Front Page > Science & Space Pluto Mission Takes Aim at Last Unvisited PlanetBrian HandwerkNational Geographic News February 15, 2005 Amateur astronomer Clyde Tombaugh discovered Pluto 75 years ago this week. The last planet found in our solar system remains the only one never visited by an Earth probe—but NASA's New Horizons mission hopes that distinction won't last much longer. "We're planning on a launch in January of 2006," said program executive Kurt Lindstrom from NASA's Washington, D.C., headquarters. "This year we are assembling [the spacecraft] and beginning testing." If the mission launches on time, the craft would reach...