Geology topics

Research about Moon

Source-linked reports with geographic coverage including Moon.

At least 109 records · Page 6Linked to original sources

USGS1972

Orbital-science investigation: Part C: photogrammetry of Apollo 15 photography

Mapping of large areas of the Moon by photogrammetric methods was not seriously considered until the Apollo 15 mission. In this mission, a mapping camera system and a 61-cm optical-bar high-resolution panoramic camera, as well as a laser altimeter, were used. The mapping camera system comprises a 7.6-cm metric terrain camera and a 7.6-cm stellar camera mounted in a fixed angular relationship (an angle of 96° between the two camera axes). The metric camera has a glass focal-plane plate with reseau grids. The ground-resolution capability from an altitude of 110 km is approximately 20 m. Because of the auxiliary stellar camera and the laser altimeter, the resulting metric photography can be used not only for medium- and small-scale cartographic or topographic maps, but it also can provide a basis for establishing a lunar geodetic network. The optical-bar panoramic camera has a 135- to 180-line resolution, which is approximately 1 to 2 m of ground resolution from an altitude of 110 km. Very large scale specialized topographic maps for supporting geologic studies of lunar-surface features can be produced from the stereoscopic coverage provided by this camera.

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USGS1972

Orbital-science investigation: Part F: regional geology of Hadley Rille

Study of the sinuous Hadley Rille (fig. 25-45) was a primary goal of the Apollo 15 mission. Local geology of the rille near the landing site is described in section 5 of this report. Preliminary study of orbital photography from Hasselblad, metric, and panoramic cameras makes possible a description of some regional relationships of the rille. Considerable use is also made of a preliminary topographic map (10-m contour interval) of part of the rille (part C of this section). Contours in the mare area generalized from the map (fig. 25-35(a)) are shown in figure 25-46.

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USGS1972

Orbital-science investigation: Part G: lineaments that are artifacts of lighting

Many Apollo 15 orbital photographs, particularly those taken at low Sun-elevation angles, reveal grid patterns of lineaments. In some circumstances, the grid pattern is present in areas where structural control seems unlikely. For example, in an oblique view (fig. 25-52), the ejecta blankets of two fresh impact craters seem to have two intersecting sets of lineaments. Because previous studies of impact craters indicate that concentric and radial trends are commonly present, that this pattern is unexpected. A crater-saturated surface on which a faint grid of linear markings can be discerned is shown in figure 25-53. Again, this pattern is unexpected for a surface that has been exposed to random impacts. In both situations, the azimuths of the main lineaments are approximately symmetrical to the direction of the Sun.

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USGS1972

Orbital-science investigation: Part H: sketch map of the region around the candidate Littrow Apollo landing sites

The photograph in figure 25-59 and the corresponding map (fig. 25-60) show the geology of part of the lunar surface just east of the Littrow rilles at the eastern edge of Mare Serenitatis. The most striking feature of the region is the extremely low albedo of the area mapped as Eld in the western half of the map. The low albedo is believed to be caused by a thin layer of pyroclastic volcanic material at the surface. Another notable feature is the fresh-appearing ridges that cross the mare and the adjacent terra. The fine-braided texture of these ridges contrasts markedly with the rounded, subdued topography more common to such features, an indication that the ridges here may be unusually young. Also evident is a well-exposed succession of marelike plains units, which probably represent different stages in the filling of the Serenitatis basin. Several sets of rilles are present; most are roughly tangential to the basin and terminate against the different plains units according to the relative ages. In the northwest corner of the map is a relatively fresh volcanic crater chain (Cch) from which material appears to have been ejected over the surrounding terrain, forming rays of volcanic ejecta. The area thus includes an unusually wide variety of lunar features.

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USGS1972

Orbital-science investigation: Part J: preliminary geologic map of the region around the candidate Proclus Apollo landing site

The Proclus Crater region was mapped to test the value, for photogeologic mapping purposes, of Apollo 15 metric photographs and to estimate the scientific value of the area as a potential landing site. A metric photographic frame (fig. 25-67) serves as a base for a map of the region around the Proclus Crater (fig. 25-68), and adjacent frames were overlapped with the base frame to provide stereographic images. The excellent stereocoverage allows easy simultaneous observation of topography and albedo. The large forward overlap and the extensive areal photographic coverage provide the best photogeologic data available to date. Brief study has already refined earlier interpretations of the area (refs. 25-7 and 25-32). Although volcanic units have been shown to be extensive in this region, mass wasting apparently has been more important than volcanism in shaping terra landforms.

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USGS1972

Orbital-science investigation: Part K: geologic sketch map of the candidate Proclus Apollo landing site

A panoramic camera frame (fig. 25-69) was used as the base for a geologic sketch map (fig. 25-70) of an area near Proclus Crater. The map was prepared to investigate the usefulness of the Apollo 15 panoramic camera photography in large-scale geologic mapping and to assess the geologic value of this area as a potential Apollo landing site. The area is being considered as a landing site because of the availability of smooth plains terrain and because of the scientific value of investigating plains materials, dark halo craters, and ancient rocks that may be present in the Proclus ray material.

