[meteorite-list] Atmospheric ablation marks on Tektites?

From: Sean T. Murray <stm_at_meteoritecentral.com>
Date: Sat, 5 Apr 2008 12:25:54 -0400
Message-ID: <00b701c89739$b9d39380$6501a8c0_at_platinum>

Michael,

Yep - it's amazing that something so simple as a piece of glass has caused
so much churning for over 100 years. The vast majority agrees they are of
cosmic origin, most believe that they are from impacts on earth, but there
are still those that believe the moon is directly involved. I've also read
some other bizarre ideas - the coolest of them (to me) was the idea that the
reason tektites are not always formed is that maybe they come from the
impact of a huge ball of silica glass that slams into earth - A big
meteorite just made of glass... how cool would that be.

So far, everything I read simply states that tektites come from multiple
sources. And don't worry about the "noob" stuff - I've only been diving
into this for a few months, so I'll still say something way off base (as
Doug points out with my "still a lot of debate" comment.) It's almost
always wrong to make any general statement about tektites as a whole... the
LDG debate is still ongoing as to how it was formed, but most people tie it
to an impact event, and as an impactite. I've seen pictures (and have a few
pieces) of LDG that show some of the splash-form types of characteristics of
tektites, but nothing with a "crust" or a true regmaglypts.

- Tektite and impactite - different animals.

- LDG and Darwin glass - Terrestrial - it really helps that there are
inclusions that are of the local material stuck in them. They also have a
slightly higher concentration of water (in ppm) that make them different
than a true tektite. The shaping that is seen in those glasses is not as
nearly as convincing as the Australasian glasses.

 -Ventifacts is the more correct answer. But considering the company that
tektites keeps with our other cosmic collectibles, I'm gonna stick with
pseudo-regmaglypts until someone beats me up.

 - Yes - there are a lot of good documentation that spells out the
composition of tektites. (Get Povenmire's book and McCall's book). The
chemical composition of the tektites is the thing that really drives a lot
of the controversy. The glass, in many cases, is very pure and free of
water - it's hard to say how it was made since it breaks a few of the glass
making rules and regulations :) They have found tektite like material on
the moon (if it was found here on earth no one would have argued that it was
not a tektite), but they are very small. It was thought that the first
trips to the moon would have seen and brought back big, standard lots of
tektites if that is where the originated - but they did not. many people
changed their minds on the lunar origin after the moon landings. When they
found microtektites on the moon, they ascribed them to impacts on the
moon... after all, it is generally accepted that the moon and the earth are
made from each other, so there will always be similarities.

Another fun origin note:
John O'Keefe was another of the proponents of the lunar origin of tektites.
He died in 2000, and on his funeral program he had wanted the following
phrase added:
"Tektitae De Luna Sunt!" - "tektites are from the moon!"
That's conviction.

Sean.

----- Original Message -----
From: "Michael Gilmer" <michael_w_gilmer at yahoo.com>
To: <Impactika at aol.com>
Cc: <meteorite-list at meteoritecentral.com>
Sent: Saturday, April 05, 2008 11:07 AM
Subject: Re: [meteorite-list] Atmospheric ablation marks on Tektites?


