NASA's "New Horizons" Pluto mission has reached a milestone.  The exploratory probe is about eight years into a 10-year mission, headed for the outer edge of the solar system.  Alan Stern is associate administrator for the NASA project.

“It sounds like science fiction, but it's not,” Stern says.  “Our spacecraft crossed the orbit of Neptune, headed for Pluto.  We've waited a long time for something like this.”

Stern says we don't really know very much about Pluto

“Pluto has winds,” he says, “it has polar caps, it has a fascinating surface that we know is changing with time -- and atmosphere that is undergoing global change.”

New Horizons launched in January 2006 and should arrive at its destination in two years -- then head into deep space.