Nature

China’s Chang’e-6 collects first rock samples from Moon’s far side

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China’s Chang’e-6 robotic Moon lander has wrapped up two days of drilling into the lunar surface of the far side of the Moon and the ascender has blasted back into space. The spacecraft, with its precious rock samples, is now in lunar orbit, waiting to dock with the orbiter for the trip home. It is the first time that samples have been taken from the far side of the Moon.

The Chang’e-6 lander made a successful touchdown on the Moon early Sunday morning (Beijing time) at a preselected site in the South Pole-Aitken (SPA) basin, the oldest and largest lunar impact basin. Since then, Chang’e-6 has autonomously deployed its drill and scoop to collect soil and regolith — rocky material covering the Moon’s surface. Together, the samples are expected to weigh up to 2 kilograms. “The sampling process has gone very smoothly,” says Chunlai Li, the mission’s deputy chief designer at the National Astronomical Observatories of China in Beijing.

With the specimens loaded and sealed, the ascender fired its engine at 7.38 a.m. Tuesday morning to lift off from the landing site, and reached its designated lunar orbit six minutes later, according to the China National Space Administration (CNSA) in Beijing.

“China is successfully carrying out complex operations on the lunar far side,” says Jonathan McDowell, an astronomer at the Harvard–Smithsonian Center for Astrophysics in Cambridge, Massachusetts. “The launch of the ascent stage was the first time anyone has taken off from the far side.”

Captivating basalt

Li says that Chang’e-6’s precise landing location is 41.63º S and 153.99º W, which means that the samples will mainly consist of basalts — dark, cooled lava. Similar material has previously been brought back to Earth for analysis from the Moon’s near side.

The basalts are estimated to be around 2.4 billion years old — much younger than the SPA basin itself, says planetary geologist Alfred McEwen at the University of Arizona in Tucson. “There should also be fragments of older rocks in the regolith they collected,” McEwen says.

Scientists hope to use samples returned from the SPA basin to precisely measure its age and to improve their understanding of the early history of the Earth and other planets, notes planetary geologist Jim Head at Brown University in Providence, Rhode Island.

Regardless of whether this information can be gleaned, the scientific value of the samples, if successfully returned, will be very high, he says. They will be the first rocks ever retrieved from the Moon’s far side, which has dramatically different topology compared with the near side. “Obtaining dates and compositional information from the many hundreds of fragments sampled by the Chang’e-6 drill and scoop is like a having treasure chest full of critical parts of lunar history, and will very likely revolutionize our view of the entire Moon,” he says.

Rock then dock

In the coming days, Chang’e-6 will face one of the trickiest parts of the mission — rendezvous and docking of the ascender with the orbiter and transferring the samples, says McDowell. “You have two robots orbiting the Moon separately at 5,900 kilometres per hour, which have to come together and touch each other gently without crashing into each other,” he says.

The Chang’e-6 samples’ trip to Earth is expected to last about three weeks, and will end around 25 June with the return capsule piercing through Earth’s atmosphere and landing in the grasslands of the Siziwang Banner in northern China’s Inner Mongolia autonomous region.

Planetary scientist Michel Blanc at the Research Institute in Astrophysics and Planetology in Toulouse, France, who watched the launch of Chang’e-6 on Hainan Island in China a month ago and has followed the key steps of the mission, says that its scientific impact cannot be overemphasized, because it will not only bring the first sample from the lunar far side, but also from one of the lowest-altitude regions of the Moon, where the surface might be closest to the mantle.

“We planetary scientists are crossing fingers for the success of the rest of the mission,” Blanc says.



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