In and exclusive interview for The Sky at Night, Patrick Moore talks to Mike A'Hearn, the NASA scientist behind the spectacular Deep Impact mission. With amazing precision, he sucessfully designed an impactor to hir the fast moving coment Tempel-1. Its success has revealed new information about our Solar System.Also, the new Horizon mission will soon leave for the distant planet Pluto. Patrick Moore finds out more about this daring mission to thw edgo of our solar system and discusses whether Pluto is a planet or just another large Kuiper Belt object.