From This Month In 2019: A Journey to the Moon’s Secret Side

C.O.O.L.ᵀᴹ Time Capsule: This Month in History — January

Written by: Vickie Liou

On January 3, 2019, China made history by becoming the first country to successfully land a spacecraft on the far side of the Moon—a place no spacecraft had ever safely landed before.

Figure 1. The location of China on the world map. (Image created with MapChart)

Why had no one done this until then?

It starts with a simple fact about the Moon.

Did you know that we only ever see one side of the Moon from Earth?

This happens because the Moon rotates on its axis at nearly the same rate that it orbits Earth—a phenomenon called tidal locking. As a result, the same side of the Moon always faces us, while the other side remains permanently hidden from view. (Learn more about tidal locking in this NASA article: https://science.nasa.gov/moon/tidal-locking/)

This hidden half is often called the “dark side of the Moon,” not because it lacks sunlight, but because it faces away from Earth.

For centuries, humans have wondered what the dark side looked like.

In 1959, the Soviet spacecraft Luna 3 became the first to photograph the Moon’s far side, sending back blurry but groundbreaking images. Later missions orbited the Moon and collected more data—but none ever landed there safely.

That’s what makes China’s Chang’e-4 mission so remarkable.

Unlike earlier missions that intentionally crash-landed, Chang’e-4 was designed to soft-land—touching down intact so it could continue collecting scientific data. This had never been done on the Moon’s far side.

The challenge? The Moon itself blocks all direct communication with Earth.

To solve this, China launched a relay satellite called Queqiao, which orbits beyond the Moon and relays signals between Earth and the lander—making communication possible for the first time.

Once safely on the surface, the Chang’e-4 lander and Yutu-2 rover began sending back images and scientific data about the Moon’s geology, space environment, and radio signals, opening an entirely new chapter in lunar exploration.

Figure 2. The Chang’e-4 lander that landed on the far side of the Moon. (Image Credit: Chinese National Space Agency, CNSA & Chinese Academy of Sciences, CAS via Bruce Murray Space Image Library)

For the first time in human history, we weren’t just looking at the far side of the Moon—we were standing on it.

What might we discover next, now that the far side of the Moon is no longer out of reach?

Reference:

Li, C., Zuo, W., Wen, W., Zeng, X., Gao, X., Liu, Y., Fu, Q., Zhang, Z., Su, Y., Ren, X., Wang, F., Liu, J., Yan, W., Tan, X., Liu, D., Liu, B., Zhang, H. & Ouyang, Z. (2021). Overview of the Chang’e-4 mission: Opening the frontier of scientific exploration of the lunar far side. Space Science Reviews, 217(2), 35.