BEIJING -?Jiaolong, China's manned deep-sea submersible, returned Tuesday to Jiangyin of coastal Jiangsu province after a 52-day scientific expedition in the northwest Pacific Ocean.

Its carrier, Xiangyanghong 09 which set sail early July from Fuzhou of Fujian Province, traveled more than 9,000 nautical miles for the submersible's first expedition since 2014.

The expedition team said Jiaolong dived 10 times to survey cobalt-rich crusts and life forms inhabiting the bottom of the sea, clocking around 99 hours in total.

The sub collected 116 biological samples, 22 rock samples, 100 kg of cobalt-rich crust and 24 kg of polymetallic crust samples, as well as 1,232 liters of seawater from the Pacific Ocean. Experts also tested a remotely operated underwater vehicle, Longzhu.

The expedition team said some repairs will be made to Jiaolong before it heads for the Southwest Indian Ocean in a mission in November, when it will study polymetallic sulfides.

China began in 2002 to work on the ambitious ocean exploration program.

Named after a mythical dragon, Jiaolong reached 7,062 meters underwater in the Pacific's Mariana Trench with a dive in June 2012.