The world’s long-overdue, fitful transition to renewable energy is hobbled by an Achilles’ heel: It requires staggering quantities of natural resources. Manufacturing enough electric vehicles to replace their fossil-fueled counterparts will require billions of tons of cobalt, lithium, copper, and other metals. To meet the exploding demand, mining companies, carmakers, and governments are scouring the planet for potential mines or expanding existing ones, from the deserts of Chile to the rain forests of Indonesia. Meanwhile, what might be the richest source of all—the ocean floor—remains untapped. The US Geological Survey estimates that 21 billion tons of polymetallic nodules lie in a single region of the Pacific, containing more of some metals (such as nickel and cobalt) than can be found in all the world’s dryland deposits.