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At least 667 records · Page 37

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NASA NTRS1972

Analysis and interpretation of lunar laser altimetry.

About 4.5 revolutions of laser altimetry were obtained by Apollo 15. This altimetry indicates a 2-km displacement of the center of mass from the center of figure toward the earthside. The terrae are quite rough, with frequent changes of 1 km or more in successive altitudes at about 33-km intervals. The mean altitude of terrae above maria is about 3 km with respect to the center of mass, indicating a thickness of about 24 km for a high-alumina crust. The maria are extremely level, with elevations varying not more than plus or minus 150 m about the mean over some stretches of 200 to 600 km. However, different maria have considerably different mean elevations. The largest unanticipated feature found is a 1400 km wide depression centered at about 180 deg longitude, and 2 km deep with respect to a 1737-km sphere (about 6 km deep with respect to the surrounding terrae). This basin has the appearance of typical terrae, although there are indications of a ring structure of about 600-km radius in the Orbiter photography. Altitudes across circum-Orientale features suggest that Mare Orientale is also a deep basin. The data appear to corroborate a model of early large-scale differentiation of a crust, followed a considerable time later by short intense episodes of mare filling with low viscosity lavas.

Kaula, W. M.↗

NASA NTRS1973

The filling of the lunar mare basins.

The surface of each mare is not a homogeneous geomorphological unit, but displays a variety of geomorphologies. The interpretation of this phenomenon depends on the assumptions one is willing to accept. If the filling of the mare basins occurred relatively slowly, then the geomorphologies are a time function and indicate a time span of not less than three quarters of a billion years between the beginning and the end of the mare filling activity. If, on the other hand, the maria were filled by lava immediately after the basin formation and remained liquid for a relatively long time during which the extensive bombardment stopped, then the different morphologies indicate vagaries in the final stages of the bombardment and of the cooling history.

Ronca, L. B.↗

NASA NTRS1973

Basaltic vitrophyre 15597 - An undifferentiated melt sample.

The vitrophyric nature and textural appearance of the Apollo 15 sample 15597, and the unusual compositions of its pigeonite centers and chromites, as well as the extreme chemical zonation of its pyroxenes, give strong evidence that this rock arrived on the lunar surface in an entirely liquid state. It may represent a 'primitive melt,' or at least a precursor from which mare lavas were derived.

Weigand, P. W.↗

NASA NTRS1973

Bombardment as a cause of the lunar asymmetry.

The moon is asymmetric in crustal thickness and also in the distribution of maria and gamma radioactivity. Early bombardment of the moon by planetesimals, in both heliocentric and geocentric orbits, is examined as a possible cause of the asymmetries. The presence of a massive companion (earth) causes a spin-orbit coupled moon to be bombarded nonuniformly. The most pronounced local concentration of impacts would have occurred on the west limb of the moon, when it orbited close to the earth, if low-eccentricity heliocentric planetesimals were still abundant in the solar system at that time. A very intense bombardment of this type could have redistributed crustal material on the moon, thinning the west limb crust appreciably. This would have caused a change in position of the principal axes of inertia, and a reorientation of the spin-orbit coupled moon such that the thinnest portion of its crust turned toward one of the poles. Erupting lavas would have preferentially flooded such a thin-crusted, low-lying area. This would have caused another readjustment of principal moments, and a reorientation of the moon such that the mare areas tipped toward the equator.

Wood, J. A.↗

NASA NTRS1973

Major and trace elements in igneous rocks from Apollo 15.

The concentrations of major and trace elements have been determined in igneous rocks from Apollo 15. All materials analyzed have typical depletions of Eu except for minerals separated from sample 15085. Four samples have concentrations of trace elements that are similar to those of KREEP. The samples of mare basalt from Apollo 15 have higher concentrations of FeO, MgO, Mn, and Cr and lower concentrations of CaO, Na2O, K2O, and rare-earth elements (REE) as compared to the samples of mare basalt from Apollos 11, 12, and 14. The samples can be divided into two groups on the basis of their normative compositions. One group is quartz normative and has low concentrations of FeO while the other is olivine normative and has high concentrations of FeO. The trace element data indicate that the samples of olivine normative basalt could be from different portions of a single lava flow.

