The far side of the Moon – often misnamed the “dark side” – remains one of the most intriguing and misunderstood regions in lunar science. Invisible from Earth due to the Moon’s tidal locking, this hemisphere was unseen by humanity until the dawn of the space age. In recent years, interest in the far side has grown due to its unique geology, scientific value, and potential for future exploration.
This article explores the history of far side exploration, what has been discovered, why it’s important for science and exploration, and what future missions may reveal.
Understanding the Far Side
The far side of the Moon is the hemisphere that never faces Earth due to the synchronous rotation of the Moon. While both sides of the Moon experience day and night, the far side cannot be seen directly from the surface of our planet without spacecraft.
The two hemispheres of the Moon differ significantly:
- The near side is dominated by large, dark basaltic plains called maria, which are relatively smooth.
- The far side is heavily cratered and mountainous, with very few maria and a thicker crust.
This asymmetry has puzzled scientists for decades and suggests differing thermal and impact histories between the two hemispheres.
First Views: Soviet and American Missions
The first images of the far side came from the Soviet Union’s Luna 3 mission in 1959, marking a significant achievement in early space exploration. Luna 3’s grainy photographs revealed a surface covered in craters, unlike the maria-rich near side.
Later missions provided higher-resolution images:
- Zond 3 (1965): Soviet probe that returned improved far side images.
- Apollo Missions: Crewed spacecraft like Apollo 8 orbited the Moon, giving astronauts direct visual observations of the far side.
However, most of these missions were limited to flybys or orbital views. No landers or rovers visited the far side until the 21st century.
Geological Features of the Far Side
The far side hosts a number of distinctive geological structures:
- South Pole–Aitken Basin: One of the largest and oldest impact basins in the Solar System, it spans about 2,500 kilometers in diameter. Scientists believe it exposes materials from deep within the lunar mantle.
- Tsiolkovskiy Crater: A striking far side crater with a central peak and lava-flooded floor, visible in high-resolution images.
- Crustal Thickness: The far side’s crust is much thicker than that of the near side, likely influencing the lack of volcanic maria.
These features offer a unique laboratory for studying early Solar System history, crustal formation, and impact processes.
Chang’e 4: First Soft Landing on the Far Side
In January 2019, China’s Chang’e 4 mission achieved the first soft landing on the far side, deploying the lander and the Yutu-2 rover in the Von Kármán crater within the South Pole–Aitken Basin.
Because direct communication with the far side is impossible from Earth, the mission required a dedicated relay satellite, Queqiao, positioned at the Earth-Moon L2 point.
Chang’e 4 has provided:
- Spectroscopic data on far side regolith
- Ground-penetrating radar scans revealing subsurface structures
- Biological experiments on plant growth in lunar conditions
The mission demonstrated the technical feasibility of sustained operations on the far side.
Importance for Astronomy
The far side of the Moon is shielded from Earth’s radio noise, making it an ideal location for future low-frequency radio astronomy. Potential applications include:
- Observing cosmic dawn – the period when the first stars formed.
- Studying solar and planetary emissions without Earth-based interference.
- Deploying long-baseline radio arrays on the lunar surface.
Concepts such as the Lunar Crater Radio Telescope (LCRT) and other robotic deployments could transform lunar radio astronomy.
Scientific Significance
The far side’s unique features have broad implications for planetary science:
- Crustal Evolution: Studying far side geology helps explain the Moon’s asymmetric evolution.
- Impact History: The ancient, well-preserved impact structures preserve a record of the inner Solar System’s violent past.
- Lunar Volcanism: Investigating the scarcity of maria may reveal details about internal heat flow and volcanic history.
Furthermore, regolith studies may inform in-situ resource utilization for future lunar bases.
Challenges of Exploring the Far Side
Far side missions face several technical and logistical barriers:
- Communication: Without line-of-sight to Earth, missions require relay satellites or orbital infrastructure.
- Navigation and Autonomy: Ground commands experience longer delays, increasing the need for on-board autonomy.
- Launch Windows and Trajectories: Reaching a precise far side location demands accurate insertion and lunar orbit planning.
Despite these challenges, Chang’e 4 has demonstrated that such missions are feasible with modern technology and planning.
Future Missions
Interest in the far side continues to grow, with multiple missions in development:
- Chang’e 6: China’s follow-up sample return mission, expected to retrieve far side regolith for laboratory analysis.
- NASA Artemis Program: Although initial Artemis missions focus on the South Pole region, long-term goals include far side exploration using Gateway as a staging platform.
- Lunar far side observatories: Proposed missions aim to deploy telescopes or sensor arrays in shielded lunar basins.
As these missions progress, the far side will become a focus of international collaboration and lunar science.
Summary
The far side of the Moon offers a uniquely preserved landscape with significant scientific and exploratory value. Since its first imaging in 1959 and especially after China’s Chang’e 4 landing, it has transitioned from mystery to a domain of active investigation. Its thick crust, lack of maria, and massive impact basins open windows into lunar formation and planetary processes. Its isolation from Earth makes it a promising site for next-generation astronomy.
While exploration remains complex, future missions – both robotic and crewed – will continue to unlock the secrets hidden on the lunar hemisphere we cannot see from Earth.
