The Magellan mission scientific objectives were to study land forms and tectonics, impact processes, erosion, deposition, chemical processes, and model the interior of Venus. Magellan showed us an Earth-sized planet with no evidence of Earth-like plate tectonics. At least 85% of the surface is covered with volcanic flows, the remainder by highly deformed mountain belts. Even with the high surface temperature (475 C) and high atmospheric pressure (92 bars), the complete lack of water makes erosion a negligibly slow process, and surface features can persist for hundreds of millions of years. Some surface modification in the form of wind streaks was observed. Over 80% of Venus lies within 1 km of the mean radius of 6051.84 km. The mean surface age is estimated to be about 500 My. A major unanswered question concerns whether the entire surface was covered in a series of large events 500 My ago, or if it has been covered slowly over time. The gravity field of Venus is highly correlated with the surface topography, which indicates the mechanism of topographic support is unlike the Earth, and may be controlled by processes deep in the interior. Details of the global tectonics on Venus are still unresolved. #magellan #nasa #space #spacecraft #venus
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