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  • 1
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    Two lunar global asymmetries (1984)
    In:  Other Sources
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    Publication Date: 2019-01-25
    Description: The Moon's center of mass is displaced from its center of figure about 2 km in a roughly earthward direction. Most maria are on the side of the Moon which faces the Earth. It is assumed that the Moon was initially spherically symmetric. The emplacement of mare basalts transfers mass which produces most of the observed center of mass displacement toward the Earth. The cause of the asymmetric distribution of lunar maria was examined. The Moon is in a spin orbit coupled relationship with the Earth and the effect of the Earth's gravity on the Moon is asymmetric. The earth-facing side of the Moon is a gravitational favored location for the extrusion of mare basalt magma in the same way that the topographically lower floor of a large impact basin is a gravitationally favored location. This asymmetric effect increases inversely with the fourth power of the Earth Moon distance. The history of the Earth-Moon system includes: formation of the Moon by accretion processes in a heliocentric orbit ner that of the Earth; a gravitational encounter with the Earth about 4 billion years ago resulting in capture of the Moon into a geocentric orbit and heating of the Moon through dissipation of energy related to tides raised during close approaches to the Earth(5) to produce mare basalt magma; and evolution of the Moon's orbit to its present position, slowly at first to accommodate more than 500 million years during which magmas were extruded.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar Planetary Inst. Conf. on the Origin of the Moon; p 32
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  • 2
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    Lunar microcraters - Implications for the micrometeoroid complex (1975)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: (For abstract see issue 03, p. 459, Accession no. A75-13187)
    Keywords: LUNAR AND PLANETARY EXPLORATION
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  • 3
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    Catastrophic rupture of lunar rocks - A Monte Carlo simulation (1975)
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    Publication Date: 2019-06-27
    Description: A computer model based on Monte Carlo techniques was developed to simulate the destruction of lunar rocks by 'catastrophic rupture' due to meteoroid impact. Energies necessary to accomplish catastrophic rupture were derived from laboratory experiments. A crater-production rate derived from lunar rocks was utilized to calculate absolute time scales. Calculated median survival times for crystalline lunar rocks are 1.9, 4.6, 10.3, and 22 m.y. for rock masses of 10, 100, 1000, and 10,000 g, respectively. Corresponding times of 6, 14.5, 32, and 68 million years are required before the probability of destruction reaches 0.99. These results are consistent with absolute exposure ages measured on returned rocks. Some results also substantiate previous conclusions that the catastrophic-rupture process is significantly more effective in obliterating lunar rocks than mass wasting by single-particle abrasion. The view is also corroborated that most rocks presently on the lunar surface either are exhumed from the regolith or are fragments of much larger boulders rather than primary ejecta excavated from pristine bedrock.
    Keywords: LUNAR AND PLANETARY EXPLORATION
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  • 4
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    Was the formation of a 20-km-diameter impact crater on the moon observed on June 18, 1178 (1976)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Meteoritics; 11; Sept. 30
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  • 5
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    Lunar microcraters and interplanetary dust fluxes (1976)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: Conflicting depth/diameter ratios reported for lunar microcrater pits, microcrater pit morphology and size distribution, the composition and structure of pit glasses, and various alternative 'clocks' for estimating exposure time of microcrater pits are examined. Surface exposure time 'clocks' discussed include: galactic cosmic ray tracks, cosmogenic nuclides (involving changes in host rock isotopic composition induced by nuclear reactions), tracks produced in lunar top surfaces by nuclei accelerated during solar flares, and solar wind sputtering. 'Calibration' of the disparate types of surface exposure time 'clocks' with one another is discussed. The sensitive relationship between determinations of meteoroid flux and surface exposure time is examined.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Interplanetary dust and zodiacal light; Jun 10, 1975 - Jun 13, 1975; Heidelberg
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  • 6
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    Mixing of the lunar regolith (1974)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: A probabilistic model for mixing and turnover rates for the lunar regolith due to meteoritic impact is presented and evaluated using results from laboratory impact experiments and estimated meteoritic fluxes. The upper millimeter of the lunar surface is shown to be the primary mixing zone in the regolith and an important source for impact melts and vapors. Below this 'mixing layer' the rate of mixing and turnover decreases very rapidly with increasing depth, consistent with well-preserved stratigraphy and resident times deduced from deep drill core tube samples.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar Science Conference; Mar 18, 1974 - Mar 22, 1974; Houston, TX
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  • 7
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    New lunar microcrater evidence against a time varying meteoroid flux (1978)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: An attempt to measure the relative times of formation of 25 microcraters on lunar rock 60015 is discussed which was carried out as part of a study of the flux of interplanetary dust and possible time variations of that flux over periods of 1000 to 1 million yr. The data obtained could indicate that the formation rate of 100-micron-sized pits was lower in the past as compared with the formation rate of micron-sized pits, that the flux of particles forming 100-micron-sized pits may have varied relative to that of particles forming micron-sized pits, or that 100-micron-sized pits are forming now at a higher rate, relative to the formation rate of accretionary disks, than in the past. The last suggestion is shown to be almost untenable, and the overall results are found to lead to a logical paradox. It is concluded that the attempt probably failed and that the reason for failure raises serious questions regarding the use of lunar rock surfaces as meteoroid detectors.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Space research XVIII; Proceedings of the Open Meetings of the Working Groups on Physical Sciences; Jun 07, 1977 - Jun 18, 1977; Tel Aviv; Israel
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  • 8
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    Lunar surface processes - Report of the 12054 consortium (1978)
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    Publication Date: 2019-07-13
    Description: A variety of lunar surface phenomena were studied using a well-characterized glass-coated ilmenite basalt, 12054, which had a simple surface residence history. Surface processes related to the following effects were studied: microcraters, solar flare and cosmic ray tracks, cosmogenic Al-26, solar wind sputtering, accreta or accretionary material, solar wind implanted noble gases, and loose dust accumulation.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar and Planetary Science Conference; Mar 13, 1978 - Mar 17, 1978; Houston, TX
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  • 9
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    Density, chemistry, and size distribution of interplanetary dust (1975)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: Depth/diameter ratios measured for 98 craters in lunar glass targets reveal a broad distribution with a single strong peaking between 0.55 and 0.8. The measured values indicate a mean meteoroid density greater than 1 g/cu cm and probably less than 4 g/cu cm. Microprobe analyses show that typical glass pit liners on silicate targets contain only approximately 0.1% or less of meteoritic material. The size-frequency distribution of meteoroids was analyzed for a fractured glass surface of 60095, and a very steep size distribution of submicron meteoroids is indicated. As in the case of 15205, a dip at approximately 5 micron in the size-frequency distribution is detected.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar Science Conference; Mar 17, 1975 - Mar 21, 1975; Houston, TX
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  • 10
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    The asymmetric distribution of lunar maria and the earth's gravity (1976)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: The paper investigates the hypothesis that the asymmetry of the moon with respect to the distribution of maria, reflected in that the surface area of the moon covered by mare material is far greater on the earth-facing side than on the far side, is due to the action of the earth's gravity at a time when the moon was less distant from the earth than today. Such conditions would lead to gravitationally favored areas on the moon such that mare basalt magmas might erupt preferentially on the front side of the moon. Gravitational asymmetry is also discussed in terms of its effect on the shape of the moon, its center of mass, its moments of inertia, and the time scale for the evolution of its orbit.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar Science Conference; Mar 15, 1976 - Mar 19, 1976; Houston, TX
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