Out There - Brief Article

SINCE THE DAWN OF SPACE EXPLORATION, we've tended to think of ourselves as making bold steps into the cosmos, when in fact we've hardly ventured very far at all. The U.S. and Soviet space programs have focused almost everything they've got on the nearest objects in our solar system--the moon, a mere 240,000 miles away; Venus, at 26 million miles; and Mars, 49 million miles away. The next planets in the echelon of the solar system--Jupiter and Saturn--have received much less attention because they're magnitudes farther away--390 million miles and 794 million miles at their closest.

Only two spacecraft--Voyager 1 and Voyager 2--have come close to the outer solar system planets of Uranus and Neptune. And neither probe was really intended to fly that far. Yet the more we begin to discover about the outer planets, as our article in this issue on Neptune reveals, the more they tell us about how Earth and the rest of the inner solar system were formed.

When Voyager 2 first brought Uranus into view in 1986, no one got very excited. The planet hung in the sky as featureless as a balloon. But eight years later, when the Hubble Space Telescope began sending images of Uranus's satellites and rings, a few pictures showed enormous bright spots. "We thought, wait a minute, this is odd--why does Uranus have clouds?" says Heidi Hammel, of the Space Science Institute.

A closer look has revealed a surprisingly active weather system. "Even on our ground-based images, we are seeing the northern hemisphere of Uranus chock-full of clouds" says Hammel. Why, then, did Voyager 2 encounter a sleeping giant? Bad timing, says Hammel: When Voyager 2 went by, it was winter. And because it takes Uranus 84 years to orbit the sun, the winters there last 21 years. Now, however, it's springtime on Uranus. The northern hemisphere is slowly revealing itself to modern astronomers for the first time and has created a stir.

"We never would have noticed this had we not had a few `accidental' shots from the Hubble that forced us to take a closer look," says Hammel. "That's the way it is in astronomy: Serendipity leads you to new discoveries." Well, not just serendipity. Someone has to decide to look. As most of the articles in Discover reveal, curiosity leads to new discoveries too. Our article on Israeli ornithologist Reuven Yosef is a case in point. If Yosef and other bird-watchers in Israel had not chosen to look, no one would have learned that as many as half of Europe's birds depend on a single swamp in Eilat for the survival of their species. Ultimately, survival of our own species may depend on that same sort of curiosity about the heavens above us.

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