In 2015, a spacecraft calledNew Horizonsflew by Pluto at 32,000 miles per hour, taking pictures all along the way.Alan Sternled the planning of the mission for NASA, and he joins us to talk about the years of work that went into sending the New Horizon more than 3 billion miles from Earth. His new book, written with astrobiologistDavid Grinspoon, is called“Chasing New Horizons: Inside the Epic First Mission to Pluto”(Picador).