In their decade-long struggle to extend space exploration to distant Pluto, planetary scientists claimed a partial victory last Thursday when NASA announced it has chosen a final spacecraft design for the mission. The winning entry, dubbed New Horizons, was submitted by a multi-institution team led by S. Alan Stern (Southwest Research Institute) and the Johns Hopkins University's Applied Physics Laboratory. It bested four competing proposals, including another finalist called POSSE (Pluto and Outer Solar System Explorer).

The announcement came a few weeks earlier than expected, catching Stern and several hundred colleagues by surprise during a meeting of planetary scientists in New Orleans. Getting to Pluto is "the most important piece of unfinished business in solar-system exploration," says Andrew Cheng, APL's project scientist for this effort. Stern concurs, adding, "It's more than just the last planet — it's a different kind of object." In addition to its reconnaissance of Pluto and its moon, Charon, the New Horizons spacecraft is expected to study Jupiter intensively and to visit two or three objects in the distant Kuiper Belt, of which the ninth planet may be the largest member.

With an estimated cost of $288 million, the mission plan calls for a single spacecraft launched in January 2006. A slingshot flyby of Jupiter will shorten the travel time by many years, setting up a close brush with diminutive Pluto as early as 2016. According to Stamatios M. Krimigis, who heads APL's space division, the probe will inherit the "mature, highly redundant system design" utilized in the forthcoming Contour (Comet Nucleus Tour) spacecraft. New Horizons will be equipped with four instruments — including two imagers — for analyzing surface features and atmospheric compositions. Team members include Patsy Tombaugh, whose late husband, Clyde, discovered Pluto in 1930; and Bill Nye, "the Science Guy."

Congress has already authorized $30 million for one year to begin development, but the mission selection will become little more than symbolic unless the political climate for outer-planet exploration changes. A year ago the Bush administration proposed deferring the Pluto effort for at least a decade, arguing instead for a dedicated mission to the Jovian moon Europa and the development of advanced propulsion technologies for outer-planet exploration. But buoyed by lobbying campaigns and strong public support, Congress kept the prospects for Pluto alive. Despite the looming budgetary fight, Stern remains optimistic. "Pluto is my life's work," he says. "I'll do whatever it takes to get this to the launch pad."