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Deep trenches, unexplored surfaces and a long, treacherous journey: Sounds like a voyage to Mars, but it also describes the trip to the bottoms of Earth's own oceans, about which we know even less than the Red Planet.

What better way to explore the unknown than with an array of robotic subs? Human-occupied underwater vehicles are limited by how long they can stay underwater, and those that are unmanned traditionally have had to be connected to ships via a long control cable. Due to advances in programming and communication, some have been able to go cordless.

Earlier this year, ScientificAmerican.com reported on a few of these submersibles. Here’s an update on where a couple free-ranging subs are now.

One independent swimmer, Nereus, has now reached the Pacific's Mariana Trench, the deepest part of the ocean, reports the BBC. It's the first time in more than 10 years that a vehicle has ventured into the trench, and a dive last Sunday took the sub down to a depth of more than 35,761 feet (10,900 meters).

"With a robot like Nereus, we can now explore virtually anywhere in the ocean," Andy Bowen, principal developer of the sub at the Woods Hole Oceanographic Institution, told the BBC. "The trenches are virtually unexplored, and I am absolutely certain Nereus will enable new discoveries."

Another autonomous oceangoing vehicle was launched off the coast of New Jersey in April. Rutgers University's RU27—aka The Scarlet Knight, after the school's mascot—is gliding across the Atlantic via the Gulf Stream current, measuring temperature, salinity and water density along the way, reports Wired. Notes from the research team reveal that the glider craft is making good time and even comes to the surface from time to time to check in (via remote communication) with the researchers back home—calls they wait anxiously for.

View a ScientificAmerican.com slide show about mini subs.

Image courtesty of Woods Hole Oceanographic Institution

1 Comments

1. 1. dyoerger_nereus 10:26 PM 6/4/09

   Nereus was not used in its "wireless" form on our dives to the Challenger Deep. The press release that can be found at www.whoi.edu tells the whole story. Nereus can run as an AUV (Autonomous Underwater Vehicle, untethered) or with a fiber optic tether (ROV, remotely operated vehicle, tethered). In the AUV mode, communications must use acoustics which are limited to bandwidths far less than a dial-up line. But in ROV mode the optical fiber carries several channels of gigabit ethernet, which can carry high-quality video signals.
   
   We had the option of running Nereus in its AUV configuration but chose to use the ROV option, with its abundant real-time feedback, for our engineering trials to the Challenger Deep. The fiber optic tether resembles lightweight fishing line. Unlike traditional tethers used on ROVs, the thin optical fiber allows the vehicle great freedom of movement, and we were able to exploit this capability on our 11km dives and at a hydrothermal vent site at 3km depth. On our first 11km dive, we examined the deep basin and the base of the tectonic plates on each side, travelling several kilometers. The combination of high bandwidth and maneuverability opens up many new options for seafloor exploration.
   Again, I urge your readers to check out our web site
   http://www.whoi.edu/page.do?pid=7545&tid=282&cid=57586&ct=162
   for an accurate description of our recent test.
   Dr. Dana Yoerger
   Senior Scientist
   Woods Hole Oceanographic Institution
   Aboard RV Kilo Moana with the Nereus team

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