Hundreds of complex and diverse features called coronae-circular structures associated with myriad types of volcanic and tectonic activity-have been identified on the surface of Venus. Obtaining quality, high-resolution topography from a planetwide survey is vital to verifying our conclusions. We failed to identify systematic variations in flexural parameters based on type, geologic setting, or morphologic class.

Stress calculations predict extensional faulting where nearly all profiles intersect concentric fractures. 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. 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. Most mechanical thicknesses are estimated as 24 K km −1. We discuss the implications of low values that were also noted in earlier gravity studies. We derive elastic thicknesses of ∼2 to 30 km (mostly ∼5 to 15 km) with Cartesian and axisymmetric models at 19 coronae. 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. 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. 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.

Signatures of lithospheric flexure were previously identified at a dozen or more large coronae on Venus.

Flexture definition