Last April, engineers on a ship in the middle of the Pacific Ocean held their breath as a 25-tonne mining tractor lay stranded on the silty ocean floor, more than 4km below the surface. On the 13th and final trial dive of a world-first experiment, a robot had broken free of its tether and lay in some of the darkest waters on Earth. “I’m not superstitious,” Kris De Bruyne, engineer and project manager with Belgium’s Global Sea Mineral Resources (GSR), told a science conference examining the impact of deep-sea mining. “But I will never name a dive ‘thirteen’ again.” A remote underwater vehicle helped engineers regain control within days as independent scientists watched on. But the incident galvanised public resistance to mining the deep seas.
Having lain undisturbed for millennia, the murky depths of the Pacific will be busy in the coming years, as prospectors put their deep-sea mining machines – which some have compared to giant vacuum cleaners – through...