The People Who Have Explored the Deepest Places on Earth

Thousands of metres beneath the ocean surface, the world becomes almost completely dark, freezing cold and exposed to pressures hundreds of times greater than those at the surface.

Yet a small group of explorers have spent years travelling into this extreme environment, reaching places that almost nobody else on Earth has ever seen.

Rob McCallum Has Explored All Five Oceans

Australian diver and expedition leader Rob McCallum is one of those explorers. He has travelled to the deepest parts of all five oceans, including the Mariana Trench, and has explored the wrecks of the Titanic and the German battleship Bismarck.

He has also descended into the Clarion–Clipperton Zone, a huge area of the Pacific Ocean where valuable mineral-rich rocks known as polymetallic nodules cover parts of the seabed.

Some of the nodules are about the size of potatoes or baseballs and contain metals such as nickel, cobalt, copper and manganese.

A World Four Kilometres Below the Surface

At depths of around four kilometres, the environment is unlike anything humans experience on land. Equipment must withstand enormous pressure, while operations depend on complex machines working in freezing seawater.

McCallum says the nodules may look like easy-to-collect treasures scattered across the ocean floor, but reaching them is far more complicated than simply picking them up.

Victor Vescovo Has Reached the Deepest Points

American explorer Victor Vescovo has also piloted submersibles to the deepest points of all five oceans. His experience has given him a close look at the technical difficulties involved in operating so far below the surface.

He warns that equipment failures at extreme depths can become enormously expensive because machines may have to be brought thousands of metres back to the surface for repairs.

In 2021, a prototype mining vehicle operated by Belgian company Global Sea Mineral Resources was lost after its connecting cable broke. The vehicle eventually had to be recovered from a depth of about 4,500 metres.

The Race to Explore the Seabed

The deep ocean is attracting growing attention because polymetallic nodules contain minerals used in modern technology. Companies and investors are examining whether these resources could eventually be collected on a commercial scale.

However, commercial deep-sea mining is not yet legal under an international regulatory framework, and experts continue to debate whether the technology can become economically viable without causing unacceptable environmental damage.

A Frontier Humans Still Barely Know

Despite decades of exploration, much of the deep ocean remains difficult to access. Every expedition can reveal unfamiliar landscapes, unusual geological formations and new challenges for underwater technology.

For explorers such as McCallum and Vescovo, travelling to these depths is not simply about finding valuable minerals. It is also about entering one of the least familiar environments on Earth and discovering what lies beyond the limits of ordinary human experience.

Source: ABC News, with photography and material from AFP, AP and explorers featured in the report.