The Abyss: Deepest Part of the Oceans No Longer Hidden

Nereus is first undersea vehicle to enable routine scientific investigation of ocean depths worldwide.

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The Abyss is a dark, deep place, but it's no longer hidden. At least when Nereus is on the scene. Nereus is a new type of deep-sea robotic vehicle, called a hybrid remotely operated vehicle (HROV).

Nereus dove to 10,902 meters (6.8 miles) on May 31, 2009, in the Challenger Deep in the Mariana Trench in the western Pacific Ocean, reports a team of engineers and scientists aboard the research vessel Kilo Moana.

The dive makes Nereus the world's deepest-diving vehicle, and the first vehicle to explore the Mariana Trench since 1998.

"Much of the ocean's depths remain unexplored," said Julie Morris, director of the National Science Foundation (NSF)'s Division of Ocean Sciences, which funded the project. "Ocean scientists now have a unique tool to gather images, data and samples from everywhere in the oceans, rather than those parts shallower than 6,500 meters (4 miles). With its innovative technology, Nereus allows us to study and understand previously inaccessible ocean regions."

Nereus's unique hybrid-vehicle design makes it ideally suited to explore the ocean's last frontiers, marine scientists say. The unmanned vehicle is remotely operated by pilots aboard a surface ship via a lightweight, micro-thin, fiber-optic tether that allows Nereus to dive deep and be highly maneuverable. Nereus, however, can also be switched into a free-swimming, autonomous vehicle mode.

"Reaching such extreme depths is the pinnacle of technical challenges," said Andy Bowen, project manager and principal developer of Nereus at the Woods Hole Oceanographic Institution (WHOI). "The team is pleased that Nereus has been successful in reaching the very bottom of the ocean to return imagery and samples from such a hostile world. With a robot like Nereus we can now explore anywhere in the ocean. The trenches are virtually unexplored, and Nereus will enable new discoveries there. Nereus marks the start of a new era in ocean exploration."

Nereus (rhymes with "serious") is a mythical Greek god with a fish-tail and a man's torso. The vehicle was named in a nationwide contest open to high school and college students.

The Mariana Trench forms the boundary between two tectonic plates, where the Pacific Plate is subducted beneath the small Mariana Plate. It is part of the Pacific Ring of Fire, a 40,000-kilometer (25,000-mile) area where most of the world's volcanic eruptions and earthquakes occur. At 11,000 meters, its depth is about the height a commercial airliner flies.

To reach the trench, Nereus dove nearly twice as deep as research submarines are capable of, and had to withstand pressures 1,000 times that at Earth's surface--crushing forces similar to those on the surface of Venus, according to Dana Yoerger of WHOI and Louis Whitcomb of Johns Hopkins University, who developed the vehicle's navigation and control system and conducted successively deeper dives to test Nereus.

"We couldn't be prouder of the stunning accomplishments of this dedicated and talented team," said Susan Avery, president and director of WHOI. "With this engineering trial successfully behind us, we're eager for Nereus to become widely used to explore the most inaccessible reaches of the ocean. With no part of the deep seafloor beyond our reach, it's exciting to think of the discoveries that await."

Only two other vehicles have succeeded in reaching the Mariana Trench: the U.S. Navy-built bathyscaphe Trieste, which carried Jacques Piccard and Don Walsh there in 1960, and the Japanese-built robot Kaiko, which made three unmanned expeditions to the trench between 1995 and 1998.

Trieste was retired in 1966 and Kaiko was lost at sea in 2003.

The Nereus engineering team believed that a tethered robot using traditional technologies would be prohibitively expensive to build and operate.  So they used unique technologies and innovative methods to strike a balance between size, weight, materials cost and functionality.

Building on previous experience developing tethered robots and autonomous underwater vehicles (AUVs), the team fused the two approaches together to develop a hybrid vehicle that could fly like an aircraft to survey and map broad areas, then be converted quickly into a remotely operated vehicle (ROV) that can hover like a helicopter near the seafloor to conduct experiments or to collect biological or rock samples.