Mathematics – Logic
Scientific paper
Dec 1969
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1969esrv....5..255q&link_type=abstract
Earth Science Reviews, Volume 5, Issue 4, p. 255-278.
Mathematics
Logic
2
Scientific paper
The five initially selected Apollo sites are landing dispersion ellipses located on smooth plains of the equatorial region of the Moon. Regional geologic studies suggest that the plains were formed by innumerable coalescing volcanic flows and that the areas including the landing sites are among the most youthful of the lunar volcanic terrains. Recent photogeologic investigations of the fine structure of the lunar surface have disclosed that the originally cohesive rock surfaces have been modified by impacting projectiles which have produced an extensive debris blanket having properties which vary as a function of exposure age. The five sites consist of debris-mantled sequences of interstratified units of cohesive volcanic rocks and fragmental impact debris. The volcanic rocks are most likely of basaltic composition in sites 2, 3, 4 and 5 in Mare Tranquillitatis, Sinus Medii, and Oceanus Procellarum, but those of site 1 in southern Mare Tranquillitatis near the terra may be of different composition. Surface debris at each site is primarily of local, impact origin, although a few impact erratics and an extremely small amount of extra-lunar material may be present. Debris in all sites is poorly sorted, with centimetersize blocks common on the surface, but with a mean diameter in the 50 μ range. Thickness of the debris blanket is variable in each site, thickest near clusters of large craters and thinnest in regions where large craters are less frequent, but all intercrater areas appear to be mantled. Landing site 4 in southern Oceanus Procellarum has the thinnest layer of debris, the most widespread distribution of centimeter-size fragments, and probably the smallest proportion of shock-metamorphosed and extra-lunar debris. The substrate rocks there are the youngest of the Apollo sites. Properties of the debris layer are similar in sites 2, 3, and 5, but differ slightly from those in site 4. Debris is thicker than in site 4, and surface fragments are less uniform and are concentrated about large craters. The proportion of shock metamorphosed and extra-lunar material among fine-grained components of the debris is probably greater. Site 1 is unique in its setting but has a layer with thickness and large fragment distributions similar to those of sites 2, 3, and 5. The main observable difference between this and other sites is that site 1 appears to have a greater proportion of highly eroded, large craters. There is uncertainty as to whether this indicates that the substrate rocks of this area are of lower strength, and possibly different composition, or whether the normal cycle of impact erosion has been interrupted by episodes of pyroclastic mantling of the surface.
Oberbeck Verne R.
Quaide William L.
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