Exploring the Solar System

Venus, a burning-desert world hidden under bitter clouds of sulfuric acid and carbon dioxide, may once have been awash with oceans of near-boiling water.

For hundreds of millions of years, most of the water on Venus was liquid near the boiling point. But the water finally dried up, according to three scientists at NASA's Ames Research Center in Mountain View, California, south of San Francisco.

Greenhouse effect. In what they call a moist-greenhouse or wet-greenhouse effect, the Ames team says the water on Venus was able to remain liquid for a few hundred million years because planet temperatures actually were cooler than Earth scientists once thought and because of the proportion of carbon dioxide to water vapor in the atmosphere of Venus.

Venusian seas dried up slowly as hydrogen eventually escaped into space. Oxygen formed compounds with other elements and was incorporated into the planet's crust.

Essential water. Scientists say liquid water seems essential to life. The Ames researchers said the oceans of Venus might still have been liquid at 200 to 300 degrees Fahrenheit because of intense pressure. But that may have been too hot for life to begin. If not, it probably did not last long enough for life to begin.

Venus, nearly Earth's twin in size, has atmospheric pressure on the surface 90 times that of Earth. The temperature on the surface may be as high as 900 degrees Fahrenheit. Venus is the second planet from the Sun, after Mercury. Earth is third. Mars is fourth. There are nine known major planets.

The interplanetary space probe Magellan left Earth in 1989 to fall into orbit around Venus in 1990. It sent back a large volume of spectacular radar images that were used to create a detailed map of Earth's cloud-shrouded sister planet.

Solar System: The Sun
Inner System: Mercury Venus Earth Mars
Outer System: Jupiter Saturn Uranus Neptune Pluto
Other Bodies: Moons Rings Asteroids Comets

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