Robot Submarine Takes a Dive to the Deepest Spot in the Ocean

By Eliza Strickland | June 2, 2009 6:03 pm

mariana trenchRobotic explorers on Mars get a lot of veneration for their daring feats, as well they should–but let’s not neglect the robots that are busy exploring the most inaccessible regions of our own planet. On Sunday, a robot submarine known as Nereus dove to a depth of 6.8 miles to investigate the Mariana Trench in the western Pacific Ocean. Nereus descended all the way to the deepest cranny of the trench, a spot known as the Challenger Deep, and spent more than 10 hours making observations in a spot that is deeper than Mount Everest is high.

For the expedition, the team had to build a new breed of remotely-operated submarine … which is capable of going deeper than any other while still filming and collecting samples. Sunday’s dive makes it the world’s deepest-diving vehicle [currently in operation], and the first vehicle to explore the Mariana Trench since 1998 [New Scientist]. So far, researchers have released only a single image (pictured), showing Nereus’s robotic arm scooping up sediment.

The unmanned “hybrid” vehicle can either be remotely operated by researchers aboard a surface ship via a lightweight tether, or it can be switched over to a free-swimming, autonomous mode. Traditional robotic systems use a steel-reinforced cable made of copper to power the vehicle, and optical fibers to enable information to be passed between the ship and the vehicle. If such a cable were used to reach the Mariana Trench, it would snap under its own weight before it reached that depth. To solve this challenge, the Nereus team adapted fiber-optic technology … to carry real-time video and other data between the Nereus and the surface crew. Similar in diameter to a human hair and with a breaking strength of only eight pounds, the tether is composed of glass fiber with a very thin protective jacket of plastic [U.S. News & World Report]. Nereus carried 25 miles of the slender tether, which it gradually unspooled. For power, it used more than 4,000 lithium-ion batteries.

At the bottom of the ocean, Nereus has to withstand pressure 1,000 times more intense than that felt on Earth’s surface–which is akin to the pressure that would be experienced on the planet Venus. Only two other vehicles have ever reached the bottom of Challenger Deep: US bathyscaphe Trieste, which carried Jacques Piccard and Don Walsh in 1960, and the Japanese robot Kaiko, which made three unmanned expeditions to the trench between 1995 and 1998. Trieste was retired in 1966, and Kaiko was lost at sea in 2003 [New Scientist].

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Image: Woods Hole Oceanographic Institution

MORE ABOUT: AUV, earth science, ocean, robots
  • Nick

    Wait… if two other craft have already been to the bottom of the Challenger Deep, how is this the deepest dive ever?

    And I’m really confused about the tether – why do they say they replaced optical fibers with fiber-optic technology… is there some non-fiber-optic optical fiber technology?

  • Justin

    For your first question,

    I don’t think the other two robots went to the deepest part of the trench like this one did?

  • http://deleted Anaconda

    It is spectacular that Science and technological advancement have allowed this achievement. Although, not at this depth, oil companies are sending submersibles to ever greater depths all the time and doing impressive feats of engineering (constructing pumping stations and what not) to produce oil from ultra-deep water.

    Question: The Mariana Trench is considered to be a subduction zone by conventional geology, but is there any actual scientific evidence for this conclusion?

    What I mean by “scientific evidence” is deposits or scraped off sediment at the bottom of the trench or other physical identifiers Science can study and then infer from that subduction is actually happpening in this area.

    As much as geology maintains that subduction is a fact, there is a lack of actual physical evidence that indeed subduction takes place.

    Deep submersibles could go a long way to providing evidence one way or the other.

  • Eliza Strickland

    Nick — now I’m confused, too. The first news reports said that Nereus had taken the deepest dive in history, beating out the previous two expeditions, but I think they should have said that Nereus is the deepest diving vehicle currently in operation.

    Nereus reached 10,902 meters down. But the Trieste reportedly reached 10,916 meters, and the Japanese Kaiko reportedly reached 10,911 meters. My apologies for the error in the headline. I’ll correct it now.

    As to your second question — their innovations were doing away with the heavy copper power cable (it used batteries instead), and using a new kind of ultra-light fiber optic cable.

  • Jim

    Why not use wireless technology to send info to surface?

  • Bob Parker

    Jim – there’s no way to go ‘wireless’ from that depth. In general, you can’t transmit radio waves through water. Navy submaries can receive ELF (Extreme Low Frequency) signals at very shallow depths, but the bandwidth is quite low, so transmissions are limited to short simple messages – even more restricted than Twitter posts!
    One could go ‘wireless’ by using sound pulses, but again the potential bandwidth is quite low.
    The Navy is experimenting with laser-based communication for subs, but that is limited by the depth of water that UV light pulses can penetrate – a few hundred feet under the best cicumstances.
    Bottom line: the only way to transmit significant amounts of data from more than a few hundred feet deep is with electrical signals through a wire or light pulses through a fiber optics cable.

  • Charlie Wentz

    Is there any hope that robots can recover the black box from this latest airplane crash in the Atlantic?


  • Joh

    they first have to locate the plane (impossible) wouldnt be useless to send a 1 meter (or whats the size) robot down there to check 100km area, meter by meter, that would require months (interrupted by strong atlantic conditions

  • Jason

    Didn’t they say finding the Titanic was impossible?


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