Engineering topics

Bindschadler, Duane L.

Publications and source records attributed to Bindschadler, Duane L..

26 records · Page 2

NASA NTRS1992

Coldspots and hotspots - Global tectonics and mantle dynamics of Venus

Based on geologic observations provided by Magellan's first cycle of data collection and recent models of mantle convection in spherical shells and crustal deformation, the major topographic and geologic features of Venus are incorporated into a model of global mantle dynamics. Consideration is given to volcanic rises, such as Beta Regio and Atla Regio, plateau-shaped highlands dominated by complex ridged terrain (e.g., Ovda Regio and Alpha Regio), and circular lowland regions, such as Atalanta Planitia. Each of these features is related to either mantle plumes (hotspots) or mantle downwellings (coldspots).

Bindschadler, Duane L.↗

NASA NTRS1992

Magellan observations of Alpha Regio - Implications for formation of complex ridged terrains on Venus

The deformational features that make up the complex ridged terrain (CRT) of Alpha Regio are characterized, and observations of these features and their interpretations are used to evaluate quantitative models for the formation of Alpha Regio. In particular, two models are considered: a hotspot or mantle plume model and a coldspot or mantle downwelling model. Based on an analysis of the observed morphology of structures, their distribution, superposition and crosscutting relationships, and Magellan altimetry, a sequence of deformational events is suggested, and the observed topography, tectonics, and volcanism are compared with the predictions of the hotspot and coldspot models. It is found that a number of observations are more consistent with the downwelling than a hotspot model. This is particularly true of margin-parallel compressional features near the plains-CRT boundary in much of Alpha Regio.

Bindschadler, Duane L.↗

NASA NTRS1992

The morphology and evolution of coronae on Venus

The morphology and morphometry of a number of coronae and related features on Venus are discussed with reference to new data from the Magellan spacecraft. The specific features discussed are concentrated in the portion of Venus imaged during about the first three months of Magellan mapping. Sequences of events and basic geophysical processes involved in the formation of these features are inferred.

Squyres, Steven W.↗

NASA NTRS1991

Corona structures on Venus - Models of origin

The present study assesses the mantle diapir models of corona origin using the basic characteristics of coronas: relatively raised topography, annuli of compressional ridges, volcanism, and peripheral trough. Both rising and and sinking diapirs are modeled quantitatively. Rising mantle diapirs are caused by heating at depth, while sinking mantle diapirs may result from cooling or a phase change causing increased density and negative buoyancy at the base of the lithosphere. The hotspot model is most consistent with the major characteristics of coronas, with gravitational relaxation occurring as a modificational process. The sinking mantle diapir produces dominant central compression that is not observed at coronas. Higher-resolution image and altimetry data from Magellan can be used to distinguish more fully between the two models. Coronas in various states of formation and degradation can be identified in the Venera 15/16 data, suggesting that the process may be continuing today.

Stofan, Ellen R.↗

NASA NTRS1991

Morphology and evolution of coronae and ovoids on Venus

Coronae and ovoids on Venus were first identified in Venera 15/16 data. They are distinctive and apparently unique to the planet, and may be important indicators of processes operating in the Venusian mantle. Magellan images have provided the first high resolution views of coronae and ovoid morphology. Herein, the general geologic character is described of coronae and ovoids, and some inferences are drawn about their geologic evolution. Coronae are circular to elongate features surrounded by an annulus of deformational features, with a relatively raised or indistinct topographic signature and, commonly, a peripheral trough or moat. Ovoids are circular to elongate features other than coronae with either positive or negative topographic signatures, associated with tectonic deformation and volcanism. The relationship of these two geologic features to each other and to Venusian geology is briefly discussed.

Squyres, Steven W.↗

NASA NTRS1991

Tessera terrain, Venus - Characterization and models for origin and evolution

Tessera terrain is the dominant tectonic landform in the northern high latitudes of Venus mapped by the Venera 15 and 16 orbiters and is concentrated in the region between the mountain ranges of western Ishtar Terra and Aphrodite Terra. Tesserae are characterized by regionally high topography, a high-degree of small scale surface roughness, and sets of intersecting tectonic features. Available Pioneer Venus line of sight gravity data suggest that tessera terain is compensated at shallow depths relative to many topographic highs on Venus and may be supported by crustal thickness variations. Three types of tessera terrain can be defined on the basis of structural patterns: subparallel ridged terrain (Tsr), trough and ridge terrain (Ttr), and disrupted terrain (Tds). Observed characteristics of tessera terrain are compared to predictions of formational and modificational models in order to begin to address the question of its origin and evolution. It is found that horizontal convergence and late stage gravitational relaxation are basic observations for subparallel ridged terrain and disrupted terrain.

Bindschadler, Duane L.↗

NASA NTRS1990

Mantle flow tectonics - The influence of a ductile lower crust and implications for the formation of topographic uplands on Venus

The crust and mantle of Venus can be represented by a model of a layered structure stratified in both density and viscosity. This structure consists of a brittle-elastic upper crustal layer; a ductile weaker crustal layer; a strong upper mantle layer, about 10 percent denser than the crust; and a weaker substrate, representing the portion of the mantle in which convective flow occurs which is a primary source of large-scale topographic and tectonic features. This paper examines the interactions between these four layers and the mantle flow driven by thermal or compositional variations. Solutions are found for a flow driven by a buoyancy-force distribution within the mantle and by relief at the surface and crust-mantle boundary. It is shown that changes in crustal thickness are driven by vertical normal stresses due to mantle flow and by shear coupling of horizontal mantle flow into the crust.

Bindschadler, Duane L.↗

NASA NTRS1986

Vega landing sites - Venera 15/16 unit analogs from Pioneer Venus reflectivity and RMS slope data

Pioneer Venus radar data on surface properties have been used to compare the Vega spacecraft landing sites with the northern 1/4 of Venus mapped by the orbiters Venera 15 and 16. The regions surrounding both landing sites possess surface reflectivity and small-scale roughness properties most similar to those of mapped volcanoes and volcanic plains regions and different surface properties than those of mapped tectonic units. Regions analogous to the Vega 1 site are relatively rare, covering 2.8 percent of the mapped surface. Vega 2 analogs are much more common and cover 22.6 percent of the surface. Neither landing site is representative of the nearby highlands of Aphrodite, but the Vega 2 landing site is similar to much of the northern plains of Venus.

Bindschadler, Duane L.↗