John A. O'Keefe

The origin of tektites.

The tektites called Muong Nong type by V. Barnes apparently represent the parent material from which other types are derived. In these tektites are found clues (coesite, angular voids) which indicate that they have not been substantially remelted since the event which detached them from the planet or satellite on which they were formed.From the nickel-iron spherules and the coesite it is deduced that the tektites were detached by meteorite impact. From the absence of cosmogenic isotopes and the distribution over the earth it is deduced that the source was either the earth or the moon. Calculations of rates of diffusion in silicates indicate that tektites could not have been produced from terrestrial sedimentary rocks; it has long been remarked that they are different from terrestrial igneous rocks. A lunar origin is therefore considered likely, in agreement with aerodynamic evidence. Contrary indications from the geochemical likeness of tektites to terrestrial materials, especially at the Ries Kessel and the Bosumtwi crater are noted, but these indications are considered to be outweighed by the difficulties of giving a physical account of a terrestrial origin.Interpreted as lunar materials, the tektites suggest that large portions of the lunar surface are covered with ash-flow tuff of a peculiar type, remarkably free of water and other volatiles. They also give evidence concerning the origin of the moon.

Solar Constant: Constraints on Possible Variations Derived from Solar Diameter Measurements

Climatically significant variation of the solar constant (the energy output of the sun) implies measurable change in the solar radius. The available data limit variations of the solar radius between 1850 and 1937 to about 0.25 arc second; modeling of the sun indicates that the solar constant did not vary by more than 0.3 percent during that time.

EVIDENCE FROM THE MOON'S SURFACE FEATURES FOR THE PRODUCTION OF LUNAR GRANITES

Abstract If tektites come from the moon, they indicate a granitic constitution for a considerable portion of the outer crust, especially if allowance is made for the chemical effects of volatilization (loss of alkalies). The evidence for granitic rocks from the morphology of the moons surface is considered in this paper. The displacement of the center of the moons visible face with respect to the center of mass is considered evidence of the existence of isostasy on the moon. It is shown that this displacement is not merely a limb phenomenon, amd that it is probably not explicable in terms of the kind of lumpy interior proposed by Urey to explain the differences of the moments of inertia. Evidence for characteristic granite landforms, including tholoids and laccoliths, is summarized. The possibility that the maria are produced by the fluidization of volcanic ash is considered. The transporting fluid is considered to be the contained gases as in a terrestrial ash flow. Ash flows on the earth are responsible for the emplacement of a large fraction of all volcanic ash. From a study of the physics of ash flows, it is concluded that the fluidization should be more effective on the moon. It should require only about 1 30 as much gas to transmit a given amount of rock, an amount which is well within reasonable expectations for the gas yield from the rocks. It is concluded that the morphology of the moons surface does not contradict the notion that large amounts of acid rock are present on its surface.

The chemical durability of tektites—A laboratory study and correlation with long-term corrosion behavior

Leach tests carried out on tektite specimens (indochinites and australites) under high-dilution conditions show a common behavior characterized by low leach rates (1.8 × 10−5g · m−2 · d−1or 7.2 × 10−12m · d−1 at 23°C) and an activation energy of (79.6 ± 0.7) × 103J · mol−1. The extent of selective leaching is very small, of the order of 10−8 m. Extrapolation of test results over the lifetime of the tektites gives an excellent agreement with field observations on the extent of corrosion, and this is an important step in establishing the validity of laboratory tests as a basis for the development of models and predictions concerning long-term durabilities at least in the limiting case of high dilution or rapid flow. The results are also shown to be in agreement with various previous observations on the corrosion resistance of tektites. The chemical durability of tektites is observed to be consistent with their composition, highlighting requirements for high corrosion resistance in glasses; these requirements include a silica content in excess of 67 mol%, an extremely low water content and an alkali content which is low both absolutely and relative to the di- and poly-valent metal oxide levels. It is shown that artificial glasses which fulfil these criteria are no less corrosion-resistant than the corresponding natural glasses. These conclusions have bearing on the development as well as on the evaluation of glasses intended for very long service, such as radioactive waste vitrification media.

Lunar ring dikes from orbiter I.

Orbiter photographs of the wall of a large circular formation on the moon show that the wall is a convex body resembling a flow of viscous lava. The slopes are less than the angle of repose of dry rock; hence an explanation in terms of mass wastage is hard to support. The viscosity is approximately 1013 centimeter-gram- second units, indicating an acid lava.

Leaching of natural and nuclear waste glasses in sea water

Microtektites, some with a SiO2 content as low as 50%, exhibit a very limited extent of corrosion after having been exposed to interaction with their environment in sea-bed sediments for periods of 105a. Measurements carried out on a bottle-green microtektite glass composition in de-ionized water show that this glass has relatively high leach rates, as expected on the basis of its low SiO2 content (≈ 50%) and high modifier content (≈ 20%). However, is sea water the leach rates are smaller by at least 2 orders of magnitude, in agreement with the small extent of microtektite corrosion observed in nature (typically<5μ). Systematic studies of leachant composition effects show that the suppression of leaching in sea water is probably due to the presence of high levels of Mg. Measurements were also carried out on man-made silicate glasses related in composition to nuclear waste glasses. Although the compositions of the man-made glasses are different in many important respects from the composition of microtektites, it was found that the leach rates of the man-made glasses, too, are smaller by about 2 orders of magnitude in sea water compared with their values in de-ionized water. Surface analysis of glasses exposed to sea water shows that the predominant feature is the formation of a layer which is very rich in Mg.

Surveyor v: discussion of chemical analysis.

Material of basaltic composition at the Surveyor V landing site implies that differentiation has occurred in the moon, probably due to internal sources of heat. The results are consistent with the hypothesis that extensive volcanic flows have been responsible for flooding and filling the mare basins. The processes and products of lunar magmatic activity are apparently similar to those of the earth.

ORIGIN OF TEKTITES

A comet of the size recently postulated by H. C. Urey would leave a large crater. It is shown, from aerodynamic theory, from observations of distribution around terrestrial impact craters, and from experimental nuclear explosions, that the observed distribution of tektites cannot be the result of impact on the earth, whether cometary or meteoritic. It is further shown, from aerodynamic theory, from observation of a meteor shower, and from study of the breakup of artificial satellites, that the distribution of tektites can be accounted for as a result of fusion stripping of a satellite, as originally suggested by Suess.

Lunar Sample 14425: Characterization and Resemblance to High-Magnesium Microtektites

Measurements by energy-dispersive x-ray analysis of the surface of lunar sample 14425, a large glass bead, yield a noritic composition enriched in aluminum and magnesium and, as compared with other norites, depleted in iron and especially calcium. The sample is close in composition to the most basic microtektites. Spherical inclusions of nickel-iron, flattened where they protrude, are found to be enriched in sulfur and phosphorus, at least at the surface. The inclusions form approximately 1 percent of the volume.

Stress differences and the reference ellipsoid

Hullet suggestion that gravity anomalies are related to other geophysical phenomena, including faults and pole position