From massive asteroids and deadly bursts of radiation to microscopic alien viruses, each one of these cosmic dangers may end human civilization as we know it. Can we prepare for the inevitable calamity that may be coming our way? Or are we doomed to oblivion?

Earth's moon is only one of hundreds in the solar system--each of them a mysterious and often bizarre world. Could alien moons offer a key to exploring outer space and perhaps even finding a new home for humanity?