Remote-controlled robots will journey to the bottom of the ocean in search of copper, nickel, cobalt, gold, and platinum as global demand for minerals surges. The world's first deep-sea mining operation will kick off in early 2019 when a Canadian firm, Nautilus Minerals Inc., lowers a trio of massive remote-controlled mining robots to the floor of the Bismarck Sea off the coast of Papua New Guinea in pursuit of rich copper and gold reserves. The machines, each the size of a small house, are equipped with rock-crushing teeth resembling the large incisors of a dinosaur. The robots will lumber across...