Special Ship Retires in Yokosuka

25 January 2026, Yokosuka 

— Research ship 'Mirai' holds its final public viewing; formerly 'Mutsu', active in the Arctic and other regions

The research vessel 'Mirai' (about 8,700 tons) of the Japan Agency for Marine-Earth Science and Technology (JAMSTEC) in Yokosuka, Kanagawa Prefecture, which had been in operation for 28 years for observing the Arctic Ocean and deploying large observation buoys in tropical seas, was retired, and its final public viewing was held on the 25th at Yokosuka New Port Pier in the city.

Its predecessor was Japan's first nuclear-powered ship, the 'Mutsu,' which was launched in 1969. In 1974, there was a radiation leak accident off the eastern coast of Aomori Prefecture. After repairs and test voyages, the ship was divided into three sections. The central part, which contained the nuclear reactor, was removed, and the bow and stern were reused and fitted with diesel engines, transforming it into the 'Mirai.' The nuclear reactor is on display at the Mutsu Science and Technology Museum in Mutsu City, Aomori Prefecture.

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From the Nuclear-Powered Ship to "Mirai" 

The journey of "Mirai" was itself a testament to the culmination of Japanese science and technology. Its predecessor was Japan's first nuclear-powered ship, "Mutsu." In 1997, it was reborn as a state-of-the-art research vessel powered primarily by a diesel engine, enabling observations in previously challenging conditions, such as extremely cold seas and rough weather. With a length of 128.5 meters and a weight of 8,706 tons, its size was also a weapon for ensuring stable data collection even in turbulent waves. 

Over 28 years, it traveled approximately 2.3 million kilometers (equivalent to 58 trips around the Earth). It made over 20 Arctic voyages, alerting the world to the severe reality of declining sea ice. In research that forecasts humanity's future—such as studies on climate change phenomena and global warming—it was recognized by scientists worldwide as a "floating ocean laboratory." 

Currently, construction is underway on "Mirai II," which is scheduled to take over the duties of Mirai, with completion aimed for around November this year.