$8M robo-submarine implodes deep under the ocean

The Nereus unmanned deep-sea vehicle is lost at sea after attempting a dramatic dive into an ocean trench.

Nereus in happier times. Advanced Imaging and Visualization Lab, Woods Hole Oceanographic Institution

Being a machine at the forefront of exploration isn't easy. For every Mars Curiosity rover, there is a Jade Rabbit.

One pioneer of deep-ocean research has now met with a watery fate. The Nereus robotic deep-sea vehicle was declared lost over the weekend, likely a victim of the massive stresses it was under during a daring ocean-trench dive.

Nereus was 6.2-miles deep into the Kermadec Trench near New Zealand when contact was lost. Emergency recovery protocols failed. Pieces of the craft were discovered floating on the ocean surface near the dive site, confirming a catastrophic failure. The team speculates that pressure as high as 16,000 pounds per square inch may have caused Nereus to implode.

The pioneering submersible was built by the Woods Hole Oceanographic Institution in 2008 at a cost of $8 million. According to the institution, "Its mission was to undertake high-risk, high-reward research in the deepest, high-pressure parts of Earth's ocean." The risk may have ultimately won out, but the rewards were significant.

"Nereus helped us explore places we've never seen before and ask questions we never thought to ask. 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," Timothy Shank, chief scientist for the project, said in a statement.

CNET's Daniel Terdiman met Nereus in person in 2010 and called it "one of the most exciting developments in underwater research in years." The loss is huge, but scientists are focusing on what Nereus was able to achieve during its short life. It journeyed to the deepest point in the ocean in the Mariana Trench, brought back previously unknown animal specimens, and greatly expanded our understanding of the ocean trenches. That's a pretty impressive career for an underwater vehicle.

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