X-McShaka

NEW YORK - Other than the hellish heat, a crushing carbon dioxide atmosphere, and corrosive clouds of sulfuric acid, Venus is a lot like Earth, scientists said yesterday.

In a news conference at the Paris headquarters of the European Space Agency, the scientists, working on the agency's Venus Express mission, played up the Venus-as-Earth's-twin angle in presenting their newest findings, including signs of lightning, surprising swings of temperature, and additional evidence that Venus could have once had oceans the size of Earth's.

"They're really twins which are just separated at birth," said Dmitri Titov, the mission's science coordinator. "The key question is why those twins are so different."

Understanding the dynamics and history of Venus's turbulent atmosphere could lead to a better understanding of the role that such heat-trapping gases as carbon dioxide play in shaping the climate of planets, including Earth.

Eight articles describing the observations of Venus Express, the first craft to visit the planet in about a decade, appear in the current issue of the journal Nature.

Venus is roughly the same size, mass, and composition as Earth. And before the space age, planetary scientists imagined an Earth-like environment, perhaps even jungles, obscured by Venus's perpetual cloud cover. But in 1958, when astronomers measured intense microwaves emanating from the planet, they got a hint it was not as lush as they had imagined.

Visits by spacecraft confirmed that the surface temperatures exceed 800 degrees Fahrenheit, hot enough to melt tin. Although Venus is closer to the sun than is Earth, the clouds reflect much of the sunlight, and the high temperatures largely result from the heat-trapping effects of a dense atmosphere that is almost pure carbon dioxide.

Scientists imagine that Venus formed with much liquid water, just like Earth, but that because it is closer to the sun, the water began to evaporate. Water vapor, also a greenhouse gas, trapped heat.

The Venus Express detected bursts of radio waves known as "whistlers," which, at least on Earth, are generated by lightning, and also found large temperature swings between the daytime and nighttime sides of Venus.

BRON