Cutting the Cord

January 8, 2014 (posted January 9, 2014)
by David Levin

When a strong wind is blowing, the view over the side of Atlantis can be a strange one. With each wave, the ship pitches and rolls. As it moves, the horizon, which normally looks like a fixed line in the distance, seems to come to life. It disappears beneath the stern, then leaps up far above the deck, where it hangs for an instant before diving back out of sight. It's an optical illusion, of course. We're the ones moving, not the rest of the world.

While this steady motion isn't dangerous for the ship, it does put a damper on the researchers' sampling efforts. For the past day and a half, the high seas have made it impossible to relaunch Jason. The constant rocking could swing the 9,000-pound vehicle into the side of the ship as it goes overboard, or strain the winch cable that keeps it tethered to Atlantis. As a result, Jason has spent the last 36 hours parked on the ship’s stern, waiting to return to the seafloor once the weather improves.

Finally, at 10 a.m. today, word begins to spread among the scientists: the Jason team has made a judgment call. The sea is still rough, but it has died down just enough to go ahead with the launch as planned.

Start, then stop

The scientists scramble into action, grabbing samplers and sensors to send to the ocean floor. Before the vehicle dives again, they'll drop an elevator filled with equipment over the side, including four of WHOI geochemist Jeff Seewald's Isobaric Gas-Tight samplers (IGTs) and crates containing flow meters and chemical sensors. They will also send down the Large Volume Pump (LVP), an instrument that can pull a few hundred liters of vent fluid through a large filter, capturing huge numbers of microbes in the process.
 
Back on the stern of the ship, Jason technicians and engineers once again swarm the vehicle, checking electrical connections and testing its robotic arms, while researchers finish last-minute preparations in Atlantis’ main lab. Everything seems to be falling into place.

Suddenly, the lab door opens, and Jason Expedition Leader Tito Collasius enters, shaking his head. "We have a problem," he tells the waiting researchers. "The tether cable is broken. We'll need to replace it. Could be five or six hours before we're ready to go."

The tether he’s describing is a 60-meter-long yellow cable that leads from Jason to its sister vehicle, Medea. Inside its thick plastic sheath, three copper wires deliver electrical power to Jason, and tiny fiber-optic lines, barely thicker than a hair, send control signals and video data at incredible speeds between the vehicle and the ship. One of those lines, which is made of a thin, glasslike material, has snapped—meaning that the Jason pilots would not be able to steer the vehicle in the water.

It's a setback, but Rick Sanger, Jason electronics technician, takes it in stride. "A tether cable is sort of like the tires on your car," he said. "Sometimes you'll get 50,000 miles out of them without a problem, and other times, you'll get a flat. You just have to deal with those problems as they come up."

Fortunately, just like a car, the Jason team carries a spare, so rather than trying to repair the broken fiber-optic cable, they can replace the entire tether with a fresh one. That’s not a simple task, however. First, the team needs to drain the oil that fills the boxes and tubes that contain Jason's electrical components. Then they snake a new tether cable into the heart of the vehicle, a procedure that can take most of a day to complete.

Now what?

While that work is being done, the researchers start to wonder what this delay could mean for them. If Jason can't be fixed today, some samples that the scientists were counting on obtaining today won't come in.

For some groups, that's not a problem—Dionysis Foustoukos' team has enough vent fluid to last them another day, so they'll continue with their high-pressure experiments (you might remember those from January 6).

For others, the broken tether could cause a hiccup in their work. Microbiologist Craig Taylor, who oversees the Large Volume Pump, is getting concerned. The LVP, you’ll remember, has already been sent to the seafloor on an elevator. It is set on a timer that will start up its motor at 11 tonight. If Jason isn’t there to place the pump’s nozzle into a vent, the device will pull in ordinary seawater instead of vent fluid.

Likewise, Nadine Le Bris and Leonid Germanovich, who are recording the chemistry and flow rate of vents, can’t deploy their sensors and measuring devices on the seafloor without Jason, so their research is temporarily on hold.

Jesse McNichol and François Thomas are growing bacteria inside of IGTs and are in a similar situation. They’ve run out of vent fluid, so to continue with their experiments, they'll need to collect fresh samples using the IGTs that went down on the elevator earlier this morning. Like the Large Volume Pump, they must be deployed at the vent by Jason.

A new record

For Thomas, at least, the delay may not be catastrophic. If no samples are available, he said, he might take the time to catch up on some sleep. He and McNichol need to tend to their experiment every few hours, so the pair often stays up late into the night.

A nap isn’t in the cards today, however. Just three hours after the tether problem was discovered, the Jason technicians announce that they’ve installed the spare in record time, and the dive will continue as planned this afternoon.

Thomas sighs and heads back to work, thinking about a cup of coffee to stay awake.

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