Ribbon spacing in Venusian tessera: Implications for layer thickness and thermal state

Abstract

We report on measurements of characteristic extensional wavelength represented by ribbons in Venusian tessera terrain. Fourier power spectra for ribbons in 35 areas from 9 geographic regions show dominant wavelengths of 2 to 6 km. We used these values to estimate mechanical layer thickness during ribbon formation at 0.6 to 2.9 km. Because ribbons accommodate extension of a single strong layer overlying a ductile substrate, we conclude that the base of this mechanical layer corresponded to the local brittle-ductile transition (BDT) during ribbon formation. Maintaining a BDT at <3 km depth for a significant length of time requires a locally hot environment, as over a plume impinging on thin lithosphere. These results indicate that locally hot conditions prevailed at widely distinct locations in the past.