Photo taken on May 18, 2019 shows an unmanned remote sensing submersible equipped for Chinese research vessel Science. Chinese research vessel Science left the eastern city of Qingdao Saturday, on an expedition to the little-known seamounts in the Mariana Trench, the world's deepest natural trench. Researchers will study the topography, hydrology and bioecology of the western Pacific Ocean's typical seamount, said Xu Kuidong, chief scientist of the mission with the Institute of Oceanology of the Chinese Academy of Sciences. (Xinhua/Li Ziheng)

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