We couldn't survive without it - and in this episode, Naked Science reveals the scientific marvel of the Earth's unique and complex atmosphere. A precariously thin but vital blanket of air, see how a chance interplanetary collision and a remarkable plant mutation created the only planet in the solar system with an atmosphere rich in oxygen - the potent gas that powers our planet. This episode explores how the atmosphere carries rivers of life-giving water and acts like an invisible wall against deadly space matter. Then, meet the only man to have ever braved its hostile upper reaches... and survived!