A newly discovered photograph may provide the answer to one of the 20th century's greatest unsolved mysteries — the disappearance of Amelia Earhart. The legendary American pilot vanished 80 years ago this month somewhere over the Pacific. She was attempting to be the first woman to fly around the world. What is known is that Earhart and navigator Fred Noonan radioed on July 2 that they were in trouble between Papua, New Guinea, and Howland Island. U.S. investigators quickly gave up the search, concluding they crashed into the ocean and formally pronounced them dead in 1939. There have been numerous theories of what happened to Earhart and Noonan. But a new television documentary shows a previously lost photograph of a woman resembling Earhart and a man who experts say is almost certainly Noonan on a dock somewhere in the Pacific. The woman has her back to the camera and is looking to her right. She has the short hair style and men's-style pants Earhart was known to favor. A barge in the background appears to be towing an object that looks like the same size as Earhart's plane. The man in the foreground has the same hairline and prominent nose as Noonan's. The photo was misplaced in a box at the National Archives in Washington and the filmmakers found it by accident. Possibly seen as spies They theorize that Japanese forces captured Earhart and Noonan, believing them to be spies and held them prisoner in the Mariana Islands. It is unknown when or how they died. The producers believe someone spying for the U.S. against Japan took the photograph. They say that may be the reason why the United States hastened to give up looking for Earhart and Noonan. Shawn Henry, a former assistant director of the FBI and Earhart aficionado, hosts the documentary. He says the aviator was abandoned by her own government and “may very well be the first casualty of World War II.” The documentary, "Amelia Earhart: The Lost Evidence," premiers Sunday night on The History Channel.