Mystery of the Far Side of the Moon | UPSC

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Introduction

  • Recently, China launched its second mission, known as Changโ€™e-6, to the far side of the Moon. If successful, it will be the worldโ€™s first mission to bring back samples from the part of the Moon that the Earth never gets to see.
  • The Changโ€™e-6 is a 53-day-long mission. After reaching the Moonโ€™s orbit, the missionโ€™s orbiter will circle the Moon while its lander will descend into the 2,500-kilometre-wide South Pole-Aitken basin on the lunar surface.
  • The impact that created the basin โ€” among the largest in the history of the solar system โ€” is thought to have dug up material from the lunar mantle. If that material can be retrieved, scientists can learn more about the history of the Moonโ€™s insides.
  • In 2019ย Chang’e-4ย became the first spacecraft to successfully land on the moon’s far side whereย no other country till date has reached.

Why do we see only one side of the Moon?

  • We see only one side of the Moon, a phenomenon known as synchronous rotation or tidal locking, which occurs due to the gravitational interaction between the Earth and the Moon.
  • Over millions of years, gravitational forces between the Earth and the Moon have caused the Moon’s rotation period (the time it takes to complete one rotation on its axis) same as its orbital period (the time it takes to orbit around the Earth). As a result, the Moon rotates on its axis exactly once per orbit around the Earth.
  • This synchronized rotation means that the same side of the Moon always faces towards Earth (the near side), while the opposite side (the far side or dark side) faces away from Earth.
      • The far side of the Moon is not always dark; it receives just as much sunlight as the near side, but it is not visible from Earth due to this synchronous rotation.

Why is it difficult to send probes on the far side of the moon than on the near side?

  • Sending probes to the far side of the Moon presents several challenges compared to missions targeting the near side:

a) Communication Challenges

  • Line of Sight: Direct communication with Earth is not possible from the far side because it is always facing away from Earth. This necessitates the use of relay satellites or positioning satellites at the Earth-Moon L2 Lagrange point to maintain communication.
  • Signal Blockage: The Moon itself blocks direct radio signals from Earth when a probe is on the far side, necessitating a relay satellite in lunar orbit or at a Lagrange point to maintain continuous contact.

b) Navigation and Landing Difficulties

  • Lack of Mapping: The far side of the Moon has been less thoroughly mapped and explored compared to the near side, making it more challenging to select safe landing sites and plan navigation routes for probes.
  • Surface Topography: The far side has more rugged terrain and a higher density of impact craters compared to the near side, which can complicate landing and navigation efforts.

c) Cost and Mission Planning

  • Complexity: Missions to the far side typically require more advanced planning, technology, and resources compared to missions to the near side, adding to their complexity and cost.
  • Mission Duration: Probes sent to the far side often have longer mission durations due to the need for communication relay infrastructure and the challenges of operating in a more remote and less accessible location.

In summary, the primary difficulties in sending probes to the far side of the Moon arise from communication challenges, navigation complexities, power management issues, and the overall higher mission complexity and cost. These factors collectively make missions to the far side more technically demanding and resource-intensive compared to those targeting the near side.

Why are Scientists interested in studying the far side of the Moon?

  • Scientists are particularly interested in studying the far side of the Moon for several compelling reasons:

a) Unique Geological Features

  • Thicker Crust: The far side has a thicker crust compared to the near side, providing insights into the Moon’s geological history and the processes that formed it.
  • Highlands: It features more highlands and fewer maria (large, dark, basaltic plains) compared to the near side, offering a different perspective on the Moonโ€™s volcanic activity and crust formation.
      • In fact, observations have shown that only about 1% of the moon’s far side is covered with maria, or craters caused by volcanic activity on the moon. This sharply contrasts the object’s near side, 31% of which is covered with maria.
  • Impact Craters: The far side has more and better-preserved impact craters, which can provide valuable information about the history of impacts in the inner solar system.

b) Scientific Advantages

  • Radio Astronomy: The far side is shielded from the Earthโ€™s radio emissions, making it an ideal location for radio telescopes to study the universe without interference from human-made signals.
  • Pristine Environment: The lack of human activity and debris on the far side offers a more pristine environment for conducting experiments and observations.

