A voyage to the bottom of the Pacific Ocean has ended with the loss of a multimillion-dollar robotic vehicle in a catastrophic implosion, just north of New Zealand.
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The one-of-a-kind unmanned Nereus was in the final stages of a 10-kilometre dive into the Kermadec Trench when it crumpled under the tremendous water pressure.
Its builder and operator, the US Woods Hole Oceanographic Institute, said Nereus' mission was to undertake high-risk, high-reward research in the deepest parts of the ocean. ''Nereus helped us explore places we've never seen before and ask questions we never thought to ask,'' said the institute's chief scientist Timothy Shank, who also helped to conceive the vehicle.
Researchers aboard the expedition ship Thomas G. Thompson said they lost contact with the vehicle seven hours into a planned nine-hour dive at the deepest extent of the trench on Saturday. The institute's science editor Ken Kostel blogged from the ship that ''everything was going fine'' before the loss, with core samples taken of the sea floor, video transects taken and sea-life collected.
''We'd just completed collecting a sea cucumber for the respirometer and were getting Nereus ready to head to the underwater elevator,'' Mr Kostel said. ''Then the camera feeds abruptly went dark, and we lost communication with the vehicle.''
The remotely-operated Nereus' only connection to the surface was a fibre-optic cable, but it was also programmed to raise itself if necessary. ''We were nearing the time window associated with the first of those back-up releases when one of the ship's crew spotted some white objects in the water,'' he said. ''Then more. The rescue boat went in and three crew members began scouring the surface with nets as more and more white dots appeared. By then we knew. Nereus was gone.''
The fragments of Nereus led the institute to say in a statement that a portion of the vehicle likely imploded under pressure as great as 1125 kilograms per square centimetre.
Built in 2008 for $US5 million, Nereus has successfully travelled to the deepest point in the ocean, the 11-kilometre Challenger Deep, and explored the world's deepest known hydrothermal vents along the Cayman Rise in the Caribbean Sea.
''Extreme exploration of this kind is never without risk,'' said the institute's director of research, Larry Madin. ''The unfortunate loss of Nereus only underscores the difficulty of working at such immense depths and pressures.''
