Venus

Venus, the second planet from the Sun, orbits inside Earth's orbit, and so never appears very far from the Sun in our sky. It typically either rises as a "morning star" shortly before sunrise or sets as an "evening star" shortly after sunset.

Venus is the second brightest object in the night sky, after the Moon. In fact, when it is close to the horizon, some people unfamiliar with the night sky will mistake it for a distant streetlight, or even a UFO! Venus is so bright because it is covered with thick clouds which reflect sunlight.

Venus is unusual in that it rotates in a retrograde direction - spinning backwards compared to most of the other planets. If Earth rotated the same way Venus does, we would see the Sun rise in the west and set in the east.

Not Much Life Here, but There's Lots of Atmosphere

Venus and Earth have often been called "sister" planets because their sizes, masses, and densities are nearly the same, but Venus is very different from the Earth many ways. The thick layer of clouds that make Venus so bright also traps heat very well. So well, in fact, that the surface of Venus is over 470°C (900°F).

Earth's atmosphere is less than 0.1% carbon dioxide (CO₂), but around 95% of Venus' atmosphere is composed of the gas. Because of the large amount of carbon dioxide, Venus has what scientists often call a "runaway greenhouse effect." Sunlight which makes it through the clouds warms the surface of the planet, but heat energy cannot easily escape back out through the CO₂.

As if the temperature on Venus wasn't extreme enough, atmospheric pressure is 90 times that of the Earth's.

Beneath the Clouds

The thick atmosphere makes it nearly impossible to see the surface of Venus. In 1961, scientists were first able to see through the clouds using radar imaging. The studies conducted from Earth revealed what appear to be shallow craters and possibly volcanoes. At Venus' equator, there is a canyon 1,500 km long, which might have been caused by the movement of Venus' crust. A large smooth area on the surface could be the remnants of a volcanic lava flow.

During the 1970s and 80s, a number of probes from the Soviet Union landed on Venus and sent back photographs of the surface. Due to the hostile conditions, most of the probes functioned less than an hour. At one site the photographs showed sharp-edged, angular rocks, while smoother regions were visible at another landing site.

In December of 1978, two American Pioneer Venus probes arrived at the planet. One probe began circling Venus, photographing the upper layer of clouds. The other probe survived impact on the surface and sent 67 minutes worth of data from the ground, including evidence of fine dust on the surface. The apparent volcanic features on Venus indicate that it has the widest and therefore the largest volcanic mountains (though not the tallest) in the solar system.

In August of 1990, the Magellan spacecraft was launched into space to begin a series of orbits around Venus. Magellan used a pair of radar instruments to make detailed three-dimensional views of the surface. The craft found that unlike Earth, there was no evidence of continental drift. Over 80% of the planet is covered with volcanic flows.

The images have revealed many of Venus' surface features: craters, mountain chains, volcanic domes and volcanoes that resemble Earth's, and possibly sand dunes. Even with the harsh atmosphere, erosion is very slow on Venus - many surface features are older than 500 million years.

Information Source:  http://www.moreheadplanetarium.org/index.cfm