TODAY, deep-ocean mining is done only by the oil and gas industry. Yet the dream of mining the mineral wealth of the deep has never gone away. Now two firms hope to succeed where others have failed.

Nautilus Minerals, based in Vancouver, is the more advanced of the pair. It has an exploratory licence from Papua New Guinea and has already begun drilling operations 1,600 metres below sea level off the east coast of the country. Another company, Neptune Minerals, based in London and Sydney, has completed test drilling in the deep waters near New Zealand.
Nautilus's deep-water exploration relies on a modified deep-sea remotely operated vehicle (ROV) of the kind normally used in the oil and telecoms industries. It has a manipulator hand containing drilling and cutting tools that allow the robot to retrieve samples of rock from the ocean bed. So far the drilling has only been exploratory, but the prospects look good.
The presence of these rich deposits has been known about for years, says Steven Scott, a geologist at the University of Toronto. He has been researching underwater geology since the 1980s, and in the 1990s he co-discovered the deposit that Nautilus is exploring. So why has it taken so long to move towards the commercial exploitation of deep sea massive sulphide deposits? Mr Heydon says it is because the ROV technology has only recently become capable enough. He eventually hopes to use rock-cutting ROVs that will drive across the sea floor, grinding ore as they go and sending it to the surface via a tube at a rate of 400 tonnes per hour. It might also be possible to lift large deposits using compressed air.

All of this can be done, Mr Heydon believes, for about half as much as opening a new landª²based mine. Nautilus has spent about $12m in the past year on exploration, and Dr Scott says one test drilling found deposits 19 metres deep. Unlike manganese nodules, which are like golf balls scattered across the seabed, these deep-ocean deposits occur in small areas around extinct hydrothermal vents. Such concentrated deposits ought to make underwater mining highly efficient.

Even if the economics stack up, however, Nautilus and Neptune must overcome concerns over environmental damage. Dr Scott argues that underwater mining will be far less disruptive to the environment than terrestrial mining: there will be no piles of waste rock, since the deposits are directly on the sea floor. And whereas the oil industry lays pipelines underwater, mining would not leave any permanent structures behind. But governments will need to be convinced of the merit of these arguments before mining can begin.