[meteorite-list] backwards evolution1

From: Darryl S. Futrell <futrelds_at_meteoritecentral.com>
Date: Thu Apr 22 09:46:24 2004
Message-ID: <025f01c0dc92$189619c0$d14d173f_at_pavilion>

PART 1

THE ‘BACKWARDS’ EVOLUTION OF THE DEBATE ON TEKTITE ORIGIN

Darryl S. Futrell
In the mid-1960s, about half of the world’s ten or twenty most active
tektite researchers favored a lunar origin for tektite glass. Whatever
happened to most of the people that believed in a lunar origin?
Scientific discussion in print on the origin of tektite glass by westerners
began in 1787 when Joseph Mayer described moldavites as a glassy species of
lava. The first mention of tektites other than moldavites was in 1844, when
Charles Darwin described Australian tektites as obsidian.
Between 1797 and the late 1950s, at least fifty other scientists had
expressed their opinions. Several thought they were a type of meteorite, a
few thought they were man-made glasses, and V. E. Barnes at first considered
that they might be fulgurites. But most, early on, believed tektites were a
type of terrestrial obsidian. R. D. M. Verbeek, in 1897, was the first to
consider them to be obsidian ejected from lunar volcanos.
In 1933, the influential British scientist L. J. Spencer, after studying
glass melted from soils at two nickel-iron meteorite impact craters, decided
tektites had been formed in the same manner. By the late 1950s, A. J.
Cohen, F. Heide, Z. Kopal, and E. L. Krinov had come to agree with Spencer.
H. C. Urey postulated tektites had been formed by the impact of a comet.
But, had any of these scientists ever studied the very significant layered
tektites before choosing the terrestrial impact melt theory?
The only layered tektites (also called Muong Nong-type) in captivity and
available to western world scientists for study during that time period were
a number of specimens from the Indochina region. They were in the National
Museum of Natural History in Paris. In 1935 A. Lacroix briefly described
them, in French, in two papers; illustrating two very small specimens in
one.
Certainly a few, if not all of these six scientists had read one or perhaps
both of these papers. I’ve learned that F. Heide did acquire two small
samples of layered tektites from the Paris museum, and perhaps some of the
others did also. Seeing only a few small samples, however, isn’t
necessarily very enlightening. I can find no evidence in the literature or
by my inquiries that any of the others, during this period of time, had any
hands on experience with this type of tektite and its obvious volcanic
structures.
So, the terrestrial impact melt tektite theory bandwagon that so many dozens
of other scientists have since climbed aboard, was set in motion by several
scientists who apparently had little or no experience with this major and
most significant type of tektite glass.
The Dutch scientist G. H. R. von Koenigswald, who produced at least twelve
tektite papers over a period of forty years beginning in 1935, wrote in 1975
that he had seen small samples of layered tektites in Paris many years
earlier, but had found them to be inconclusive. It wasn’t until about 1974,
while looking at many larger layered tektites in a collection in Heidelberg,
that he realized they must have had the same manner of origin as banded
obsidian from Indonesia which he had collected in the 1930s. These
observations resulted in his final tektite paper, in which he concluded
tektites are volcanic products ejected from the moon.
I acquired some small layered tektites from the Paris museum in 1967, plus
several larger specimens a few years later direct from Thailand. However,
it wasn’t until 1973, when I was able to visit a volcanic dome with obsidian
outcrops in the Coso Range of California, that I first noticed the many very
obvious structural similarities between layered tektites and banded
obsidian, This led to several published descriptions of internal structures
in layered tektites that could only have been formed during re-occurring
volcanism.
In the early 1960s, the terrestrial impact melt theory for the origin of
tektites gained two additional supporters of note. One was S. R. Taylor,
who became an associate editor of two of the most relevant journals:
Geochimica et Cosmochimica Acta, in 1964, and Meteoritics, in 1988. I see
he is still in that position in March, 2001 in the case of (now) Meteoritics
and Planetary Science, and I don’t have a recent copy of the other journal
available.
The other was V. E. Barnes, who, late in 1960 collected a large number of
layered tektites in Thailand and published several related papers. He chose
to explain layered tektites as being terrestrial impact melts that flowed
along gently inclined surfaces to collect in puddles in low places. Many
others agree with this concept to this day. However, there are others,
including myself, who have presented evidence that layered tektites, shown
by several researchers to be welded accretions of microtektites, could not
have flowed in any manner from one point to another. Numerous layers are
only microns thick, and those aware of the behavior of molten glass know
flow of such thin layers would be impossible! Besides, molten glass would
adhere to, and/or pick up, everything that it would come in contact with if
it had been subjected to any "flow"! I’ve examined thousands of layered
tektites and found that most were slightly stretched while still soft, on a
scale of mm to a few cm, and a number of others experienced slumping or
compression with resulting folding on a cm scale. That is the total extent
of any "flow"!
Also, in the early 1960s, several other scientists, including NASA
scientists Dean R. Chapman and John A. O’Keefe, proposed that tektites were
impact melts ejected from the moon. By the mid-1960s the world’s top ten or
twenty tektite researchers were more or less evenly divided on the two
impact melt theories. However, by 1970, this balance began to change
drastically, for a variety of reasons:
1. Everyone in the 1960s who believed tektites were lunar figured that they
had to be ejected impact melts because a few of them contained some very
small nickel-iron spherules which they felt had to be from impacting
meteorites. This theory would have required most of the lunar surface to
have a relatively high silica content, as do most tektites. This is because
impact is a non-selective process. But then, almost all of the Apollo lunar
samples turned out to have a lower silica content. So, by the early 1970s,
the situation became rather untenable for the lunar impact people. It wasn’
t determined until 1983 that these NiFe spherules in tektite glass were NOT
a result of meteorite contamination, but were endogenous in origin. This
eliminated the impact origin and ejection requirement, but by then, most of
the "lunar" people, with the exception of O’Keefe, had moved on to other
jobs and were working on other subjects. For instance, NASA researcher
Dean Chapman, who by 1971 had published some thirteen papers demonstrating
that the ablation evidence on Australian tektites requires a lunar origin,
left NASA and became a professor of astronautics and aerodynamics at
Stanford.

PART 2 TK
Received on Mon 14 May 2001 12:22:08 PM PDT