Into The Abyss

Rebecca Morelle talks to explorers of deep ocean trenches, from film-maker James Cameron to biologists discovering dark realms of weird pink gelatinous fish and gigantic crustaceans.

The deepest regions of the ocean lie between 6,000 and 11,000 metres. Oceanographers term this the Hadal Zone. It exists where the floor of abyss plunges into long trough-like features, known as ocean trenches. The hadal zone is the final frontier of exploration and ecological science on the planet.

At its most extreme, the water pressure rises to 1 tonne per square centimetre and the temperature drops to 1 degree C. Despite the challenging conditions, some animals survive and thrive in the trenches. Because the technical challenges to operating down there are so high, we are only now just learning what is down there and how creatures adapt to live in the extremes.

Based at the University of Aberdeen in Scotland, deep sea ecologist Alan Jamieson is one of the premier explorers of life in the hadal zone. In the programme, he talks through some of the latest video footage he's acquired from the depths of the Kermadec Trench in New Zealand - not by visiting in person but by dropping cameras on a deep sea probe called a hadal lander to the distant sea floor. The images were gathered on an expedition two months ago and revealed new habits of hadal creatures.

Rebecca does talk to two people who have ventured to the far limit of the hadal zone: US Navy Lieutenant Don Walsh who went down to the bottom of Challenger Deep in the Mariana Trench in 1960, and Hollywood director James Cameron who, 52 years later, repeated Walsh's voyage to 11,000 metres down.

Exploring the ocean's deepest realm: the hadal zone, from 6,000 to 11,000 metres down.

Series taking listeners down to the deepest parts of the ocean.

Rebecca Morelle talks to explorers of deep ocean trenches, from film-maker James Cameron to biologists discovering dark realms of weird pink gelatinous fish and gigantic crustaceans.

The deepest regions of the ocean lie between 6,000 and 11,000 metres. Oceanographers term this the Hadal Zone. It exists where the floor of abyss plunges into long trough-like features, known as ocean trenches. The hadal zone is the final frontier of exploration and ecological science on the planet.

At its most extreme, the water pressure rises to 1 tonne per square centimetre and the temperature drops to 1 degree C. Despite the challenging conditions, some animals survive and thrive in the trenches. Because the technical challenges to operating down there are so high, we are only now just learning what is down there and how creatures adapt to live in the extremes.

Based at the University of Aberdeen in Scotland, deep sea ecologist Alan Jamieson is one of the premier explorers of life in the hadal zone. In the programme, he talks through some of the latest video footage he's acquired from the depths of the Kermadec Trench in New Zealand - not by visiting in person but by dropping cameras on a deep sea probe called a hadal lander to the distant sea floor. The images were gathered on an expedition two months ago and revealed new habits of hadal creatures.

Rebecca does talk to two people who have ventured to the far limit of the hadal zone: US Navy Lieutenant Don Walsh who went down to the bottom of Challenger Deep in the Mariana Trench in 1960, and Hollywood director James Cameron who, 52 years later, repeated Walsh's voyage to 11,000 metres down.

Exploring the ocean's deepest realm: the hadal zone, from 6,000 to 11,000 metres down.

Series taking listeners down to the deepest parts of the ocean.

The deep ocean contains extraordinary ecosystems, full of life forms found nowhere else on the planet. Some of those same habitats are unusually rich in valuable minerals. Could we and should we mine them?

Hydrothermal vent systems are one of the deep ocean habitats which have gained the interest of mining concerns. Volcanically-heated water gushes from the sea floor. The chemically-charged water sustains unique ecosystems, the like of which aren't seen anywhere else on Earth. There are gigantic worms and clams which are nourished by bacteria within their tissues - the bacteria themselves are fuelled by chemicals in the water, in the way plants on the surface use light. There are vast swarms of blind, heat-guided shrimps.

The superheated waters are also rich in metals such as copper, silver and gold which crystallise when the hot water meets the cold ocean. Great chimneys of metallic ores and rock form in this process. The concentration of metals is typically much higher than those of terrestrial ore deposits. Mining companies are keen to exploit them if the costs of extracting them from deep beneath the waves are favourable. Given growing demand from an increasingly industrialised world, the corporations believe the profits are set to outweigh the costs. Underwater robotic bulldozers and monster sized vacuum cleaners are ready for their first deployments and operations.

Many marine biologists view these prospects with alarm. The impact of mining on hydrothermal vents and other mineral-rich deep sea habitats will destroy life in the immediate extraction areas and may cause unknown kinds and scales of damage down current and distant from mining areas. The pace of life and its rate of recovery is notoriously slow in the deep ocean. Biodiversity in this realm has barely been documented and studied.

Should we be damaging tracts of the ocean bed before we know what's there and what the wider consequences will be? On the other hand, might industrial mining deep under water be preferable environmentally and socially to mining on land where there are people as well as animals?

Rebecca Morelle and David Shukman of BBC News investigate.

Producers: Andrew Luck-Baker and Kate Stephens.

Is mining the deep ocean the solution to the world's growing demand for valuable metals?

Series taking listeners down to the deepest parts of the ocean.

The deep ocean contains extraordinary ecosystems, full of life forms found nowhere else on the planet. Some of those same habitats are unusually rich in valuable minerals. Could we and should we mine them?

Hydrothermal vent systems are one of the deep ocean habitats which have gained the interest of mining concerns. Volcanically-heated water gushes from the sea floor. The chemically-charged water sustains unique ecosystems, the like of which aren't seen anywhere else on Earth. There are gigantic worms and clams which are nourished by bacteria within their tissues - the bacteria themselves are fuelled by chemicals in the water, in the way plants on the surface use light. There are vast swarms of blind, heat-guided shrimps.

The superheated waters are also rich in metals such as copper, silver and gold which crystallise when the hot water meets the cold ocean. Great chimneys of metallic ores and rock form in this process. The concentration of metals is typically much higher than those of terrestrial ore deposits. Mining companies are keen to exploit them if the costs of extracting them from deep beneath the waves are favourable. Given growing demand from an increasingly industrialised world, the corporations believe the profits are set to outweigh the costs. Underwater robotic bulldozers and monster sized vacuum cleaners are ready for their first deployments and operations.

Many marine biologists view these prospects with alarm. The impact of mining on hydrothermal vents and other mineral-rich deep sea habitats will destroy life in the immediate extraction areas and may cause unknown kinds and scales of damage down current and distant from mining areas. The pace of life and its rate of recovery is notoriously slow in the deep ocean. Biodiversity in this realm has barely been documented and studied.

Should we be damaging tracts of the ocean bed before we know what's there and what the wider consequences will be? On the other hand, might industrial mining deep under water be preferable environmentally and socially to mining on land where there are people as well as animals?

Rebecca Morelle and David Shukman of BBC News investigate.

Producers: Andrew Luck-Baker and Kate Stephens.

Is mining the deep ocean the solution to the world's growing demand for valuable metals?

Series taking listeners down to the deepest parts of the ocean.