Does the face of Venus reveal whether she is Earth’s fraternal twin or identical twin separated at birth?

Abstract:

Venus has nearly the same diameter and bulk composition as Earth, yet lacks a dynamo and evidence for plate tectonics. Its dense CO₂ greenhouse creates a surface T of 460°C. Orbital and landed spectroscopy indicate a basaltic crust, with possible analogs to terrestrial continents. Radar images and altimetry reveal a volcanic surface, with regions of intense tectonic deformation, including rifts, mountain belts and large, intensely deformed plateaus. The sparse impact craters give a resurfacing age of 0.3-1 b.y. Their distribution cannot be distinguished from a random one, and fit models with either a single, rapid resurfacing pulse or ongoing resurfacing. Incorporating geologic constraints favors ongoing resurfacing. Ar isotope data indicate less interior outgassing than Earth, assuming a similar volatile inventory. Gravity and topography data, along with geologic features, provide evidence for ~10 large mantle plumes, similar to the number on Earth. The gravity/topography data at these hotspots suggests no low viscosity zone, perhaps implying a dry interior. Positive thermal emissivity from the Venus Express mission correlate with volcanic flows at several hotspots and can be interpreted as unweathered basalt, implying geologically recent activity. In addition, there are ~500 coronae, which are unique to Venus and likely form via small-scale upwelling, downwelling, or a combination. Many of the larger coronae may be sites of plume-induced subduction (see Davaille abstract), although subduction does not appear to create plates. I will discuss possible reasons Venus and Earth may have evolved differently and supporting evidence from surface observations. Did early impact or magma ocean history modify interior volatile or radiogenic content? Does high surface T and its effect on rheology and mineralogy inhibit plate tectonics? What is the evidence for a wet or dry interior? What could new missions tell us about these questions?