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Re: Tektite / Impactite

Dear Louis and list,

It is always difficult for me to make posts on the tektite origin topic. I
have some trouble on occasion controlling my impulse to make pejorative
remarks.

Even after thirty years of looking at them, I certainly do not know
everything about tektites, but I wish that the discussion could at least
deal with facts and not opinion. This has been the reason for two
individuals I spend time with leaving the list.

There can be a great difference between ones opinion and the facts. And I
know some of my opinions in life are wrong. That difference should be
maintained by the way our posts are written. It is healthy of course to
discuss hard topics that is what makes our list interesting, but to
overstate ones opinion, as if it is fact, when it is not substantiated by
evidence does a disservice to the members of the list who are not
specialists in that area or who are new to our field of science.

We have for instance been told in recent months that there is a twenty meter
thick layer of undevitrified pyroclastic glass over a large area of the
Aristarcus Plateau on the Moon (you can insert tektite glass for that).
There was no statement that this was opinion, it was said as if it is a
proven fact. It is not. We were told that Libyan Desert Glass is the result
of the break up in the atmosphere of a mini glass asteroid, again not stated
as opinion, but as fact.

Often the data submitted by tektite experts is based on visual observations,
sometimes in conjunction with actual testing sometimes not. Ideally
observation should not be in conflict with the other less subjective methods
for finding evidence. Here again we have the recurring discussion of welded
micro tektites, faulting and breccias based on visual observations and not
held by all experts with other more plausible explanations derived from
controlled analysis.

My observation is that there is a continuity of quality to the natural
glasses associated with impacts.  That which is near the crater is often
bubbly and that which is gone from the location by what ever mechanism is
often of high quality. With varying qualities at distance between the
extremes. There is a range of quality within the Muong Nong type and also to
a far lesser extent within spashforms. Cratering clearly does produce a
variety of glass products. There are dozens of craters with glass of all
different quality ranges. It is only the tektite glass which is the problem
for lunar theorist. And only one strewnfield has no crater at the present
time associated with it. There is no necessity to find an off world source
for one or two products when the others are clearly made here.

To attempt to compare the industrial processes of glass making and what is
observed in the product at 3000 degrees, with what can occur in a gigaton
impact event where the temperature is 50,000 degrees would seem to this
writer to be of limited value. Recent data indicates that the temperature
may remain high and that the viscosity of the melted rock is so low at those
temperatures that release of gas bubbles is not a problem.

I agree there are unresolved issued in both theories, but it is my opinion
that it is poor science to ignore the overwhelming weight of evidence in
favor of a terrestrial origin by impact to select a lunar volcanic origin
which no longer has any real strong points in its favor, and presents even
harder problems and hurdles.

A long list of posts and threads can be derived from my last statement if
the individual areas get discussed. Could be fun.

I hope this does not hurt any feelings but I find it is our opinions and the
defense of them that is more often the source of argument and strife than a
discussion of the facts. If we can keep our discussion on the established
facts and not personal assertion we can also keep from losing the members of
our list who are interested in learning and discussing the science.

Thanks for the opportunity to say this,
Jim Tobin

----- Original Message -----
From: <Impactika@aol.com>
To: Meteorite List <meteorite-list@meteoritecentral.com>
Sent: Thursday, November 04, 1999 7:37 PM
Subject: Tektite / Impactite


> Hello List Members,
>
> Thank you very much all of you for your answers.
> I knew I could count on the experts!!
>
> And if I understand you right: moldavites and indochinites are tektites
but
> the other types of impact glasses (Darwin, Libyan, bombs,  .... ) are
> impactites.
>
> Did I get it right?
> Anne
>
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