Up to 6,000 metres (19,700 feet) beneath the surface of the Pacific Ocean between Mexico and Hawaii, billions of potato-shaped metallic nodules are scattered across the seabed. The Clarion-Clipperton zone’s reserves of vital metals such as nickel, cobalt and manganese could surpass the total known reserves on land, according to some estimates. While no commercial mining has yet taken place on the underwater plain, the International Seabed Authority has issued 17 exploration contracts for the...