Chang’e-4 made the first-ever soft landing on the far side of the moon at 10:26 Thursday morning, marking a breakthrough in human exploration of the universe, according to a statement the China National Space Administration (CNSA) sent to the Global Times on Thursday.

The probe sent back images at 11:40 am, about one hour after landing in the Von Karman Crater of the South Pole-Aitken Basin, said the administration, unveiling the moon’s far side for the first time in lunar exploration history. 

The far side of the moon refers to the hemisphere that never faces the Earth and cannot be seen directly from the Earth.  

The lunar lander touched down and sent signals from the moon’s far side to the Earth for the first time, launching “a new chapter in human exploration of the moon,” according to the administration’s statement. 

The probe’s lander and rover successfully separated on Thursday night, Xinhua reported. The first photo of the Yutu II rover landing on the far side of the moon was snapped by a camera attached to the lander and sent to Earth via the Queqiao satellite. 

The name Yutu II was picked for the rover of Chang’e-4 from 42,945 online suggestions from all over the world including Light, Walking Man and Elf, CNSA announced on Thursday night.

The rover looks like its predecessor Yutu, or Jade Rabbit, China’s first lunar rover launched in 2013.

An image of the moon’s dark side. Chang’e-4’s lander descends to the moon’s surface. Photo: China National Space Administration (CNSA)

But the newer rover has adaptable parts and an adjustable payload configuration to deal with the more complex terrain on the far side of the moon, the Xinhua News Agency reported Thursday.

Hashtags related to Chang’e-4’s moon landing had been viewed more than 100 million times as of press time on Thursday evening.  

Internet users almost universally welcomed the landing. 

“Chang’e flying to the moon is a myth and we are realizing the myth,” Sina Weibo user Zanjia posted. 

“Congratulations to China’s Chang’e-4 team for what appears to be a successful landing on the far side of the Moon. This is a first for humanity and an impressive accomplishment!” tweeted NASA Administrator Jim Bridenstine.

An image shot after Chang’e-4’s soft landing on the moon’s dark side. Photo: China National Space Administration (CNSA)

‘Blind landing’

Rocks on the moon’s far side are comparatively more ancient than those on the front, Pang Zhihao, a Beijing-based aerospace expert, told the Global Times on Thursday. 

Chang’e-4 will help humanity learn the origin and evolution of the moon and help with low-frequency radio astronomical observations, Pang said. Those observations may well lead to some major astronomical discoveries, he noted. 

It was not easy for Chang’e-4 to land in the heavily cratered, mountainous South Pole-Aitken Basin, he said.

The basin was created by the impact of a meteor and is one of the largest known impact craters in the solar system. It is about 2,500 kilometres in diameter and 13 kilometres deep, according to Xinhua.

Unlike the Chang’e-3 probe landing on the Sinus Iridum, or the Bay of Rainbows, on a parabolic trajectory, the Chang’e-4 probe made a vertical descent at the Von Karman Crater, said the CNSA. 

“The Von Karman Crater is believed to have great scientific research potential. The region is also comparatively flat, making it safer for Chang’e-4 to land there,” Pang said.

A vertical landing helped Chang’e-4 avoid hitting rocks on the far side. As Chang’e-4 cannot directly communicate with the Earth, the probe relays communication – with a 1-minute delay – through the satellite Queqiao, or Magpie Bridge, said CNSA. 

Such a time difference creates the conditions for a “blind landing,” meaning the probe must land on its own, using information installed in advance.

To ensure a safe landing, Chang’e-4 was equipped with an autonomous diagnosis system to detect and resolve problems for itself. 

The probe can also work at night to record the temperature of the far side, another improvement on Chang’e-3, Pang said. 

Cooperative future

More than 100 spacecraft and probes have been launched onto the moon since the 1950s, but none soft-landed on the moon’s far side, Zou Yongliao, deputy director of the National Space Science Center under the Chinese Academy of Sciences, said at a press conference in November 2018.

Chang’e-4 is carrying eight payloads including a low frequency radio spectrometer from Germany and detectors from Sweden.

Instruments will conduct low-frequency radio astronomy observations, research the structure of the moon’s surface and study neutron radiation on the moon’s far side.     

CNSA said that with data provided by the Chang’e-4 probe, they would like to jointly explore the universe in cooperation with foreign space agencies, research institutes and space enthusiasts. 

Broader mission

The Chang’e-4 landing moves China a step closer to the establishment of a moon base. The lunar exploration project was initiated in 2004 as China’s first step into deep-space exploration. 

The Chang’e-1 to Chang’e-5 lunar probes constitute the first of three phases from unmanned lunar exploration through manned moon landings to the establishment of a moon base. 

The construction of the moon base will be controlled by artificially intelligent robots and occasionally managed by human beings after astronauts are sent to the moon, China News Service reported in March, citing Zhao Xiaojin, Party chief of the China Academy of Space Technology at the China Aerospace Science and Technology Corporation.

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