Search for missing MH370 jet could turn on robot subs

This 2011 photo provided by Sylvain Pascaud shows the ship Alucia and the REMUS 6000 robot sub during the search for Air France Flight 447. Unmanned subs, also called autonomous underwater vehicles or AUVs, played a critical role in locating the wreckage of the lost Air France jet, two years after it crashed in the middle of the south Atlantic. The find allowed searchers to recover the black boxes that revealed the malfunctions behind the tragedy. Sylvain Pascaud, Associated Press

Two miles down or more and darker than night, the ocean becomes a particularly challenging place for human searchers.

If the wreckage of a missing Malaysian airliner rests somewhere in the Indian Ocean's depths, then investigators will likely need to entrust the hunt at least partly to robot submarines and the scientists who deploy them to scan remote swaths of the seafloor.

Such unmanned subs, called autonomous underwater vehicles or AUVs, played a critical role in locating the carcass of a lost Air France jet in 2011, two years after it crashed in the middle of the south Atlantic. The find allowed searchers to recover the black boxes that revealed the malfunctions behind the tragedy.

That search keyed off critical information: The search area for the Air France jet was much smaller than that for Malaysia Airlines Flight 370, and the first pieces of wreckage were recovered within days of the crash.

Even then, it required two years and four deep water search missions before a team from the Woods Hole Oceanographic Institution, using an AUV equipped with side-scan sonar, located the jet about 12,800 feet (3,900 meters) underwater.

"Air France 447 is a bit different from Malaysian Air 370 in that we had a few more clues to work with," said Dave Gallo, who led the search team from Woods Hole, located on Massachusetts' Cape Cod. The independent research institution has offered its services to investigators but has not been asked to join the current search effort.

Before unmanned subs can be sent down to look for the Malaysian jet, the search zone must be narrowed considerably. That depends on finding wreckage on the surface. Officials cautioned Wednesday that search planes, which have scoured the ocean for more than three weeks without finding any sign of the downed jet, aren't certain to find any wreckage and that investigators may not be able to determine the reason for its disappearance.

The size of the search area changes daily because of factors such as currents; on Wednesday it was 85,000 square miles (221,000 square kilometers).

But if investigators can zero in on an approximate crash location, they will likely turn to AUVs to begin the methodical task of tracking back and forth across miles of ocean floor in search of anomalies that might be wreckage.

"I like to think of it as mowing the lawn. You want to cover every bit of it," Gallo said.

"You need a little bit of luck and a lot of prayer that the oceans are going to cooperate, and then off you go."

The unmanned subs used by the Woods Hole team were developed as tools to research and monitor relatively shallow coastal waters, measuring variables like salinity and temperature over wide areas for hours on end. But AUVs are increasingly harnessed to perform some of the most demanding underwater jobs.

The U.S. Navy uses them to search for underwater mines because they can stay below the surface of even very cold water much longer than any diver, without the worry of exposing a human to danger. Energy companies employ unmanned subs to survey the floor at underwater drill sites.

In 2009, California's Waitt Institute sent down a pair of AUVs that surveyed more than 2,000 square miles of South Pacific ocean bottom over 72 days in an unsuccessful search for Amelia Earhart's plane.

The area off western Australia where search planes and aircraft are looking for the Malaysian jet slopes from about 2,600 feet (800 meters) to about 9,800 feet (3,000 meters) deep. But part of the zone drops into the narrow Diamantina trench, about 19,000 feet (5,800 meters) down.

"Let's hope the wreck debris has not landed over this escarpment. It's a long way to the bottom," said Robin Beaman, a marine geologist at Australia's James Cook University.

The U.S. Navy last week sent a Bluefin-21 autonomous sub to Australia to prepare for an eventual deep water search. That sub can dive to about 14,800 feet (4,500 meters). The largest unmanned subs used by Woods Hole researchers are built to reach depths of about 19,700 feet (6,000 meters).

