Venus Radar Mapper
Launch Date: May 04, 1989
Mission Project Home Page - http://www2.jpl.nasa.gov/magellan/
The Magellan spacecraft, named after the sixteenth-century Portuguese explorer whose expedition first circumnavigated the Earth, was launched 4 May 1989, and arrived at Venus on 10 August 1990.
Magellan's Map of Venus
The Magellan spacecraft imaged more than 98% of Venus at a resolution of about 100 meters; the effective resolution of these images is about 3 kilometers. A mosaic of the Magellan images (most with illumination from the west) forms the image base. Gaps in the Magellan coverage were filled with images from Soviet Venera 15 and 16 spacecraft in the northern quarter of the planet, with images from the Earth-based Arecibo radar in a region centered roughly on 0 degrees latitude and 0 degrees longitude, and with a neutral tone elsewhere (primarily near the south pole).
The composite image was processed to improve contrast and to emphasize small features and was color-coded to represent elevation. Gaps in the elevation data from the Magellan radar altimeter were filled with altimetry from the Venera spacecraft and the U.S. Pioneer Venus missions.
Magellan collected radar images of 98 percent of the planet's surface, with resolution 10 times better than that of the earlier Soviet Venera 15 and 16 missions. Altimetry and radiometry data also measured the surface topography and electrical characteristics.
Key Scientific results:
- Study of the Magellan high-resolution global images is providing evidence to understand the role of impacts, volcanism, and tectonism in the formation of Venusian surface structures.
- The surface of Venus is mostly covered by volcanic materials. Volcanic surface features, such as vast lava plains, fields of small lava domes, and large shield volcanoes are common.
- There are few impact craters on Venus, suggesting that the surface is, in general, geologically young - less than 800 million years old.
- The presence of lava channels over 6,000 kilometers long suggests river-like flows of extremely low-viscosity lava that probably erupted at a high rate.
- Large pancake-shaped volcanic domes suggest the presence of a type of lava produced by extensive evolution of crustal rocks.
- The typical signs of terrestrial plate tectonics - continental drift and basin floor spreading - are not in evidence on Venus. The planet's tectonics is dominated by a system of global rift zones and numerous broad, low domical structures called coronae, produced by the upwelling and subsidence of magma from the mantle.
- Although Venus has a dense atmosphere, the surface reveals no evidence of substantial wind erosion, and only evidence of limited wind transport of dust and sand. This contrasts with Mars, where there is a thin atmosphere, but substantial evidence of wind erosion and transport of dust and sand.
The spacecraft made a dramatic conclusion to its highly successful mission when it was commanded to plunge into the planet's dense atmosphere Tuesday, 11 October 1994 to gain data on the planet's atmosphere and on the performance of the spacecraft as it descended.