For the first time, close-up photos of the far side of the moon have been achieved – an achievement credited to the Chinese lunar rover Yutu-2. Discoveries from the photos could be important for future missions.
The Chinese Yutu-2 is the first rover to visit the side of the moon never seen from Earth. This far side now appears to be quite different from the side that we do see when we look up at night. The far lunar side appears to have stickier, firmer ground and to harbor a greater amount of small rocks and impact craters.
Despite several reconnaissance missions to the moon, manned and unmanned, the far side has remained unexplored territory. This is largely due to the difficulty of communicating with Earth from there. Nevertheless, China’s Chang’e 4 mission landed the Yutu-2 rover, which has been roaming the surface ever since.
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Now roboticist Liang Ding of the Harbin Technology Institute in China and his colleagues have discovered something about the composition and characteristics of the lunar bottom on the other side. They looked at how the Yutu-2 moves, and at radar and spectrometry measurements.
The researchers, who declined to be interviewed for this article, found that the rover didn’t skid and slide as much as you’d expect if it had been traveling on the near side of the moon. This indicates that the distant moon side is relatively flat. In addition, the ground seemed to stick more easily to the rover’s six wheels, meaning it’s probably less powdery.
This knowledge is not only useful for designing future lunar rovers. Understanding soil composition and rock distribution can also teach us about the history of the moon itself.
“The presence of more small rocks can tell us something about the age of the surface,” says emeritus professor of planetary sciences Lionel Wilson of the University of Lancaster in the United Kingdom. ‘The bigger rocks are then worn out. If you wait long enough, a stone will automatically reduce to particles that are only a few millimeters in size.’
Electromagnetism
The Yutu-2 rover also found a dark green, glittering material at the bottom of a crater, similar to glassy material found in samples from the Apollo missions. It is the first time such a mineral, probably a remnant of an earlier impact, has been found on site.
“Any information about the history of impacts—from massive collisions to atomic-scale pinpricks—is important and valuable,” Wilson says.
The other side of the moon is very calm electromagnetically. This is because radiation from the earth cannot reach it. This side is therefore very suitable for astronomy. If we want to build observatories there, we need in-depth knowledge of the surface and soil composition. Future missions can investigate this.
“Exploration of the far side of the moon is still in its infancy,” said Sara Russell, professor of planetary sciences at the Natural History Museum in London. “It’s a whole new world to explore. There is much we have yet to discover; and that makes it very exciting.’