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December 15, 2018

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The Dummy’s Guide to Chang’e-4: a mission to the moon’s dark side

CHINA’S Chang’e-4 Lunar Lander and Rover were launched from the Xichang Satellite Launch Center in Sichuan Province on December 7. The mission, which has already reached the moon but has yet to touch down, will see the first ever manmade objects land on the mysterious dark side of the moon. But what exactly is the mission all about?

What’s the point of this mission?

To put it simply, the aim of the Chang’e-4 mission is to land on the far side of the moon and then deploy a rover. Both the lander and the rover will perform a multitude of tests to further not only our knowledge of the moon, but also, it’s hoped, about the formation of the universe. This mission will naturally build upon previous ones and support future Chang’e missions.

What will Chang’e-4 do on the moon?

Both the lander and the rover will perform tests that include observing radio signals, testing and analyzing the composition of the surface, as well as the overall composition and age of the moon itself, plus a number of other small tests and experiments.

One of the main aspects of the mission is to analyze low-frequency radio signals. The far side of the moon is perfect for these tests since it is permanently shielded by the radio waves emanating from Earth.

Another primary goal of the mission is to analyze material ejected when the Von Kármán crater was created. The crater, 180 kilometers wide and about 13 kilometers deep, is the planned landing site for the Chang’e-4 early next year. Because of its depth and the sheer amount of material ejected when the crater was formed, scientists hope to be able to analyze material from deep within the moon’s surface which could, ultimately, not only give clues about how the moon was formed, but how planets evolve in general. A number of other small tests and experiments will be undertaken, including seeing how seeds and insect eggs inside a small, sealed container interact — if the eggs hatch they will produce carbon dioxide, and the plants will produce oxygen through photosynthesis. Scientists will watch closely to see if some sort of a synergy is formed between the two processes — such findings could ultimately help us colonize the moon or other planets in the future.

Why is the far side so important?

Apart from the fact that man has not yet explored the far side of the moon from the surface, the “dark side” offers several factors that make research important. As mentioned above, the far side of the moon is shielded from Earth’s radio signals, and it is home to the Von Kármán crater.

Why is it called “the dark side”?

The far side of the moon isn’t always dark, but it is constantly facing away from us due to the moon revolving at the same rate as it rotates. It is called “the dark side” because it is out of our view and thus relatively unknown.

How do we communicate with Chang’e-4, then?

The Chang’e-4 program is helped out by the relay satellite Queqiao, which has a clear line of sight to Earth and the far side of the moon. Signals and instructions from scientists on Earth will literally bounce from Queqiao down to the Chang’e-4.

Why is the program called Chang’e?

The Chang’e Lunar Exploration Program is named after the Moon Goddess Chang’e, a character from a famous Chinese fable. Legend has it that the Moon Goddess’ husband, Houyi, was given a potion for immortality. He didn’t drink it, instead hiding it at home.

But Chang’e was forced to drink it herself when one of her husband’s apprentices tried to steal the potion, ultimately sending her floating to the moon for eternity.

Astronauts on the Apollo-11 mission were told by mission control to look out for Moon Goddess Chang’e on approach before the first moon landing in 1969.

What did the previous Chang’e missions do?

The Chang’e-1, which set off in 2007, scanned the entire surface of the moon in huge detail. The Chang’e-2, launched in 2010, returned to scan the surface in even greater detail. Chang’e-3 landed on the moon in December 2013 and launched a rover which explored 3 square kilometers. It also observed galaxies and other formations using ultra-violet light.

So, when will we know if Chang’e-4 was a success?

Current projections are that the Chang’e-4 Lander and Rover will touch down on the dark side of the moon in early January. We will no doubt be informed as new information is beamed back to Earth via the Queqiao relay satellite. Until then, let’s keep our eyes on the moon!


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