Neptune is assessing deposits to which it holds the rights in territorial waters north of New Zealand's North Island. Nautilus and its joint-venture partner, Placer Dome - a Canadian gold-mining company - are collecting samples from a deposit to which Nautilus holds the rights in the Bismarck Sea off the eastern coast of Papua New Guinea.

Speaking at the American Association for the Advancement of Science annual meeting, Scott said the big question for the companies is the economic potential of undersea deposits of polymetallic sulfides, sulfur-rich seafloor ore bodies produced worldwide in underwater volcanic regions by structures called black smokers.

Black smokers form when seawater seeps into the porous sea bottom, is heated and re-emerges through vents carrying dissolved minerals. When hot water hits cold seafloor water, the minerals precipitate, creating the chimney-like towers. Over time, the towers collapse and accumulate to form ore deposits, some of which are rich in gold, silver, copper, lead and zinc.

Scott was the first mining geologist to explore black smokers. In 1982 he joined members of the Scripps Institute of Oceanography and the Woods Hole Oceanographic Institution in the submersible Alvin to explore newly discovered black smokers 2,000 meters below the waves in the Gulf of California off the coast of Mexico. He said that after more than two decades of promoting the possibility of mining the deposits created by black smokers, the present ventures represent a move that has required mining companies to cross a watery psychological barrier.

"Twenty years ago," he said, "most mining companies didn't want to hear about this possibility. They thought it was too difficult, but now some are seeing that it's a lot easier to go down through a couple of thousand meters of water than through a couple of thousand meters of rock."

Scott said that at present, the deepest undersea mines - diamond mines off the coast of southern Africa - are under just a few hundred meters of water, but the offshore oil and natural gas industry has developed technologies that can extend that range significantly.

The oil and gas industry went offshore in a major way in the mid-1940s. Today, about one-third of the world's oil comes from under the sea. There are producing wells in 1,500 meters of water off the coast of Brazil, and there is drilling some 2,500 meters down in the Gulf of Mexico.

The key challenge is developing technology to extract mineral ore from the depths. Scott said he envisions the use of "deep sea versions of robotic coal mining machines," which pipe ore up to mining ships, or semi-submersible platforms such as those used by the offshore oil industry. He said deep-sea robotics is a mature industry, driven in large part by the needs of offshore oil exploration and recovery.

Deep-sea mining technology was given a major kick-start by the approximately $650 million spent internationally in an aborted effort to develop sea floor manganese nodule mining technology in the 1970s and '80s. Manganese nodules, often rich in nickel and copper, are formed by the slow precipitation of the minerals from seawater. The nodules cover vast areas of the deep ocean floor known as the abyssal plains.

Scott said he initially was drawn to black smokers as a way of understanding the formation of polymetallic sulfide deposits on dry land, such as those mined at the Kidd Creek copper and zinc mine in northern Ontario, and in many other countries in the world, including the United States.

"We wanted to know whether marine geology held clues for the occurrence of these terrestrial deposits - and it does," Scott said, adding that one of his postdoctoral students has returned from a vessel drilling Nautilus claims off the Papua New Guinea coast. She is exploring the role that bacteria play in creating these mineral deposits.

"Getting samples from the interior of these deposits is rare," Scott said. "What we're interested in from the perspective of pure science is what microorganisms are in these deposits and what they're doing. Are they in fact causing mineralization?"

Regarding environmental impact, Scott said he thinks deep undersea mining could be less damaging than terrestrial mining. "The ocean mining companies are going to have environmental problems like there are with any industrial process," he said. "There's understandably going to be legitimate concern from many in the public."

Seafloor mining avoids many of the problems associated with terrestrial mining, however, Scott continued. There is no acid mine drainage, because acids are neutralized by the alkaline seawater. Because sulfide deposits sit on the sea floor, they require no excavation or waste-rock piles, and no permanent structures would be left behind. The mining also would not touch active black smokers, regions known to support a rich diversity of submarine life.

Scott said although he sees their economic potential, he also supports protecting black smokers. He has advocated establishment of the world's first deep-ocean park, the Endeavour segment of black smokers along the Pacific submarine Juan de Fuca Ridge, off Canada's west coast.

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