Yutu-2 rover moves toward crater inspection.

China’s Chang’e-4 mission to the farside of the Moon is expected to provide “breakthrough findings.”

As the lander and the recently dispatched Yutu-2 rover survey their lunar surroundings, important discoveries are on tap.

“The farside of the Moon has very unique features, and has never been explored in situ, so Chang’e-4 might bring us breakthrough findings,” said Zou Yongliao, director of the lunar and deep space exploration division of the Chinese Academy of Sciences, as quoted in a recent Xinhua news story.

Soviet Luna 3 image from October 1959.
Credit: NSSDC Image Catalog/Goddard Space Flight Center

Nearside/farside differences

Apollo 8 farside view.
Credit: NASA

The farside of the Moon was first imaged by the former Soviet Union’s Luna 3 probe. As for humans seeing the farside, that occurred during the Apollo 8 mission in December 1968.

The Moon’s nearside and farside are different: the nearside has more and relatively flat lunar mares, while the farside is peppered with impact craters at different sizes.

“There are great differences in terms of substance composition, terrain and landforms, structure and the age of rocks. For instance, about 60 percent of the nearside is covered by mare basalt, but most part of the farside is covered by lunar highland anorthosite. Of the 22 lunar mares, 19 are located on the near side,” said Zou.

Hidden information

Credit: NASA/GSFC/Arizona State University

Chang’e-4 landed within the South Pole-Aitken (SPA) Basin, the largest and deepest basin in the solar system. The touchdown was in Von Kármán crater, a 110 miles (186-kilometers) wide region.

“With the Chang’e-4 probe, we can detect information hidden deeply inside the Moon. I believe there will be surprising scientific findings,” Zou said. “The rocks on the farside are more ancient. The analysis of their substance composition might help us better understand the evolution of the moon,” he told Xinhua.

The Chang’e-4 lander/rover are geared with instruments developed by scientists from Sweden, Germany and China to study the lunar environment, cosmic radiation and the interaction between solar wind and the lunar surface.

Advanced Small Analyzer for Neutrals (ASAN) device.
Credit: Swedish Institute of Space Physics

Water on the Moon

The Swedish Institute of Space Physics (IRF) in Kiruna developed the 1.4 pound (650 grams) Advanced Small Analyzer for Neutrals (ASAN) device. The aim of the instrument is to study how the solar wind interacts with the lunar surface.

ASAN was built in collaboration with the Chinese National Space Science Center (NSSC). It is the first time an energetic neutral atom sensor is deployed on the lunar surface. From a vantage point of only a few decimeters above the regolith surface, ASAN will measure energy spectra of energetic neutral atoms originating from reflected solar wind ions under different solar wind illumination conditions.

On a roll. China’s Yutu-2 rover on the Moon’s farside.

ASAN is mounted on the Yutu-2 rover making it possible to perform measurements at different locations. The measurements could shed light on the processes responsible for the formation of water on the Moon.

Lunar night

The next step for ASAN is the instrument commissioning.

“The first science data are expected before February, 11th”, says Martin Wieser, researcher at the Swedish Institute of Space Physics and principal investigator of ASAN.

“The lunar night is especially difficult, but both the rover and our instrument are designed to withstand these extreme conditions. ASAN is mounted inside a thermally insulated payload compartment that is open during daytime and closed during night time to cope with the low temperatures. We keep our fingers crossed that all systems will work as designed”, says Wieser.

Pre-launch prepping of Yutu-2 rover.
Credit: China Central Television (CCTV)/China National Space Administration (CNSA)/Screengrab/Inside Outer Space

Smarter, stronger

Yutu-2 needs solar power to operate. After sunset, this power source is not available and the temperatures will drop significantly during the two-week-long lunar night.

Xinhua also notes that, although the rover of the Chang’e-4 probe looks similar to its predecessor Yutu of the Chang’e-3 probe, Chinese space engineers have made Yutu-2 lighter, smarter, stronger and more reliable.

Scientists hope Yutu-2 will travel farther that Yutu-1 and send more images of the farside scenery.

Weighing nearly 300 pounds (135-kilograms) Yutu-2 is 4.4 pounds (2 kilograms) lighter than its predecessor. At that weight-class it is the lightest rover ever sent to the Moon, said Jia Yang, deputy chief designer of the Chang’e-4 probe, from the China Academy of Space Technology (CAST).

The main reason for the weight reduction is the removal of a robotic arm and its replacement with the Swedish ASAN instrument, said Jia.

The first close-up photo of the Moon’s farside, taken by a monitoring camera on the Chang’e-4 lander showed the direction the rover would drive on to the lunar surface. Top of image shows the rails the rover will use to access the surface.



Design life

Two panoramic cameras on the wheeled robot can take high-resolution, color images.

The rover has a design life of three months and can cross rocks as high as 7.9 inches (20 centimeters).

Yutu-2 will automatically enter a dormant state based on the level of sunlight, and it can also enter the work state on its own.

“We made this adjustment because communication between ground control and the Chang’e-4 probe on the farside of the Moon is not as convenient as communication with Chang’e-3 on the nearside,” said Zhang.

Preventing short circuits

China’s first lunar rover Yutu-1 suffered a mechanical fault after driving about 375 feet (114 meters) five years ago.

“How to solve that problem so that it won’t happen again was the main challenge in developing the new rover,” said Zhang Yuhua, another deputy chief designer of the probe.

“We have improved the layout of the wires on the new rover and taken measures to prevent short circuits. We also made a fault isolation design so that if a problem occurs, it will not affect the whole system,” said Sun Zezhou, chief designer of the Chang’e-4 probe. “We are confident our new rover can run farther on the Moon and obtain more scientific results,” Sun said.

Artwork depicts Chang’e-4 touchdown on Moon’s farside.
Credit: CCTV/Screengrab/Inside Outer Space


What’s next?

According to Zhang Yuhua, deputy chief commander and designer for the Chang’e-4 lunar mission in a story posted by China Global Television Network (CGTN):

“What’s next for the rover is to take a picture of the front side of the lander, after that, it will go to its planned area and start a series of scientific exploration projects in the Von Kármán crater,” said Zhang.












Leonard David is author of Moon Rush: The New Space Race to be published by National Geographic in May 2019.

To pre-order Moon Rush: The New Space Race, go to:




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