Why Cameron’s Mariana Trench dive matters

by Michael Richardson

Most people live and work on land. Some journey by air, or go to sea. But all return to the land. Our terrestrial view of the world defines exploration.

As we spread and settle on land that was once wilderness, there seems little left on Earth to explore. We know that space is still a vast, mysterious frontier. But we seldom think of the oceans as watery terra incognita, blinkered as we are by our land view.

However, the sea floor is an extension of the land. It has mountains, valleys and plains, although they are hidden by seawater. Little is known about the deep recesses of either the sea or the sea bed.

Yet the oceans and seas play a vital role in sustaining life. They cover nearly three-quarters of Earth’s surface, provide around half the oxygen we breathe, and are an important source of protein for a rapidly growing world population.

We need to know much more about the oceanic world because pollution, overfishing and acidification from excessive absorption of carbon dioxide produced by burning fossil fuels and clearing forests are changing the seas, perhaps irrevocably and certainly in ways that make them less productive.

The deep sea, below about 200 meters, is by far the world’s largest habitat, providing more than 80 percent of the space for life on Earth to exist, from giant whales to minute phytoplankton.

This is why the audacious March 26 descent to the deepest place in the ocean by multimillionaire Hollywood film director, James Cameron, of “Titanic” and “Avatar” fame, is important. It will stimulate much-needed popular interest and scientific research into oceanic life.

Lowered from a surface support ship by cable in a unique, high-tech one-person capsule designed and built in Australia to withstand extreme pressure and cold, Cameron reached Challenger Deep, the bathtub-shaped depression at the lowest point of the Mariana Trench in the Pacific Ocean west of the Philippines, 11,033 meters under the surface.

The trench is a mega-scale submerged Grand Canyon that stretches for 2,400 km along the seabed in a subduction zone where the Pacific plate slides below the Mariana plate, creating a volatile region of earthquakes and volcanoes.

Before Cameron, only one manned submersible, sent down by the U.S. Navy in 1960, has reached the bottom of Challenger Deep. It stayed for just 20 minutes and the two explorers on board could see very little because of the bottom silt they had stirred up. Since then, only unmanned remotely operated vehicles — the Japanese Kaiko in 1995 and the U.S. Nereus in 2009 — have been down.

Cameron is filming documentaries in collaboration with the National Geographic Society. He is also working closely with the Scripps Institute of Oceanography, the University of Hawaii and other scientific groups.

His sub’s scientific tools included a water sampler, a sediment collector, a “slurp gun” for catching animals without hurting them, and a robotic manipulator arm. Also deployed were three “landers” to perform complementary research. The landers sink to the sea floor unattended then rise on a timer or remote signal.

The deepest a fish has ever been recorded is about 8,370 meters. Further down, the main interest is in rock and sediment samples that could help researchers answer questions about subduction processes and the way fluids and mud are cycled through Earth’s mantle.

Bacteria and other organisms plucked from the depths will enable scientists to understand how they withstand such extreme conditions.

Until now, the world’s most advanced submersibles were built by the governments of the U.S., China, France, Russia and Japan. But as budgetary constraints bite state oceanic research, wealthy private explorers in partnership with scientists are taking up the challenge.

Just behind Cameron is adventurer and entrepreneur Sir Richard Branson. His Virgin Oceanic arm has developed a solo-manned sub that has small wings and is designed to “fly” along the bottom of trenches that crisscross the ocean bed at the boundaries of tectonic plates, instead of going straight down to the depths like the Cameron capsule.

Starting later this year, the Branson engineering team and its scientific collaborators plan to journey to the deepest part of each of Earth’s five oceans. Less than three percent of the sea floor has been explored, and none of the deepest points of the main oceanic trenches have been reached by manned submersibles, except for Challenger Deep.

Virgin Oceanic says it aims to provide a vertical sequence of sea life by using the sub in the southern Mariana Trench to record and collect specimens from its axis over 10 km deep and then up the face of a nearby fault escarpment to near the surface, documenting changes in ecosystems along the way.

This could provide the first complete record of biological diversity from top to bottom in the world’s oceans.

Michael Richardson is a visiting senior research fellow at the Institute of South East Asian Studies in Singapore.