Book excerpt: Rain of Iron and Ice shows us the unmistakable evidence—from spaceprobe flybys of the planets to the scars on our own Earth—of cataclysmic comet and asteroid impacts. By comparing what we know about the earth's geology and paleontology with the ages of the other planets and moons in our solar system, Lewis makes the strongest case yet for sudden, dramatic extinctions and assesses the risks to planet Earth.