Photo taken on Sept. 4, 2017 shows the root of a huge coral collected by Chinese research vessel Kexue. Chinese research vessel Kexue, carrying an underwater robot and an unmanned submersible, finished a month-long scientific exploration in the western Pacific Ocean Tuesday. Xu Kuidong, chief scientist on board the ship, said the researchers sent the unmanned submersible 15 times to Caroline Seamount, where no exploration had been made before, to collect 400 marine samples from 170 species. (Xinhua/Zhang Xudong)
