Nereus. Robotic Deep-sea Vehicle Lost on Dive to 6-Mile Depth

Nereus’s mission was to undertake high-risk, high-reward research in the deepest parts of Earth’s ocean where pressure on the vehicle can be as great as 16,000 pounds per square inch. (Photo by Advanced Imaging and Visualization Lab, Woods Hole Oceanographic Institution)

On Saturday, May 10, 2014, at 2 p.m. local time (10 p.m. Friday EDT), the hybrid remotely operated vehicle Nereus was confirmed lost at 9,990 meters (6.2 miles) depth in the Kermadec Trench northeast of New Zealand. The unmanned vehicle was working as part of a mission to explore the ocean’s hadal region from 6,000 to nearly 11,000 meters deep. Scientists say a portion of it likely imploded under pressure as great as 16,000 pounds per square inch.

Nereus was built in 2008 by the Deep Submergence Lab at the Woods Hole Oceanographic Institution (WHOI) with primary funding from the U.S. National Science Foundation (NSF) to descend to the deepest parts of the ocean and to operate either autonomously or to be controlled remotely from the surface. WHOI engineers incorporated a number of novel technologies into its design for use in remote operations, including an optical fiber tether for use in remote operations, ceramic flotation, and lithium-ion batteries. Its mission was to undertake high-risk, high-reward research in the deepest, high-pressure parts of Earth’s ocean. At the time it was lost, it was 30 days into a 40-day expedition on board the research vesselThomas G. Thompson to carry out the first-ever, systematic study of a deep-ocean trench as part of the NSF-sponsored Hadal Ecosystems Study (HADES) project under chief scientist Timothy Shank, a WHOI biologist who also helped conceive the vehicle.

On the HADES cruise, Nereus brought back to the surface specimens of animals previously unknown to science and seafloor sediment destined to help reveal the physical, chemical, and biological processes that shape the deep-ocean ecosystem and that make ocean trenches unlike almost any other part of the planet. (Photo by Ken Kostel, Woods Hole Oceanographic Institution)

Nereus helped us explore places we’ve never seen before and ask questions we never thought to ask,” said Shank. “It was a one-of-a-kind vehicle that even during its brief life, brought us amazing insights into the unexplored deep ocean, addressing some of the most fundamental scientific problems of our time about life on Earth.”

Researchers on the Thompson lost contact with the vehicle seven hours into a planned nine-hour dive at the deepest extent of the trench. When standard emergency recovery protocols were unsuccessful, the team initiated a search near the dive site. The team onboard spotted pieces of debris floating on the sea surface that were later identified as coming fromNereus, indicating a catastrophic implosion of the vehicle. The ship’s crew is recovering the debris to confirm its identity and in the hope that it may reveal more information about the nature of the failure.

The Kermadec Trench runs northeast from the North Island of New Zealand to the Louisville Seamount Chain. It is the fifth deepest oceanic trench in the world and formed by subduction, a geophysical process in which the Pacific tectonic plate is pushed beneath the Indo-Australian Plate. (Illustration by Jack Cook and E. Paul Oberlander, Woods Hole Oceanographic Institution)

In addition to the Kermadec Trench, Nereus had successfully traveled to Challenger Deep in the Mariana Trench—the deepest point in the ocean—and explored the world’s deepest known hydrothermal vents along the Cayman Rise in the Caribbean Sea. It had been scheduled to return to the Mariana Trench in November as part of the second HADES expedition. Already on the first HADES cruise, Nereus had brought back to the surface specimens of animals previously unknown to science and seafloor sediment destined to help reveal the physical, chemical, and biological processes that shape the deep-ocean ecosystems in ocean trenches, which are unlike almost any others on the planet.

WHOI is a leader in the development of autonomous robotic vehicles for the exploration of the ocean, including the hybrid vehicle Nereus, which functioned as a remotely operated vehicle via an optical fiber tether and also as a free-swimming autonomous vehicle. It was one of only four submersibles in history to reach the deepest part of the ocean in the Marianas Trench.