c) Understanding Lunar Evolution

  • Asymmetry: Studying the far side helps scientists understand the Moonโ€™s asymmetry, including why the near side and far side are so different in terms of geology and surface features.
  • Lunar Dichotomy: Investigating the differences between the two sides aids in understanding the processes that caused the dichotomy, such as variations in internal heating, crust formation, and volcanic activity.

d) Potential for Future Exploration

  • Resource Exploration: The far side might contain untapped resources, such as minerals and water ice, that are crucial for future lunar exploration and potential colonization.
  • Strategic Location: Understanding the far side is essential for planning future missions, including potential bases or observatories that could be established in this relatively unexplored region.

e) Broader Implications

  • Planetary Formation: Insights gained from studying the far side of the Moon can be applied to understanding the formation and evolution of other planetary bodies, both in our solar system and beyond.
  • Comparison with Near Side: By comparing data from both sides, scientists can develop more comprehensive models of lunar formation and evolution, leading to a better overall understanding of the Moon.

In summary, the far side of the Moon offers unique opportunities for scientific research and discovery, providing valuable information that complements what is already known from studies of the near side.

Answer Writing Practice for UPSC Mains

Topic: Awareness in the fields of Space (GS Mains Paper 3)

  • Discuss the scientific significance of exploring the far side of the Moon and analyze the technical challenges associated with conducting missions to this region. (Answer in 250 words)

Model Answer

  • Recently, China launched its second mission, known as Changโ€™e-6, to the far side of the Moon. If successful, it will be the worldโ€™s first mission to bring back samples from the part of the Moon that the Earth never gets to see. Exploring the far side of the Moon holds immense scientific significance and presents several technical challenges that must be addressed for successful missions.

Scientific Significance:

  • Geological Diversity: The far side of the Moon differs significantly from the near side in terms of geological features. It has a thicker crust, more highlands, and fewer maria (basaltic plains). Studying these differences can provide insights into the Moon’s formation and its early geological processes. For instance, the abundance of impact craters on the far side offers a window into the history of impacts in the inner solar system.
  • Radio Silence: The far side is shielded from Earth’s radio signals, making it an ideal location for radio astronomy. It allows astronomers to observe the universe with minimal interference, offering opportunities to study cosmic phenomena such as the early universe, pulsars, and the cosmic microwave background radiation. This can lead to breakthroughs in our understanding of astrophysics and cosmology.
  • Solar System Evolution: By comparing the near and far sides of the Moon, scientists can better understand the processes that shaped not only the Moon but also other planetary bodies in the solar system. This comparative analysis aids in unraveling the evolutionary history of our celestial neighborhood.
  • Resource Exploration: The far side may harbor valuable resources such as water ice in permanently shadowed craters. These resources are crucial for sustaining future lunar missions and can serve as potential refueling stations for deep space exploration missions.

Technical Challenges:

  • Communication: Direct communication with Earth is impossible from the far side due to the Moon’s blocking effect. This necessitates deploying communication relay satellites in lunar orbit or at Lagrange points to maintain continuous contact with Earth-based mission control.
  • Navigation and Landing: The rugged terrain and high density of impact craters on the far side pose challenges for landing and navigation. Limited mapping data increases the risk of landing in hazardous areas, requiring advanced imaging and terrain analysis techniques.
  • Mission Complexity and Cost: Conducting missions to the far side requires advanced technology, longer mission durations, and higher costs compared to missions targeting the near side. Comprehensive planning and international collaboration are necessary to overcome these challenges effectively.

In conclusion, exploring the far side of the Moon offers profound scientific rewards in understanding lunar geology, advancing astronomy, and preparing for future exploration beyond Earth. However, it demands overcoming substantial technical hurdles related to communication, navigation, and mission logistics. Addressing these challenges is crucial for unlocking the full potential of lunar exploration and expanding humanity’s knowledge of the cosmos.

 

References:

 

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