SANYA, Hainan - The crew of China's 38th ocean scientific expedition returned to Sanya, Hainan province, south China, Wednesday.

The 59-day trip marks the conclusion of the first stage of a 124-day mission.

"Xiangyanghong 09," the mother ship, left east China's Qingdao on Feb 6 with the country's first deep-sea manned submersible Jiaolong and more than 150 personnel.

The researchers planned to conduct surveys in the northwest Indian Ocean, the South China Sea, Yap Trench and the Mariana Trench in the west Pacific Ocean.

During their first trip in the northwest Indian Ocean, Jiaolong helped scientists discovered 27 areas with hot liquid sulfide, called "black chimneys" by researchers, which can provide clues about the origins of life.

After a quick rotation of crew and material supply, the ship will embark on its second phase on April 9.

The whole voyage will last until June 9.

Named after a mythical dragon, Jiaolong reached its deepest depth of 7,062 meters in the Mariana Trench in June 2012.