Pomona College Magazine
Spring 2004
Volume 40, No. 3

Spring 2004 Contents
PCM Archives

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Related Links
Main: Goodbye Galileo
NOAA Website
NASA Website

  Sidebar: Pluto or Bust

Three billion miles.

Nine years of rocket-powered space flight, just to get to a place where the sun is merely the brightest star in the sky.

Ask Colleen Hartman why she fought so hard to help sell NASA on the upcoming "Pluto mission," and the former director of the space agency's Outer Planets Program doesn't miss a beat.

"I get excited about Pluto because we've never been there," says the relentlessly energetic Dr. Hartman, who spent more than a decade beating the drums for the $488-million "New Horizons" voyage to distant Pluto, now scheduled for liftoff in 2006. "Pluto is the ninth and last planet in the solar system--and it's the only one we've never seen up close. With this mission, we're going to get a glimpse of the tiniest planet in our solar system, and also at the nearby Kuiper Belt. This is a totally new region for space exploration. Who knows what surprises may be waiting for us, three billion miles out there?"

An astrophysicist who's also an accomplished computer engineer, Hartman says she's especially intrigued by the ingeniously conceived power plant that will keep the golf cart-sized Pluto probe racing toward its target.

"The trip to Pluto will be a long, long, cold journey," says the veteran space-explorer, "and the biggest problem you face is finding an energy source that will power the instruments and other devices on board.

"You can't do it with electrical batteries, because they're big and heavy and they don't last very long. And you can't use sunlight, because once you get past Mars, solar radiation falls off rapidly and it becomes far too weak to use for energy."

The solution? "All you need is a radioisotope thermal-electric generator [RTG], which uses decaying radioactive material [plutonium] to produce heat that can be converted into electricity.

"With an RTG, you've got an almost limitless supply of energy to power all the electrical devices on board. And of course, you can also use 'celestial mechanics' to add speed at times, by taking advantage of the 'slingshot effect' produced by gravity, as the spacecraft passes various planets."

So what will the "New Horizons" probe hopefully find in 2015, as it soars within 6,000 miles of Pluto, with a diameter only one-fifth as large as Earth's? "I don't think anyone knows the answer to that question," says Hartman, while noting that some astronomers believe the runt of the solar system may actually be an enormous comet.

"When it comes to Pluto, you're stepping off the edge of the known solar-system world. And that's exactly why I've always been so enthused about this project. You know, when I was a student at Pomona, I used to complain that all the big discoveries had already been made. Galileo had already looked through his telescope, and the microbe-hunters had already discovered germs with their microscopes.

"But after studying the planets for 20 years at NASA, I've come to see how wrong I was, as a student. The fact is, we've barely scratched the surface. We've only begun to understand the planets and the deep space beyond them.

"I think the Pluto mission will be a wonderful way for all of us to keep reminding ourselves about the mystery and the wonder waiting for us, as we continue our quest to explore the universe." 

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