NASA has selected a proposal to proceed with Phase B (preliminary design studies) for a Pluto-Kuiper Belt (PKB) mission, intended to explore the most distant planet in the solar system. The mission will also explore the Kuiper Belt beyond Pluto, a source of comets and believed to be the source of much of Earth's water and the simple chemical precursors of life.

The scientific value of this mission is highly dependent on a 2006 launch that achieves a flyby of Pluto well before 2020. In order to ensure this launch date, NASA has established two conditions that must be successfully met at the conclusion of Phase B.

First, the mission must pass a confirmation review that will address significant risks such as schedule and technical milestones and regulatory approval for launch of the mission's nuclear power source. Second, funds must be available. Congress provided $30 million in fiscal 2002 to initiate PKB spacecraft and science instrument development and launch vehicle procurement; however, no funding for subsequent years is included in the administration's budget plan.

The mission, called New Horizons: Shedding Light on Frontier Worlds, is led by Principal Investigator Dr. S. Alan Stern of the Southwest Research Institute, Boulder, Colo. He will lead a team including The Johns Hopkins University Applied Physics Laboratory, Laurel, Md.; Ball Aerospace Corp., Boulder, Colo.; Stanford University, Palo Alto, Calif.; and NASA's Goddard Space Flight Center, Greenbelt, Md., and Jet Propulsion Laboratory, Pasadena, Calif.

"Both proposals were outstanding, but New Horizons represented the best science at Pluto and the Kuiper Belt as well as the best plan to bring the spacecraft to the launch pad on time and within budget," said Dr. Ed Weiler, Associate Administrator for Space Science at NASA Headquarters, Washington. Each team conducted a three-month concept study including management, science content, technical aspects, cost and schedule for a complete mission, including launch vehicle, spacecraft and science instrument payload.

The proposal outlines how the team would undertake the major science objectives defined in the January 2001 Announcement of Opportunity. The spacecraft would use a remote sensing package that includes imaging instruments and a radio science investigation, as well as spectroscopic and other experiments, to characterize the global geology and morphology of Pluto and its moon Charon, map their surface composition and characterize Pluto's neutral atmosphere and its escape rate.

Pluto, the smallest planet, is actually a Kuiper Belt Object, a class of objects composed of material left over after the formation of the other planets. Pluto has large quantities of ices of nitrogen and simple molecules containing carbon, hydrogen and oxygen that are the necessary precursors of life. Given Pluto's weak gravity, these ices would be largely lost to space if Pluto had come close to the Sun. Instead they remain there as a representative sample of the primordial material that set the stage for the evolution of the solar system as it exists today, including life.

"Visiting Pluto and other Kuiper Belt objects would be like visiting a deep freeze containing samples of the most ancient material in our solar system, the stuff that all the other planets including Earth were made of," said Dr. Colleen Hartman, Solar System Exploration Director in NASA's Office of Space Science. "But the most exciting thing about going to an unexplored planet is what we may find there that we're not expecting."

NASA will work with Dr. Stern to further define the costs and to finalize the design of the spacecraft and its accommodation of the instrument sets. Stern, as Principal Investigator, bringing together teams from academia, industry and NASA centers, will lead the PKB mission. It will be implemented following the highly successful management model of NASA's Discovery Program.