Project Galileo: final mission status
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Galileo Jupiter Europa flyby↗
Engineering topics
Bindschadler, D. L.
Publications and source records attributed to Bindschadler, D. L..
Project Galileo: final mission status
A summary of spacecraft performance in the harsh jovian environment and a report of final subsystem and instrument status are provided.
Galileo Jupiter↗
Project Galileo: farewell to the major moons of Jupiter
Galileo has completed its survey of the large moons of Jupiter.
Galileo↗
Project Galileo: from Ganymede back to Io
Engineering data on spacecraft and instrument performance in this harsh environment is very useful to designers of future missions to Jupiter and its moons.
Ganymede↗
Joint Galileo/ Cassini observations of the Jovian system
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Galileo Cassini Jupiter magnetosphere Io Ganymede ↗
Project Galileo: surviving Io, meeting Cassini
Galileo has completed the long awaited Io flybys of the Galileo Europa Mission and the Galileo Millennium Mission, and is now pumping up its apojove in each succeeding orbit in preparation for the chance to perform a dual spacecraft observation of the Jupiter System.
Galileo↗
Large Topographic Rises on Venus: Implications for Mantle
Topographic rises on Venus have been identified that are.
Venus mantle upwelling topographic rises tectonics↗
A mechanism for crustal recycling on Venus
Entrainment of lower crust by convective mantle downflows is proposed as a crustal recycling mechanism on Venus. The mechanism is characterized by thin sheets of crust being pulled into the mantle by viscous flow stresses. Finite element models of crust/mantle interaction are used to explore tectonic conditions under which crustal entrainment may occur. The recycling scenarios suggested by the numerical models are analogous to previously studied problems for which analytic and experimental relationships assessing entrainment rates have been derived. We use these relationships to estimate crustal recycling rates on Venus. Estimated rates are largely determined by (1) strain rate at the crust/mantle interface (higher strain rate leads to greater entrainment); and (2) effective viscosity of the lower crust (viscosity closer to that of mantle lithosphere leads to greater entrainment). Reasonable geologic strain rates and available crustal flow laws suggest entrainment can recycle approximately equal 1 cu km of crust per year under favorable conditions.
Lenardic, A.↗
Venus' center of mass - center of figure displacement and implications
Earth, Moon, Mars, and Venus all have centers of mass (C.M.) that are displaced from their centers of figure (C.F.) by amounts which range from 340 meters (Venus) to 2.5 km (Mars). These offsets have all been calculated from the first degree terms in spherical harmonic expansions of topography. We describe an alternate method for calculating C.M. - C.F. offsets directly from a global topographic data set and apply it to Venus. Using Magellan altimetry, we find that Venus' C.F. is displaced approximately 280 meters from its C.M. in the direction of Western Aphrodite Terra (4.4 deg S, 135.8 deg E). We investigate several simple models for this offset and find that it is most consistent with thickened crust in Ovda and Thetis Regiones (which constitute most of W. Aphrodite). The location of the C.F. offset also places constraints on the degree of crustal thickening in Western Ishtar Terra and/or this highland's mode of origin. We favor a model in which offset due to thick crust in Western Ishtar Terra is balanced by an opposing offset due to cold, downwelling mantle material beneath the highland.
Bindschadler, D. L.↗
Volcanic rises on Venus: Geology, formation, and sequence of evolution
Large centers of volcanism on Venus are concentrated primarily in the equatorial region of the planet and are associated with regional topographic rises. Analysis of both radar images and geophysical data suggest that these uplands are sites of mantle upwelling. Magellan radar imaging provides a globally contiguous data set from which the geology of these regions is evaluated and compared. In addition, high resolution gravity data currently being collected provide a basis to assess the relationship between these uplands and processes in the planet's interior. Studies of the geology of the three largest volcanic highlands (Beta Regio, Atla Regio, Western Eistla Regio) show them to be distinct, having a range of volcanic and tectonic characteristics. In addition to these large areas, a number of smaller uplands are identified and are being analyzed (Bell Regio, Imdr Regio, Dione Regio (Ushas, Innini, and Hathor Montes), and Themis Regio). To understand better the mechanisms by which these volcanic rises form and evolve, we assess their geologic and geophysical characteristics.
