A dynamic model of Venus's gravity field

Kiefer, W. S.; Richards, Mark A.; Hager, Bradford H.; Bills, B. G.

doi:10.1029/gl013i001p00014

Cited by 94 publications

(96 citation statements)

References 17 publications

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“…These values are not consistent with compensation occurring solely by crustal thickening, but require some form of dynamic support from the mantle via stresses induced by ascending mantle plumes (e.g., Vezolainen et al, 2004) or substantial thinning of a thick ($300-600 km) thermal lithosphere (Kucinskas and Turcotte, 1994;Schubert, 1995, 1997;Orth and Solomatov, 2011). If a lowviscosity asthenosphere were present at shallow mantle depths, as is the case of Earth, the predicted GTRs and apparent depths of compensation resulting from dynamic support would be considerably smaller than measured as a result of the decoupling of stress between the lithosphere and mantle (e.g., Kiefer and Hager, 1991;Kiefer et al, 1986). This seems to imply that in contrast to Earth, Venus lacks a low-viscosity zone (Huang et al, 2013;Pauer et al, 2006), which is most likely a result of a volatile-poor mantle.…”

Section: Venusmentioning

confidence: 96%

Gravity and Topography of the Terrestrial Planets

Wieczorek¹

2015

Treatise on Geophysics

132

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Section: Venusmentioning

confidence: 96%

Gravity and Topography of the Terrestrial Planets

Wieczorek¹

2015

Treatise on Geophysics

132

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“…They further interpreted the topography of Eastern Aphrodite Terra to represent a normal spreading center, and the plateaus of Western Aphrodite Terra to represent a mantle plume or hot spot superposed on normal spreading to produce an Iceland-like plateau of thickened crust. Other workers have proposed on the basis of gravity and topography data that Aphrodite Terra represents the location of upwelling mantle plumes or hot spots (Kiefer et al, 1986;Herrick et al, 1989), with no crustal spreading.…”

Section: B Aphrodite Terramentioning

confidence: 99%

Processes of crustal formation and evolution on Venus: An analysis of topography, hypsometry, and crustal thickness variations

Head

1990

Earth Moon Planet

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On Venus, present evidence indicates a crust of predominantly basaltic composition and a relatively young average age for the surface (several hundreds of millions of years). Estimates of crustal thickness from several approaches suggest an average crustal thickness of lo-20 km for much of the lowlands and rolling plains and a total volume of crust of about 1 x 10" km3, approximately comparable to the present crustal volume of the Earth (1.02 x 10" km3). The Earth's oceanic crust is thought to have been recycled at least lo-20 times over Earth history. The near-coincidence in present crustal volumes for the Earth and Venus suggests that either: (1) the presently observed crust of Venus represents the total volume that has accumulated over the history of the planet and that crustal production rates are thus very low, or (2) that crustal production rates are higher and that there is a large volume of "missing crust" unaccounted for on Venus which may have been lost by processes of crustal recycling.Known processes of crustal formation and thickening (impact-related magma ocean, vertical differentiation, and crustal spreading) are reviewed and are used as a guide to assess regional geologic evidence for the importance of these processes on Venus. Geologic evidence for variations in crustal thickness on Venus (range and frequency distribution of topography, regional slopes, etc.) are outlined. The hypothesis that the topography of Venus could result solely from crustal thickness variations is assessed and tested as an end-member hypothesis. A map of crustal thickness distribution is compiled on the basis of a simple model of Airy isostasy and global Venus topography. An assessment is then made of the significance of crustal thickness variations in explaining the topography of Venus. It is found that the distinctive unimodal hypsometric curve could be explained by: (1) a crust of relatively uniform thickness (most likely lo-20 km thick) comprising over 75% of the surface, (2) local plateaus (tessera) of thickened crust (about 20-30 km) forming less than 15% of the surface, (3) regions of apparent crustal thicknesses of 30-50 km (Beta, Ovda, Thetis, Atla Regiones and Western Ishtar Terra) forming less than 10% of the surface and showing some geologic evidence of crustal thickening processes (these areas can be explained on the basis of geologic observations and gravity data as combinations of thermal effects and crustal thickening), and (4) areas in which Airy isostasy predicts crustal thicknesses in excess of 50 km (the linear erogenic belts of Western Ishtar Terra, less than 1% of the surface).It is concluded that Venus hypsometry can be reasonably explained by a global crust of generally similar thickness with variations in topography being related to (1) crustal thickening processes (orogenic belts and plateau formation) and (2) local variations in the thermal structure (spatially varying thermal expansion in response to spatially varying heat flow). The most likely candidates for the formation and evolution of the...

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“…The effects of depth variation of viscosity on geoid anomalies and topography have been reported in previous works (Ceuleneer et al, 1988;Hager and Richards, 1989;Kiefer and Hager, 1992;Kiefer et al, 1986;Morgan, 1965a;Ricard et al, 1984;Richards and Hager, 1984;Richards et al, 1988;Robinson and Parsons, 1988). They considered stratified viscosity or continuously varying viscosity with depth due to the effects of pressure on rheology, and they simply omitted the indirect effect of temperature in the viscosity, which occurs even if the activation energy is assumed to be zero.…”

Section: Depth-dependent Viscositymentioning

confidence: 90%