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8 - Planetary structural mapping
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- By Kenneth L. Tanaka, U.S. Geological Survey, Flagstaff, Robert Anderson, Jet Propulsion Laboratory, California Institute of Technology, Pasadena, James M. Dohm, Department of Hydrology and Water Resources, University of Arizona, Tucson, Vicki L. Hansen, Department of Geological Sciences, University of Minnesota Duluth, George E. McGill, University of Massachusetts, Amherst, Robert T. Pappalardo, Jet Propulsion Laboratory, California Institute of Technology, Pasadena, Richard A. Schultz, Geomechanics – Rock Fracture Group, Department of Geological Sciences and Engineering, University of Nevada, Reno, Thomas R. Watters, Center for Earth and Planetary Studies, National Air and Space Museum, Smithsonian Institution, Washington, DC
- Edited by Thomas R. Watters, Smithsonian Institution, Washington DC, Richard A. Schultz, University of Nevada, Reno
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- Book:
- Planetary Tectonics
- Published online:
- 30 March 2010
- Print publication:
- 17 December 2009, pp 351-396
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Summary
Summary
As on Earth, other solid-surfaced planetary bodies in the solar system display landforms produced by tectonic activity, such as faults, folds, and fractures. These features are resolved in spacecraft observations directly or with techniques that extract topographic information from a diverse suite of data types, including radar backscatter and altimetry, visible and near-infrared images, and laser altimetry. Each dataset and technique has its strengths and limitations that govern how to optimally utilize and properly interpret the data and what sizes and aspects of features can be recognized. The ability to identify, discriminate, and map tectonic features also depends on the uniqueness of their form, on the morphologic complexity of the terrain in which the structures occur, and on obscuration of the features by erosion and burial processes. Geologic mapping of tectonic structures is valuable for interpretation of the surface strains and of the geologic histories associated with their formation, leading to possible clues about: (1) the types or sources of stress related to their formation, (2) the mechanical properties of the materials in which they formed, and (3) the evolution of the body's surface and interior where timing relationships can be determined. Formal mapping of tectonic structures has been performed and/or is in progress for Earth's Moon, the planets Mars, Mercury, and Venus, and the satellites of Jupiter (Callisto, Ganymede, Europa, and Io).
3 - Venus tectonics
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- By George E. McGill, University of Massachusetts, Amherst, Ellen R. Stofan, Proxemy Research, Laytonsville, Suzanne E. Smrekar, Jet Propulsion Laboratory, Pasadena
- Edited by Thomas R. Watters, Smithsonian Institution, Washington DC, Richard A. Schultz, University of Nevada, Reno
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- Book:
- Planetary Tectonics
- Published online:
- 30 March 2010
- Print publication:
- 17 December 2009, pp 81-120
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- Chapter
- Export citation
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Summary
Summary
Venus has a pressure-corrected bulk density that is only 3% less than that of the Earth. In contrast, the surface environments of these two planets are very different. At the mean planetary radius the atmospheric pressure and temperature on Venus are 95 bars and 737 K, respectively. Liquid water cannot exist on the surface, which implies the absence of the processes most effective for erosion and sediment transport on Earth. The planet is completely shrouded in clouds, and temperatures of the lower atmosphere do not vary much from equator to poles, resulting in winds not capable of significant erosion. Most of the materials exposed on the surface of Venus apparently formed during approximately the last 20% of solar system history, with no significant clues to conditions on the planet during prior eons. Because the dense atmosphere has destroyed small bolides, the smallest surviving impact craters have diameters of ~2 km, and the total population of impact craters is less than 1000. The dominant terrain on Venus is plains, which constitute ~80% of the planet's surface. Impact craters are randomly distributed on these plains, and thus differences in the relative age of surface materials based on differences in crater frequency are not statistically robust.
The global topography of Venus does not include the diagnostic plate-boundary signatures that are present on Earth, and thus plate tectonics has not been active on Venus during the time represented by the current surface materials and features.