A manned submersible left from Yokosuka, Kanagawa Prefecture, on Saturday for a round-the-world cruise to conduct deep-sea research on the origin and evolution of life.
The Shinkai 6500 and its support ship, the Yokosuka, will study deep places where water hotter than 500 degrees is spewing from the seabed, and the creatures that live there, its operator said.
The team will sail westbound for a year through the Indian, Atlantic and Pacific oceans, the Japan Agency for Marine-Earth Science and Technology said.
The 10-meter-long submersible also will examine oil fields and undersea mountains in the southern Atlantic off Brazil, providing the first manned research in the area.
Hiroshi Kitazato, chief of the agency's Institute of Biogeosciences, said the agency hopes to discover "a clue to the revelation of the origin of life."
Completed in 1989, the submersible can dive to 6,500 meters and has a sphere-shaped space at the front big enough for two operators and a researcher.