China lands sample return probe on moon

The shadow of one of Chang’e 5’s landing legs is visible in this image from the spacecraft after touching down on the moon Tuesday. Credit: CNSA

A Chinese spacecraft successfully touched down on the moon Tuesday, beginning what engineers have described as the most challenging phase of the mission to drill, scoop, and seal rocks for launch back into orbit later this week and return to Earth in mid-December.

The Chang’e 5 lander set down in the moon’s Oceanus Procellarum, or Ocean of Storms, region in the northern hemisphere of the near side of the moon, east of a volcanic plateau named Mons Rümker.

The landing occurred at 10:11 a.m. EST (1511 GMT) Tuesday, according to the China National Space Administration. The space agency reported the lander touched down at 43.1 degrees north latitude and 51.8 degrees west longitude on the moon.

The robotic sample return mission launched from China’s Wenchang spaceport Nov. 23 aboard a heavy-lift Long March 5 rocket, then arrived in lunar orbit Saturday.

The Chang’e 5 mission’s landing craft detached from its orbiter and return section Sunday to begin a series of descent maneuvers.

CNSA said Chang’e 5’s final descent began at 9:57 a.m. EST (1457 GMT) from a velocity of 3,800 mph (1.7 kilometers) per second under the power of 1,700-pound-thrust throttleable engine, culminating in a brief hover roughly 300 feet, or 100 meters, above the lunar surface to allow on-board sensors to find a smooth landing site.

After reaching the surface, the spacecraft deployed power-generating solar arrays and a communications antenna to begin its two-mission on the moon, CNSA said.

The landing Tuesday signaled the start of a frenetic pace of activities on the lunar surface. The Chang’e 5 lander was expected to begin digging into the lunar crust within a couple of hours after arriving on the moon, first using a drill and then a scoop on a robotic arm to collect rocks for return to Earth.

If successful, Chang’e 5 will be the first mission to bring back rocks from the moon since the Soviet Union’s Luna 24 mission in 1976.

Chang’e 5 is designed to extract up to 4.4 pounds, or 2 kilograms, of material from a depth of up to 6.6 feet, or 2 meters, below the lunar surface.

If all goes according to plan, Chang’e 5’s ascent vehicle will take off Thursday to climb back into orbit around the moon, using its landing platform as a launch pad. The ascent vehicle is expected to rendezvous and dock with the mission’s return module in lunar orbit Saturday, then transfer the lunar samples into the orbiter. The return craft will begin maneuvers to head for Earth for a high-speed re-entry and landing in China’s Inner Mongolia region in mid-December.

The successful landing Tuesday marked the third time China has soft-landed a spacecraft on the moon, following the Chang’e 3 mission in 2013 and Chang’e 4 in 2019. Chang’e 4 became the first spacecraft to achieve a soft landing on the far side of the moon, a feat enabled by the placement of a purpose-built Chinese data relay satellite in deep space.

Chang’e 3 and Chang’e 4 carried rovers to serve as mobile scouts exploring the lunar landscape. Chang’e 5’s mission on the lunar surface has no mobile rover.

Clive Neal, a lunar scientist at the University of Notre Dame, said China had proven it can land on the moon with previous missions.

“But then they have to collect the sample,” Neal said in an interview shortly after Chang’e 5’s launch. “The interesting thing is they launch from the moon, get into lunar orbit, and then rendezvous with the Earth re-entry vehicle that will bring that sample back to Earth safely and uncompromised. When the Soviets did it in 1976, the last time, it was direct to Earth. They launched from the moon and came straight back to Earth. This one has an extra step in there, which has to go well in order for the sample to actually make it back.

“But given the capability they’ve demonstrated with doing things for the first time, such as the far side landing and roving, I expect things to be successful, and hope they are,” Neal said in an interview with Spaceflight Now.

“We have never done a whole process of taking and sealing samples,” said Peng Jing, deputy chief designer of the Chang’e 5 mission at the China Academy of Space Technology, in an interview aired on China’s state-run CCTV television channel. “This part of the work mainly depends on several complicated structures including the drill … the robotic arms used to scoop up rocks and regolith on the lunar surface, and actually a high vacuum sealing device designed to ensure that the sample can remain in its intact status.”

Scientists want to make sure the lunar specimens are sealed for the return to Earth to avoid contamination.

Another challenge will be Chang’e 5’s launch from the lunar surface, the first takeoff from the moon since the 1970s. The ascent module must launch on a precise trajectory to rendezvous with the return module in lunar orbit, and ground teams did not know the lander’s exact orientation on the moon’s surface until after touchdown.

“We need to precisely anticipate the location and speed of the two spacecraft flying (in) lunar orbit,” Peng told CCTV. “Because the probes don’t match in size — our ascender weighs just around 300 to 400 kilograms (660 to 880 pounds) during docking, while the (orbiter) weighs nearly 2,000 kilograms (4,400 pounds). Any error could knock off the smaller spacecraft, and that would make the docking job much more difficult than before.”

After transferring the samples to the Earth return spacecraft, Chang’e 5 will fire engines to break out of lunar orbit and head for home.

The return carrier will re-enter the atmosphere at some 25,000 mph, or 40,000 kilometers per hour, significantly faster than a re-enter from low Earth orbit. The capsule will will land around Dec. 15 in China’s Inner Mongolia region, where teams will retrieve the moon specimens and transport the material to a lab for analysis.

Nine missions have returned moon samples to Earth, including NASA’s six Apollo missions with astronauts, and three robotic Luna spacecraft launched by the Soviet Union. NASA’s Apollo missions brought back 842 pounds (382 kilograms) of rocks from the moon.

There is evidence that rocks in Chang’e 5’s landing zone are much younger than those returned by the Apollo astronauts. Those specimens are some 3.5 billion years old, created during a period of active volcanism in the first billion years of the moon’s existence.

Lava plains to the east of Mons Rümker appear to be less battered by asteroid impacts, suggesting rocks there could be less than 2 billion years old. But models of the moon’s evolution suggest its internal heating should have diminished by that time, rendering volcanoes extinct, Neal said.

“It will be exciting to look at the age of these samples coming back and also the actual compositions of them,” Neal said.

“We haven’t returned samples form the moon in 44 years, since Luna 24, a long time ago,” said James Head, a planetary scientist at Brown University, in an interview broadcast on China’s CGTN television network. “The best way to learn about the moon is by returning samples. That’s true for any planetary body because we can do analyses in the lab that are far superior than what we can do remotely or in situ.”

“Chinese scientists have said that samples from different ages are needed to form a complete picture of the moon,” Peng said. “Through analysis, they think the samples we will collect from the northwest region of Oceanus Procellarum are relatively young. By combining those samples with the previous ones, we will have a better understanding of the moon’s formation and evolution.”

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Follow Stephen Clark on Twitter: @StephenClark1.