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USGS1972

Orbital-science investigation: Part L: selected volcanic features

Preliminary examination of Apollo 15 orbital photographs indicates a large number of volcanic features. One area of exceptionally interesting volcanic activity is depicted in figure 25-74. Located approximately at latitude 25° S and longitude 123° E on the lunar far side, this region also is covered by panoramic camera photographs AS15-9954, 9956, 9958, and 9960 and by stereoscopically overlapping frames AS15-9959, 9961, 9963, and 9965.

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USGS1972

Orbital-science investigation: Part O: regional variations in the magnitude of heiligenschein and causal connections

Approximately 35 reasonably good candidates for specialized photometric studies were found during a thorough examination of the frames exposed by the Apollo 15 metric camera. Of these, the majority was of value in heiligenschein studies (refs. 25-36 to 25-38). A few were of value for limited-interval delineation of the photometric functions of crater walls, wherein it is now known from past Apollo Program studies that younger craters have walls much more Lambertian in reflective properties than those of the standard lunar surface (ref. 25-39). It has now become apparent that some difficulty exists in such crater-wall studies with regard to varying the domain of mathematical definition over which such photometric functions are delineated to encompass much more of phase-angle-brightness-longitude space than has already been carried out Nearer to zero-phase angle, the brightness of the illuminated wall becomes so intense compared with the general luminance of the surrounding lunar terrain that it approaches the saturated region of the D /log E curve of the photograph where D is density and E is exposure. Conversely, for phase angles approaching 180°, most of the illuminated wall is seen so obliquely that the image size is small and reliable photometry is difficult. Also, difficulties inherent in the methodology exist—the descriptive geometry used to extract configurations begins to fail as craters become either too old or are imaged too near a vertical view Nevertheless, some useful candidates for crater-wall studies have been found in the Apollo 15 data, although their analysis is too lengthy for incorporation in this preliminary report.

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USGS1972

Orbital-science investigation: Part P: the process of crater removal in the lunar maria

The processes by which craters disappear from the lunar surface have been of principal concern since the first high-resolution pictures of the lunar maria were returned by Ranger VII. Those pictures revealed that craters smaller than a few hundred meters on the lunar maria vary morphologically from sharp and pristine features to shallow, highly subdued depressions. The constancy of the population density of these smaller craters (with diameters of less than 1000 m) was predicted by Moore (ref. 25-40) and Shoemaker (ref. 25-41), who concluded that these craters were in a steady-state condition.

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USGS1972

Preliminary geologic investigation of the Apollo 16 landing site

The Apollo 16 landing site in the lunar central highlands encompassed terra plains and adjacent mountainous areas of hilly and furrowed terra. These morphologic units, representing important terrane types in the lunar highlands, had been interpreted as volcanic on most premission geologic maps. However, it became apparent during the mission that there are indeed few or no volcanic rocks or landforms at the site but rather that the area is underlain by a wide variety of impact-generated breccias.

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USGS1972

Preliminary examination of lunar samples: Part A: a petrographic and chemical description of samples from the lunar highlands

More than four-fifths of the surface of the Moon consists of a profoundly cratered irregular surface designated terra or highlands by analogy with the terrestrial continents. These terra regions have much higher albedos than the physiographically lower and much smoother mare regions. The difference in albedo can now be ascribed to a fundamental difference in the chemical and mineralogical character of these two regions. Lunar samples from landing sites in the mare regions and high-resolution photographs taken from lunar orbit have shown that the lunar maria are underlain by extensive lava flows. Isotopic dating of samples from four mare regions (refs. 7-1 to 7-4) indicate that mare volcanism covered a time span of 600 million years, beginning approximately 3.7 billion years ago. The intensely cratered character of terra regions is due to both the greater antiquity of these parts of the Moon and the higher flux of incoming objects that hit the Moon during very early lunar history (ref. 7-5). In contrast with the mare region, the origin of the underlying material of the terra is not easily inferred from physiographic criteria. The surface manifestations of early plutonic or extrusive igneous activity — if indeed they ever existed — were erased from the terra regions by the intense early bombardment of the lunar surface. Some portions of the highlands may be exceptions to this generalization; in particular, large craters such as Ptolemaeus, Hipparchus, Albategnius, and Alphonsus. The regions bounded by these craters are much smoother than the typical densely cratered highlands. These regions are generally assumed to be physiographic lows that have, in some way, been filled by younger material. The nature of the material and the mechanism by which it was introduced into the basins are not well understood. On the basis of rather detailed studies of the physiographic and albedo characteristics of the basin material, it has been suggested (ref. 7-6) that the filling of the highland basins was a result of volcanic processes similar to those which filled the large mare basins. Some highland basins also contain hilly, hummocky regions that bear no relation to large crater rims or crater ejecta. These regions have been interpreted as extrusive igneous features formed by viscous, silicic, igneous liquids (ref. 7-6).