“Extreme exploration of this kind is never without risk, and the unfortunate loss of Nereus only underscores the difficulty of working at such immense depths and pressures,” said WHOI Director of Research Larry Madin. “Fortunately there was no human injury as a consequence of this loss. WHOI scientists and engineers will continue to design, construct and operate even more advanced vehicles to explore and understand the most remote and extreme depths of our global ocean.”

In addition to NSF support, funding for Nereus also came from the Office of Naval Research, the National Oceanic and Atmospheric Administration, the Russell Family Foundation, and WHOI.

“We are grateful to our partners for helping build such a breakthrough technological innovation in deep-ocean exploration and to the many engineers, technicians, and scientists at WHOI and around the world who helped realize our vision of a full-ocean-depth research vehicle,” said WHOI President and Director Susan Avery. “Nereus may be gone, but the discoveries it enabled and the things it helped us learn will be an indelible part of its legacy.”

The Woods Hole Oceanographic Institution is a private, non-profit organization on Cape Cod, Mass., dedicated to marine research, engineering, and higher education. Established in 1930 on a recommendation from the National Academy of Sciences, its primary mission is to understand the ocean and its interaction with the Earth as a whole, and to communicate a basic understanding of the ocean’s role in the changing global environment. For more information, please visit


HROV Nereus from the water during its second expedition in 2009 to investigate hydrothermal vents along Earth’s deepest mid-ocean ridge in the Cayman Trough. On May 31, 2009, the robotic vehicle successfully reached the deepest part of the world’s ocean—the Challenger Deep in the Mariana Trench in the western Pacific Ocean. The one-of-a-kind vehicle can operate either as an autonomous, free-swimming robot for wide-area surveys, or as a tethered vehicle for close-up investigation and sampling of seafloor rocks and organisms. Take an Interactive Tour of Nereus to learn more. (Photo courtesy Advanced Imaging and Visualization Laboratory, Woods Hole Oceanographic Institution)

Hybrid Remotely Operated Vehicle Nereus: Exploring the oceans’ deepest depths

Humans have been able to venture into just a tiny fraction of Earth’s deepest trenches at the bottom of the oceans—and then for only brief visits and at considerable expense. Expanding on these pioneering expeditions, scientists and engineers at Woods Hole Oceanographic Institution have built a new efficient, multi-purpose “hybrid” vehicle that can explore and operate in the crushing pressures of the greatest ocean depths.

On its first mission, the new vehicle, called Nereus (rhymes with “serious”), explored the deepest part of the ocean, Challenger Deep—a nearly 7-mile-deep trench east of the Marianas Islands in the western Pacific. The trench extends farther below the sea surface than Mount Everest reaches into the sky. In the future, Nereus could also be used under ice-capped polar waters.

Why is Nereus called a “hybrid” ROV?

Nereus, an unmanned vehicle, operates in two complementary modes. It can swim freely as an autonomous underwater vehicle (AUV) to survey large areas of the depths, map the seafloor, and give scientists a broad overview. When Nereus locates something interesting, the vehicle’s support team can bring the vehicle back on board the ship and transforms it into a remotely operated vehicle (ROV) tethered to the ship via a micro-thin, fiber-optic cable. Through this tether, Nereus can transmit high-quality, real-time video images and receive commands from skilled pilots on the ship to collect samples or conduct experiments with a manipulator arm.

How did Nereus get its name?

Nereus is a mythical Greek god with a fish tail and a man’s torso. The name was chosen in a nationwide contest open to junior high, high school, and college students.

High-tech components make Nereus smaller and lighter, enabling the vehicle to travel deeper for longer periods 

  • When operating in ROV mode, Nereus trails a hair-thin optical fiber, up to 25 miles in length, from a support ship. Like a high-speed Internet connection, the fiber can transmit high-quality video images to scientists on the ship. It also enablesNereus’s operators to have precise, interactive control of the vehicle.
  • Nereus uses lightweight ceramic materials to provide buoyancy and shield electronics from intense seafloor pressure, replacing traditionally used (but heavier) metals and glass materials.
  • To supply energy, Nereus carries rechargeable lithium-ion battery packs, similar to those powering laptop computers. Each pack contain more than 2,000 batteries.

Source: Whoi

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