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At least 811 records · Page 45

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NASA NTRS1975

Description and test results of a water basin to determine ground effect in hover using small models

A water basin test facility was established capable of measuring forces and moments of small models of VTOL aircraft, simulating hover in and out of ground effect. Because the models and the operation of the facility are inexpensive, the water basin is particularly suitable for testing the relative characteristics of a great number of model configurations for preliminary design development. Results from a variety of models are given. Lift, pitching moments, and rolling moments are given with and without engine failure simulation in ground effect, and with and without pitched and banked conditions.

Renselaer, D. J.↗

NASA NTRS1975

Seismic effects from major basin formations on the moon and Mercury

Grooved and hilly terrains occur at the antipode of major basins on the moon (Imbrium, Orientale) and Mercury (Caloris). Such terrains may represent extensive landslides and surface disruption produced by impact-generated P-waves and antipodal convergence of surface waves. Order-of-magnitude calculations for an Imbrium-size impact on the moon indicate P-wave-induced surface displacements of 10 m at the basin antipode that would arrive prior to secondary ejecta. Comparable surface waves would arrive subsequent to secondary ejecta impacts beyond 1000 km and would increase in magnitude as they converge at the antipode. Other seismically induced surface features include: subdued, furrowed crater walls produced by landslides and concomitant secondary impacts; emplacement and leveling of light plains units owing to seismically induced 'fluidization' of slide material; and perhaps the production and enhancement of deep-seated fractures that led to the concentration of farside lunar maria in the Apollo-Ingenii region.

Schultz, P. H.↗

NASA NTRS1974

Thickness of mare material in the Tranquillitatis and Nectaris basins

The present work reports on the construction of an isopach map of basin-filling materials based on data obtained from buried craters and partially buried craters in the Tranquillitatis and Nectaris basins. The data suggest that materials filling irregular maria are thin. Improved relief measurements based on Apollo metric photography are required for more accurate topographic mapping.

De Hon, R. A.↗

NASA NTRS1974

Smooth plains and continuous deposits of craters and basins

Apollo 16 photographic data are analyzed which suggest that smooth plains are related in origin to large primary cratering events, and that the plains material is mainly the ejecta of local and regional primary impact craters with only minor contributions from distant craters and basins. This material, then, has been emplaced in its present location by secondaries of distant craters and directly by primary craters near the site. Calculations indicate that the material excavated from large primary craters typically excavates much larger amounts of material from local terrain when it impacts in the secondary crater field. There is a correlation between the extent of development of smooth plains inside large high-land craters and the erosional state of the crater rims and walls. It is incorrect to consider the continuous deposits to be solely basin ejecta.

Oberbeck, V. R.↗

NASA NTRS1974

Chronology of lunar basin formation

The lunar anorthositic rocks 60025,86 and 60015,22 give Ar-40/Ar-39 ages of about 4.19 and 3.50 b.y., respectively. Two coarse fine anorthositic rock fragments 78503,7,1 and 72503,8,12 have ages of 4.13 and 3.96 b.y., respectively. The rock 60025 is the first large lunar rock with an age well in excess of 4.0 b.y. Evidence for the conclusion that the cratering events reset the radiometric ages is discussed. The chronology of the lunar basin forming events is deduced from the ages of the lunar highland impact breccias. Using the ages of lunar breccias, we have deduced a chronology for the last five lunar basin forming events. It is concluded that the 'lunar cataclysm' is the Imbrium event.

Schaeffer, O. A.↗

NASA NTRS1974

Lunar basins - Tentative characterization of projectiles, from meteoritic elements in Apollo 17 boulders

The ancient meteoritic components are considered, taking into account the significance of high siderophile abundances in highland rocks. Because this component occurs in breccias which have remained closed systems for at least 3.9 aeons, it can properly be called an ancient meteoritic component. It appears that the ancient meteoritic bodies represent a distinct population, different from present-day meteorites. Attention is given to the assignment of the lunar meteorite groups to individual basins and to the origin of basin-forming objects.

