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New Robotic Submarine To Explore Deepest Ocean

May 6, 2009

The $5 million Nereus robotic submarine is undergoing final preparations to dive to the deepest-known part of the oceans, BBC News reported.

A successful mission would make it the first autonomous vehicle to visit the Challenger Deep, an area some 36,089 feet below the Pacific Ocean.

The submarine will first perform a series of increasingly deep test dives before making the attempt in late May or early June “” something only two other human operated vehicles have done so far.

Andy Bowen of the Woods Hole Oceanographic Institution (WHOI) and one of the designers of Nereus, said instead of jumping directly into the deep end of the swimming pool with the vehicle, they plan to dip their toe in first.

Ian Rouse, head of the deep platforms group at the National Oceanography Center, Southampton, considers the project a “great technical challenge”.

He told BBC News there are vehicles that can do a better job than Nereus below 21,325 feet, but between 21,325 feet and 36,000 feet Nereus has the field pretty much to itself due to its design.

Rouse said the Nereus team is very experienced in designing and building other underwater vehicles and he has no doubt it will succeed.

Located in the Marianas Trench near the island of Guam in the west Pacific, the Challenger Deep is the deepest-known part of the ocean, where the crew expects tests to begin between May 23 and June 6.

At just over 36,000 feet, it is the deepest abyss on Earth and 1.2 miles deeper than Mount Everest is high. Pressures can reach 1,100 times the pressure at the surface.

Bowen said building something to operate in such an extreme environment is a huge challenge from an engineering perspective.

As of now, the deepest-rated vehicles are able to descend to just over 21,000 feet, allowing scientists access to 95 percent of the seafloor.

However, Nereus aims to change this to 100 percent and will even allow scientists to survey a much larger area than previous subs.

Depending on the type of mission, Nereus is able to switch between free-swimming and tethered configurations. Nereus is able to fly pre-programmed missions in this configuration, mapping vast swathes of the seafloor.

Bowen said it has sufficient onboard intelligence and batteries that enable it to find areas of particular interest through the use of chemical sensors, sonar and digital photography.

The submarine will automatically return to the ship after completing its mission and at that point it can be converted to a remote-operated vehicle (Rov)””which involves adding a mechanical arm that lets it gather samples and deploy instruments.

The vehicle also supports a single 25-mile fiber optic cable that allows scientists to control the vessel from the ship.

It takes around 12 hours on the ship’s deck to transform the sub between the two different modes.

Nereus will be the first hybrid vehicle to visit the entire ocean floor and will also be the only vehicle currently in operation with this capability.

The sub uses rechargeable lithium-ion batteries””similar to those used in laptop computers””for power and a single hairs-width fiber optic cables for control and telemetry. The vehicle can remain submerged for 20 hours after each charge.

The Nereus engineers have also replaced traditional materials, such as titanium and glass used to build similar craft, with new, lightweight materials.

Professor Chris German, also of WHOI, said it employs very thin-walled and light ceramic material that is made to withstand such huge pressures.

Other scientists involved in the dive are keen to get their hands on the new vehicle to explore the ocean depths.

Tim Shank, a biologist at WHOI, believes all kinds of new life forms will be discovered. “There are going to be novel habitats, novel species and novel adaptations,” he said.

He added that previous discoveries at shallower depths have taught scientists to “expect the unexpected”, for example there are shrimps found at vents in the Atlantic that swarm by the millions without the use of eyes.

Shank explained that the creatures have a U-shaped sensory structure on their back instead of eyes, which may be used to detect heat.

“Nobody would have anticipated that this one species would have evolved this kind of adaptation,” he said.

Geologists who are eager to directly study destructive Earth processes, such as where the oceanic crust is recycled into the planetary interior, could also use the vehicle for future research missions.

German said although they can study mid-ocean ridges where new ocean crust is produced, they aren’t able to study the other end in the same way.

Such areas, known as “subduction zones,” are commonly found along the edge of the Pacific, where oceanic crust plunges under buoyant continental crust.

Experts say the Marianas Trench””the location of the Challenger Deep””was formed when the Pacific Plate was thrust beneath the smaller Mariana Plate.

“Given that, among other things, it is in these subduction zones that the world’s largest earthquakes ever recorded, [these areas] are potentially, really quite significant,” German said.

Image Caption: After four years of design and construction, Nereus took its first plunge in deeper waters during a test cruise in December 2007 off the Waianae coast of Oahu, Hawaii.  The one-of-a-kind vehicle can operate either as an autonomous, free-swimming robot for wide-area surveys, or as a tethered vehicle for close-up investigation and sampling of seafloor rocks and organisms.  (Photo by Robert Elder, Woods Hole Oceanographic Institution)

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