Helmke, P. A.↗

NASA NTRS1973

Mapping of the major structures of the African rift system

The author has identified the following significant results. The new fault map of the main Ethiopian rift, based on aerial photo compilations, generally agrees well with the maps produced from ERTS-1 imagery. Characteristically, the ERTS-1 imagery shows some of the major faults to be more extensive than realized from ground studies, though due to the angle of sun illumination some east-facing fault scarps are not easily discernible on the imagery. The Corbetti caldera, shows up surprisingly poor on the imagery, and is shown to be an adjunct to an older, larger caldera now occupied by Lakes Awassa and Shallo. The lithological boundaries mapped by De Paola in the rift are difficult to discern on the ERTS-1 imagery. On the Somalian plateau, east of the rift, a denuded caldera has been identified as the source of much of the lavas of the Batu Mountains. Further south, ERTS-1 imagery amplifies the structural and lithological mapping of the Precambrian rocks of the Shakisso-Arero area, and of the Kenya-Ethiopia border region. For the first time with some certainty, it is now possible to say that on the evidence of the ERTS-1 imagery, the Western Rift does not continue northeast beyond the Sudan-Uganda border, and is thus not to be sought in western Ethiopia.

Mohr, P. A.↗

NASA NTRS1973

Preliminary geologic investigation of the Apollo 17 landing site

A geological investigation of the Apollo 17 lunar landing site was conducted. The Taurus-Littrow valley is interpreted as a deep graben formed by structural adjustment of lunar crustal material to the Serenitatis impact. Materials of the valley fill were sampled at many stations. Ejecta around many craters on the valley floor consist of basalt, showing that the graben was partly filled by lava flows. The geological objectives of the Apollo 17 mission are divided into orbital and lunar surface data collection. The data obtained for both types of investigation are presented in tables, photographs, and drawings.

Muehlberger, W. R.↗

NASA NTRS1973

Some volcanic and structural features of Mare Serenitatis

Relationships between volcanic and structural features along the southern edge of Mare Serenitatis as determined from low angle lighting in Apollo 17 photographs are discussed. Observational summaries are given of: (1) contact relations between the dark border material and the central mare fill, (2) a late stage lava flow with associated cinder cones, and (3) certain structural features related to the development of the mare basin and its associated volcanic landforms. A chronologic summary is given of volcanic and structural events believed to be critical to understanding the development of Mare Serenitatis.

Bryan, W. B.↗

NASA NTRS1973

Volcanism in the Lunar Maria

The formation, modification, and deformation of lunar maria by extended volcanic and tectonic processes are examined. Data also cover lava flows, sinuous rilles, mare ridges, faults, and fracture systems. Stages involved in the modification of impact craters by tectonism, volcanism, younger impacts, and mass wasting are included.

Richard A Young↗

NASA NTRS1973

Small structures of the Taurus-Littrow region

Apollo 17 photographs of small structures expressed as scarps, ledges, flow fronts, and mare type ridges are compared in an effort to determine the origin of such structures. The resulting data revealed that these structures were probably developed as lava extrusions from fractures and fissures along with associated faulting and folding.

Scott, D. H.↗

NASA NTRS1973

Volcanic features of far side Crater Aitken

Volcanic features of the far side Aitken Crater including post-impact volcanism and volcanic events extending beyond the period of mare type crater flooding are discussed. The features attributed to extrusions of viscous lava are also discussed.

Bryan, W. B.↗

NASA NTRS1974

Satellite geological and geophysical remote sensing of Iceland

The author has identified the following significant results. ERTS-1 imagery provides sufficient resolution to discern two effects of geothermal activity at the Namafjall geothermal area: snowmelt anomalies and delineation of altered ground. The fallout pattern of tephra from Hekla's 1970 volcanic eruption can be mapped where sufficient depth of deposition destroyed the vegetation. Lava flows from the volcanic eruptions at Askja and Hekla can be delineated. Low sun-angle imagery of snow-covered terrain has permitted the mapping of new structural and volcanic features beneath the icecaps. Coastline changes on the islands of Surtsey and Heimaey can be mapped. Variations of sediment plumes from glacial rivers on the south coast give a qualitative indication of seasonal changes in melting rates of glaciers. ERTS-1 imagery has been shown to be especially amenable to portrayal of changing glaciological phenomena: surging glaciers, collapse features in icecaps caused by subglacial volcanic (?) and geothermal activity and resulting jokulhlaups, and variations in size of glacier-margin lakes. A fifth vegetation class has now been added: lichen-covered bedrock. The high latitude permits more precise analysis of landforms, vegetation distribution, occurrence of snow cover, glaciers, and geologic structure.

