Just before 10:30 am Beijing local time on January 3, the robotic spacecraft Chang’e 4 made a soft landing in the South Pole-Aitken Basin area of the moon, otherwise known as the “far side” or “dark side” of Earth’s only natural satellite.

It is the first spacecraft in history to attempt or achieve a landing on this unexplored area, which is never visible from Earth.

After keeping the details of the mission under wraps until the last minute, China announced the successful landing and shared the first lunar images captured by the unmanned space probe via state media. As no direct communication link exists, the images had to be bounced off another satellite before being relayed back to Earth, BBC News reported.

China National Space Administration /Xinhua News Agency/Jin Liwang/Getty Images
An image taken by China's Chang'e-4 probe after its landing on the far side of the moon on January 3, 2019, becoming the first spacecraft soft-landing on the moon's uncharted side never visible from Earth.

The moon has been the object of human fascination—and scientific observation—for centuries. Although from our perspective it does not appear to spin, in reality the moon rotates about every 27 days, which is about the same amount of time it takes to orbit the Earth once. During this whole process, we can see only about 59 percent of the moon’s surface, while the other 41 percent—known as the “dark side” of the moon—is concealed from our view.

Soon after the Soviet satellite Sputnik became the first spacecraft to orbit Earth in 1957, both the Soviet and U.S. space programs began focusing on the next great objective: the moon. The Soviet Union initially had more success, as its first two Luna probes made the first escape from Earth’s gravity and the first lunar impact in 1959. That same year, Luna 3 achieved another first, taking a photographic survey of the moon’s far side. Despite their grainy quality, these early images revealed that the previously unseen hemisphere had few of the smooth, dark spots that we observe on the moon’s surface. Scientists initially mistook these volcanic plains for lunar seas, and called them maria (from the Latin word for sea).

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Photograph of the far side of the moon taken by the Luna 3 space probe on October 28, 1959.

Since then, the National Aeronautics and Space Administration (NASA) has collected tens of thousands of images of the far side of the moon, which has allowed them to make better predictions about what that distant surface might look like.

But in 2016, China’s growing space program announced its plans to make a historic landing on the far side of the moon. Since 2003, when the country launched its first astronaut, the multibillion-dollar space program run by the Chinese military has been right on schedule with achieving the landmarks it set for itself.

In late 2013, the unmanned spacecraft Chang’e 3 made a soft landing on the lunar surface, making China the third nation (after the United States and the former USSR) to reach the moon. The rover Yutu or “Jade Rabbit,” which deployed from Chang’e 3 after the landing, discovered a new type of basaltic rock during its exploration of a volcanic crater in the Mare Imbrium (what we see as the right “eye” of the “Man in the Moon”).

China National Space Administration /Xinhua News Agency/Getty Images
The first image of the moon's far side taken by China's Chang'e-4 probe.

Despite such advances in lunar knowledge, the Chinese space program began by repeating feats that its U.S. and Soviet counterparts achieved decades ago. But the Chang’e 4 mission to make a soft landing on the far side of the moon represents a first in the history of space exploration. 

As Liu Jizhong, dean of China’s Lunar Exploration & Aerospace Engineering Center, told Agence France-Presse at the time: “The implementation of the Chang’e 4 mission has helped our country make the leap from following to leading.”

Launched on December 7, 2018, the Chang’e 4 arrived in lunar orbit five days later and began lowering itself toward the moon. After its successful landing, it will explore the so-called Von Kármán crater within the vast South Pole-Aitken Basin. The basin itself is the largest known impact crater on the moon and one of the largest in the entire solar system. The distance from its depths to the tops of the highest surrounding peaks measures some 15 km (or eight miles), almost twice the height of Mount Everest.

In addition to taking pictures and soil samples, the space probe is also set to plant a mini-garden on the moon. According to Chinese state news agency Xinhua, it is carrying six live species from Earth, including cotton, potato, rapeseed, yeast and a flowering plant called arabidopsis, which may produce the first flower to grow on the Moon.