walls of Meteor Crater...."
>
> It suggests a NW direction of travel... is this correct? And how do we 
> know?
>
> Does the "underthrust displacement" imply that the impactor was traveling 
> from the SE toward the NW?
>
> Eric