Several more or less unsatisfactory theories have been proposed for the origin of lunar sinuous rills such as Schroeter's Valley. This paper presents a new explanation of the formation of these rills, namely, that they are valleys eroded by nuees ardentes. Characteristics of the rills, including form and association, are cited in support of this theory. Supporting evidence is found in the similarity of the rills to furrows eroded by nuees ardentes on the earth.

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An Interpretation of Schroeters Valley and Other Lunar Sinuous Rills

Figure and inhomogeneities relationship for moon, Mercury, Venus, Mars and earth, discussing circular basins and mascons

Lunar and planetary mass concentrations.

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 moon's surface is considered in this paper. The displacement of the center of the moon's 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 moon's surface does not contradict the notion that large amounts of acid rock are present on its surface.

Winifred Sawtell

Papers

Evidence from the Moon's Surface Features for the Production of Lunar Granites