China has broken new ground in space exploration by initiating the Chang’e-4 lunar probe mission to the far side of the moon. Interestingly, this is the first time in history that a lunar probe will explore the ‘dark’ side of the moon. Although images have been captured of the far side by previous spacecrafts, none has ever landed. The Chang’e-4 lunar probe mission derives its name from the moon goddess in Chinese mythology. Comprising of a lander and a rover, it heralds a significant step forward in extraterrestrial exploration.
Site of Landing
The rover aims to land in the Von Kármán, a crater situated on the far side of the moon. This challenge has never been attempted previously due to the crater’s inaccessible location.
Mission Objectives
The instruments mounted on the rover and the lander aim to identify the make-up of rocks and soil on the far side of the moon. Part of the mission’s purpose is to study the effects of solar wind striking against the lunar surface, which has implications for future lunar expeditions. Furthermore, the probe is tasked with testing the efficacy of making radio astronomy observations from the moon’s far side, free from earthly noise and interference. As an unexpected bonus, the Chang’e-4 will also conduct a biology experiment to test whether plant seeds can sprout and silkworm eggs can hatch under the moon’s low gravity conditions.
Landing Challenges
Aside from its geographical location, the far side of the moon also poses severe landing challenges. Unlike the near side, which always faces earth and offers ample flat areas for rovers to land, the far side is marked by precarious mountainous terrains.
Communication Challenges
Because the moon is tidally locked to the Earth’s rotation, it obstructs radio signals from reaching the dark side. This barrier makes it hard to directly communicate with the rover. However, China has ingeniously found a way around this by launching a relay satellite, Queqiao, in May 2018. The satellite orbits above the moon’s far side and serves as a mediator, relaying messages between Earth and the lander.
The Far Side of the Moon and Tidal Locking
A particular segment of the moon remains hidden from our view on Earth due to a phenomenon known as tidal locking. This occurs when an object’s orbital period matches its rotational period. As a result, the moon takes 28 days to revolve around the Earth, and the same amount of time to rotate once on its axis, keeping one face consistently towards the Earth.
| Tidal Locking Definition | The synchronisation of an object’s orbital period with its rotational period |
| Effects of Tidal Locking on the Moon | Same face of the Moon always faces Earth |
China’s Lunar Missions: A Brief Overview
China launched two orbital missions around the moon – Chang’e-1 and Chang’e-2, in 2007 and 2010 respectively. These were followed by two rover missions, Chang’e-3 and Chang’e-4, in 2013 and 2018. Additionally, China is planning to launch the Chang’e-5 robotic spacecraft that will not only land on the moon but also return rock samples to Earth for further study. The launch is expected to take place in 2019, reinforcing China’s frontline position in lunar exploration.
