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FAQ: Nereus

Hybrid remotely operated vehicle (HROV) Nereus was confirmed lost 9,990 meters (6.2 miles) below the sea surface in the Kermadec Trench northeast of New Zealand on May 10, 2014, at about 2:45 p.m. local time (10:45 p.m. Friday EDT). The unmanned vehicle was working as part of a mission to examine the ocean's hadal zone from 6,000 to nearly 11,000 meters deep, when a portion of Nereus likely imploded under pressure as great as 16,000 pounds per square inch.

The science team is continuing its research to determine the composition and distribution of hadal species and ecosystems, the role of hadal pressures, the food supply and the distribution of carbon and biomass of trench organisms, and the role deep trenches play in shaping the diversity and evolution of life in our deep ocean. The team includes biologists, chemists, geologists, and engineers from nine institutions: Japan Agency for Marine-Earth Science and Technology, National Institute of Water and Atmospheric Research in New Zealand, National Oceanography Centre at the University of Southampton, Scripps Institution of Oceanography, University of Aberdeen, University of Hawaii, University of Oregon, Whitman College, and WHOI.

Over the next several weeks, engineers at the Woods Hole Oceanographic Institution (WHOI) will investigate the vehicle and system's failure in order to advance our technical knowledge and apply it to building the next generation of vehicles and systems for operating at such depths. At the same time, scientists will continue to analyze the new specimens and high-definition video of never-before-seen life forms recently collected at the Kermadec Trench by Nereus.

WHOI remains committed to exploring the deepest parts of the ocean and is continuing to develop and apply the tools and technology, and research to do so.

What was the vehicle doing at the time it was lost?
At the time it was lost, it was 30 days into a 40-day expedition on board the research vessel R/V Thomas 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.

The vehicle was working at a depth of 9,990 meters (6.2 miles). During its final dive, it had collected sediment samples in two sets of push cores and the team had recorded video of nearly two hours of transects and individual animals that thrive in the hadal environment at the bottom of the Kermadec Trench.

Link: http://web.whoi.edu/hades/kermadec-2014/

Was the vehicle insured?

Yes, the vehicle was insured.

Were there any injuries?
The loss of the Nereus vehicle did not cause any injury to humans nor any damage to the research vessel.

How much did the vehicle cost to develop?
Built in 2008, HROV Nereus cost approximately $8 million to design, develop, build, and test. Primary funding came from the U.S. National Science Foundation, with additional funding from the Office of Naval Research, the National Oceanic and Atmospheric Administration, the Russell Family Foundation, and Woods Hole Oceanographic Institution.

The replacement cost of the vehicle is approximately $3.1 million.

Link: http://www.whoi.edu/main/nereus/funding-sources

What have been some of the highlights Nereus offered the scientific community?
In 2009, Nereus made an historic dive to Challenger Deep in the Mariana Trench—the deepest point in the ocean. At the time, Nereus was the only vehicle capable of such a dive. Now HOV DEEPSEA CHALLENGER is the only vehicle remaining that has reached that depth. Since that time, Nereus made two expeditions to the Cayman Trough in the Caribbean Sea, helping to identify previously unknown hydrothermal vents—the world's deepest—and then exploring them. Nereus also was the first ROV to be controlled in a tetherless mode, through the use of a newly developed optical modem. Those tests were done in Guam in Sept.-Oct. 2012.

Does the loss of Nereus mean WHOI will deploy HOV DEEPSEA CHALLENGER?
No. The human occupied submersible, DEEPSEA CHALLENGER, is not certified by an international classification agency such as the American Bureau of Shipping. Such a certification is required by internal policy and our insurers for all vessels and human occupied submersibles operated by WHOI.

What is next in terms of WHOI’s deep-sea technology?
The institution’s Deep Submergence Lab has been in the process of designing and building the next generation Nereus vehicles called Nereid, a group of submersibles that will explore the ocean at different depths and in different modes of operation. The Nereid U-I will enable exploration and study under sea ice; the Nereid HT will operate using a hybrid tethering system; and a third vehicle, Nereid 11km will be capable of reaching the 11,000-meter depth that Nereus achieved.


Chief Scientist Timothy Shank responded to media questions from aboard the R/V Thomas G. Thompson about the loss of the vehicle, the research cruise to the Kermadec Trench, and what it means for hadal research. The following are excerpts from interviews with Nature, Science, and National Geographic.

