Probing Pluto and beyond

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In what could be considered an ironic twist in NASA's evolving role, unmanned missions to the farthest reaches of the solar system are providing more excitement and knowledge than manned missions. Perhaps that's because these days astronauts traveling into low-earth orbit on an aging shuttle fleet act more like mechanics and ferry operators, while clunky robots like Stardust and Deep Impact are expanding humanity's understanding of the universe. This is quite a reversal from the intensity of the space race several decades ago, when astronauts like Neil Armstrong, not robots, were seen as heirs to the legacy of Columbus and Magellan.

This week, the capsule Stardust returned to earth after a seven-year, 2.9-billion-mile mission collecting particles from the comet Wild 2's coma -- the cloud of debris that emanates from a comet's icy surface. Because scientists believe comets remain virtually unchanged since the formation of the solar system -- some 4.5 billion years ago -- they hope that their first look at these particles will yield tantalizing results. "It's hard to describe what it feels like," said one lead scientist. "It's an incredible thrill." When was the last time a NASA scientist felt such enthusiasm after a shuttle mission?

Six months ago, the Deep Impact spacecraft met up with the asteroid Tempel 1, dropping a probe into the asteroid's trajectory. The resulting collision bored a crater into Tempel 1's surface, while the nearby spacecraft captured photographs and collected debris. As with comets, scientists hope their study of asteroids will broaden our understanding of the solar system's origins (not to mention offering more practical knowledge, like how to take out an asteroid headed toward Earth).

And today, NASA hopes to launch its New Horizons spacecraft from Cape Canaveral. The expected nine-year journey will take New Horizons 3 billion miles from Earth, traveling at speeds never before reached by a manmade craft (47,000 mph), to rendezvous with lonely Pluto, the last of the solar system's nine planets yet to be explored.

The combined cost of these three missions is about $1.3 billion, or just around the average cost of a single shuttle mission. That's still not exactly cheap, but the contrast should be considered as NASA struggles to justify the shuttle's relevance (especially when the success of a shuttle mission, at least to the general public, is determined by whether all astronauts return safely).

More importantly, robots should not be hogging all the glory. NASA must expedite the shuttle's phaseout and get to the business of realizing the president's goal of putting a man on Mars.