Jiaolong manned deep-sea submersible completes expedition

China's Jiaolong manned deep-sea submersible returned to its homeport in Qingdao, Shandong province, on Friday morning.

The submersible's mother ship, Xiangyanghong 09, returned to the National Deep-Sea Base in the coastal city around 8:30 am, bringing to an end the nation's 38th oceanic expedition and the submersible's five-year trial run.

During the 138-day expedition that started on Feb 6, Xiangyanghong 09 sailed nearly 34,000 kilometers into the South China Sea, northwestern Indian and northwestern Pacific oceans, while Jiaolong conducted 30 dives to make scientific investigations and collect samples, said a news release from the State Oceanic Administration.

Researchers from the State Oceanic Administration, Ministry of Education, Chinese Academy of Sciences and China Geological Survey took the Jiaolong deep into the water and collected 624.6 kilograms of seabed rocks, 5,968 liters of seawater as well as 2,115 marine creatures, it added.

During the expedition, the submersible made five dives in the Mariana Trench, the world's deepest known trench, and Yap Trench, both in western Pacific Ocean. These operations have enabled scientists to better understand the trenches' geochemical and biological conditions, according to the news release.

After this mission, Jiaolong will receive a yearlong overhaul and technical upgrade before starting its formal operation, which, compared with the trial run, will travel farther away from China and deeper into the ocean and will conduct more dives each year, he said.

Named after a mythical dragon, Jiaolong is China's first manned deep-sea research submersible. It was developed by Chinese designers starting 2002 and entered service in 2010, making China the fifth country in the world having deep-sea exploration technology after the United States, France, Russia and Japan.

During a test dive in June 2012, Jiaolong reached its deepest depth - 7,062 meters - in the Mariana Trench. From January 2013, the submersible began a five-year trial run, during which time it made 152 dives.