Morgan, J. W.↗

NASA NTRS1975

Transport and emplacement of crater and basin deposits

Material is ejected from impact craters in ballastic trajectories; it impacts first near the crater rim and then at progressively greater ranges. Ejecta from craters smaller than approximately 1 km are laid predominantly on top of the surrounding surface. With increasing crater size, more and more surrounding surface will be penetrated by secondary cratering action, and these preexisting materials will be mixed with primary crater ejecta. Ejecta from large craters, and especially basin-forming events, not only excavate preexisting local materials, but also are capable of moving large amounts of material away from the crater. Thus mixing and lateral transport give rise to continuous deposits that contain materials from within and outside the primary crater. As a consequence, ejecta of basins and large highland craters have eroded and mixed highland materials throughout geologic time and deposited them in depressions inside and between older crater structures.

Oberbeck, V. R.↗

NASA NTRS1975

An inundation study of the Lower Magdalena-Cauca River Basin

Annual floodings affect about 35,000 sq km of the Lower Magdalena-Cauca River Basin in the northern part of Colombia. Efforts made to determine the effects of inundation extension and complex factors involved in the flooding problem are reported. An integrated survey was made of the entire river basin with the object of land reclamation in the lower part and determining the effects of inundation extension and other complex factors on flooding. Modern remote sensing techniques were for the study.

Vanes, E.↗

NASA NTRS1976

Geologic structure of the eastern mare basins

The thickness of mare basalts in the eastern maria are estimated and isopachs of the basalts are constructed. Sub-basalt basin floor topography is determined, and correlations of topographic variations of the surface with variations in basalt thickness or basin floor topography are investigated.

Dehon, R. A.↗

NASA NTRS1976

Comparison of impact basins on Mercury, Mars and the moon

The statistics of basins on the moon, Mercury, and Mars are compared. The basic similarities of basins on Mars, Mercury, and the moon argue convincingly that they result from the same processes. Variations in onset diameters and relative abundances, however, suggest that these basic processes are modulated by second-order factors.

Wood, C. A.↗

NASA NTRS1977

Global seismic effects of basin-forming impacts

A Lagrangian computer program is used to study the effects of large impacts on planetary surfaces. More specifically, the global seismic effects for cratering energies of 10 to the 24th and 10 to the 25th J between the Copernicus and Imbrium lunar events are investigated. The phenomenologies for assumed solid and molten planetary interiors are compared. The main results of this investigation are: (1) far-field effects are found to be largely independent of cratering mechanisms, (2) antipodal seismic effects, which are of substantial magnitude, are greatly enhanced by focusing, (3) the most violent activity takes place at significant depth, (4) seismic effects are more pronounced for a molten planet than for a solid one, and (5) tensile failure may occur at depths of tens of kilometers beneath the antipode, or over the entire surface at shallower depths. These results suggest that the unusual terrains antipodal to large planetary basins may have been greatly modified by seismicity generated by the basin-forming impacts, and that the impacts may have brecciated the entire lithospheres of the terrestrial planets as the lithospheres formed and thickened

Hughes, H. G.↗

NASA NTRS1978

Formation of lunar basin rings

The outer rings of impact basins are interpreted as the bounding rings of the excavated basin cavities analogous to Copernicus-type crater rim crests. It is suggested that the inner rings are strata from depth uplifted during excavation of the transient cavity. Spacing relations and morphology appear to indicate a transition from central peaks to rings but not from terraces to rings. Evidence related to terrestrial craters with rings or peaks produced by meteorite impacts suggests that one or more crater rims may form inside the main, outer crater rim, resulting in nested craters. There is some evidence that peaks grade into inner rings as material is ejected from their cores in progressively larger impacts. Multiply layered materials may produce multiple rings by differential excavation of the layers.

