Outer space and silver hair

NASA scientists will grow old, or at least a lot older, waiting for their latest probe to reach its target - Pluto.


There's plenty of gray hair on the heads of scientists leading NASA's New Horizons mission to Pluto. But they all vow they'll still be on the job when their unmanned spacecraft reaches the farthest planet from the sun - in July 2015.

"Yes, we'll all be there," said a confident Glen Fountain, 63, the mission's project manager at the Johns Hopkins University's Applied Physics Laboratory near Laurel, where New Horizons was planned and built.

The team's pledge to stick with the job could become even tougher to fulfill than they'd like. The $700 million project is set to launch Jan. 17 from the Cape Canaveral Air Force Station in Florida - the first flight ever to Pluto and the longest mission ever planned, with the fastest spacecraft ever.

But so vast is the distance - Pluto averages 3.7 billion miles from the sun, about 40 times farther than Earth - that a four-week delay in launch would cost the mission's silver-haired captains five additional years, until 2020, before their work pays off. An extended mission to regions beyond Pluto could add seven more years.

They're more than willing to wait. As dark, cold and far away as it is, "Pluto is a treasure trove of scientific discoveries waiting to be uncovered," Andrew Dantzler, 43, director of NASA's solar system division, told reporters this week at NASA headquarters.

Pluto is unlike any other planet in the solar system, he said, and "as such, it holds many clues to how the solar system was formed, also perhaps how other systems formed."

It was the last of the nine planets to be discovered - in 1930 by the American astronomer Clyde Tombaugh. It orbits the sun at distances ranging from 2.8 billion to 4.6 billion miles.

If Earth were in Baltimore, and Mars (at its closest) were 40 miles away in Washington, D.C., a spacecraft would have to fly 4,000 miles - to Geneva, Switzerland - to reach Pluto.

Thanks to that distance and Pluto's tiny size, even the Hubble Space Telescope has managed only the crudest images of the planet's mottled surface. Its largest moon, Charon, wasn't discovered until 1978. Hubble scientists spotted two more moons only last May.

So planetary scientists are understandably impatient for a closer look at this oddball planet. Smaller than Earth's moon, Pluto circles the sun once in 248 Earth years. It is neither a rocky planet like Mercury, Venus, Earth and Mars, nor a gas giant like Jupiter, Saturn, Uranus and Neptune.

Instead, it's made mostly of rock, plus water, nitrogen, carbon monoxide and methane, all frozen solid at minus-387 degrees Fahrenheit. In 1988, scientists discovered that some of Pluto's ices escape as gas to form a tenuous atmosphere that changes with the planet's seasons.

The mission's top scientist, Alan Stern, 48, of the Southwest Research Institute in Boulder, Colo., described Pluto as "a scientific wonderland for atmospheric scientists."

Is it a planet?

Even so, planetary experts have long debated whether Pluto is even a planet.

In the 1950s, Dutch-American astronomer Gerard Kuiper suggested Pluto might actually belong to a population of ice balls thought to orbit the sun beyond Neptune. He theorized that the icy realm is the source of comets that periodically zip through the inner solar system.

Since 1992, astronomers have found more than 1,000 of these objects, more than 5 billion miles from the sun, in what they now call the "Kuiper Belt." They range in size from 30 to 1,250 miles across.

"So this class of planets, which we have not yet reconnoitered, is in reality the most populous class of planetary bodies in our solar system," Stern said.

Although some astronomers argue that Pluto isn't a planet but rather the king of the Kuiper Belt objects (KBOs), Stern insists the big KBOs have now qualified as planets instead, like Pluto. Which would give our solar system far more than the nine planets identified in science textbooks.

"Pluto looked like a misfit because it was the only one we saw," Stern said. But "just as a Chihuahua is still a dog, these ice dwarfs are still planetary bodies."

They qualify, he said, because they're large enough for their own gravity to pull them into a spherical shape. "They've surely passed the test for planethood," he declared.

Scientists' fascination with Pluto and the KBOs is rooted in the notion that these objects are frozen keys to the solar system's formation 4.5 billion years ago.

That's why the National Academy of Science ranked a mission to Pluto, and the Kuiper Belt beyond, as the highest priority for U.S. space science in this decade.

The challenge for APL's designers was to build a spacecraft that could survive a 10- or 15-year journey through the coldest, darkest reaches of the solar system and arrive ready to work.

Swift traveler

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