The deep sea is perhaps the largest and most unexplored habitat on our planet. Between 6000m and 11000m lies the Hadal Zone, the deepest parts of our ocean. The Hadal Ecosystems Studies (HADES) Program is a collaborative project, funded by the National Science Foundation, aimed to pursue the foremost questions in trench and hadal ecosystem science, determining the composition and distribution of hadal species, the role of pressure, food supply, physiology, depth, and seafloor topography on deep-ocean communities and the evolution of trench life.
The goal of this expedition was to systematically explore the Kermadec Trench, a 700-mile long trench North of New Zealand where two tectonic plates, the Pacific and Indo-Australian, overlap to form a subduction zone.
Scientists at Woods Hole Oceanographic Institution developed HROV Nereus to explore beyond the tiny fraction of ocean we, as humans, can visit.
On its first mission, Nereus explored the very deepest part of the Oceans, the Challenger Deep, a nearly 7-mile-deep trench in the Pacific. A depths far greater than Everest is high, Nereus operated at pressures over 16,000lbs per square inch, or nearly 1,000 times what we experience here on land.
Nereus could operate in two complementary modes: It could swim freely as an autonomous underwater vehicle (AUV) or as a remotely operated vehicle (ROV) tethered to the ship via a micro-thin, fiber-optic cable. Through this tether, Nereus could 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.
Working hours on a research vessel are 24/7. Scientists often plan for years on how to use each and every minute of precious ship time and the researchers on the Thomas Thompson were no exception. At all hours, landers were being deployed or recovered, fish traps emptied, or HROV Nereus was completing a 12 hour traverse of the trench. As a filmmaker coming onboard the RV Thompson, I was confident of my stamina and ability to deal with odd sleep schedules yet I felt worn and sluggish when trying to keep up with the crew when a new catch of amphipods hit the dissection table. So when I woke up on the morning of May 10 to empty labs and black video screens, I knew something had happened to Nereus.
At 15,000psi, the implosion would have been exceptionally violent. Nereus contained hundreds of ceramic spheres specifically designed for providing bouyancy under the enormous pressures of even the deepest trenches. Any guess at why Nereus imploded is little more than speculation but it's easy to imagine one of these spheres, perhaps with only a microscopic fracture, failing under the pressure to trigger a chain reaction of similar implosions througout the vehicle. The scientists watching the video feed saw nothing more than a black screen, the same that would have been seen from a disconnect with the fiber optic cable.
Hours later, as the scientific crew of the Kermadec Trench expedition gathered the floating remains of Nereus from the ocean surface, I was struck by the significance of such a loss. Nereus was truly unique and the only full-ocean depth ROV of its kind in the US. It took years of research, development, and tests for its realization. For many of the scientists onboard, Nereus was the only option for gathering specimens, sediment and data at these depths. Its maneuverability and robotic arm were vital to performing experiments and manipulating pieces of equipment. We understand only a fraction of the processes happening in the deep ocean, an area larger than North America. Losing Nereus meant losing the ability to interact with this environment, to explore a massive portion of our planet unknown to us.
As a newcomer, the numerous deployments and procedures on this expedition often had the illusion of being routine. Before May 10, I rarely thought about the risks of exploratory science and the sacrifices one must be willing to make in the name of discovery. I often find myself comparing the deep ocean to space and I think that comparison goes beyond simply sending robots to places we are unable to go. The deep ocean, like space, is unforgiving. It is a frontier, and to try and visit that frontier means accepting that failure is an option. The loss of Nereus was not the result of negligence. There was nobody at fault. The loss of Nereus was an unfortunate cost of exploring the deepest, most unknown parts of our planet. It is a cost I am willing to accept and feel the real tragedy is the time we must now spend unable to explore the deep ocean and remain ignorant of its secrets.
When we think of deep sea fish, many will picture creatures like the angler fish, vampire squids and bioluminescent jellies. Most of these animals hang out at depths of 900 to 3000 meters. Go deeper. At 8,000 meters below the ocean's surface, pressures of nearly 12,000lbs per square inch crush and inhibit the very cells in animals' bodies and proteins fail to fold correctly. In fact, only one vertebrate has been found to live at these depths: the snailfish.