Media playback is unsupported on your device Media caption The concern is for the impact mining could have on ecosystems

A new and controversial frontier in mining is opening up as a British firm joins a growing rush to exploit minerals in the depths of the oceans.

UK Seabed Resources is a subsidiary of the British arm of Lockheed Martin.

It has plans for a major prospecting operation in the Pacific.

The company says surveys have revealed huge numbers of so-called nodules - small lumps of rock rich in valuable metals - lying on the ocean floor south of Hawaii and west of Mexico.

The exact value of these resources is impossible to calculate reliably, but a leading UN official described the scale of mineral deposits in the world's oceans as "staggering" with "several hundred years' worth of cobalt and nickel".

An expedition to assess the potential environmental impact of extracting the nodules will be launched this summer amid concerns that massive "vacuuming" operations to harvest the nodules might cause lasting damage to ecosystems.

With the support of the British government, UK Seabed Resources has secured a licence from the United Nations to explore an area of seabed twice the size of Wales and 4,000m deep.

Under the UN's Convention on the Law of the Sea, mining rights on the ocean floor are controlled by a little-known body, the International Seabed Authority, which since 2001 has issued 13 licences - with another six in prospect.

These licences, valid for 15 years, have been bought for $500,000 each by government organisations, state-owned corporations and private companies from countries including China, India, Russia, Japan and South Korea.

The high prices fetched for copper, gold and rare-earth minerals are leading to a surge in interest in mining the ocean floor. The idea first surfaced in the 1970s but was dropped because the costs were too high and the technology could not cope.

The nodules are known to contain up to 28% metal - 10 times the proportion found on land.

Image copyright NERC Image caption The chimneys contain many metals in high abundance

A similarly high metal content is found in another target for seabed mining: hydrothermal vents, chimneys formed by extremely hot water, rich in minerals. We reported on the discovery of the world's deepest vents last month.

Stephen Ball, chief executive officer of Lockheed Martin UK, owner of UK Seabed Resources, says the engineering experience of offshore oil and gas operations and the trend to rising mineral prices have now combined to make seabed mining feasible.

"It's another source of minerals - there's a shortage and there's difficulty getting access, so there's strategic value for the UK government in getting an opportunity to get these minerals," he told the BBC.

China's domination of the global production of rare-earth minerals in particular has fuelled the search for other sources of materials essential for everything from electronics to wind turbines.

But many marine scientists and conservationists have warned that the implications of this deep-sea gold rush are not yet understood - and that mining nodules or hydrothermal vents could prove catastrophic for seabed ecology.

Mr Ball said exploration over the next three years would establish whether a system to vacuum up the nodules could be designed to cause minimal impact. The nodules typically lie in a shallow layer of silt.

He said he believed it would be "perfectly feasible to create a benign method to extract these minerals from extreme depths without disturbing the seabed."

"But until we've demonstrated that, there will be a debate around that."

One risk is that the mining operations could generate huge plumes of sediment that could drift through the sea - choking any marine life that feeds by ingesting water and filtering out its food sources.

Michael Lodge, general counsel for the International Seabed Authority, told me that the authority's aim was to encourage a new mining industry to exploit seabed minerals but within strict environmental controls.

"The nodules are generally lying in sediment that is between 2-6in (5-15cm) thick that's been there undisturbed for millions of years. We simply don't know the recovery times or the distribution of species - there are lots of uncertainties."

He described mining hydrothermal vents as "more invasive" because it would involve breaking up the uppermost metre of the sea floor and piping the rock fragments to the surface.

Cold War heritage

A Canadian company, Nautilus Minerals, is hoping to be the pioneer of vent mining with plans for operations off the coast of Papua New Guinea. However, work is currently delayed because of a legal dispute. The concern is for the impact mining could have on ecosystems

Nautilus would use massive robotic machines, which are being built in Wallsend, near Newcastle-upon-Tyne, by a firm with long experience of marine engineering, Soil Machine Dynamics.

Nautilus says that it is devising strategies for minimising the environmental impact, by trying to contain any disturbed sediment and leaving parts of the seabed untouched so the mined area can be recolonised by marine life.

A leading biologist, Professor Cindy Van Dover of Duke University in North Carolina, has carried out research for Nautilus and says life might recover after a single mining event but that no-one can be sure.

"How do we do this so a hundred years from now somebody doesn't look back at us - at me - and say 'Oh my God, I can't believe they were so stupid and let this happen in a particular way'.

"So how do we do it right? How do we do it sustainably?

Michael Lodge has also said questions will remain about profitability while the final terms of mining licences are settled.

The authority was set up to encourage and manage this new sector but any future business, such as the Lockheed Martin subsidiary UK Seabed Resources, will have to pay royalties to the authority to be distributed to developing countries. The exact details have still to be negotiated.

Research into seabed minerals has a long and slightly conspiratorial history, starting in the Cold War with the United States and the Soviet Union surveying the oceans ahead of possible future conflict.

Surveys of seabed nodules in 1970s were also used as a cover by the US for the secret retrieval of a lost Soviet submarine.

Now, the legacy of all that research and exploration is the growing likelihood of large-scale mining operations, fuelled by rising mineral prices, in many parts of the ocean in the coming decades.

Follow David on Twitter