Does this loss mean you won't be able to your work in ocean trenches?
No, we have free-falling hadal camera landers - essentially tripods with a camera, lights, depth sensor, and current meter, and several kinds of baited traps. But these instruments give us only a snapshot or short video clip of what species are attracted to bait and they do not provide us with the ability to examine the complex details of ecosystems or collect samples needed to fully understand them.  

This means the ability for humans to study a critical part our planet in a comprehensive and systematic manner has been lost for the time being. To traverse over the seafloor, document, and sample animals and their habitats, conduct the first systematic study of hadal ecosystems is for now, lost.

We can put landers on Mars (400 million kilometers away at its most distant from Earth) and have them explore the surface of this planet for years, but the best we could do, even with Nereus, was study the seafloor 10 kilometers down for only 10 hours at a time. At best. We can no longer do even that.

Why do we know so little about this part of our planet?
Severe technical challenges associated with the extremes of hydrostatic pressure have historically prevented major advances in studying these regions. As a result, hadal systems have been among the most poorly investigated habitats on Earth. The development of Nereus over the past five years prompted our team of scientists from around the world to jointly identify some of the most important questions in hadal science and to form this program and expedition.

Nereus was a one-of-a-kind vehicle. With its loss goes our ability to fully conduct this research, including metabolic experiments and documenting and sampling completely unknown seafloor and life, including new known life forms--as Nereus did just days before she was lost.

The loss of Nereus for our current expedition is disheartening and difficult, but the loss of Nereus for future hadal work is devastating. It means that more than one-third of the ocean’s depth range is beyond our reach.

Besides its deep-diving capabilities, what was significant about this vehicle?
It should be noted that Nereus was really a prototype that we, the science community, wanted to turn into a workhorse. As a result, we have been adding sampling capabilities to it for years. We had also worked hard to open hadal research to more of the science community and to educate people about the importance of the hadal region and hadal research and had been broadcasting live from the seafloor six miles down via a satellite ‘telepresence’ connection on the final dive. There has been a tremendous upsurge of global interest to study these deep hadal regions, in part due to the desire to understand life’s adaptation to massive pressures, cellular function in the deep ocean, the evolution of life, and the unknown role the deep environs play in the global carbon cycle, which is so important now for understanding climate change.

We had been operating Nereus exclusively in the remotely operated vehicle (ROV) mode, because the ability of the vehicle in this configuration to obtain targeted imagery of trench animals and their habitats, conduct experiments at various depths within the trench, and collect samples of the sediments, microbes, and trench fauna is essential to our research program. The capabilities of Nereus as an ROV, with a highly capable 7-function manipulator arm, high-definition cameras (including one ultra-high-definition 4K camera) are fundamental to the goals of our expedition.  

What had Nereus accomplished on the Kermadec Trench research cruise?
Our mission to the Kermadec Trench was ambitious, demanding Nereus be a scientific workhorse. During our mission, the vehicle discovered unknown trench habitats, perhaps a dozen new species, the rates of animal respiration more than six miles down, how life on floating volcanic rock may be brought down into the trenches as a food source for trench animals, and the view of how animals exist in such deep habitats.

We had been on the sedimented bottom of the Kermadec Trench at 9,990 meters or 6.2 miles down (we think the deepest part of this trench is close to 10,063 meters) for over six hours. Nereus had collected cores of sediment and animals (two sea cucumbers and two polychaete worms) to measure their respiration rates (uptake of oxygen) when we started to move toward a free-falling lander called an ‘elevator’ (a 6-foot by 6-foot platform) that we can release with flotation to bring items back to the surface ship for recovery.  

How did events unfold?
At 13:02 (GMT) on May 9, 2014, all of our monitors (five camera feeds) turned immediately black. While everyone in the control room gasped with disappointment, we knew this was not unusual, as this happened at the end of each of the 14 dives on this expedition.

Sometimes it happens by accident, when the fiber breaks somewhere along the strand, perhaps having wrapped around a rock or some part of the vehicle. We purposefully cut the light fiber at the vehicle to begin its ascent back to the ship.

The next step was to bring up the vehicle and reload it for the next dive to the same location. We then typically speak to the vehicle using acoustic communication (a unique language of sound packets sent back and forth) and tell the vehicle to drop its weights and ascend back to the surface. This is when burn wires on Nereus will automatically ‘dissolve’ and drop weights (as it has done for 75 dives).

