TV-PG
S3 • E6 Dec 16, 2008 45m6.8
At this very moment, celestial forces prowl the Universe and threaten man's very existence. They're asteroids and comets--and they've left their imprint on planet Earth, literally. Initially, they helped build planets through violent collisions. During this fiery bombardment period, they may have even seeded Earth with water and the building blocks for life.
