Chang’e 4 is a Chinese space probe that landed on the far side of the Moon on January 3, 2019. It not only studied the chemical composition of the rocks in this location, but also conducted the first experiment in history to grow plants on another celestial body.

The Chang’e 4 spacecraft

Chinese space program

January 3, 2019, was a triumph for the Chinese space program. The rest of humanity also had reason to rejoice. For the first time in history, the Chang’e 4 spacecraft landed on the far side of the Moon, which we never see from Earth.

The road to this landing was quite long. China was late to the lunar race between the US and the USSR. The PRC had to implement its lunar program in the 21st century. It began with two spacecraft that operated in lunar orbit, photographing and remotely sensing the Moon. Both were named after Chang’e, the Chinese goddess of the Moon.

Initially, the Chang’e 1 spacecraft operated in lunar orbit from 2007 to 2009. It made general observations, which were hardly surprising at the time, since the US had already found water on our satellite.

Chang’e 1.
Source: moonregistry.forallmoonkind.org

However, in 2010, Chang’e 2 was launched to the Moon. It photographed the surface of our satellite from an altitude of only 100 km. In 2012, based on the data it collected, the Chinese government presented the most detailed map of the Moon at that time, and it was confirmed that all this time, the Chinese had been looking for a landing site for Chang’e 3.

Around that time, the first discussions about China’s lunar ambitions began, but no one knew how seriously to take them, since only two countries – the US and the USSR – had successfully landed on the Moon at that point.

However, on December 14, 2013, Chang’e 3 landed in the Sinus Iridum of the Mare Imbrium. It was not only the first spacecraft in 37 years to remain intact after reaching the surface of our satellite. It also carried the Yutu rover, named after the jade rabbit, a character from Chinese legends who is said to have prepared the powder of immortality on the Moon. At that time, China was able to explore the material of our satellite for the first time and confirm that it was exactly as American and Soviet scientists had determined.

The Chang’e 3 landing site.
Source: Wikipedia

The Chang’e 4

However, all this was a repeat of achievements made many years ago. In order to challenge the US, which had already announced plans to return to the Moon, it was necessary to show that Chinese missions could provide the global scientific community with data that no one had previously had access to.

This was the goal of the Chang’e 4 probe. In terms of design, it was a copy of the previous mission, with the same cameras and spectrographs, and even carried the Yutu-2 rover on board. However, this device was to land on the far side of the Moon, which humans first saw only in 1959 and, before the Chinese attempt, had only seen from orbit.

Moreover, Chang’e 4 was supposed to land in the Von Kármán lunar crater, which covers the much older and largest basin on our satellite, the South Pole-Aitken basin. Once, at the dawn of the solar system’s existence, a body much larger than the asteroid that ended the dinosaurs crashed into the Moon, which, scientists believe, led to the asymmetry of its two hemispheres: the visible and the reverse.

South Pole-Aitken basin.
Source: Wikipedia

Almost all experimental data confirming this was obtained thanks to the Chinese missions Chang’e 4 and Chang’e 5, which followed it. But for them to be possible, it was first necessary to ensure their connection with Earth. This mission was entrusted to the Queqiao-1 relay satellite, which was launched to the Lagrange 2 point of the Earth-Moon system, i.e., directly behind our natural satellite.

Queqiao-1 began operating in May 2018, and in December of the same year, Chang’e 4 was launched to the Moon. It remained in orbit around our satellite for some time, and on January 3, 2019, it landed at the planned location. On the same day, it began scientific research and took photographs.

Yutu-2 rolled off the platform and began performing spectroscopic analysis of the rocks. After a few days, scientists had to interrupt their work because night fell on the Moon and the temperature dropped to extreme levels. However, two weeks later, when dawn finally broke, the mission resumed its work.

Yutu-2 .
Source: news.cgtn.com

In total, Chang’e 4 lasted more than a year and a half. Technically, the mission is not yet complete. It is currently in sleep mode. Ultimately, it accomplished its main task: it examined the mantle rock emissions and noted how they are similar to and different from those found on the visible side of the Moon.

Growing plants on the Moon

The biggest difference in the design of Chang’e 4 from previous spacecraft was the addition of a module for biological experiments. It consisted of germinating seeds. This had been done repeatedly in space before, but it was all in Earth orbit.

It was Chang’e 4 that became the first spacecraft to successfully grow cotton, potato, and rapeseed seeds on another celestial body. This happened a few days after landing, and photos of the tiny sprouts went viral around the world. The experiment was supposed to last 100 days. During this time, the capsule with the samples had to be heated and humidified.

Plants on the Moon.
Source: nextshark.com

Incidentally, it also contained yeast spores and Drosophila fly eggs. So, theoretically, an entire ecosystem could have developed on board in later stages. However, with the onset of the lunar night, the temperature outside dropped too sharply, and too much electricity was needed for heating. Therefore, the experiment had to be interrupted.

Nevertheless, it is considered successful and was extremely important for global science. It proved the fundamental ability of plants to overcome the most difficult stage of their development in space conditions. In the future, humans will inevitably live in space, and we will need oxygen and nutrients that plants can provide. To achieve this, large modules with artificial biospheres will need to be created on planets. Similar to the one that was on board Chang’e 4.