Hodges, C. A.↗

NASA NTRS1980

Discharge forecasts in mountain basins based on satellite snow cover mapping

The author has identified the following significant results. A snow runoff model developed for European mountain basins was used with LANDSAT imagery and air temperature data to simulate runoff in the Rocky Mountains under conditions of large elevation range and moderate cloud cover (cloud cover of 40% or less during LANDSAT passes 70% of the time during a snowmelt season). Favorable results were obtained for basins with area not exceeding serval hundred square kilometers and with a significant component of subsurface runoff.

Martinec, J.↗

NASA NTRS1979

Impact crater and basin control of igneous processes on Mars

The possible role of impact craters in controlling local Martian endogenic activity is reviewed. Martian impact craters exhibiting evidence for endogenic modification are considered, including the style of modification. In addition, the cooling history of a mafic body intruded beneath impact craters of different sizes which contain water-ice deposits are examined, and results are related to modified Martian craters. This analysis is extended to basin-sized structures, and evidence for impact basin control of major volcanic and tectonic provinces is considered.

Schultz, P. H.↗

NASA NTRS1982

Upper mantle heterogeneity: Comparisons of regions south of Australia with Philippine Basin

The nature of mass anomalies that occur beneath the regions of negative residual depth anomalies were identified. Residual geoid anomalies with negative residual depth anomalies are identified in the Philippine Basin (negative) and in the region south of Australia (positive and negative). In the latter region the geoid anomalies are eastward and the depth anomaly is northeast. It is suggested that the negative depth anomaly and the compensating mass excess in the uppermost mantle developed in the Eocene as the lithosphere of the west Philippine basin formed. Heating of the deeper upper mantle which causes slow surface wave velocities and negative gravity and geoid anomalies may be a younger phenomenon which is still in progress.

Source record↗

NASA NTRS1982

Lava flooding of ancient planetary crusts - Geometry, thickness, and volumes of flooded lunar impact basins

The present study is concerned with the determination of the geometry, thickness, volumes, and style of emplacement of lava extruded onto an ancient planetary crust, giving particular attention to crustal regions characterized by the topography of impact basins. Attempts to establish thicknesses and volumes are based on four approaches, related to crater morphometry, crater penetration, stratigraphy, and geophysical techniques. The considered technique is applied to two areas related to lunar impact areas. The Orientale basin is investigated, taking into account the style of flooding, the geometry of deposits and implications for loading of the lithosphere, and aspects of lava thickness and vertical mixing. An analysis of the Archimedes-Apennine Bench region is also conducted, giving attention to the number of data points, rim heights of fresh lunar craters, and the premare nature of impact crater data points.

Head, J. W.↗

NASA NTRS1981

The evolution of the lunar Nectaris multiring basin

The paper begins by discussing the pre-Nectaris crust, the formation of the basin, its age and its geophysics. The pre-mare basalt deposits are categorized into smooth plains deposits, cratered and patterned plains, knobby terrain, and massifs, and the structure, chemical composition, and probable origin of these are discussed. Alternative scenarios for the formation of the plains are that they consist of impact melt ejecta, ejecta overlying smoothed-out preexisting topographic material, or ejecta overlying extrusive deposits. The mare deposits are assessed in terms of their composition, basalt ages and thickness, and eruption styles. A probable age of 3.6 billion years for the basalts is given. The tectonics of mare ridges and fractures and floor-fractured craters are gone into. Post-mare cratering is also discussed. It is concluded that the morphology of multiring basins is strongly dependent on lithosphere thickness.

Whitford-Stark, J. L.↗

NASA NTRS1982

Mare basin filling on the moon - Laboratory simulations

Laboratory simulations of lavas filling a stylized lunar multi-ringed basin demonstrate several relationships between the morphology of the emplaced lavas and various eruption conditions. The rate of effusion is the primary control on the gross shape of the accumulated lavas, with relatively low rates (e.g., Hawaiian style) leading to shield volcanoes and high rates (e.g., flood eruptions) producing flat, ponded lavas. Pre-flow topography can have a significant effect on the general form of individual flows and the position of flow features such as lava channels. Rootless vents develop in many parts of the flow, including areas apparently related to the position of basin rings, giving the false appearance of aligned true vent systems.

Greeley, R.↗