China has yet again proved its spacefaring prowess with another successful touchdown on the moon.

Quoting the China National Space Administration (the CNSA, China’s equivalent of NASA) at 6:23 am on Sunday, Beijing Time: “On June 2, with the support of the Queqiao 2 relay satellite, the Chang’e 6 lander and ascender successfully landed in the preselected landing area in the South Pole-Aitken Basin on the far side of the moon.”

It is difficult to convey the significance of this achievement, but it involves the implementation of various sophisticated spacecraft communication and mission control capabilities and several technological breakthroughs. This is taken together with the implementation of a careful lunar retrograde orbit design to insert the spacecraft into the correct path. Indeed — as there is no direct line of sight between the Chang’e 6 lander (and all its instruments) and Earth, it is instead necessary to use a special in-orbit “Magpie bridge” Queqiao 2 relay satellite. This was sent to the moon in advance of this mission specifically for the purpose of triangulating signals from Earth to Queqiao 2 and from Queqiao 2 to the Chang’e 6 lander. Its vital role and capability were already demonstrated for the previous far-side Chinese mission, Chang’e 4, in 2019, with the initial Queqiao 1 relay satellite.

Why does this (Chang’e 6)mission matter? First, this is only the second time in history that any spacecraft has landed on the lunar far side. ... Second, this will be the first time in history that moon rocks from a completely different lunar geological environment can be transported back to Earth

The Chang’e 6 lunar spacecraft landed on a carefully chosen spot on the lunar far side in the South Pole-Aitken Basin region. Its primary mission? To replicate the previous amazing Chang’e 5 mission’s success and bring about 2 kilograms of moon rocks back to Earth. Indeed, Chang’e 6 was originally envisioned as a backup mission for Chang’e 5 if things had gone awry. Happily, the tremendous success of Chang’e 5 enabled the CNSA to instead re-scope this mission to the lunar far side and hence provide the possibility for major new science in the process.

Why does this mission matter? First, this is only the second time in history that any spacecraft has landed on the lunar far side, and is also the second Chinese mission to achieve this, so double happiness. The lunar far side is never seen from Earth because the moon’s rotational period matches the time it takes for the moon to orbit Earth. The two are in so-called “lockstep”.

Second, this will be the first time in history that moon rocks from a completely different lunar geological environment can be transported back to Earth. As the latest Chinese lunar surface maps show, in their recently released excellent lunar atlas, the far side looks very different from the side we are all used to seeing. The far side has a far more battered terrain from massive bombardments of asteroids billions of years ago. No lunar “mare” is created from massive lava flows unlike the beautifully named Sea of Tranquility of Apollo fame on the near side. Indeed, the first Chinese lunar-rock sample return mission, Chang’e 5, was a treasure trove of geological surprises. The returned samples revealed the material was far younger than those large Apollo samples and, indeed, even the few hundred grams the Russians managed to return from the moon in the 1970s.

This raises interesting questions about the geological history and active processes at work on the moon at far later time periods than previously thought. Our own HKU research on a small sample of Chang’e 5 moon rocks will hopefully help shed light on this, too.

Back to Chang’e 6: The more-rugged far-side terrain makes landing a trickier prospect, so various new processes were employed to give the mission the best chance, including an autonomous obstacle avoidance system to automatically detect surface irregularities using a visible-light camera. This provided the data needed to select a safe landing area.

The combination then hovered about 100 meters above the safe landing area and used a laser 3D scanner to detect obstacles on the lunar surface to select the final landing site before a slow vertical descent. As the combination approached the lunar surface, it shut down the engine and touched down via free fall, protected by a cushioning system.

Shortly after the vessel’s landing, the lander lunar rock sampling technologies will be deployed to both scoop top-surface material with a robotic arm and use a drill to collect subsurface rocks to bring back to Earth.

One important additional fact to realize is that the Chang’e 6 lander is not just about the sample return mission, even if it is by far the most important. It is also an international endeavor, with several science payloads on the lander from France, Italy and Sweden; and a so-called iCube-Q CubeSat, deployed in lunar orbit from Pakistan. The international instruments on the lander include the Negative Ions at the Lunar Surface device, developed by Sweden and the European Space Agency; and the Detection of Outgassing RadoN device from France. There is also the Italian passive laser retro-reflector that precisely measures distances from the lander to lunar orbit.

I confess I remain bemused by some commentators who talk about how such missions “could” be a pathway to China emerging as a dominant space power when the reality, as far as I see it, is that it already is, with much more to come.

The author is director of the University of Hong Kong’s Laboratory for Space Research.

The views do not necessarily reflect those of China Daily.