Hera will take a close look at asteroid rammed by NASA spacecraft 2 years ago
                                
                                
                                    (Newser) -
                                    A spacecraft blasted off Monday to investigate the scene of a cosmic crash. The European Space Agency's Hera spacecraft rocketed away on a two-year journey to the small, harmless asteroid  rammed by NASA  two years ago in a dress rehearsal for the day a killer space rock threatens Earth,...