China's longest expedition to the frozen world of Antarctica wrapped up on April 10 when a crew returned to the Waigaoqiao Dock in Shanghai. The trip's completion capped 25 years of South Pole research and exploration.

HARD WORK: Researchers on China's 25th Antarctic expedition measure the movement of icebergs on January 31, 2009 (XINHUA)

The 173-day mission also involved the most manpower ever-204 people, including six Korean helicopter crew members and one Belgian journalist. The crew completed 39 research projects and nine logistics tasks. The mission's crowning achievement-China's first, and the world's sixth, interior Antarctic research station, completed on January 27. Exploration authorities consider it a great achievement to mark the 25th anniversary of China's first journey to the bottom of the world.

The crew constructed the Kunlun Station at Dome Argus (Dome A), the pole's highest icecap at 4,093 meters above sea level. Dome A, an area once considered "unreachable," is one of the harshest environments on Earth-oxygen content is only 60 percent that of the surrounding interior, the weather is frightfully erratic and it is one of the coldest places in the world. Even in the summer the highest temperature stands at -35?.

NEW HOME: China's first inland Antarctic research base, Kunlun Station, officially began operations on February 2, 2009 (XINHUA)

The station will be used to study glaciology, astronomy, topology, geophysics, atmospheric sciences and space physics. Scientists will use it as a base from which to extract and study deep glacier ice cores and mountains under the Antarctic ice. They will also carry out astronomical and terrestrial magnetic observations.

Researchers hope to complete other studies on the effects of extreme weather on human psychology and physiology, and to test medical supplies, equipment and pharmaceuticals.

Nearly 30 countries have established research stations around the South Pole, but most of them, including China's Changcheng and Zhongshan stations, are located along the coastal areas of the continent. Scientists said they needed to build a station deeper into the icecap to carry out more cutting-edge research.

So far only seven countries, including China, the United States, Russia, Japan, France, Italy and Germany, have built inland Antarctic research stations.

The first step

When Kunlun Station was officially opened on February 2, Li Yuansheng said he held his tears back. Li, leader of the Dome A station traverse and construction team, has completed six Antarctic missions since 1996.

The search for Dome A's highest spot was launched but ended fruitlessly some 13 years ago because of the difficulty of the terrain. The researchers were forced to endure difficult conditions on the journey, eating only simple foodstuffs designed for astronauts and sleeping huddled together inside the container.

In 1999, Chinese researchers made their third attempt to look for the spot but again failed and had to retreat halfway from their destination, leaving gas barrels and a national flag as road signs for future expeditions.

Six years later, in January 2005, Li's team made their way to the dome again and saw the signs they had left. "All of the crew got off the vehicles, tears in their eyes," said Li.

This time, they successfully scaled the dome, the highest ice feature in Antarctica. "For 10 minutes or so we were just so excited that we walked here and there just to leave many footprints," said Li. Then they started the search for the highest spot on Dome A and found it after eight days of driving and measuring.

China's 24th expedition team again reached Dome A in January 2008. They carried out research along the way and decided upon the site for Kunlun Station.