On Friday, China launched a second lander on the lunar far side. If the mission is successful, it will be the first in history to bring back a sample from the part of the moon that Earth never sees.
The mission is called Chang’e-6, named after the Chinese moon goddess and pronounced “changa”. It took off on time at 5:27 p.m. local time under dark skies from the Wenchang Space Site on Hainan Island in southern China, was carried into space by a Long March 5 rocket. About 32 minutes after launch, the spacecraft separated from the rocket and the mission proceeded on a 5-day journey to the moon.
Why the far side of the moon?
Unlike the Earth, whose crustal erosion and displacement constantly renews its surface, the moon remains frozen in time. By studying samples from different parts of the lunar surface, scientists are looking for information about the origin and evolution of the Earth’s satellite. But so far, the United States, the former Soviet Union and China have collected samples only from the near side of the moon.
The far side of the moon—not actually the dark side of the moon—is distinguishable from the near side. It has a thicker crust, more craters and fewer maria, or plains where lava once flowed. But no one really knows why the two sides of the moon are so different.
“People want to know why this happened,” said Yi Xu, a professor at the Institute of Space Science of Macau University of Science and Technology and a member of the Chang’e-6 science team. “If we can collect some samples from the far side, then we can maybe get some clues to these questions.”
What will Chang’e-6 do?
Chang’e-6 is the latest in a series of Chinese lunar missions designed to orbit or land on the moon. The shipment will take 53 days.
The first to visit the far side of the moon, in 2019, was Chang’e-4, which included a rover to explore the moon’s Von Karman crater. China remains the only nation to send a lander to the other half of the Moon.
“China has found its niche, to explore the lunar far side,” said Roberto Bugiolacchi, a planetary geologist also at Macau University of Science and Technology who has analyzed data from previous Chinese lunar missions.
In 2020 another mission, Chang’e-5, collected nearly four pounds of regolith from the near side of the moon and brought it back to Earth. Scientists in other countries, including some in the United States, recently asked to study these samples.
Chang’e-6 will follow in the footsteps of Chang’e-5, but on the lunar far side. It will take five days after its release mission to reach the moon. There, it will orbit the moon for about 20 days. Then, after a brief 48-hour surface stay, it will spend additional weeks in lunar orbit in preparation for a five-day return trip to Earth.
The mission’s orbiter will circle the moon while its lander descends into the 1,616-mile-wide South Pole-Aitken Basin on the lunar surface. The impact that created the basin – among the largest in the history of the solar system – is believed to have gouged material from the lunar mantle. If this material can be recovered, scientists can learn more about the history of the moon’s interior.
“It’s very, very exciting,” said Jim Head, a planetary geologist at Brown University who worked with Chinese researchers to analyze the Chang’e-5 lunar sample. “Like before the Apollo samples were returned. But now, it’s the other side of the moon.”
According to Yuqi Qian, a lunar geologist at the University of Hong Kong, Chang’e-6 is equipped with a camera, spectrometer and radar to survey its environment and select a spot to collect a sample. It will collect soil from the surface using a mechanical arm and collect a subsurface sample from 6.5 feet down with an auger.
A lander vehicle will then lift off from the moon, passing the sample to the orbiter’s reentry unit for return back to Earth.
Because the same side of the moon always faces Earth, it is impossible to make direct communications with the lunar far side. In 2018, China sent the Queqiao satellite into lunar orbit to transmit information from Chang’e-4 to Earth. In March, it launched a second satellite called Queqiao-2. The pair will be used in conjunction to stay in contact with Chang’e-6 while collecting samples.
How does Chang’e-6 fit into China’s broader space exploration goals?
China’s lunar exploration program is one aspect of the country’s growing presence in space, which includes missions to Mars and beyond visits to asteroids. The Chang’e mission series, planned in the 1990s, included three phases: orbit, landing, and sampling. So far, it has a 100% success rate.
With the return of the Chang’e-6 sample, Dr Qian said, China’s lunar exploration will shift to a new strategy: research, manufacture and exploitation. His next two missions are already underway.
Chang’e-7, expected to launch in 2026, will search for water near the lunar south pole. Chang’e-8 will survey material in the same area that could potentially be used to build future infrastructure, according to the China National Space Agency.
China hopes to send astronauts to the Moon in 2030 and is also working to establish a permanent, international lunar research base by the 2030s.
What other missions have taken place on the moon this year?
If the first leg of Chang’e-6’s journey is successful, the spacecraft will be the third to land on the Moon in 2024.
Japan reached the moon with the Smart Lander for Investigating Moon, or SLIM, on January 20. The small spacecraft ended up in an awkward configuration, with its engine nozzle facing space. But it also made Japan the fifth country to reach the surface of the Moon. Unexpectedly, the SLIM lander continued operation on the lunar surface long after Japan’s space agency expected to lose contact with the robotic vehicle.
The second moon landing of the year was the first by a private spacecraft. Odysseus, built by Intuitive Machines of Houston, reached the lunar surface on February 22. But the spacecraft capsized, limiting the amount of science it could complete before it froze during the lunar night. Intuitive Machines has plans for another mission soon.