Williams, R. S., Jr.↗

NASA NTRS1974

Research in volcanic geology, petrology and planetary science at MIT, 1969 to 1974

The behavior of volcanoes was studied by geologic mapping, petrologic investigations of lava and xenoliths, physical measurements, and theoretical modelling. Field observations were conducted in Alaska (Nunivak Island), Iceland, Hawaii (Mauna Kea), Italy (Etna, Stromboli), and Arizona. The results are discussed and compared with known data for lunar and planetary gelogy. Field methods used for the volcano research are cited and a list is given of all participating scientists and students. Publications and abstracts resulting from the research are also listed.

Mcgetchin, T. R.↗

NASA NTRS1973

Observations of Mare Serenitatis from lunar orbit and their interpretation

Visual observations are investigated of color differences of Serenitatis mare materials from orbit complement photography and other remotely sensed data. The light tan gray inner fill of the Serenitatis basin is younger than the dark blue gray annulus; the latter continues into and appears to be contemporaneous with the fill of Mare Tranquillitatis. Mare ridges occur in both the inner basin fill and the dark annulus of Serenitatis. Ridges are interpreted as the result of structural deformation and up-doming after the solidification of the basaltic lavas. On the southeastern rim of the Serenitatis basin is the darkes blue gray unit within which Apollo 17 landed. Highland massifs surrounding this unit have unstable slopes which are believed to be the result of localized tectonic activity. On the southwest rim of the basin are the dark tan to brown gray mantling materials of the Sulpicius Gallus Formation. Farther west on the rim are dark blue grap patches which resemble the mare material of the Serenitatis dark annulus.

El-Baz, F.↗

NASA NTRS1974

Mauna Kea

Mauna Kea, the highest of Hawaii's five volcanoes, is the only high landmass in the central Pacific Ocean basin to bear unmistakable signs of Pleistocene glaciation. The stratigraphic record indicates that a summit ice cap formed and disappeared at least four times in the last 250,000 years, and that volcanic eruptions characterized not only the interglacial intervals, but also two of the glacial periods as well. Exposed rock units on the upper slopes of Mauna Kea have been divided into two major groups based on gross lithologic character. The Hamakua Group comprises the bulk of the subaerial shield of the volcano and consists largely of thin-bedded pahoehoe flows of olivine basalt. The overlying Laupahoehoe Group consists of a thin cap of alkalic lavas and pyroclastic layers confined largely to the upper slopes of the mountain. Interstratified with the volcanic units are sedimentary formations that provide evidence of four episodes of ice cap glaciation.

Porter, S. C.↗

NASA NTRS1974

East Puna

This field trip mostly involves volcanic features that can be seen from roads in the east Puna District. Most of the features are associated with the eruptions of 1750(?), 1790(?), 1840, 1955, 1960, and the recent flows from Mauna Ulu on the Keauhou Lava Plains during the years 1969 to 1973. Particular emphasis is given to the 1955 and 1960 volcanic activity that occurred near the village of Kapoho.

Macdonald, G. A.↗

NASA NTRS1973

The origin of sinuous rilles

This report describes the distribution and morphology of sinuous rilles and presents data on rille geometry. Examples of the relation between sinuous rilles and the regional structure are given. Leading theories for the origin of sinuous rilles are discussed and evaluated. It is concluded that the general weight of evidence is against water erosion. The ash flow theory is not excluded, but evidence in its favor is weak. The best explanations involve lava tube formation for certain sinuous rilles, and faulting for others. In some cases, a gradation between faulting and igneous activity is noted.

Gornitz, V.↗

NASA NTRS1973

Orbital observations of the lunar highlands on Apollo 16 and their interpretation

From orbital altitudes, the lunar highlands display the same surface characteristics on both the far and near sides. Rugged terra and plains forming materials all appear as if dusted with a uniform mantle. No stratigraphy or evidence of layering are seen in highland craters, with the possible exception of South Ray Crater in the Descartes landing site area. Among the discussed small scale features of the lunar highlands are: fine lineaments, that appear to be real rather than artifacts of lighting, on both horizontal and inclined surfaces; ridge-like scarps that cut across highland topography; and benches that are believed to be high lava marks rather than talus accumulates.

Mattingly, T. K.↗