Prior to the test run of a new robotic vehicle last month, underwaterresearch vehicles operated no deeper than 6,000 meters. Nereus changedthat.
The robotic craft, developed and operated by , dove to 10,902meters in the western Pacific, pushing the frontiers of explorationinto unknown depths, says , project manager for the .
"Nereus is a tool which we hopethe scientific community will use to make important discoveries aboutthat final 4,000 meters of the ocean," he says.
Bowen says thehybrid design allows Nereus to be operated remotely while tethered toits mother ship or to run as a free-swimming craft controlled byonboard computers.
"It performs a series of routine surveysgathering routine information about the sea floor, using sensors suchas sonar and digital photography to map out the area of interest ingreat detail."
Using these maps, scientists onboard thesurface ship direct Nereus in its tethered mode through a fiber-opticcable. Bowen explains this lighter cable replaces the steel reinforcedcopper wire cables used by traditional robotic systems.
"We areable then to go in with a mechanical arm and high-quality cameras andactually interact directly with the sea floor under human control."
Becausethe 40-kilometer-long tether is so light - it weighs less than akilogram and is nearly as thin as a human hair - it does not snap underits own weight and can withstand the crushing pressure of the deepocean. The cable uncoils from both ends - a canister onboard the robotand one attached to the surface vessel.
"And so as the vehiclegoes about its business, it is essentially trailing a piece of glassfiber behind it, which allows us to range freely while remaining incontact with the surface ship. And that's really the big breakthroughwith the Nereus system. At the end of the mission, we actually cut thefiber and then bring the end onboard the ship and dispose of it andrecharge the batteries, and we're ready to go again."
Nereusweighs 3 tons and is just over 4 meters long and 2 meters wide. It ispowered by 4,000 lithium batteries. The craft carries ballast weightsin its descent to 11,000 meters, diving at 20 to 30 meters a minute foreight hours. The weights, Bowen says, are dropped on the sea floor.
"Itreally neither sinks or floats and using its propulsion system, whichis a series of small propellers, we can actually drive the vehiclearound near the sea floor much in the same way you might think of ahelicopter. And that driving is done by a pilot 7 miles [11 kilometers]away on the surface vessel through a joystick."
Last month,Nereus dove nearly twice as deep as previous submersibles to reachChallenger Deep in the Mariana Trench, the deepest known place onearth. It's here near the Island of Guam in the Western Pacific thatmany of the world's volcanic eruptions and earthquakes occur. AndyBowen says the mission's success paves the way for new scientificdiscoveries and ocean theories.
"Certainly, the role, forexample, of the trench in the carbon cycle; how carbon is recycledwithin the [earth's] crust. Things such as earthquakes, various otherchemical processes are an important part of coloring in a picture aboutthe ocean that is critically important to our understanding of theglobal environment."
During its 10-hour dive to ChallengerDeep, Nereus sent back high-quality video, gathered rocks and samplesof deep ocean sediments and returned with microbes and small worms thatlive in extreme depths. But, Bowen says, Nereus has barely scratchedthe surface of the ocean floor, and he expects a research team to mountan expedition with Nereus within a year.
