It's hard to imagine that large meteorites colliding with Earth with the power of 20 Hiroshima bombs can bring anything but cataclysm. Ever since a link was made between meteorite impacts and mass extinctions on Earth, we have feared rogue asteroids destroying our planet. There is no doubt, these objects can be takers of life - but is it possible that giant asteroid impacts were actually essential for the creation of life on Earth NOVA follows a series of discoveries behind a remarkable theory of how the violent destroyers of life could also have created the very special conditions - of chemistry and energy - that made life possible in the first place.