When Mao Zedong, the main founder of the People's Republic of China, wrote in May 1965 about his ambition to "rise high to the sky and pick the Moon" in a poem during a visit to the Jinggang Mountain in south China's Jiangxi Province, the first rural revolutionary base established by the Communist Party of China in 1927, China had barely made any marks in space exploration. The country had to wait five more years before sending its first indigenous satellite to the space atop the Long March 1 rocket.

On November 24, 2020, the Long March 5, the country's largest carrier rocket, sent the Chang'e-5 lunar probe into the space. When the return capsule touched down on Earth in north China's Inner Mongolia Autonomous Region 24 days later, it brought back 1,731 grams of lunar samples, the first space materials China ever brought back to Earth.

These are also the first lunar samples humans have brought back to Earth in more than four decades. The last sample from Moon, weighing 170 grams, was brought back by the Soviet Union's Luna 24 spacecraft in 1976.

To prevent total loss of these precious samples in disasters, they were divided for storage in different locations, and one of these locations is Shaoyang, Hunan Province in central China, the birthplace of Mao. 

"This is a tribute to Mao; his wish has now become a reality," Wu Yanhua, deputy head of the China National Space Administration (CNSA), said at a press briefing on the completion of the mission held on December 17, 2020.

Major milestone

The return of the capsule marked the successful conclusion of stage III of China's lunar exploration plan first approved in 2004. Based on the achievements of the previous two stages, which focused on orbiting around and landing on the Moon, respectively, the Chang'e-5 mission made major technological breakthroughs in the return to Earth.

The new challenges as compared to previous missions included collecting and packing the samples on the Moon, transferring them to the return vehicle, and launching an ascender on the moon to send them back to Earth.

To save payload and bring back more samples, an orbiter was left in the lunar orbit while the lunar lander-ascender assembly went down to the moon surface to take samples. This required ducting in the lunar orbit when the ascender returned with samples. It was challenging for these small machines to meet and dock with each other at such a distance from Earth.

"The systems had to be highly autonomous considering the limited control and support we could provide from Earth," said Hu Hao, chief designer of China's stage III lunar exploration program.

Another major challenge was the high speed of the return vehicle at its reentry into Earth's atmosphere, which was close to the second cosmic velocity, the speed needed to escape the gravitational field of Earth without further propulsion. The speed was much higher than that of all previous missions and required better heat resistance and control abilities.

The moon samples brought back by the mission are crucial for scientists to learn more about the Moon. The last time China's aerospace experts got their hands on a sample of the Moon was in 1987, when a gram of moon rock was given to China by the U.S. as a gift. It was part of the hundreds of kgs of lunar samples collected during the Apollo missions.

The samples are different from those brought by previous sample-taking missions by the U.S. or the Soviet Union. Chang'e-5 landed at a higher latitude on the Moon near Mons Rümker at the northeastern corner of Oceanus Procellarum (Ocean of Storms), which is the largest of the dark basaltic plains of the Moon that are visible to the naked eye. Scientists believe that some of the rocks in this region are much younger than all other lunar samples, and that research on samples from this area will add to current knowledge on the volcanic activities on the moon surface, which will help figure out the origin and evolution of the Moon.

To China's aerospace experts, the significance of the success of the mission lies more in its implications for further stages of the lunar exploration program. "Through the first three stages, we have gained the basic lunar exploration ability and a reserve of manpower, which has laid a solid foundation for our future operations," Hu said.

Deeper exploration

China's lunar exploration program comprises a series of missions, with the final goals of manned landing and building a base on the Moon. For the next stage, Stage IV, the goal is to build a prototype research station there, which will be made up of multiple probes in the lunar orbit and surface.

The Stage IV comprises four missions, with the first mission already completed when Chang'e-4 landed on the far side of the Moon in January 2019, the first time a manmade spacecraft landed on that side of the Moon. The missions yet to be launched are Chang'e-6 to 8.

Chang'e-6, set to be launched this year, will attempt to bring back samples from the south pole of the Moon. The area is of intense scientific interest with a large amount of water ice and one of the largest impact craters in the solar system, the South Pole-Aitken basin.

The Chang'e-7 and Chang'e-8 spacecraft will also land near the south pole to further analyze the region and test new technologies, including detecting and extracting materials that could be useful to future human explorers, such as water and hydrogen.

These missions are also laying the groundwork for other planetary explorations. The Tianwen-1 orbiter and rover are already on their way to Mars. They are expected to arrive in the planet's orbit and start orbiting this February, to be followed by a landing on the red planet in May. Other planned missions include a sample-gathering mission to Mars, a mission to sample an asteroid, as well as a mission to Jupiter.

A key requirement to conduct these missions is rockets. Chang'e-5 was launched by the Long March 5 rocket, which was designed with the mission in mind. For future missions, more powerful rockets are needed. Currently, the Long March 9 rocket, a heavy-lift vehicle for manned landing and deep space exploration, is being studied, which will have its first launch around 2030.

Another focus of China's space program is to build a low-Earth space station to gain more experience in human spaceflight. The plan is to conduct 11 launch missions, including four manned spacecraft, in two years. When it is built, it will be China's third and biggest space station where many experiments will be performed.

"When the station is built and the key technologies are verified, we will then investigate the feasibility of manned landing on the Moon," said Wu. 

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