[meteorite-list] The "asteroid" that killed the dinosaurs

From: E.P. Grondine <epgrondine_at_meteoritecentral.com>
Date: Tue, 29 Apr 2008 12:22:27 -0700 (PDT)
Message-ID: <679258.22700.qm_at_web36906.mail.mud.yahoo.com>

Hi all, and Elton in particular-

I stopped in yesterday at U. of Illinois and chatted
with Dr. Susan Kieffer of their geology department,
the source for the story of the "asteroid" that killed
the dinosaurs and the "comet" that formed Sudbury.
Despite the fact that they were in finals, she
generously shared a few minutes of her time with me
and gave me some reprints that explained what had
happened.

Her involvement began when Walter Alvarez was looking
for some help with the global distribution of shocked
quartz from the KT impact, and was hitting some
problems with ejecta energies, and particularly with
the problem that the shocked quartz was ejected
without melting. They published their conclusions in
Science, 18 August 1995.

Elton, this may strike you as unusual, but they had
no knowledge of the physics of armor piercing shaped
charges, in particular the transport mechanics of
them.
Tektite and impact spherule formation were not covered
in much depth.

(I reattach Elton's earlier note on this to the list
to this message.)

Now we have the "blueberries" on Mars to examine along
with tons of horse manure from NASA about water and
their formation to wade through as well.

So Elton, you're not the only one having problems with
the math - Dr. Alvarez had problems with it as well,
and given that he was one of the nations top nuclear
physicists, that's damn hard math.

E.P. Grondine
Man and Impact in the Americas


Date: Mon, 04 Jan 1999 04:03:44 -0500
From: Elton Jones <jonee at epix.net>
To: "E.P. Grondine" <epgrondine at yahoo.com>
CC: meteorite-list at meteoritecentral.com
Subject: Re: Lunar Tektites

Let me add one more item to the ejecta mechanism.
Indulge me, if you may, as I develop background. I
want to explain a munitions dynamic which can be may
used to understand the ejecta dynamics of target rock
and jetting stream at the instant after first contact.

Placement of explosives with different shapes can be
used to focus a hot(kelvin-hot) jetting stream or to
construct a pressure/containment vessel,as in the Fat
Man plutonium bomb. In the field of munitions, we
have what is called a "shape charge" (aka HEAT) which,
when detonated, produces a directed, hot, gas jet,
contained only by the converging shock waves as it
dissipates in one direction. As it jets, it carries
along with it the copper liner of the charge. Only
the liner is deformed from a flat piece of metal into
a hollow tube in a "nano-moment".

What is interesting is how the tube forms. Based on
high speed x-ray photography, we see the elongation of
the wall of the copper-tube comes from the inside
out. As molten copper is forced by hot gas from the
copper plate back at the point of detonation, it is
added to the tip. Apparently, the velocity of the
stream gets faster inside the tube such that the last
bit of copper is added to the front of the tube. This
tube is powerful enough to punch through armor plate
in that aforementioned "nano-moment".

Even more interesting is the fact that the armor plate
material which is being hammered out of the way in
this nano-moment, is ducted back down what we believe
is a concentrically flowing, bi-directional pipeline
as
the energy of the jet ultimately dissipates. This
occurs without pinching off the outward bound stream .
 The diameters from front to back taper very little.
The tube diameter and length are proportional to the
diameter to the initial charge. Whether or not the
target object is encountered by the jet , it behaves
the same over munitions-significant distances.
There is no observable reverse flow if not fired into
a solid object.

Final point here is that for years, we believed one
thing about this process until X-ray photography
showed us something entirely unforeseen.

I have seen the discussion of a the pressure
convergence behind a impactor at the instant after
impact. It appears that there is a similar
but larger jet which is focused by back pressures
rushing around the body till they collide. At this
point they jet out and back in a stream of material
from the country rock and impactor in what I have seen
called "an atmospheric blow-out event".

Therefore, I am wondering if the dynamics of focused
explosives--its curious bi-directional and
simultaneous gas stream, and the highly directional
pressures-- could account for the containment of the
ejected
material (vaporized or not) up the column. Could it
do so long enough for there to be a coalescence in the
absence of the atmospherical cooling requirements for
tektite formation.? I would find it remote that much
of the material would retain strata from before the
impact, but I could theorize the deposition of
successive coatings accumulating on the tube surface
before it exceeded its elasticity and separated into
successive globs of glass.

The math is beyond me but is it plausible, based upon
what we believe happens if the jet behaves like
munitions jets do? If so, does this reduce the
dependence of atmosphere in tektite formation? Does
tektite formation fall back to sufficient escape
velocity, suitable target rock, and sufficient sized
impactors to allow a grand scale formation of a
jetting structure?

EL Jones

"E.P. Grondine" wrote:

> Let's try this out:
>
> When an impactor hits, the central impact area is
vaporized; the area next out from the center becomes
dust; the next, shocked small ejecta; further out
still you have large solid but shocked chunks thrown
out,
with some put into orbit.
>
> On Earth, the atmoshpere cools the rock vapor enough
to congeal it into larger globs which are the source
for tektites, but our Moon has no atmosphere, so the
rock vapor does not congeal, but instead the rock
vapor particles loose their heat and fall back to the
Moon's
surface as dust, which in turn is compacted by gravity
back into rock.

On Mars, the gravity well again is shallow enough and
the atmosphere thin enough that again the vapor makes
it into space and cools into dust, without being
congealed.

In other words, before you have globs of molten rock,
you have to have rock vapor. Is this even broadly
correct?

Best wishes -

EP

> ---Spacerocks at iname.com wrote:
> >
> > This is a follow-up to Louis's post. I do not
understand why tektites have to be an either/or
phenomenea. Why can't tektites be from Earth AND
(some) from the Moon? (Its a floor wax, no its a new
desert topping- from SNL). I think the lack of a
crater or impactite from the Australasian strewn field
gives the lunar (impact IMO) origin a lot of weight.
Also the huge eliptic strewn field points to a
extaterrestial source.
> >
> > If we can have Lunar meteorites, why not tektites?
 The fact that they don't match the returned SURFACE
material from 6 sites is flimsy evidence. The Moon
could look a lot more like the Earth deeper down, and
should since its originated as an impact with the
Earth. Why not some Martian tektites as well? I
would expect these to be noticably different.

Just my 2 scents worth.


 


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Received on Tue 29 Apr 2008 03:22:27 PM PDT