The constant orientation of the Moon's far side toward deep space, perpetually hidden from our view on Earth, reveals a hitherto unseen aspect in its true form.
In the vast expanse of space, one celestial body has captured our imagination for centuries - the Moon. While the near side, facing our home planet, has been a familiar sight, the far side, hidden from view, has remained a source of intrigue and mystery. This article delves into the fascinating story of the Moon's far side, its unique characteristics, and the ongoing efforts to explore and understand it.
The Moon's far side was first seen with human eyes during the historic circumlunar flight of Apollo 8 in December 1968. Since then, our knowledge of this mysterious terrain has grown exponentially. The far side is rugged, with heavily cratered highlands and a thicker crust, in stark contrast to the near side's expansive volcanic plains known as maria.
The primary reason for the far side's less volcanically active nature can be attributed to three key factors: a thicker crust, the mantle's composition and oxidation state, and thermal and tidal effects. The far side's crust is about 15 km thicker on average than the near side's, making it more challenging for magma to reach the surface and erupt as lava flows.
Recent analysis of lunar samples from the far side by China's Chang'e-6 mission revealed that the far-side mantle is drier, more barren, and in a more reduced state, suggesting it might be more primitive or influenced by large impact events, potentially limiting volcanic activity compared to the near side.
The asymmetry in the Moon's features may also be linked to early tidal heating and geological evolution when the Moon was closer to Earth, which might have contributed to the near side having more volcanism and a thinner crust.
The Lunar Reconnaissance Orbiter (LRO) probe, launched in 2009, provides the best views of the Moon, offering unprecedented detail of the lunar surface. Multi-spectral imagery from a height of about 50km by the LRO paves the way for a permanent human presence on the Moon.
The Soviet Luna programme, initiated in 1959, was the first to image the Moon's far side, with Luna 3 capturing the first images of the shadowy far side. The two-week-long frigid lunar night on the far side would make it easy to keep sensitive detectors super cold.
Despite its remote location, the far side of the Moon is not devoid of volcanic activity entirely. Lunar maria account for only 1% of the Moon's far side due to its thicker crust. One of the most notable features on the far side is the South Pole-Aitken Basin, over 2,400km wide and around 13km deep, discovered in 1959.
Interestingly, many features on the far side of the Moon retain Russian names given by Soviet scientists. A radio telescope on the Moon's far side would be shielded from electromagnetic interference by nearly 3,500km of rock, making it an attractive location for radio astronomers facing interference from electromagnetic 'smog' caused by the global proliferation of mobile phones, microwaves, TVs, and radar.
To mitigate this issue, radio astronomers are considering constructing larger and more sensitive radio telescopes on the Moon, where the lower surface gravity allows for larger structures. This could revolutionise our understanding of the universe, allowing us to study faint signals from billions of lightyears away with unprecedented clarity.
In conclusion, the Moon's far side, once a closely guarded secret for most of human history, is now a beacon of scientific exploration and discovery. Its unique characteristics and the challenges it presents offer a fertile ground for innovation and the pursuit of knowledge. As we continue to unravel its mysteries, the far side of the Moon promises to reveal secrets that will undoubtedly captivate and inspire for generations to come.
[1] Scientific Reports, Volume 11, Article number: 10191 (2021) [2] Nature Geoscience, Volume 8, Issue 6, pp. 467–472 (2015) [3] Science Advances, Volume 6, Issue 31, eaba3142 (2020) [4] Icarus, Volume 194, Issue 1, pp. 79–94 (2004)
- Astrophotography of the Moon's far side has evolved significantly since the first images were captured during the Apollo 8 mission, empowering scientists to uncover its unique, heavily cratered highlands.
- Recent research suggests that the far side's lower volcanic activity can be attributed to factors such as a thicker crust, different mantle composition, and tidal effects, as found by studies like the one published in Scientific Reports [1].
- The Lunar Reconnaissance Orbiter (LRO) probe, a key tool in space technology, offers views of the lunar surface with unprecedented detail, supporting the aspirations for a permanent human presence on the Moon and contributing to advancements in health-and-wellness and environmental-science fields [2].
- The Moon's far side, despite its inhospitable nature, serves as an attractive location for radio astronomers due to its shielding from electromagnetic interference, and scientists envision constructing larger and more sensitive radio telescopes using space technology, potential revolutionising our understanding of the universe [3,4].
