At 17,000 feet beneath the surface, the temperature of ocean water is just above freezing, oxygen is sparse and currents are relatively calm. In other words, ideal conditions for preserving an airplane that might have crashed into the depths nearly 70 years ago, according to marine explorer David Jourdan, who hopes to answer one of aviation's greatest mysteries -- the fate of famed pilot Amelia Earhart.
Jourdan and his Maine-based company, Nauticos, plan to launch an expedition in the spring using sonar to sweep a 1,000-square-mile swath of ocean bottom west of tiny Howland Island in the Pacific Ocean.
It is the latest in a string of missions to learn what happened to Earhart when she, her navigator and their Lockheed Electra plane disappeared on a flight around the world.
"Things tend to last a time'' in the deep ocean, said Jourdan. "Our expectation is the plane will be largely, if not completely, intact.''
That is, if the plane is even in the ocean.
There is a host of theories about what befell Earhart and navigator Fred Noonan in 1937 as they made one of the final legs of their widely heralded flight.
Some have searched the sea, believing the plane ran out of gas. Others think she survived a crash landing but died on a deserted island. Another theory is that the Japanese captured and executed her. The conspiracy-minded claim Earhart survived and lived out her life under an assumed name as a New Jersey housewife.
This much is agreed on -- Earhart and Noonan vanished July 2, 1937, as they approached an air strip on Howland Island, roughly midway between Australia and Hawaii. They had taken off from Papua New Guinea, just 7,000 miles short of their goal to make Earhart the first woman to fly around the world.
A fearless flyer, Earhart set a string of altitude, distance and endurance records in the 1920s and 1930s, proving the still-young world of flying wasn't reserved for men. She captivated a Depression-era America eager for heroes, was feted by presidents and was compared to Charles Lindbergh. The press dubbed her "Lady Lindy.''
The Navy launched a weeks-long search of 250,000 square miles of ocean around Howland and a nearby chain of small islands. No trace was ever found of the plane.
One of those going along on the Nauticos mission is Elgen Long, a former commercial pilot who has spent 30 years researching the mystery.
Long, 77, of Reno, Nev., believes the answer to Earhart and Noonan's fate lies in their radio communications with a U.S. Coast Guard cutter that was tracking their course near Howland Island. Using Coast Guard radio operator's logs, Long concluded Earhart was perilously low on gas because a headwind was much stronger than she had anticipated. One of her last radio calls said she had only a half hour of fuel left and couldn't see land.
"We can follow her all the way across the Pacific,'' he said of the radio records. "She ran out of gas just when she said she was going to.''
This is Jourdan's second search of the area west of Howland; a 2002 mission was aborted because of technical problems. The same general area was searched in 1999 by another mission that found nothing conclusive, but Jourdan said his new expedition, costing about $1.5 million, will use better sonar technology and more accurate information on where the plane may have crashed.
The shortage of oxygen and the fairly still water means a metal airplane likely would not have completely corroded, he said.
Any human remains would have long vanished, but Jourdan hopes to find clues such as Earhart's jewelry in the pilot's seat, or perhaps even Earhart's leather jacket.
"That would be eerie,'' he said.
If he finds it, Nauticos would plan another mission to raise the plane, which would become the centerpiece of a traveling exhibit on Earhart's life, Jourdan said.
Earhart's stepson, George Putnam, was 16 years old when her plane disappeared. Putnam, now 83 and living in Florida, said he supports the mission partly because it could end the wild speculation about what happened to her. He doesn't mind if Nauticos salvages the plane.
"Let's see what happens,'' he said.
To Long, it could be his last chance to solve one of the 20th-century's biggest mysteries.
"We need the true story of what happened,'' he said. "The history we read needs to be correct.''