China's state-of-the-art manned submersible, Jiaolong, dived to a depth of 6,965 metres at the Mariana Trench in the western Pacific and returned safely to the surface late yesterday afternoon with samples of water and sea life.
The dive mission, which started at 5am and lasted about 10 hours, was aimed at testing Jiaolong's ability to reach 7,000 metres. The vessel, with three crew on board, stayed at a depth of 6,965 metres for several hours while they conducted research.
They sent their first picture, taken at a depth of 4,500 metres, to the submersible's mother ship, Xiangyanghong 09, showing part of Jiaolong's sample collection area.
The trip had been delayed by one day for repairs after engineers discovered during a regular check on Monday morning that sea water had seeped into an oil pipe in the submersible's hydraulic system and caused some corrosion.
Jiaolong left Jiangsu on board the Xiangyanghong 09 on June 3 and dove to a depth of 6,671 metres on Friday.
Xu Qinan, Jiaolong's chief designer, told the China.com.cn news portal yesterday that the successful dive meant that China could now search 99 per cent of the world's oceans, exploring for deep-sea resources and collecting biological samples around the globe.
Six dives at the Mariana trench have been scheduled for Jiaolong on this voyage, with an attempt at reaching 7,000 metres set for its fifth dive.
Jiaolong reached a depth of 3,759 metres in the South China Sea last summer, making China the fifth country in the world to master the technology required to send a manned submersible to a depth of more than 3,500 metres.
Xu said the Jiaolong is equipped with advanced underwater sound detection and terrain searching capabilities. It can also transmit images and sound at high speeds.
Beijing is keen to develop deep-sea resources and is hoping the submersible can discover vast deposits of metals believed to lie on the sea floor.
China has filed applications to the International Seabed Authority with a view to exploiting deep sea mineral resources in international waters.
Japanese media reports have said that Tokyo is concerned about potential military threats posed by China's deep-sea submersible.
In its annual white paper on national defence last year, Japan said that China's military maritime activities, including naval operations near Japan, should be watched closely.
Only the United States, France, Russia and Japan also have manned submersibles capable of reaching depths of 6,000 metres.
The number of countries, including China, that have manned submersibles capable of reaching depths of at least 6,000 metres