Contrary to popular belief and Pink Floyd, the dark side of the moon isn’t, well, dark. It’s bathed in the same amount of the sun’s rays as the near side is; it just never turns to face Earth. This has made it somewhat difficult to study. But the far side has just been metaphorically illuminated by China’s Chang’e-4 lander, which completed the first successful soft landing on the far side of the moon on January 3. The examination of the mysterious pockmarked surface offers up a plethora of discoveries that could tell us the origin of the universe, establish a greenhouse on the moon, and determine the chemical composition of lunar rock on the far side.
The far side of the moon has been out-of-bounds territory for space agencies because it is very hard to communicate with, thanks to radio signals not being able to travel through the entire moon between it and Earth. In fact, the first humans to ever glimpse the far side of the moon were the Apollo 8 astronauts as they orbited around it. Chang’e-4, therefore, has to go through a communications-relay satellite, called Queqiao (literally “magpie bridge”). The Chinese National Space Administration (CNSA) launched the satellite on May 20, 2018 in preparation for its landing.
But because of the inability for radio signals to pass through, the far side is also a prime spot for an astronomical observatory. This is why Chang’e could give us information about the origins of the universe. After the urging of several astronomers, a low-frequency radio telescope has been included among the lander’s several capabilities. The microwave background radiation, discovered by Arno A. Penzias and Robert W. Wilson in 1965, will be measured and could help us discover more about the Big Bang, the event that created the entire universe. In order to do this, they will use the Advanced Small Analyzer for Neutrals (ASAN).
The main goal of the Chang’e mission is to study the lunar composition of the far side. An ancient collision event left a colossal crater on the moon, called the Aitken Basin, which is exposed to deep lunar crust and mantle materials. This would be unprecedented in terms of figuring out the internal structure of the moon. The far side is also helpful in this aspect because the lack of lava flows has left an intact record of impact craters. The moon’s surface is also surprisingly full of water. One theory for its existence is that solar winds (highly charged particles including hydrogen) react with the oxygen in the minerals of the surface. But this is notoriously hard to replicate in a lab, so it’s most easily observed where it happens naturally: on the actual moon. Discovering how this water is created could have long-ranging implications for a manned base on the moon, where harvesting water from the surface could be much cheaper than bringing it. Less weight means less money, and in the billions of dollars it takes to do these kinds of missions, every cent counts.
Directly after landing, Chang’e deployed a rover that made the first tracks of its kind in the soft lunar soil, with solar panels spread out like a baby chick learning to fly for the first time. The rover, dubbed Yutu-2, is named after the jade-rabbit, which was the pet of the moon goddess, Chang’e. The rover sent back images of far side surfaces on January 3.
Perhaps the most interesting among the capabilities of Chang’e is the fact that it houses a biosphere filled with cotton seeds and insect larvae. Unfortunately, only ten days after the cotton seeds sprouted, the low lunar temperatures proved too dangerous, and the 100-day experiment was terminated on January 13. Despite its brevity, the experiment was still a success; seeds germinated, which could have long-lasting implications for a self-sustaining moon base. Overall, Chang’e-4 is historic, groundbreaking, and maybe could even be the start of a second space race between the U.S. and China.