Dave talks to Alan Stern and David Grinspoon, coauthors of Chasing Pluto: Inside The Epic First Mission to Pluto. When Voyager 2 flew by Neptune in 1989, it closed out the golden age of solar system exploration. But it left one unexplored body: Pluto. Stern was part of a group of scientists known as "The Pluto Underground." For years the proposed, lobbied and planned for a robotic mission to what was then, "the ninth planet." The mission that would be eventually called New Horizons went through