> Hi!
>
> Ok, now I figuring out this tektite issue. I want
> to thank everyone for their kind informative
> responses.
>
> First, I had no idea that tektites were so
> controversial!
>
> Well, I did have *some* idea, but I thought it was
> generally accepted by the meteorite community that
> tektites of all types were impact artifacts and were
> not the product of atmospheric-entry or
> extra-terrestrial processes. I knew that there were
> alternate theories for the origins of tektites, but
> I thought these theories were mostly fringe in nature
> and not commonly accepted by the Met community at
> large. It appears I have a lot more reading to do
> on tektites.
>
> "Ventifact" does indeed seem to be the best term
> available to describe regmaglypt-like features on
> LDG and other similar glasses. Features that suggest
> orientation or flow-lines are also wind-driven
> ventifacts I assume.
>
> As others said though, this does not reasonably
> explain
> the appearance of "button" tektites of the
> Australite variety. Although I must admit, the first
> time I saw a button-type tektite, my first thought
> was not atmospheric-ablation or sculpting. My first
> thought was a splatter-type impact artifact. If you
> have ever taken a spoonfull of viscous batter and
> dropped it on the floor, the outer edges of the mass
> will spread outward while the central area is uplifted
> somewhat. I had erringly assumed that similar
> physics were at work with the button-types. Perhaps
> a massive detonation on impact liquified a combination
> of meteorite and earthly-minerals which were blasted
> upwards and then fell back to earth - forming into a
> button when the material hit the ground again.
>
> Again, I expose my ignorance here. And I am glad I
> came to the list with this question. :)
>
> So while we are on the subject and educating a newbie
> here, let me ask a couple of tektite-related questions
> for the record, so to speak.
>
> 1) tektite and impactite - interchangeable terms or
> different animals?
>
> 2) desert glass, darwin glass - terrestrial or not?
>
> 3) When describing aesthetic features present on a
> tektite/impactite that resemble atmospheric effects,
> should one use the term "pseudo-regmaglypts" or
> "ventifacts"? Or should one go ahead and use the
> same terminology used to describe these features in
> meteorites? (orientation, flowlines, etc)
>
> 4) have impactites/tektites ever been studied in-depth
> in the lab to determine their exact source? It seems
> to me a minor mystery to solve. We can compare
> chemistries of specimens to determine a lunar or
> martian origin, but we lack the science to determine
> where a tektite formed? I'm surprised this is still
> a "controversial" issue - modern science has peeled
> back the layers of confusion on deeper mysteries
> than this.
>
> Thanks in advance for putting up with this newbies
> inquiries!
>
> MikeG
>
>
>
>
>
> --- Impactika at aol.com wrote:
>
>> Hello Mike and List,
>>
>> There is some confusion here.
>> Libyan Desert Glass is an impact glass, not a
>> tektite.
>> It is 20-30 millions years old, has gone thru many
>> changes in climate and
>> conditions in their corner of the Sahara. But in the
>> last few thousands of
>> years, it has mostly been shaped/ablated/sculpted by
>> zillions of sand storms.
>> More like Ventrifacts really
>> Does that help?
>>
>> Anne M. Black
>> www.IMPACTIKA.com
>> IMPACTIKA at aol.com
>> Vice-President of IMCA
>> www.IMCA.cc
>>
> ------------------------------------------------------------------------
>>
>> In a message dated 4/4/2008 8:37:13 PM Mountain
>> Daylight Time,
>> michael_w_gilmer at yahoo.com writes:
>> Hi Group!
>>
>> While reading through another Meteorite-related
>> message board on the WWW, I ran across a statement
>> by
>> an IMCA member that puzzles me somewhat. A
>> discussion
>> about Libyan Desert Glass was ongoing, and we were
>> sharing photos of our LDG specimens. (and I showed
>> off my new 9+ gram piece of dark-veined glass from
>> Michael Farmer - thanks Mike!)
>>
>> So the guy says :
>>
>> "This is one of my favorites and is fully oriented
>> with regmaglypts (yes, tektite impactites can have
>> atmospheric ablation patterns too)."
>>
>> Ok, here is my confusion - I was under the
>> impression
>> that tektites were formed on impact - on Earth.
>> So,
>> doesn't this mean they cannot have atmospheric
>> ablation patterns? Assuming the tektite never
>> passed
>> through the atmosphere, I don't see how this is
>> possible.
>>
>> I have seen tektites with features that resemble
>> regmaglypts and orientation, but this is just
>> chance
>> occurence, right?
>>
>> Or do I need to be schooled here?
>>
>> Thanks in advance!
>>
>> MikeG
>>
>>
>>
>>
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>>
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>
>
>
>
>
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Received on Sat 05 Apr 2008 12:25:54 PM PDT