Venus: Divergent outcomes of terrestrial planet formation

Although Venus is often referred to as the most Earth-like of the terrestrial planets, its runaway greenhouse has resulted in a dry, hot, uninhabitable surface. Its surface geology is complex, with volcanoes ranging from 500 km across, lava flows fields >800km across, mountain belts, rift zones, and terrains unique to Venus such as tesserae and coronae. It surface has an average crater retention age similar to Earth's continents, but the random nature of the impact crater population renders it useless in providing time constraints for the geologic history of Venus. At some point in the past, Venus lost an ocean's worth of water. If this water persisted on the surface for long periods of time in Venus's early history, life may have evolved. Untangling, the complex history of Venus, and what it reveals for the evolution of habitable planets, will require future missions to the surface.