They soar through the heavens, fly through the oceans and glide along land. But these are not creatures found on a wildlife safari. These are life forms from another planet. Armed with scientific fact and a little imagination, experts come together to take you on an unprecedented journey to the edges of our imagination.

Right now cosmic forces prowl the universe and threaten man's very existence. They're asteroids and comets; they've left their imprint on planet Earth, literally. Initially helping to build planets through violent collisions, during this fiery bombardment period they may have even seeded Earth with water and the building blocks for life. Since the turbulent formation of the solar system, these space rocks have continued to impact Earth. Some have been so violent that they've led to mass extinctions, including one that wiped out the dinosaur. New theories suggest that asteroid and comet dust harbour deadly viruses that may have triggered some of our worst pandemics. The possibility of future collisions remains a legitimate threat yet despite their dangers, asteroids and comets may hold vital natural resources, which could actually preserve

When mankind eventually leaves the cradle of Earth and ventures forth into the uncharted territories of the cosmos, where, and what form, will our new homes take?

It sounds like a Hollywood blockbuster: a deadly asteroid is on a collision course with Earth. But in reality, it's only a matter of time before a giant space rock threatens to wipe out civilization. An asteroid took out the dinosaurs sixty-five million years ago. Are we next? This episode analyzes the threat and explores the many ways--from a nuclear bomb to ingenious new technology--that experts are proposing to stop Armageddon

The story begins with Tyson sitting at a campfire, and telling how the wolf changed through artificial selection, and selective breeding into the dog breeds around today. He then enters the Ship of Imagination, and explains natural selection with the process that helped to create the polar bears. Along the way he talks about DNA, genes and mutation. Next he goes to a forest and describes the Tree of life, this leads him to discussing the evolution of the eye. He then discusses extinction, by going to a monument called the Halls of Extinction, dedicated to the broken branches of the tree of life. Explaining the five great Extinction events. He then tells how some life has survived, and then focuses on the tardigrade. From there he talks about what other kinds of life might have been created on other worlds. He then goes to Saturn's moon Titan. From there he speculates about life and how it first began. He then returns to Earth and tells about abiogenesis and how life changed and evolved. The show ends with an animated sequence from the original series of life's evolution from one cell to humans.

No planet beats Saturn for jaw-dropping beauty. Saturn is the most photogenic planet in all the solar system. Some of the pictures are to die for. But the postcards only tell part of the story. It really is rolling and seething inside. For ringside action, soar above the planet with its six-sided storms. Even more mystery surrounds the impressive Fountains of Enceladus where the secrets of life might spring from the moons salty geysers. And the samples are coming out in space, there's a big sign there: Free Samples: Take One.