Searchers can also use tethered submersibles, towed by ships from cable that allows for real-time data transmission to the surface and a continuous supply of power to the vehicle. But it is a very slow process. AUVs can scan a larger area more quickly, without being affected by conditions on the surface. But they must be brought back to the surface to recharge, and for researchers to download and analyze their data.

Even so, they are much better suited to the job of deep water search than any manned sub, whose descents are limited by air, light and power, as well as safety concerns, said William Sager, a professor of marine geophysics at the University of Houston.

Sager recalled that in 2000, when he climbed aboard a sub and ventured 5,600 feet (1,700 meters) down to the bottom of the Gulf of Mexico, all those factors limited time on the sea floor to just four hours, moving at a crawl. A researcher looking out a porthole into even the clearest water with a very bright light can't see beyond 100 feet, he said.

Unmanned subs are far more flexible. When Woods Hole engineers built their first REMUS 6000 sub a little more than a decade ago, they tested it off the Bahamas by driving it down a trench the scale of the Grand Canyon, said Chris von Alt, who led the team that developed the craft and then co-founded Hydroid Inc., the Massachusetts manufacturer of the subs.

The REMUS sub — nearly 13 feet long, 1,900 pounds and mustard yellow — is equipped with sonar that can be programmed to capture images of vast stretches of seafloor and the objects resting there. Powered by a lithium battery, the unmanned subs stay below the surface for 20 to 24 hours. Scientists on the surface are now able to modify instructions to the sub via an acoustic link that allows them to look at bits of data gathered by the vehicle, von Alt said.

But they don't know what the sub has found until it surfaces and its data is fully downloaded to a computer.
The task requires patience and, for researchers whose livelihoods are focused on ocean life, a willingness to harness their expertise in a grim but necessary pursuit of answers.

"That's why you do it," von Alt said. "One of (the reasons) is, 'Why did it happen?' But the other is to get closure for the families who have suffered through the tragedy."

- Contributed by AP writers Adam Geller and Nick Perry in Wellington, New Zealand and videographer Steve Andrada in Woods Hole, Mass.

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Searching the vast seabed of jet hunt zone mostly flat with one trench for MH370

This undated graphic provided by Commonwealth of Australia (Geoscience Australia) Dr. Robin Beaman

WELLINGTON, New Zealand — Two miles beneath the sea surface where satellites and planes are looking for debris from the missing Malaysian jet, the ocean floor is cold, dark, covered in a squishy muck of dead plankton and — in a potential break for the search — mostly flat. The troubling exception is a steep, rocky drop ending in a deep trench.

The seafloor in this swath of the Indian Ocean is dominated by a substantial underwater plateau known as Broken Ridge, where the geography would probably not hinder efforts to find the main body of the jet that disappeared with 239 people on board three weeks ago, according to seabed experts who have studied the area.

Australian officials on Friday moved the search to an area 1,100 kilometers (680 miles) to the northeast of a previous zone as the mystery of Malaysia Airlines Flight 370 continued to confound. There is no guarantee that the jet crashed into the new search area. Planes that have searched it for two days have spotted objects of various colors and sizes, but none of the items scooped by ships has been confirmed to be related to the plane.

The zone is huge: about 319,000 square kilometers (123,000 square miles), roughly the size of Poland or New Mexico. But it is closer to land than the previous search zone, its weather is much more hospitable — and Broken Ridge sounds a lot craggier than it really is.

And the deepest part is believed to be 19,000 feet within the range of American black box ping locators on an Australian ship leaving Sunday for the area and expected to arrive in three or four days.

Formed about 100 million years ago by volcanic activity, the ridge was once above water.

Pulled under by the spreading of the ocean floor, now it is more like a large underwater plain, gently sloping from as shallow as about 2,625 feet to about 9,843 feet deep. It got its name because long ago the movement of the Earth’s tectonic plates separated it from another plateau, which now sits about 1,550 miles to the southwest.

Much of Broken Ridge is covered in a sediment called foraminiferal ooze, made of plankton that died, settled and was compacted by the tremendous pressure from the water above.

