Magellan began its radar mapping on September 15, 1990. After three complete 243-day cycles, Magellan had mapped 98 percent of Venus. This survey will help scientists map the internal structure of Venus. Magellan is unveiling on Venus a tortured surface shaped by a history of geological violence, tectonic deformation, volcanism, and impact cratering. At least 85 percent of Venus is covered by volcanic rock - mostly lava flows that form the planers vast plains.
Mountains deformed by repeated geologic activity cover much of the remaining surface areas.
Because no rainfall, oceans, or strong winds exist on Venus, little erosion occurs. From data returned by Magellan, scientists will create and study maps of Venus for years to come. With Venus' face unveiled, we now have a better understanding of Earth's fraternal twin, and a store of information that will help us understand the evolution of our own planet. Mission ended in 1994.