On the trail of deep-sea oil

Massachusetts-built subs help scientists tracking Gulf plumes

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By Erin Ailworth
Globe Staff / June 15, 2010

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STENNIS SPACE CENTER, Miss. — The deep-sea photos on Vernon Asper’s laptop don’t look like much to the untrained eye: black squares with flecks of white and orange. But, he says, pressing a fingertip beneath one barely-there dot, that sure looks like oil to him.

Asper, a professor of marine science at the University of Southern Mississippi, will know more once he finishes analyzing data being collected by a deep-diving vessel built by iRobot Corp. in Bedford. The torpedo-shaped vessel, Seaglider 515, and several other seafaring robots are sliding through the Gulf of Mexico, assessing the oil in the water after a rig explosion off the Louisiana coast created a gusher that has turned into the nation’s worst environmental disaster.

Scientists will use the information gathered by the underwater gliders to map the oil swirling hundreds and thousands of feet beneath the ocean’s surface, and that will help them figure out how the oil is moving and where it might appear next. The information, collected with onboard sensors, is critical so cleanup crews can buffer the coast and know where to look for harmed wildlife. Government officials and researchers estimate that as much as 40,000 barrels of oil a day may have been leaking from the blown-out well drilled for BP, making it much bigger than the Exxon Valdez spill in 1989.

Researchers are essentially trying to answer two questions with the information provided by the gliders, said Breck Owens, a senior scientist at the Woods Hole Oceanographic Institution, who is piloting another type of glider, called Spray, that is working south of the spill.

“How can we help today?’’ Owens said. “And the second question is what can we do today so that if this happened in 2025 we would be ready? Would we have the right information to help? The right techniques? The right instrumentation?’’

At first, some were skeptical that oil — which is lighter than water, and therefore rises — would remain beneath the surface. But recently, Jane Lubchenco, head of the National Oceanic and Atmospheric Administration, said researchers from the University of South Florida had found “subsurface oil’’ moving much like a cloud of volcanic ash might about 40 nautical miles northeast of the well site.

“There’s definitely oil there; it’s in low concentrations,’’ Lubchenco said. “That does not mean that it doesn’t have significant impact.’’

Using the gliders to study the nearly two-month-old spill has an unexpected benefit: showcasing the cutting-edge technology in submersible robots, like Seaglider 515, that one day could advance deep-sea discoveries and other oceanic efforts.

“Every time we get a chance to demonstrate their capabilities, it helps toward selling them in the future,’’ Owens said. At least half a dozen are already on the job, including the Seaglider, Spray, and four Slocum gliders made by Teledyne Webb Research in East Falmouth.

Deep-sea submersibles were once an oddity. Perhaps the best known is Alvin, the Woods Hole-operated vehicle that surveyed the sunken Titanic in 1986. But most early submersibles were clunky, expensive, and limited by their human crew or lines tethering them to research boats. But as scientists and the government have become more interested in the ocean climate, unmanned robotic vessels like the Seaglider and Slocum, have come into wider use.

“Seaglider is out there all the time, day or night. If we have a hurricane, it won’t care. It will never get seasick or tired,’’ explained Asper, who said the $150,000 robot is less costly than a fully staffed research ship. Since their invention in 1995 at the University of Washington, Seagliders have explored the water under the ice in the Arctic, listened for whales in deep water, and tracked ocean currents, according to iRobot, which began licensing Seagliders in 2008.

Seaglider 515, a new robot, was dropped in the water off Venice, La., on May 21. From there, the battery-powered vessel cut through a tricky current, and went on its way, using a rotating brass weight instead of a rudder to change direction.

The robot finished its 100th mission last week, and has made a score of dives since, under the direction of Elizabeth Creed, lead system engineer at iRobot. Creed, working from New Jersey, remotely guides Seaglider 515 through an Internet connection, using commands that she can tap out on any basic text-editing program. When it surfaces, the glider responds by delivering data using an on-board iridium modem that calls a satellite.

“Just had a chat with it about thirty minutes ago,’’ Creed said by phone on a recent afternoon. “It came up, phoned home, took its next commands, gave me its data from its last dive, and said, ‘I’ll see you in the next five and a half hours.’ ’’

The robot’s sensors are gathering several pieces of information, including water temperature and conductivity, and whether oil might be present.

At a recent visit to his lab at the Stennis Space Center, Asper showed off some of that data, which had been compiled into rainbow-colored renderings.

“You ask a scientist a question about this, you’re going to see a lot of charts, plot graphs. It’s what we do,’’ Asper joked, before moving to show off his other glider, a bumblebee-yellow Slocum, which occupied a table in the room.

The Slocum, Asper said, can go only as deep as 200 meters, so it’s often used in shallower waters. The Seaglider can sink up to 1,000 meters, making it suitable for exploring the depths immediately around the oil spill.

The work excites him, Asper said, because people outside the science community want to know what he finds: How is oil snaking its way through the ocean? What does that mean for the fish and fowl and fishermen who depend on the sea?

“It’s interesting to everybody,’’ Asper explained. “A lot of the things we do interest us, but nobody else cares about.’’

Erin Ailworth can be reached at