Except this time, dive #76, we had no over-the-side acoustic communication with the vehicle. All communication was lost. We anticipated that the vehicle would drop its weights even without our communication- another failsafe mode- because the automated burn wires release the weights after 30 minutes and then again after 6 hours. We thus anticipated that the vehicle would arrive at the surface, so we posted people as look outs around the ship.

Nereus was meant to reach the surface at 07:30, and then again at 14:00 hours (local time). Nothing was observed that morning, just ominously grey clouds and rain. It was around 13:45 when I saw white pieces of material--- from golf ball sized to over a foot long--floating past the ship. We launched the ship’s small rescue boat and picked up pieces with nets, which we identified as structural components from inside the vehicle's hulls.

It was a horrible feeling—of denial and disbelief— at the thought of the set-back to hadal science that this represented.

What did Nereus mean to you personally?
Nereus was a vehicle that I had worked on since its inception 10 years ago- serving as a science consultant, from assisting with design elements for maximizing science output to going out with it on the first two field test programs and most recently, the two years invested in making this expedition possible. All of these moments flashed through my mind while as many of the floating pieces as possible were recovered until increasing winds and choppy seas forced the crew to stop. For the next 18 hours, I sat near the bow and watched small pieces float past the hull of the ship- my mind reeling on the past and future. In deep-ocean research, every time you put something in the water, there is a risk of never getting it back.

However, the importance of the science is far too great to get lost in mourning this vehicle. We take the lessons learned and are persistent in the need for Nereus’ capabilities to enable future hadal research. We will continue that persistence to have a strong scientific presence in the deepest regions of our ocean.

What do you consider some of Nereus’ most significant accomplishments?
Nereus’ discoveries began on her first full-ocean depth field trial in May 2009, discovering a new species of trench anemone. Another major discovery occurred when traversing the two-mile journey from one side of the Challenger Deep (Mariana Trench) to the other, giving us the world's first comprehensive view of the seafloor overlying two massive tectonic plates.

Years later on the Mid Cayman Rise, Nereus gathered sensor data that led to the discovery of several new hydrothermal vents sites- among the deepest in the world. Nereus then undertook an even more ambitious autonomous goal, deploying subsea nodes and laying a new class of fiber optic cable across the seafloor to further underwater telecommunications technology. I think the greatest contribution Nereus provided was issuing a new era in deep-ocean exploration- a prototype vehicle purpose-built for work in the deepest regions of our ocean.

What are some new discoveries you’ve found in the hadal zone so far?
Once thought to be devoid of life, trenches may actually be home to many unique species. There is growing evidence that food is plentiful there. While not known why, organic material in the ocean may get moved by currents and deposited into the trenches. In addition to looking at how food supply varies at different depths, we were investigating the role energy demand and metabolic rates of trench organisms plays in the community structure and how it differs from shallow water relatives. Exactly how animals in the trench evolved to withstand the pressures is not completely known, but we are comparing genomes of trench animals to piece together how fauna have evolved to be successful in trenches.  

We hope to determine whether life in the trenches holds novel evolutionary pathways that are distinct from others in the ocean. We know that hydrostatic pressure, which at depths found in ocean trenches can be up to 1,100 times greater than at the surface and is known to inhibit the activity of proteins. We are investigating the role that piezolytes—small molecules that protect proteins from pressure— play in the adaptation of trench animals. The use of piezolytes is a novel hypothesis and attempts to explain previous findings that not all deep-sea proteins seem to be able to evolve resistance to pressure within their structures.  We are trying to discover how life can function under the massive pressures of the hadal zones. This is important because pressure might very well be the primary factor determining which species can live there.

In addition to deep-sea life with novel adaptations, there is also evidence to suggest that trenches act as carbon sinks, making the research also relevant to climate change studies. The V-shaped topography along trench axes funnels resources—including surface-derived organic carbon—downwards. The bulk of our knowledge of trenches is only from snapshot visits using mostly trawls and camera landers. Only detailed systematic studies will advance our biological understanding and also reveal the role trenches may play as the final location of where most of the carbon and other chemicals get sequestered in our ocean, impacting the global carbon budget and ultimately climate.

Originally published: May 15, 2014