Results 181 to 190 of about 33,048 (213)
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40Ar39Ar ages from the lunar maria
Earth and Planetary Science Letters, 1971Neutron activation and stepwise heating experiments have been used to measure argon retention ages of crystalline rocks 12002, 12051 and 12065 from Oceanus Procellarum. The effects of appreciable argon loss are observed for all rocks. Ages based on the release of argon from retentive sites are, within the errors of measurement, identical and are ...
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Modelling of temperatures of selected points in lunar maria
The Moon and the Planets, 1980The purpose of this paper is to propose a numerical model representing the brightness temperature of ten selected sites of the Moon as measured in CERGA. A theoretical approach is proposed in which the temperature is expressed as a function of the local zenith distance of the Sun and a quantity depending upon the local zenith distance of the observer ...
J. Gay +4 more
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Evidence for isostasy in the lunar mascon Maria
The Moon, 1976The pronounced positive gravity anomalies in the lunar circular maria imply lack of isostatic compensation of the lunar mascons. This lack of isostasy is hard to reconcile with the rheological properties of the lunar crust. Analysis of the negative ring anomalies that appear to surround the major positive gravity peaks indicates that associated with ...
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Lunar ring structures and the nature of the maria
Planetary and Space Science, 1968Abstract Data from Lunar Orbiter and Surveyor probes are used in an examination of specific, low walled lunar rings to show that they are recent volcanic structures. The alternative hypothesis that these ‘elementary’ rings represent old, partially buried craters is challenged. Their observed distribution and the mechanism of formation deduced for
J.E. Guest, G. Fielder
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Mensuration and Isostasy of Lunar Mascons and Maria
Nature, 1969The theory that mascons have been formed by the partial filling of impact craters now leads to the conclusion that they are isostatically in equilibrium with the rocks beneath.
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Thermal instabilities and the formation of lunar maria
The Moon, 1973A model is discussed for a possible type of thermal instability in the outer layers of the Moon. An estimate is made for the temperature differential driving the instability. It is suggested that such an instability may have been involved in the formation of the lunar maria.
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Absolute ages of the lunar maria and large craters
Icarus, 1969Abstract By an analysis of the changes in rim heights of lunar craters through isostatic settling, combined with inferences from counts of small impact craters contained within and subsequent to large craters, it is concluded that: (1) the maria are not older than about 640 million years; and (2) the flux of masses which produced craters larger than ...
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Surface structure and mechanical properties of the lunar maria
Journal of Geophysical Research, 1967Structural and mechanical properties of lunar maria surface material derived from satellite and earth-based ...
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Argon-lead isotopic correlation in samples from lunar maria: Records from the ancient lunar regolith
Earth and Planetary Science Letters, 1975Abstract 207Pb/206Pb of “low temperature sited” (LTS) lead as reported by Silver (1975) increases with40Ar/36Ar of trapped argon in thirteen samples from lunar maria. This strongly supports an earlier conclusion by (1972) that large (40Ar/36Ar)T ratios represent ancient regolith records, and provides a rough (40Ar/36Ar)T timescale. The erasure of (
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Nature of the Density Reversal Beneath the Lunar Maria
Geological Society of America Bulletin, 1972The density of basalt samples from Mare Tranquillitatis and Oceanus Procellarum is 3.36 g/cm 3 . These basalts should undergo a phase change at a pressure of approximately 10 kbar (200 km lunar depth) that would increase the density to 3.74 g/cm 3 . This density is substantially higher than the average density of the moon; therefore, lunar maria must ...
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