KUALA LUMPUR, Malaysia — Satellite sightings of 122 objects floating southwest of Australia are “the most credible lead that we have” in the search for Flight 370, the Malaysian defense minister said Wednesday evening, adding that his country had asked Australia to try to recover the objects and see if they were debris from the missing jetliner.
The search for the Malaysia Airlines plane, focused now on a remote stretch of the southern Indian Ocean, resumed Wednesday after a day’s suspension due to bad weather, and at least four aircraft were scheduled to search Wednesday night, the Australian Maritime Safety Authority said in a statement.
The defense minister, Hishammuddin Hussein, said the 122 objects were visible in satellite images forwarded by Airbus Defense and Space, the main European commercial satellite company. Malaysia passed the images to Australia, which is leading the search in the area. Australian authorities did not report having located any of the objects by late Wednesday night.
In the satellite photos, which were taken Sunday, the objects are visible through gaps in clouds over an area of 154 square miles (400 square kilometers) of ocean, Hishammuddin said. The largest was about 75 feet (23 meters) in length, and some were bright, he noted without elaboration. Metal objects that had recently fallen into the ocean might be reflective.
Airbus said five of its Earth observation satellites — some equipped with high-resolution cameras, others with radar — were assisting in the search for Flight 370, and would do so as long as needed. Images and data from the satellites were being submitted to the Malaysian and Australian authorities for analysis, the company said.
The floating objects were about 1,589 miles (2,557 kilometers) southwest of Perth, authorities said. If they are found to be from the missing plane, a Boeing 777 that took off March 8 bound for Beijing with 239 people aboard, the next steps would be to figure out how far and in which direction the debris might have drifted since the aircraft came down, and then to begin an undersea search, Hishammuddin said.
The U.S. Navy has sent an undersea listening device and a sonar device to the area. But each needs to be towed far underwater behind a ship traveling scarcely faster than a person walking, so they cannot search large areas quickly.
The listening device could pick up signals from the missing plane’s cockpit data recorders, or black boxes, before the recorders’ batteries are exhausted and they stop emitting pings, which is expected to happen in two to three weeks. But to detect the pings reliably, the device must be within about a mile of the black boxes. The sonar device will continue to work after the data recorders go silent, but it needs to be even closer to detect wreckage on the seabed.
Recovering floating debris from the plane could help provide closure for the families and friends of the passengers and crew, who have expressed anguish that the plane was declared lost based on satellite data and not any tangible physical evidence. But floating debris may turn out to be of only limited help in locating the data recorders, oceanographers said. In the 18 days since the plane disappeared, the debris could have drifted hundreds of miles, according to Jianping Gan, an oceanographer at the Hong Kong University of Science and Technology who has done research aboard a Chinese icebreaker in the ocean waters around Antarctica.
Jason Ali, an earth sciences professor at Hong Kong University who has studied currents in the Indian Ocean, said, “if it has been floating for two and a half weeks, it’s not going to have much relation to the wreckage” on the seabed.
Mike Purcell, a senior engineer at the Woods Hole Oceanographic Institution in Massachusetts, who led two underwater search expeditions for the wreck of Air France Flight 447 in the Atlantic in 2010 and 2011, said that the current search zone for Flight 370 was far more remote than the location of the Air France wreckage was, and the seas and weather conditions were known to be considerably rougher.
“That can slow down your progress considerably, because it makes it more difficult to operate, to get the vehicles in and out of the water,” he said. Storms can also force the suspension of search work for days at a time, he said.
Purcell estimated that there were fewer than a dozen vehicles in the world equipped with the sonar and imaging technology required for a deep water search of this scale. They are operated by oceanographic institutes, the U.S. Navy and a handful of private companies, he said.
Purcell said searcher might have one advantage: the sea floor in the southern Indian Ocean is relatively flat, compared with the highly varied terrain of the mid-Atlantic where Air France Flight 447 was sought. The water depths are comparable in the two regions, at more than 10,000 feet.
Military submarines have sophisticated equipment for listening for signs of surface ships or other submarines. But they are designed to operate mainly within a few hundred feet of the surface, and have only a limited ability to detect pings from the ocean floor far below, transmitted through water of varying densities and temperatures moving at different speeds. Towed devices, on the other hand, can operate at great depths: the Bluefin-21, which the U.S. Navy is sending to the region, can descend to 14,700 feet, and a pinger detector can plunge 20,000 feet.
For now, aircraft from Australia and other countries have been scouring an area the size of the western and southwestern United States where the plane is believed to have flown after it sent its last automated signals to a satellite. The authorities have not extended the search to all the places in the ocean where debris might have drifted. Because the search area is so far from land — roughly a four-hour flight in each direction — planes are able to spend only a couple of hours searching at a time before they must turn back to base.
Making matters more difficult, oceanographers said, the currents in the relatively remote and little-traveled southern Indian Ocean are less well understood than those in busy sea lanes. A violent storm Tuesday, one of many in the region as the southern hemisphere’s winter approaches and days become shorter, has further churned the waters.
Furthermore, any floating debris sticking up out of the water could have been blown in different directions from the prevailing currents. “With any wind, it’ll act like a sail,” Ali said. Wave action may also have pushed objects in unpredictable directions, making it hard to calculate the past movements of any specific object.
As difficult as the black boxes may be to locate and recover, even they may not tell investigators enough to explain what happened to Flight 370, which stopped communicating with ground controllers and veered radically off course about 40 minutes after taking off.
The plane flew on for at least seven more hours, but its cockpit voice recorder would have stored only the two last hours of sound in the cockpit before the aircraft ceased operating. The separate data recorder would have stored information from various aircraft instruments and controls covering the whole flight, but that data may not reveal the intentions of whoever was in the cockpit or tell investigators if the turn off course was deliberate, as the Malaysian authorities have suggested.