Research by Peter M. Grindrod, John Guest; Dept of Earth Sciences, University College, London, UK, Ellen Stofan, Proxemy Research, Laytonsville, MD, Francis Nimmo, University of California, Santa Cruz, NASA
The Magellan Mission to Venus produced synthetic, aperture radar (SAR) images of 98% of the surface of Venus. Distinctive, radial sets of fractures are common on Venus, and also occur on Earth and Mars. The fractures which extend for very large distances are the result of magma intrusions (dikes) below the surface, causing the surface to extend, crack apart and form the graben (extension-related fracture) apparent today. On Earth, the dikes are visible in some places where the surface has been eroded down to reveal the now frozen intrusions.
Research by Peter Grindrod, John Guest, Ellen Stofan and Francis Nimmo et al, theorizes that large radial graben (extension-related fractures) are the result of sub-surface dikes which are common on Venus.
On Venus, however, the fractures become much wider closer toward the central region, and it had been suggested that these large (of the order of several kilometers) graben were the result of uplift in the center and dikes were then responsible for the narrower fractures that occur further away.
Testing this idea, the team measured the depth and extension at as many of the large radial graben as possible and they did it by detailed analysis of the Magellan Synthetic Aperture Radar (SAR) images of the surface of Venus (note - radar images, not infrared). These methods allowed them to determine the amount of strain (a measure of the deformation of the surface) experienced by the whole feature.
The team compared this strain with that predicted by previous models of uplift caused by mantle plumes, and by a magma chamber inflating beneath the surface. Both these methods couldn't recreate the high levels of strain seen at the radially fractured centers, and therefore concluded that the only way of producing this amount of strain is by the propagation of dikes below the surface.
Significance to Solar System Exploration
How do the interiors of planets and their upper regions of planetary crusts form? How did these types of fractures come to be? If similar patterns of these dikes occur on other planets or icy moons and the same theories are applicable, then it could shed important light on the basic origins of planetary interior processes.
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Last Updated: 23 February 2011