Signatures of Lithospheric Flexure and Elevated Heat Flow in Stereo Topography at Coronae on Venus

Signatures of Lithospheric Flexure and Elevated Heat Flow in Stereo Topography at Coronae on Venus Signatures of lithospheric flexure were previously identified at a dozen or more large coronae on Venus. Thin plate models fit to topographic profiles return elastic parameters, allowing derivation of mechanical thickness and surface heat flows given an assumed yield strength envelope. However, the low resolution of altimetry data from the NASA Magellan mission has hindered studying the vast majority of coronae, particularly those less than a few hundred kilometers in diameter. Here we search for flexural signatures around 99 coronae over ∼20% of the surface in Magellan altimetry data and stereo‐derived topography that was recently assembled from synthetic aperture radar images. We derive elastic thicknesses of ∼2 to 30 km (mostly ∼5 to 15 km) with Cartesian and axisymmetric models at 19 coronae. We discuss the implications of low values that were also noted in earlier gravity studies. Most mechanical thicknesses are estimated as <19 km, corresponding to thermal gradients >24 K km−1. Implied surface heat flows >95 mW m−2—twice the global average in many thermal evolution models—imply that coronae are major contributors to the total heat budget or Venus is cooling faster than expected. Binomial statistics show that “Type 2” coronae with incomplete fracture annuli are significantly less likely to host flexural signatures than “Type 1” coronae with largely complete annuli. Stress calculations predict extensional faulting where nearly all profiles intersect concentric fractures. We failed to identify systematic variations in flexural parameters based on type, geologic setting, or morphologic class. Obtaining quality, high‐resolution topography from a planetwide survey is vital to verifying our conclusions. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Journal of Geophysical Research: Planets Wiley

Signatures of Lithospheric Flexure and Elevated Heat Flow in Stereo Topography at Coronae on Venus

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Publisher
Wiley
Copyright
©2018. American Geophysical Union. All Rights Reserved.
ISSN
2169-9097
eISSN
2169-9100
D.O.I.
10.1002/2017JE005358
Publisher site
See Article on Publisher Site

Abstract

Signatures of lithospheric flexure were previously identified at a dozen or more large coronae on Venus. Thin plate models fit to topographic profiles return elastic parameters, allowing derivation of mechanical thickness and surface heat flows given an assumed yield strength envelope. However, the low resolution of altimetry data from the NASA Magellan mission has hindered studying the vast majority of coronae, particularly those less than a few hundred kilometers in diameter. Here we search for flexural signatures around 99 coronae over ∼20% of the surface in Magellan altimetry data and stereo‐derived topography that was recently assembled from synthetic aperture radar images. We derive elastic thicknesses of ∼2 to 30 km (mostly ∼5 to 15 km) with Cartesian and axisymmetric models at 19 coronae. We discuss the implications of low values that were also noted in earlier gravity studies. Most mechanical thicknesses are estimated as <19 km, corresponding to thermal gradients >24 K km−1. Implied surface heat flows >95 mW m−2—twice the global average in many thermal evolution models—imply that coronae are major contributors to the total heat budget or Venus is cooling faster than expected. Binomial statistics show that “Type 2” coronae with incomplete fracture annuli are significantly less likely to host flexural signatures than “Type 1” coronae with largely complete annuli. Stress calculations predict extensional faulting where nearly all profiles intersect concentric fractures. We failed to identify systematic variations in flexural parameters based on type, geologic setting, or morphologic class. Obtaining quality, high‐resolution topography from a planetwide survey is vital to verifying our conclusions.

Journal

Journal of Geophysical Research: PlanetsWiley

Published: Jan 1, 2018

Keywords: ; ; ;

References

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