On Friday, China launched a second lander to 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 lifted off on time at 5:27 p.m. local time under gloomy skies from the Wenchang space site on Hainan Island in southern China, carried to space by a Long March 5 rocket. About 32 minutes after the 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 Earth, whose erosion and shifting crust constantly renew its surface, the moon remains frozen in time. By studying samples from different parts of the lunar surface, scientists seek information about the origin and evolution of Earth’s satellite. But so far, the United States, the former Soviet Union and China have gathered samples only from the near side of the moon.
The far side of the moon — it is not actually the dark side of the moon — is distinct 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 Space Science Institute of Macau University of Science and Technology and a member of the Chang’e-6 science team. “If we can collect some samples on 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 mission will last 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 prior Chinese moon missions.
In 2020 another mission, Chang’e-5, gathered nearly four pounds of regolith from the moon’s near side and brought it to Earth. Scientists in other countries, including some in the United States, recently petitioned to study those samples.
Chang’e-6 will follow in Chang’e-5’s footsteps, but on the lunar far side. It will take five days after launch for the mission to reach the moon. There, it will orbit the moon for about 20 days. Then, after a brief stay on the surface of 48 hours, it will spend additional weeks in lunar orbit preparing 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 thought to have dug up material from the lunar mantle. If that material can be retrieved, scientists can learn more about the history of the moon’s insides.
“It’s very, very exciting,” said Jim Head, a planetary geologist at Brown University who collaborated with Chinese researchers to analyze the Chang’e-5 lunar sample. “Just 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, the Chang’e-6 lander is equipped with a camera, spectrometer and radar to investigate its surroundings and pick a spot to collect a sample. It will gather soil from the surface using a mechanical arm and collect a subsurface sample from as far down as 6.5 feet with a drill.
A vehicle on the lander will then lift off from the moon, passing the sample on to the orbiter’s re-entry module for its return back to Earth.
Because the same side of the moon always faces Earth, it is impossible to directly establish communications with the lunar far side. In 2018, China sent the Queqiao satellite into lunar orbit to relay information from Chang’e-4 to Earth. In March, it launched a second satellite called Queqiao-2. The pair will be used in tandem to remain in contact with Chang’e-6 during sample collection.
How does Chang’e-6 fit into China’s broader space exploration goals?
China’s lunar exploration program is one facet of the nation’s growing presence in space, which includes missions to Mars and future visits to asteroids. The Chang’e mission series, designed in the 1990s, included three phases: orbiting, landing and sampling. So far, it has a 100 percent success rate.
With the return of the Chang’e-6 sample, Dr. Qian said, China’s lunar exploration will pivot to a new strategy: investigation, construction and utilization. Its next two missions are already in development.
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 region that could potentially be used to build future infrastructure, according to the China National Space Administration.
China hopes to send astronauts to the moon in 2030 and is also working on establishing a permanent, international lunar research base by the 2030s.
What other missions have been to 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 Jan. 20. The small spacecraft ended up in an awkward configuration, with its engine nozzle pointed toward space. But it also made Japan the fifth country to reach the moon’s surface. Unexpectedly, the SLIM lander has continued to function on the lunar surface long after Japan’s space agency had expected to lose contact with the robotic vehicle.
The year’s second moon landing was the first by a privately operated spacecraft. Odysseus, built by Intuitive Machines of Houston, reached the lunar surface on Feb. 22. But the spacecraft toppled over, limiting the amount of science it could finish before freezing during the lunar night. Intuitive Machines has plans for another mission soon.