Every object in our Solar System that takes the plunge from out beyond Neptune to our inner reaches, where the rocky planets lie, will become a comet. As it nears the Sun, its ices melt, creating the tails we associate with them, and also creating a debris path that can create meteor showers if they cross Earth's orbit. For thousands of years, the most consistent, spectacular meteor shower has been the Perseids, created by Comet 109P/Swift-Tuttle. At its incredibly large size (26 kilometers across) and speed, it contains nearly 30 times the energy of the asteroid strike that wiped out...