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USGS1972

Photogeology: Part A: relative ages of some near-side and far-side terra plains based on Apollo 16 metric photography

The materials of most light or terra plains predate the lunar maria and postdate the Imbrian event. In the vicinity of the Imbrium Basin, these materials have been called the Cayley Formation (ref. 29-3) but because of the subtle diversity of the terra plains over the near side, Whilhelms and McCauley (ref. 29-4) simply called these materials Imbrian plains (Ip). The age relationships between the light plains and the Fra Mauro Formation are of principal importance in placing the Apollo 14, 15, and 16 samples in a regional context and in understanding the transitional period between the enhanced cratering rate of pre-Imbrian time and the comparatively quiescent period of impact cratering since the generation of mare surfaces.

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USGS1972

Photogeology: Part B: Cayley Formation interpreted as basin ejecta

The discovery that samples returned from the Cayley Formation at the Apollo 16 landing site consist mainly of nonvolcanic breccias (secs. 6 and 7 of this report) suggests that the hypothesis in which light plains-forming materials may be ejecta from multi-ring basins should be reevaluated (refs 29-15 to 29-17). Improved information on the morphology and distribution of the Cayley Formation, provided by Apollo 16 orbital photography, leads to a concept in which the Cayley Formation was deposited as fluidized debris that traveled beyond the presently recognizable extent of the Imbrium Basin ejecta. An elaboration of this genetic model is in preparation; the description, a summary of the model, and its implications are presented in this subsection.

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USGS1972

Photogeology: Part D: Descartes highlands: possible analogs around the Orientale Basin

The Descartes highlands are adjacent to the terra plain on which the Apollo 16 lunar module landed (fig. 29-13). A variety of volcanic origins was proposed for the highlands before the mission (refs. 29-4, 29-21, and 29-35 to 29-37), but the returned samples of the area consist almost exclusively of nonvolcanic breccias. The breccias obtained from Stone Mountain have not been identified conclusively as sample materials of the Descartes Mountains (ref. 29-35). A volcanic origin is thus not yet precluded (sec. 6 of this report), but a review of possible impact-related origins seems to be appropriate. The orbital photography acquired during the Apollo 16 mission provides excellent imagery on which geomorphic interpretations may be based. No obvious local crater is a plausible source of the material, but there may be a relation to either the Nectaris or Imbrium Basin. The less degraded Orientale Basin (fig. 29-24) provides a model by which these comparisons can be made (part F of this section).

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USGS1972

Photogeology: Part F: reinterpretations of the northern Nectaris Basin

Geologic units of the Nectaris Basin rim have been interpreted as partly impact and partly volcanic in origin (refs. 29-4, 29-21, 29-35, 29-38, and 29-39). An exclusively volcanic origin was proposed for the material in the vicinity of the Apollo 16 landing site, slightly northwest of the Nectaris Basin (ref. 29-36). In view of the dominance of breccia and the paucity of volcanic material in the returned Apollo 16 samples, it now seems appropriate to reevaluate this part of the Moon to test whether the geology of the units mapped to date can be reconciled with an impact origin. Therefore, photogeologic analysis was attempted on a strip of Apollo 16 metric photographs; the superior quality and stereographic properties of the photography permit this reevaluation (fig. 29-32). Geologic contacts, as redrawn, closely resemble those of the earlier maps cited, but some differences result because of improved photographic quality and a conscious attempt to test fully the impact hypothesis.

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USGS1972

Photogeology: Part G: structural aspects of Imbrium sculpture

Apollo 16 metric photographs taken at low to high Sun angles (from approximately 7° to 40°) provide the first stereographic coverage of the distinctive landforms collectively referred to as "Imbrium sculpture" (refs. 29-40 and 29-41). The sculpture consists of a series of nearly linear ridges and troughs extending radially outward for more than 1000 km from the rim of the Imbrium Basin. The sculpture is particularly well developed in the highlands southwest of the basin, where individual segments have lengths measured in tens of kilometers. THe origin of the ridges and troughs, whether by deposition and impact scoring by fluidized clouds of ejecta from the Imbrium Basin or by faulting and volcanism during and subsequent to basin formation, is controversial. Similar appearing features occur around other large basins on both the near and far sides of the Moon; thus, information leading to a better interpretation of Imbrium sculpture has significance throughout the Moon.

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USGS1972

Photogeology: Part J: ranger and other impact craters photographed by Apollo 16

The Apollo 16 crew photographed an unusual variety of impact craters, including the two craters produced by the impacts of Ranger 7 and 9 spacecraft, small craters produced by boulders as they bounced downslope, craters with marked bilateral symmetry, and primary craters with a wide range of morphologies and sizes. Ranger impact craters and examples of other craters are discussed briefly in this subsection.

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USGS1972

Photogeology: Part L: crater morphometry

Morphometric analysis of lunar craters (ref. 29-75) complements the more traditional photointerpretive study of crater morphology. These two indirect approaches to the scientific investigation of lunar craters continue to be productive because the preferred alternative method, direct field examination of specific large craters, is not being undertaken in the current series of manned lunar landings and will not be implemented for some time. Metric camera photography returned from the Apollo flights is essential to the continued study of lunar crater geometry. The material provides raw data of a quality far superior to and more uniform than comparable data available from Lunar Orbiter or Earth-based sources.

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