[meteorite-list] Tektite fields and rotation

From: mexicodoug at aim.com <mexicodoug_at_meteoritecentral.com>
Date: Fri, 28 Mar 2008 20:57:50 -0400
Message-ID: <8CA5F4F0BD55D05-A30-20FA_at_webmail-ne02.sysops.aol.com>

Hi Goran, Chris (and Larry L, who sent and excellent private reply),
Coriolirees,

The Paris Gun alledgedly demonstrated that shooting heavy oriented
shells at 1.6 km/s required a 1% correction over 130 kilometers range
for their particular situation. However, I tend to agree with Goran in
that wind, in a practical sense, will trump Coriolis effect for all but
*possibly* the Australaiian event and as I already mentioned earlier
"more complex effects" in relation to Chicxulub type impacts on Earth.
The first reference has the illustration of the Chespeake Bay Crater
which fits nicely with the discussion in my original post - the first
several hundred kilometers of ejecta really aren't too influences and
then we have everything else to worry about.

My though was Mars, due to its smaller radius and similar angular
rotational rate, and the absense of much atmosphere, might be a
different ball of wax. I found a paper on Coriolis influenced Earth
Crater Tektite Ejecta by the Mars crater Coriolis experts. In my
ignorance, it seems these researchers are on the right track, but still
have a lot of explaining to do to be convincing with the black box
model's assumptions. There is apparently a Mars crater mentioned in
their literature that has observed 600 km rays slightly pinwheeled (my
inaccurate word). I'll list some references from Kelly [Wilbur-]Wrobel,
who started as a grad student in Peter Schultz's group. They've studies
the tektite situation on Mars to death and have involked the Coriolis
effect to explain things including where very high energy distant
ejecta may concentrate.

Sorry for the long post, and best wishes, (references follow)
Doug

http://www.lpi.usra.edu/meetings/lpsc2003/pdf/1190.pdf
THE EFFECT OF ROTATION ON THE DEPOSITION OF TERRESTRIAL IMPACT EJECTA.
K.E.
Wrobel and P.H. Schultz, Department of Geological Sciences, Brown
University

http://www.lpi.usra.edu/meetings/lpsc2002/pdf/1728.pdf
2004.P Wrobel, K. W. and P. H. Schultz (2004), The Effect of the
Coriolis Force on Distal
Ejecta across Mars, Jour. Geophys. Res., vol. 109 (2004)

http://www.lpi.usra.edu/meetings/lpsc2006/pdf/2386.pdf
The generation and distribution of martian impact melt/glass: A
computational study with implications for
the nature of dark surface materials. K. E. Wrobel and P. H. Schultz

http://www.lpi.usra.edu/meetings/sixthmars2003/pdf/3242.pdf
ACCUMULATION OF DISTAL IMPACT EJECTA ON MARS SINCE THE HESPERIAN. K. E.
Wrobel
and P. H. Schultz


-----Original Message-----
From: G?ran Axelsson <axelsson at acc.umu.se>
To: meteorite-list at meteoritecentral.com
Sent: Fri, 28 Mar 2008 5:49 pm
Subject: Re: [meteorite-list] Tektite fields and rotation


You're right, that is a quite complex problem but solvable with
differential calculus and analytical mechanics. The problem is real and
any gunner that had to calculate projectile trajectories know that you
have to take latitude and direction into the equations.?
?
As a simple example, imagine a cannon ball being shot straight up. When
it leaves the barrel it has some angular velocity (momentum) from earth
rotation. As it rises it loose kinetic energy and gains potential
energy but nothing affects the angular momentum and just as a skater
that extends her arms after a fast rotation it looses angular speed
(but not momentum), the earth rotates faster than the cannonball. When
it falls down again it will gain angular speed and hits the earth
straight down but a bit from the gunner.?
?
Okay, that was a simplification that only works at the equator as the
coriolis effect have a real effect anywhere else on the earth.?
Think of it as a satellite orbit, you can't create an orbit that stays
on a constant latitude except on an equatorial orbit. So the coriolis
effect will rotate everything. The cannon ball will drop at a latitude
closer to the pole/equator (strikeout the wrong answer, can't calculate
that in my head... my brain is hurting...) and a bit behind you as the
earth rotates... and we are only talking about a shot straight up.?
?
Actually, there is two places on the earth where a cannonball will drop
down at the gunner when shot straight up.... guess where!?
?
It is a complex problem but it can be calculated without too much
problem. But my gut feeling is that geological and topological
differences in the target area, wind patterns and impactor direction is
bigger factors in how the tektite field develops.?
?
/G?ran?
?
Chris Peterson wrote:?
> That was my first thought as well. It's probably a fairly complex >
problem. At the least, Coriolis effects will be significant, and will >
distort the debris pattern.?
>?
> Chris?
>?
> *****************************************?
> Chris L Peterson?
> Cloudbait Observatory?
> http://www.cloudbait.com?
>?
>?
> ----- Original Message ----- From: <mexicodoug at aim.com>?
> To: <epgrondine at yahoo.com>; <meteorite-list at meteoritecentral.com>?
> Sent: Friday, March 28, 2008 12:11 PM?
> Subject: Re: [meteorite-list] Tektite fields and rotation?
>?
>?
>> Hi Ed,?
>>?
>> Since ejecta would start out with the same rotational motion as the
>> Earth, at what point and by what mechanism would you inferring that
>> it "decouples" from Earth and looses that rotational component of
its >> own motion? Good question, though!?
>>?
>> Best wishes,?
>> Doug?
>?
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Received on Fri 28 Mar 2008 08:57:50 PM PDT