China's manned submersible Jiaolong descended to 6,699 meters down in the Mariana Trench on Tuesday, recording images of two snailfish. Samples of rock, sediment, deep-sea life and sea water were also collected during the dive.

Images of creatures in the deep ocean taken by Jiaolong. /Xinhua Photo‍

Tuesday'diving  mission was Jiaolong's fourth this year in the trench. The vehicle began to work at 7:03 a.m. local time and reached the planned depth at 10:21 a.m.

Jiaolong is expected to complete four deep dives in the Mariana Trench as well as five deep dives in the Yap Trench. /Xinhua Photo

As an important part of the third stage of China's 38th scientific ocean expedition in the West Pacific, Jiaolong set off on May 16 for the Mariana Trench. It is expected to complete five deep dives in the Yap Trench to explore the adaptive mechanism and the evolutionary mechanism of creatures in the deep ocean.

Jiaolong‘s expedition is considered an important part of the third stage of China's 38th scientific ocean expedition in the West Pacific. /VCG Photo‍

"Research on snailfish, a typical deep-sea species, deepens our understanding on the evolution of deep-sea fish and their environmental adaptation mechanism," said scientist Peng Xiaotong, a researcher of the Institute of Deep-Sea Science and Engineering under the Chinese Academy of Sciences, and also the chief scientist of Jiaolong’s voyage.

Jiaolong's first dive this year in the Mariana Trench on May 23, 2017. /Xinhua Photo

Jiaolong's first dive this year in the Mariana Trench, the world's deepest known trench, took place on May 23, with a depth of 4,811 meters. The second and third dives fell on May 25 and 27, reaching 6,300 meters and 6,544 meters down the ocean, respectively.

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