Exploring The Planets - VENUS

A Global View

This mosaic of radar images taken by the Magellan spacecraft shows one hemisphere of Venus. The long belt of bright terrain called Aphrodite Terra winds along the equatorial region. This is an area of mountainous terrain where many volcanoes occur. Plains dominate the regions north and south of Aphrodite. A network of long ridge belts also appears in the north. The color of this mosaic is computer generated.

Image centered at 180 degrees east longitude
NASA Image - Catalog #PIA0040

On the Surface The surface of Venus is dry and hot--475 °C (900 °F) day and night throughout the year-- and the atmospheric pressure is 90 times that of Earth's. Few probes have entered this harsh environment, and none has survived long. Only four, all Soviet Venera spacecraft, have returned images from the surface.
The rocks on Venus are a dull gray, but sunlight filtered by the thick atmosphere gives them a yellow tint. This Venera 13 color photo shows plates of rock thought to be basalt, with dark soil between some of them. The lower photo has been corrected to show the color of the surface as it would appear under direct sunlight. This site is probably typical of the plains on Venus.	[194k JPEG] - [81k JPEG] Venera 13 images of the surface of Venus.

Topography

Sharp elevation differences characterize Earth's surface: the continental areas are much higher than the ocean basins. Venus also has a broad range of elevations, but unlike Earth most of its surface lies within a few kilometers of the mean elevation. The high terrain consists of tessera (possibly old and highly deformed areas) and a few large volcanoes.

The Atmosphere

Sometime in its history, Venus underwent a catastrophic "runaway greenhouse" process: the dense carbon dioxide atmosphere trapped heat from the Sun and raised the surface temperature to 475 °C (900 °F)--hot enough to melt lead. Any water that existed boiled away; only trace amounts remain. The upper atmosphere contains layers of clouds and hazes, most of which consist of droplets of sulfuric acid.

Circulation Patterns

Winds near the surface are only strong enough to move sand grains and dust particles, but the upper layers of the atmosphere move very fast. They circle the planet every four days, a pattern called superrotation. Venus also has atmospheric circulation patterns between the equatorial and polar areas, similar to those on Earth.

[45k JPEG]
Courtesy of Ronald Greeley, Arizona State University