One of the scientific community's flagship unmanned research submarines, used for deep-sea exploration, has been declared lost as of 2 pm (New Zealand Standard Time), May 10. It was in use by researchers aboard the scientific research vessel, the Thomas G.

With a price tag of US$8 million, the loss of Nereus represents a significant setback to the scientific community's deep-sea research capabilities. The submarine had been fitted with state-of-the-art technology including a micro-thin fiber optic wire cable capable of streaming high-quality video to operators on the vessel above. Nereus also boasted the capacity to return 45 kg (99 lb) of oceanic samples to the surface for analysis. Furthermore, the advanced submersible had the ability to work automatically, surveying vast swathes of the ocean floor, only requiring direct human control if the vessel came across an object of scientific curiosity.

The research sub was on day 30 of a 40-day research mission to study and catalog the Kermadec deep-sea trench to the North of New Zealand, as part of the NSF-funded HADES project. Nereus had reached a depth of about 6.2 miles (10 km) and was seven hours into the predicted nine-hour dive when the team declared the vessel lost.

The crew of the research vessel ran through the emergency protocols dictated for a loss of contact. When this yielded no response from the sub, the researchers began a surface search for clues as to what may have happened to the stricken explorer.

Debris identified as belonging to the Nereus submersible was found following a search by the crew of the scientific vessel, analysis of which has lead to the conclusion that the sub suffered a catastrophic failure which in turn led to explosive decompression. Scientists estimate that at the depth at which Nereus was operating, there had been roughly 16,000 pounds (7,257 kg) of force per square inch acting on the tiny submersible.

The crew of the Thomas G will continues to search for debris in an attempt to further understand the nature of the catastrophic failure.

"Nereus helped us explore places we've never seen before and ask questions we never thought to ask," stated chief scientist of the HADES project Timothy 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."

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