Elastic thickness of the Venus lithosphere estimated from topography and gravity

The very close correlation observed on Venus between topography and gravity on a regional scale is clearly related to the isostatic compensation of the topographic loads. Observed gravity anomalies over topographic features of moderate lateral extent, located in the equatorial region (0° to 40° N latitude and 10° W to 60° E longitude) are somewhat larger than those computed with a model of local isostatic compensation (of Airy type). They may rather be explained by a model of compensation including elastic forces within the lithosphere which contribute to support topographic loads through elastic stresses. We have applied the theory of lithospheric flexure : to explain in wavelength and in amplitude the observed gravity anomalies, a flexural rigidity of ∼ 4 × 10 28 dyne cm has been estimated for the Venus lithosphere in the rolling plains province. This value is very low compared to the oceanic terrestrial lithosphere (ranging from ∼ 10 28 dyne cm near ridge crests to ∼ 2 × 10 31 dyne cm near subduction zones). The corresponding thickness of the elastic upper layer able to maintain elastic stresses for long time duration is ∼ 7.5 km. This value may not be representative of the entire Venus lithosphere.