From its outpost on the solar system’s far frontier, Pluto tantalizes would-be explorers with its remoteness and mystery. This is the maverick planet: the farthest, the smallest, the darkest, the coldest, and arguably the strangest. Oddball Pluto is neither a terrestrial world (like Mercury, Venus, Earth, and Mars) nor a giant ball of gas (like Jupiter, Saturn, Uranus, and Neptune) but the sole member of its own planetary category--an ice dwarf fashioned from the dregs of the great whirling nebula of gas and dust that condensed to form the sun and the rest of the planets some 5 billion years ago.
Pluto is the last unexplored planet in the sun’s entourage. But now, at long last, NASA visionaries propose to send a low-cost, high- audacity mission--the Pluto Fast Flyby--to scrutinize the planet from close range. At least one scientist at the Jet Propulsion Laboratory (JPL) in Pasadena has fondly described the flyby as a cannonball carrying a camera and a radio. In fact, there will be two cannonballs. The Pluto Fast Flyby will be a double-duty mission consisting of twin spacecraft that will rendezvous with Pluto within one year of each other, taking two looks at a world overlooked for too long. Lean and hell-bent as marathon runners, the tiny spacecraft must race through the planning and design stages to the launchpad before the end of this decade and then beat a direct trajectory to Pluto in six or eight years--quick--before the atmosphere that currently envelops the planet freezes and falls to the surface as some exotic breed of snow.
If the mission doesn’t fly before the snow falls, astronomers will miss altogether the chance to study the atmosphere. It will have vanished. Astronomers base this bizarre weather forecast on Pluto’s present motion away from the sun: in the course of the planet’s 248-year orbit, an atmosphere of methane and nitrogen apparently bubbles out of the surface when the sun is close by, only to freeze solid again soon afterward. Pluto thus behaves somewhat like a comet, sprouting new parts near the sun’s light and heat. No other planet does that. No wonder such excitement attends the effort to go there.
The impetus for the Pluto Fast Flyby came from a postage stamp, of all things. In 1991 a series of stamps commemorating U.S. space exploration matched the planets with their spacecraft visitors: Mars- Viking, Jupiter-Pioneer, Neptune-Voyager, and so on. Only Pluto, engraved in seafoam green, hung alone against the black backdrop of space, above the legend pluto not yet explored.
That bothered me a lot, recalls Robert Staehle, now the Pluto team’s manager at JPL. He immediately began pushing for a mission to explore Pluto and discovered that he was not alone in his wish to visit the planet--that there was, in fact, an active Pluto underground of researchers scattered across the country, dreaming up mission strategies and itching to go. Staehle became the catalyst for this community. An engineer committed to NASA’s renewed interest in small, speedy spacecraft that can be built on the cheap, he was able to pull together the ideas of many people to shape a plausible Pluto initiative.
