A researcher collects samples of sea water from the CTD(Conductivity Temperature Depth) on China's research vessel KEXUE(Science) in the western Pacific Ocean, May 29, 2019. KEXUE is carrying out a 20-day long investigation over a series of seamounts in the south of the Mariana Trench in the western Pacific Ocean. They will focus on biological diversities, ecological systems and biological distributions of the seamounts that they planned to explore. (Xinhua/Zhang Xudong)