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  • 1
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    Microcraters formed in hot glass by hypervelocity projectiles (1976)
    In:  Other Sources
    Details
    Publication Date: 2011-08-16
    Description: Microcraters were formed in heated soda-lime glass by the normal incidence of spheres of plastic or fused silica with diameters between 0.8 and 4.5 microns and velocities between 2.5 and 10 km/s. The morphology of the craters in targets at temperatures up to 800 C is little different from those formed in unheated glass. Spallation still occurs to the same extent and above the same velocity threshold, but the spalls sag and sharp edges become dull in a few seconds at temperatures above the softening point. There is a small increase in the flow of glass from the central pit into a narrow lip at the higher temperatures, but this lip is often removed by spallation, especially at the higher velocities of impact. There is no evidence of a splashed lip with strings of melt overlying the spalled area. The results in conjunction with other evidence suggest that most lunar craters of micrometer size with a smooth central pit, splashed lip, and a spallation zone are the result of primary impacts.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: The Moon; 15; Jan
    Format: text
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    NASA TECHNICAL REPORTS
  • 2
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    Hollow lunar spherules and microcratering (1976)
    In:  Other Sources
    Details
    Publication Date: 2011-08-16
    Description: Craters were generated by micrometer-size, thin-walled hollow glass spheres impacting glass and stainless steel targets to determine morphological features distinguishing craters formed by hollow spheres from those formed by solid projectiles. The craters formed in both targets differed from those formed by solid spherical projectiles in that the central pit is an annular rather than a cup-shaped depression. The existence of an annular crater morphology on a surface exposed to cosmic dust would indicate the presence of thin-walled hollow spherules. Penetrations of thin-walled hollow glass beads by high velocity, solid, micrometer-size spheres are characterized by inward and outward flowing lips showing asymmetries dependent on the angle of impact.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Meteoritics; 11; June 30
    Format: text
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    NASA TECHNICAL REPORTS
  • 3
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    Lunar microcraters - Implications for the micrometeoroid complex (1975)
    In:  Other Sources
    Details
    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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  • 4
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    Microcraters formed in glass by low density projectiles (1971)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Microcraters were produced in soda-lime glass by the impact of low density projectiles of polystyrene (p = 1.06 g/cu cm) with masses between 0.7 and 62 picograms and velocities between 2 and 14 km/s. The morphology of the craters depended on the velocity and the angle of incidence of the projectiles and these are discussed in detail. It was found that the transitions in morphology of the craters formed by polystyrene spheres occurred at higher velocities than they did for more dense projectiles.
    Keywords: MATERIALS, NONMETALLIC
    Type: NASA-TM-X-67469
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 5
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    Micrometeoroids and lunar rocks (1974)
    In:  Other Sources
    Details
    Publication Date: 2019-07-27
    Description: Description of present concepts of the lunar micrometeoroid flux as deduced from microcrater observations on lunar rocks and available laboratory simulations with smooth glassy surfaces. Results examined include factors governing microcrater morphology, size frequency distribution, and correlation of lunar rock surface exposure ages with absolute crater number densities.
    Keywords: LUNAR AND PLANETARY EXPLORATION
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  • 6
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    The micrometeoroid complex and evolution of the lunar regolith (1974)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The interaction of the micrometeoroid complex with the lunar surface is evidenced by numerous glass-lined microcraters on virtually every lunar surface exposed to space. Such craters range in size from less than .1 micron to approximately 2 sq cm diameter. Using small scale laboratory cratering experiments for calibration, the observed crater-sized frequency distributions may be converted into micrometeoroid mass distributions. These lunar mass distributions are in essential agreement with satellite data. Some physical properties of micrometeoroids may be deduced by comparing lunar crater geometries with those obtained in laboratory experiments. The proponderance of circular outlines of lunar microcraters necessitates equidimensional, if not spherical, micrometeoroids.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA-TM-X-72191 , REPT-210 , Sov.-Am. Conf. on the Cosmochem. of the Moon and Planets,; Jun 04, 1974 - Jun 08, 1974; Moscow; Soviet Union
    Format: application/pdf
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