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To Pluto ... And Beyond!

Spanish Translation

By Michael D. Lemonick

NASA first considered a mission to Pluto more than 15 years ago. The most distant of the nine planets, Pluto, made of rock and ice, has long been considered a small oddball and unlike anything else in the solar system. But when the New Horizons space probe finally takes off to Pluto--as early as this week, if all goes well--it will be heading to a planet with a new image. "This little misfit is now central to our understanding of the origin of our solar system," Alan Stern, lead mission scientist, told TIME.

The reason is that Pluto is not an oddball at all. It's one of thousands of icy space chunks located in a swarm known as the Kuiper (ky-purr) Belt, in a dark, frigid zone 3 billion to 5 billion miles from the Sun. Pluto, it turns out, is not even the biggest of these objects, which astronomers call ice dwarfs. And because these little worlds have been in a deep freeze since the solar system formed more than 4 billion years ago, they are a frozen record of what conditions were like then.

Those ancient conditions are what Stern and his colleagues will try to understand when New Horizons reaches Pluto and its three moons in 2015. As the probe zips by, its cameras will snap pictures of the surface, analyze Pluto's thin atmosphere and take its temperature.

Is Pluto Even a Planet?
The new data won't help scientists decide whether Pluto, which is not as large as the Moon, should keep its title as a planet. Astronomers have found several ice dwarfs that are not much smaller than Pluto. Just last year, they identified an object in the Kuiper Belt that is even bigger than Pluto. Many astronomers argue that if Pluto is a planet, then its bigger cousin (called 2003 UB313, for now) must also qualify. The International Astronomical Union promises to make a decision on Pluto's status, but no one knows when it will come.

Prepare to Be Surprised
New Horizons will be the fastest spacecraft ever, traveling nearly 10 miles per second. At that speed, it could travel from New York to Kansas in just two minutes. It should race past the Moon in nine hours and Jupiter in 13 months and reach Pluto in nine years. The probe will then explore the Kuiper Belt for another five years. It will be launched by a mighty Atlas V rocket, and its flight will be powered by a tiny amount of radioactive fuel that just happens to be called plutonium.

Pluto and the Kuiper Belt have been full of surprises in recent years. And scientists expect the unexpected with the New Horizons mission. For many years, it was easy think of the solar system as nine lonely worlds traveling in neat rings around the Sun. But the harder astronomers look beyond Pluto, the more crowded our cosmic neighborhood seems to become.

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Did You Know?

On Pluto time - A day on Pluto would last 6.4 Earth days. One year on the icy planet would equal 248 Earth years.

Weighty matters - Pluto's gravity is so weak that a man weighing 300 pounds on Earth would weigh just 20 pounds there.

All in the family - Pluto has three moons. Two were found just last year. They are hard to see from 3.5 billion miles away!

Sign our guestbook - The probe carries a CD with the names of 430,000 people who wanted their names to fly through space.

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