China's manned submersible Jiaolong finished a dive in "Challenger Deep" in the Mariana Trench, the world's deepest known trench, on Tuesday.

The Chinese manned deep-sea research submersible Jiaolong is put into sea on May 23, 2017. [Photo: Xinhua]

The dive began at 7:09 a.m. local time. Nearly three hours later, the submersible reached the planned depth of 4,811 meters, where scientists worked for more than three hours.

They conducted observation, sampling and surveying, and collected seawater, rocks and samples of marine life, including a sea cucumber, a sponge and two starfish. The submersible also photographed the seabed.

According to the scientists, the rocks collected in this dive will help them understand how the Mariana Trench formed and evolved, while marine life samples will contribute to research on the diversity of deep-water creatures, eco-systems and biogeography.

Chinese manned deep-sea research submersible Jiaolong [Photo: baidu.com]

The whole dive lasted 8 hours and 50 minutes, and Jiaolong surfaced at about 4 p.m. local time. The submersible reached its deepest depth of 7,062 meters in the Mariana Trench in June 2012.

The latest dive was the first of 10 dives planned for the third stage of China's 38th oceanic expedition.

The third stage mission began on May 16, when the Xiangyanghong 09 ship set sail for the Yap and Mariana trenches in the western Pacific Ocean with the submersible and 96 scientists on board.

Scientists also tested the submersible's technical and communication equipment, including its mechanical arms, through Tuesday's dive.

"The submersible's general technical conditions are stable, and various staff cooperated smoothly, fulfilling the scheduled mission and laying a foundation for deeper dives in the future," said Wu Changbin, commander of the expedition's third stage.

A second dive in the trench by Jiaolong is scheduled for Thursday.