Jiaolong completes its deep-sea expedition tasks

Five years on:

In the run-up to the 19th Communist Party of China National Congress, China Daily will cover a series of key projects and advanced equipment of national importance, showcasing the country's huge improvement and relentless efforts at innovation.

From extracting methane from the bottom of the sea to exploring trenches with submersibles, China is pushing forward technology and research on all fronts to unravel the mysteries of the deep.

Jiaolong , China's manned submersible, took its final dive in the Yap Trench on Tuesday, completing the third stage of the country's 38th oceanic expedition.

The craft reached a depth of 6,681 meters at 10:15 am, carrying three people. It returned to the mother ship－ Xiangyanghong 09 －at about 5 pm.

The Yap Trench is at the southern tip of the Mariana Trench－the deepest valley in the ocean－about 200 kilometers southwest of Guam. The Mariana's deepest section drops 11 km below the surface; the Yap's deepest is 8.5 km.

Jiaolong has made five dives in each trench since the third stage of the expedition began on May 16. The expedition is scheduled to end on Sunday.

Missions in these dives include taking photos and videos of sea creatures and geography, as well as collecting samples of seawater, sediment, rocks and deep-sea life to understand the trench's geochemical and biological environment.

Studying the samples can tell scientists about how the trench was formed, said Chen Xinhua, chief scientist for the expedition's third stage. The biological samples also have great research value in fields such as deep-sea biodiversity, ecosystems and biogeography.

The dives also provide an opportunity for comprehensive testing of systems on Jiaolong . Tuesday's dive closed out a four-year rigorous testing phase. Since June 2013, the craft has made 101 dives, from the Indian Ocean to the eastern Pacific, China's National Deep Sea Center said.

The 38th oceanic expedition, which began on Feb 6, has been the longest and included the most missions yet for Jiaolong . The first of its three stages took place in the Indian Ocean for 59 days; the second was in the South China Sea for 34 days.

Final frontier

The deep sea is often regarded as Earth's final frontier. Its exploration can yield a better understanding of how organisms adapt and live in extreme environments.

For example, the Mariana Trench is an abyss whose deep water temperatures are a chilly 1 to 4 C, and pressures are 1,000 times greater than at the ocean surface. Yet life blossoms, due to hot water vents that emit chemicals such as hydrogen sulfide－food for bacteria and other microbes, which in turn support a variety of exotic creatures ranging from giant amoebas to bioluminescent fish.

Chinese scientists discovered 27 such vents in the Indian Ocean during the first stage of the expedition. In the South China Sea, they found rare biological specimens, including a branch of red coral attached to polymetallic nodules－clusters of minerals containing more than 10 elements, such as cobalt and manganese.

Collecting samples

The third stage was also fruitful. On the first dive into the Mariana Trench on May 23, the vessel collected 26.3 kilograms of basalt samples and 16 liters of seawater, according to the State Oceanic Administration.

But the most intriguing rewards were the deep-sea creatures, including a sea sponge, a brittle star, two starfish and the catch of the day, a 35-centimeter red sea cucumber.

Named after a mythical dragon, Jiaolong reached its maximum depth of 7,062 meters in the Mariana Trench in June 2012. China is building a new mother ship to operate and support the submersible, with an expected launch in 2019.

To support maritime research, China also plans to build a seafloor scientific observation network this year, the first national science project in the maritime field. The project will be completed within five years at a cost of more than 2 billion yuan ($294 million).

Once the network is completed, China will join a dozen countries in the world that have such facilities, including the United States, the United Kingdom, Germany, France and Japan.

The cable-based network, connected with nodes of detectors and samplers, will constantly monitor and study the bed of the East China Sea and South China Sea, allowing scientists to study climate change, prevent and manage marine disasters and provide data for national security purposes and future explorations.

Deep gliders

China is also making strides in building submersibles and underwater gliders that can explore uncharted depths. In March, it became the first country to collect the artificial seismic stratigraphy of the Challenger Deep, the deepest section of the Mariana Trench, according to the Chinese Academy of Sciences' Institute of Geology and Geophysics. The stratigraphy is used to study the Earth's movement, layers and geological history.

In the same month, China also broke the world diving record for underwater gliders－6,329 meters with Hai Yi, a glider designed by the academy's Institute of Automation in Shenyang, Liaoning province. The previous recorder holder was a US glider at 6,000 meters.