“Think like it’s been snowing there for tens of millions of years,” said William Sager, a professor of marine geophysics at the University of Houston in Texas.

Like snow, the layer of microscopic plankton shells tends to smooth out any rises or falls in the underlying rock. In places, the layer is up to half a mile deep.

But if the fuselage of the Boeing 777 did fall on to Broken Ridge, it would not sink much into the muck.

“The surface would be soft, it would squeeze between your toes, but it’s not so soft that you would disappear like snow,” Sager said. “Something big like pieces of an airplane, it’s going to be sitting on the surface.”

Searchers will be hoping that if the latest area turns out to be where the plane crashed — and that remains educated guesswork until searchers can put their hands on aerial debris sightings and check what it is — the fuselage did not go down on the southern edge of Broken Ridge.

That’s where the ocean floor drops precipitously — more than 2 1/2 miles in places, according to Robin Beaman, a marine geologist at Australia’s James Cook University. It’s not a sheer cliff, more like a very steep hill that a car would struggle to drive up. At the bottom of this escarpment is the narrow Diamantina trench, which measurements put as deep at 19,000 feet, though no one is sure of its greatest depth because it has never been precisely mapped.

“Let’s hope the wreck debris has not landed over this escarpment — it’s a long way to the bottom,” Beaman said.

The Diamantina trench, named after an Australian navy vessel, is one of the deeper sections of the parts of the oceans that surround Antarctica, according to Mike Coffin, the executive director of the Institute for Marine and Antarctic Studies at Australia’s University of Tasmania.

The trench’s rocky crags and crannies would make it difficult for ships using instruments like side-scanning sonar or multi-beam echo sounders to distinguish any debris from the crevices.

Searchers will especially be hoping to locate the jet’s two “black boxes,” which recorded sounds in the cockpit and data on the plane’s performance and flight path that could help reconstruct why it diverted sharply west from its overnight flight from Kuala Lumpur, Malaysia, to Beijing on March 8. The black boxes were designed to emit locator pings for at least 30 days, and are projected to lose battery power — and thus their pings — by mid-April.

The pinger can be heard as far as 2 1/2 miles away, but the distance can vary widely, depending on the state of the sea and the wreckage location, said Joseph Kolly, director of research and engineering for the U.S. National Transportation Safety Board. Black boxes can get buried or muffled by other wreckage, and thermoclines, which are layers of water with great variations in temperature, can refract the signal, he said.

The sediment on Broken Ridge is unlikely to inhibit the ping — but on the escarpment or in the trench, rocks could scatter the sound, making it harder to detect, according to Mike Haberman, a research scientist specializing in acoustics at the University of Texas, Austin.

To pinpoint the ping they hear from the surface, searchers likely will run a submersible equipped with sonar several hundred feet above the ocean floor. The unmanned underwater vehicle will putter along at a slow jog, able to “see” objects on the floor that may seem out of place. But its vision is limited — in a day it could cover an area only about the size of Manhattan, Sager said.

The observations stored in the vehicle’s memory can be accessed only by bringing it to the surface.

Under the best conditions, to survey the entire new search area could take between three months and up to nearly two years, depending on the quality of data needed to identify the debris, according to calculations by David T. Sandwell, a professor of geophysics who specializes in seafloor mapping at the Scripps Institution of Oceanography in San Diego.

Because it is such a painstaking — and expensive — process, most mapping has been focused on things that people consider useful, like underwater shipping hazards and potential oil deposits. With nothing much to interest people in the this part of the Indian Ocean, the maps tend to follow features like the volcanically active mid-ocean ridges, leaving big blank spaces in between.

There are 50-mile-wide strips of the search area where no shipboard measurements have been taken and scientists use less detailed satellite measurements and educated guesswork to depict what the floor actually looks like.

Precisely what the seafloor looks like in detail in the area of the new search is another in a long line of Flight 370 mysteries.

By JUSTIN PRITCHARD AND NICK PERRY  The Associated Press

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