天上有些旅行者永远让我们充满了恐惧和惊奇。彗星们潜藏在我们太阳系最远的区域，它们在环绕我们太阳运行的过程中不时地抚过地球。但如此具有潜在威胁的东西可能拥有生命的钥匙么? 碳基生命是否来源于它们冰冻的内部? 它们可能包含着我们太阳系诞生的信息吗？
They are celestial travelers which have forever filled us with fear and wonder. Lurking in the furthest reaches of our solar system, comets sometimes brush the Earth as they orbit our Sun. But could something so potentially destructive hold the key to life? Are the building blocks of carbon-based life forms frozen inside? Might they contain information about the creation of our solar system?
At the conclusion of two spectacular NASA missions, COMETS: PROPHETS OF DOOM examines the scientific and historical record of comets, including man's reaction to them. Did a comet lead the Wise Men to Bethlehem? Did they foretell the death of kings, the destruction of civilizations? How did Halley's Comet provide Isaac Newton with the clues for his theories of gravity? Finally, what are these cosmic snowballs made of, and can we protect ourselves if one takes a collision course toward the earth?