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Once Again: Saturn-Like Ring Around the Earth?

FYI: Regarding the discussion of an ejecta ring around Earth in K-T
times, you may be interested in the attached paper found on Lexis-Nexis
(bolded text portion about ring by me). The graph is not included with
the Lexis-Nexis news copy off the Internet. --Lou V.

-----------------------------------------------------

Copyright 1985 Information Access Company, a Thomson Corporation Company

ASAP Copyright 1985 American Association for the Advancement of
Science/Science 

February 1, 1985 

SECTION: Vol. 227 ; Pg. 515; ISSN: 0036-8075 

LENGTH: 1100 words 

HEADLINE: Lunar sample 14425: characterization and resemblance to
high-magnesium
microtektites. 

BYLINE: O'Keefe, J.A. ; Glass, B.P. 

BODY: 
Tektites, unlike stony or iron meteorites, cannot originate outside the
earth-moon system because
they lack the isotopic indications--that is, adequate levels of
sup.10.Be, sup.26.Al, and so on--of
exposure to primary cosmic rays over periods of 10.sup.6 to 10.sup.7
years (1, 2). From their
distribution on the earth, it is clear that, whether terrestrial or
lunar, they were launched by a
powerful mechanism, presumably either volcanism or some kind of impact
event. Earth
volcanism is too feeble to produce the observed strewn fields of
tektites, up to halfway around
the earth (3), and impact on the moon would yield objects with much the
same composition
(anorthositic gabbro or basalt) as most of the lunar crust. We are thus
left with two alternatives
for their origin: namely, meteorite impact on the earth or volcanic
ejection from the moon. 

The two alternatives lead to different explanations of the extinctions
that appear to be associated
with at least some tektite falls (3). If tektites are terrestrial, the
extinctions may have been due to
dust clouds in the atmosphere, thrown up by an impact event, as
implicitly suggested by Alvarez
et al. (4) and Ganapathy (5). If, however, they are of lunar origin,
then it would be expected that
the ash particles that missed the earth would organize themselves into
Saturn-like rings around the earth and that the rings would be
quantitatively sufficient to make significant climatic changes (6). 

Geochemists (7) generally favor origin from the earth because tektites
are closer to earth rocks
than to most returned lunar samples in several respects, particularly in
age, potassium-uranium
ratios, rare-earth abundances, and oxygen isotopes. Some geophysicists,
on the other hand, find
that a terrestrial origin appears to conflict with basic aerodynamic
principles (8) and with the
physical principles that underlie the practice of glass-making (9).
Clearly this paradox would be
illuminated if a tektite should be found among the returned lunar
samples. We describe the close
chemical resemblance of lunar sample 14425 to the high-magnesium,
low-silica microtektites of
the Australasian strewn field (10). 

The sample's diameter of 8.006 plus or minus 0.006 mm is constant within
about 0.1 percent
over the surface. Its mass, 0.78410 plus or minus 0.00002 g, implies a
specific gravity of 2.917
plus or minus 0.002. The glass is black in some parts and brown in
others. The surface is
decorated with mounds that have a metallic luster, the largest being
about 0.9 mm in diameter.
By x-ray (Sperry model SPX, 200 kV, working at 60 kV, 4 mA) it is found
that the interior
contains spherules up to 0.7 mm in diameter; the mounds result when
these spheres protrude
through the glass surface (Fig. 1). The total volume of the spherical
inclusions that are larger than
0.1 mm in diameter is estimated at 0.6 percent of the volume of the
sample. 

The surface composition of the glass was examined with a Cambridge 150
scanning electron
microscope together with energy-dispersive x-ray analysis at the
University of Delaware and by
similar analysis with the Philips PSEM 500 electron microscope and an
EDAX 9100 at Goddard
Space Flight Center. In order to preserve the surface, the sample was
not ground and polished,
nor was it coated (for example, with carbon); it was used as found, and
we relied on the
smoothness of much of the surface. At both laboratories the sample was
held in place with a
brass holder, which produced spurious lines of copper and zinc at both
places and lead at
Delaware. These lines disappeared when an aluminum holder was
substituted at Goddard, but
this produced anomalous aluminum values that could not be corrected
because of the aluminum
in the sample. All of these effects, in addition to some spurious lines
of gold in the Goddard
spectra, resulted from the fact that without a conducting coat, the
surface charges up and repels
the electron beam, which then wanders. It is believed that by comparison
of the three holders, it
has been possible to eliminate these effects. 

In both analyses, the small peak due to sodium was difficult to separate
from the adjoining
magnesium peak, which was about 100 times stronger. With the use of a
wavelength-dispersive
Microspec system at Goddard, a value of 0.1 percent was found for
Na.sub.2.O. 

The means of the analyses on the glass are shown together with the
standard deviations in Table
1. In Fig. 2, measurements from both laboratories are plotted against
silica content, as in the
Harker diagram. Measurements made with the aluminum holder failed to
show any substantial
difference between the light and the dark regions of the surface. 

The composition of sample 14425 is different from the other known lunar
samples, so far as we
can find. We have examined 1200 analyses of lunar glasses (11), and 100
papers on lunar
samples, including 50 described as referring to lunar norites. The
analysis of the ground-mass of
lunar sample 14068 (12), which is one of the closest fits, is plotted in
Fig. 2; it is clearly not the
same material. 

The small dots in Fig. 2 are plotted from a report (13) on bottle-green
(high-magnesium)
microtektites from the Australasian strewn field. The resemblance of the
Australasian glasses to
sample 14425 is conspicuous. Microtektites from the Ivory Coast strewn
field (not shown) do not
fit as well--for example, FeO averages 10 percent. 

Two of the mounds with metallic luster were analyzed. The largest mound
showed iron and
sulfur in a 5 to 2 ratio with a few percentages each of nickel and
phosphorus; a smaller mound
gave iron and nickel in a 4 to 1 ratio, with small quantities of sulfur
and phosphorus. A possible
interpretation would be nickel-iron spherules containing schreibersite
and troilite, such as have
been reported for tektites (14) and impactites (15). Reid et al. (16)
did not find schreibersite in
nickel-iron blebs from lunar basalts. The presence of these spherules
could be consistent either
with impact or lunar volcanism (17). 

In conclusion, we find a close chemical resemblance between lunar sample
14425 and the
high-magnesium microtektites. However, to establish that this sample is
a tektite, more data on
age, isotopic composition, and trace element abundances are required. In
particular, the rare earth
element pattern should be studied for comparison with the data of Frey
(18) on high-magnesium
microtektites. The siderophile element abundance ratios could tell us
whether the metal was
derived from a meteorite or was produced by reduction of the matrix
glass. 

GRAPHIC: Photograph; Table; Graph; Composition of glass. (table); Major
oxides plotted
against silicon dioxide. (graph) 

IAC-NUMBER: IAC 03624510 

IAC-CLASS: Health; Magazine 

LANGUAGE: ENGLISH 

LOAD-DATE: June 30, 1995 



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