Venus Planet

Venus, the second planet from the Sun, is the hottest world in the solar system. It is blanketed by a thick atmosphere that heats its surface like the inside of a greenhouse. But with a surface temperature of almost 900 degrees Fahrenheit (480 C), this place is no garden!

Other than its atmosphere, Venus is so similar to Earth that it is sometimes called Earth's sister planet. Its diameter and mass are almost identical to Earth's. Why, then, is it so hot?

The "greenhouse effect" on Venus is caused by its atmosphere. Energy from the Sun passes through the atmosphere to the planet's surface, where it is absorbed and reradiated at longer wavelengths (as heat). Venus' atmosphere traps these longer wavelengths so they cannot escape into space. The trapped heat builds up, so the planet grows hotter and hotter. The same thing happens in an automobile on a hot day. Sunlight comes through the windows and warms the inside of the car, but the heat is trapped.

Even though Venus' orbit brings it closer to Earth than any other planet, its blanket of clouds kept much of Venus a mystery. But space probes sent by the Soviet Union and the United States, as well as studies with ground-based radar, have allowed astronomers to "see" the surface of Venus for the first time. The first exploration of Venus by radar was in 1962. It revealed that Venus spins backward on its axis. If you could stand on the surface of Venus, and if you could see the Sun through the cloud cover, it would rise in the west and set in the east.

Space probes have revealed that the atmospheric pressure at the surface of Venus is 90 times that of Earth's. This atmosphere consists mainly of carbon dioxide -- the same gas that puts the fizz in soft drinks. It is not breathable. In addition, the clouds of Venus contain drops of sulfuric acid, a poisonous chemical.

Daytime on Venus is about as bright as a cloudy day on Earth, and the winds on the ground are gentle. Gravel and flattened boulders are scattered over the plains. Because of the heat and pressure on Venus, no probe landing there has ever survived for more than an hour.

More recent radar observations by the Magellan spacecraft have allowed scientists to peek through the clouds and map almost the entire surface of the planet. Magellan discovered mountains on Venus that are higher than any on Earth, as well as a valley that is longer and deeper than the Grand Canyon. It also revealed that the surface of Venus may contain active volcanoes, which occasionally vent molten rock and gas into the hellish atmosphere.

Because of Venus' heavy atmosphere, the planet's surface pressure is very high. Pressure is defined as the weight of the atmosphere pressing down on you. On Earth, we don't notice the air pressure at all. The thick atmosphere on Venus