Senske, D. A.↗
Coldspots or hotspots? The origin of plateau-shaped highlands on Venus
A compelling question for the terrestrial planets is the origin of the highland regions on Venus. Data on the topography, gravity signature, and surface morphology returned by the Pioneer Venus, Venera 15/16, and Magellan spacecraft represent a basis for dividing these highlands into two distinct groups: volcanic rises and plateau-shaped highlands. Volcanic rises are generally thought to be due to mantle upwellings in the form of large mantle plumes and are thus similar in origin to terrestrial hotspots. There is less agreement as to the origin of plateau-shaped highlands (PSH). Coldspot mantle downwelling can lead to the formation of a highland region under Venus conditions, and previous to Magellan some PSH (particularly W. Ishtar Terra and Ovda and Thetis Regiones) were suggested to be compressionally deformed regions of thickened crust created by mantle downwelling. A hotspot model proposes that such regions are formed by magmatism and tectonism related to the near-surface ascent of either the diapir-shaped large mantle plume or a solitary disturbance propagating up a plume conduit. The characteristics of both volcanic rises and plateau-shaped highlands on Venus and the models for their formation are briefly reviewed, and tests that may help to make clear which model best explains the plateau-shaped highlands are considered.
Bindschadler, D. L.↗
The spatial distribution of coronae on Venus
Coronae on Venus are large, generally circular surface features that have distinctive tectonic, volcanic, and topographic expressions. They range in diameter from less than 200 km to at least 1000 km. Data from the Magellan spacecraft have now allowed complete global mapping of the spatial distribution of coronae on the planet. Unlike impact craters, which show a random (i.e., Poisson) spatial distribution, the distribution of coronae appears to be nonrandom. We investigate the distribution here in detail, and explore its implications in terms of mantle convection and surface modification processes.
Squyres, S. W.↗
Mantle-flow tectonics and the origin of Ishtar Terra, Venus
It is proposed that western Ishtar Terra formed due to compression and crustal thickening above a cylindrical mantle downwelling. A model for crustal deformation due to downwelling successfully reproduces many observed characteristics of western Ishtar. Although axisymmetric downwelling occur in numerical models of constant-viscosity mantle convection, there is no evidence for their existence in earth's mantle, where downwellings are sheet-like. Either modes of downflow in Venus and earth are fundamentally different, or differences in near-surface conditions and material behavior selectively emphasize surface expressions of the different downwelling modes.
Bindschadler, D. L.↗
Distribution of tessera terrain on Venus - Prediction for Magellan
Tessera terrain is the dominant tectonic unit in the northern hemisphere of Venus and is characterized by complex sets of intersecting structural trends and distinctive radar properties due to a high degree of meter and sub-meter scale (5 cm to 10 m) roughness. Based on these distinctive radar properties, a prediction of the global distribution of tessera can be made using Pioneer Venus (PV) reflectivity and roughness data. Where available, Benera 15/16 and Arecibo images and PV diffuse scattering data were used to evaluate the prediction. From this assessment, it is concluded that most of the regions with prediction values greater than 0.6 (out of 1) are likely to be tessera, and are almost certain to be techonically deformed.
Bindschadler, D. L.↗
Characterization of Venera 15/16 geologic units from Pioneer Venus reflectivity and roughness data
The characterization of geologic units defined for the Venus surface on the basis of Venera 15/16 image data is presently conducted in light of Pioneer Venus reflectivity and rms slope data. Four geologic-unit groups are distinguished: smooth rocky units, rough ones, rough high-dielectric units, and diffusely-scattering ones. Models have been tested for the surface-property origins of several units, and it is determined that plains and tectonic units may be contrasted in terms not only of surface roughness but of surface-roughening tectonic deformation that appears to dominate the erosional regime of Venus.
Bindschadler, D. L.↗