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.

• Venus is the sixth largest planet and only slightly smaller than Earth.
• The second planet from the Sun, Venus is about three-fourths of Earth's distance from the Sun.
• Venus' surface temperature is around 780 degrees Fahrenheit.
• The planet looks white and featureless because the atmosphere completely hides the hot, rocky surface of Venus and traps the heat.
• The atmosphere is mostly carbon dioxide.
• Layers of clouds surrounding Venus contain sulfuric acid.
• Venus has been called Earth¹s sister because the two planets are similar in many ways.
• The two planets are made from similar materials such as rock.
• Unlike Earth, Venus has no moons.
• Venus is 67,230,000 miles from the Sun.
• The diameter of Venus is 7,521 miles.

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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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