The deepest parts of Earth's oceans are known as the hadal zone. Named after Hades, the Greek god of the underworld, it is a forbidding place worthy of its name. Consisting of deep trenches and troughs, it extends 11km (6.8 miles) below the surface of the world's oceans. Cumulatively they account for an area of seabed equivalent to the size of Australia. Yet few vehicles can survive plunging into this dark abyss.
