Far side of the Moon

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Far side of the Moon, photographed by Apollo 16

The far side of the Moon, sometimes called the dark side of the Moon, is the lunar hemisphere that is permanently turned away, and not visible from the surface of the Earth. The far hemisphere was first photographed by the Soviet Luna 3 probe in 1959, and was first directly observed by human eyes when the Apollo 8 mission orbited the Moon in 1968. The rugged terrain is distinguished by a multitude of crater impacts, as well as relatively few lunar maria. It includes the second largest known impact feature in the Solar System, the South Pole-Aitken basin. The far side has been suggested as a potential location for a large radio telescope, as it would be shielded from possible radio interference from Earth. To date, there has been no ground exploration of the far side of the Moon.


Tidal forces from Earth have slowed down the Moon's rotation so that the same side is always facing the Earth, a phenomenon called tidal locking. The other face, most of which is never visible from the Earth, is therefore called the "far side of the moon". It should be noted that over time some parts of the far side can be seen due to libration, in total 59%[1] of the Moon's surface. However, useful observation of those parts is difficult because of the low angle from Earth (they cannot be observed "full on").[citation needed]

The commonly used term "dark side of the Moon" does not refer to "dark" as in the absence of light, but rather as the unknown, as until man was able to send spacecraft around the Moon, this area had never been seen.[citation needed] While many misconstrue this to think that the "dark side" receives little to no sunlight, in reality, both the near and far sides receive (on average) almost equal amounts of light from the Sun. Only during a full moon (as viewed from Earth) is the far side of the Moon physically dark.[citation needed] The word "dark" may also refer to the fact that communication with spacecraft can be blocked while on the far side of the Moon, during Apollo space missions for example.[citation needed]


Detailed view by the Lunar Reconnaissance Orbiter (LRO)


It has also been proposed that the differences between the two hemispheres may have been caused by a collision with a smaller companion moon that also originated from the Theia collision.[3] In this model the impact led to an accretionary pile rather than a crater, contributing a hemispheric layer of extent and thickness that may be consistent with the dimensions of the farside highlands.



1959 USSR stamp commemorating first photographs of the far side of the Moon.


An example of a far side feature that can be seen through libration, is the Mare Orientale, which is a prominent impact basin spanning almost 1,000 kilometres (600 mi), yet this was not even named as a feature until 1906, by Julius Franz in Der Mond. The true nature of the basin was discovered in the 1960s when rectified images were projected onto a globe. It was photographed in fine detail by Lunar Orbiter 4 in 1967.

On October 7, 1959 the Soviet probe Luna 3 took the first photographs of the lunar far side, eighteen of them resolvable,[5] covering one-third of the surface invisible from the Earth.[6] The images were analysed, and the first atlas of the far side of the Moon was published by the USSR Academy of Sciences on November 6, 1960.[7][8] It included a catalog of 500 distinguished features of the landscape.[9] A year later the first globe (1:13 600 000 scale [10]) containing lunar features invisible from the Earth was released in the USSR, based on images from Luna 3.[11] On July 20, 1965 another Soviet probe Zond 3 transmitted 25 pictures of very good quality of the lunar far side,[12] with much better resolution than those from Luna 3.[6] In particular, they revealed chains of craters, hundreds of kilometers in length.[6] In 1967 the second part of the "Atlas of the Far Side of the Moon" was published in Moscow,[13][14] based on data from Zond 3, with the catalog now including 4,000 newly discovered features of lunar far side landscape.[6] In the same year the first "Complete Map of the Moon" (1:5 000 000 scale[10]) and updated complete globe (1:10 000 000 scale), featuring 95 percent of the lunar surface[10] were released in the Soviet Union.[15][16]





Geologist-astronaut Harrison Schmitt[citation needed], who became the second to last to step onto the Moon, had aggressively lobbied for his landing site to be on the far side of the Moon, targeting the lava-filled crater Tsiolkovskiy. Schmitt's ambitious proposal included a special communications satellite based on the existing TIROS satellites to be launched into a Farquhar-Lissajous halo orbit around the L2 point so as to maintain line-of-sight contact with the astronauts during their powered descent and lunar surface operations. NASA administrators rejected these plans based on added risk and lack of funding.





The L2 Lagrange point of the Earth-Moon system is located about 62,800 km (39,000 mi) above the far side, which has also been proposed as a location for a future radio telescope which would perform a Lissajous orbit about the Lagrangian point.

One of the NASA missions to the Moon under study would send a sample-return lander to the South Pole-Aitken basin, the location of a major impact event that created a formation nearly 2,400 kilometers (1,491 mi) across. The size of this impact has created a deep penetration into the lunar surface, and a sample returned from this site could be analyzed for information concerning the interior of the Moon.[18]

Because the near side is partly shielded from the solar wind by the Earth, the far side maria are expected to have the highest concentration of helium-3 on the surface of the Moon.[19] This isotope is relatively rare on the Earth, but has good potential for use as a fuel in fusion reactors. Proponents of lunar settlement have cited presence of this material as a reason for development of a Moon base.[20]

Alleged UFO sightings and conspiracies[edit]

  • Some conspiracy theorists, notably Milton William Cooper, have alleged that some Apollo astronauts had seen UFOs on the far side of the Moon but were told to keep quiet about them.[21][22] Some have allegedly reported seeing an alien base (code named "Luna") and even encountered aliens who told them to stay off the Moon. Some photographs circulated on the Internet purport to show a large "castle" on the Moon. However, NASA describes these claims as hoaxes,[23] and in 2006 announced plans for manned missions to the far side of the Moon.[24] Communication between the far side and Earth would require a relay satellite, perhaps at one of the trojan points.
Ironically, it was later revealed that the Pentagon had their own plan to detonate a nuclear weapon as part of the experiment Project A119. The project was created not only to help in answering some of the mysteries in planetary astronomy and astrogeology, but also as a show of force in hopes of boosting domestic morale in the astro-capabilities of the United States, a boost that was needed after the Soviet Union took an early lead in the Space Race and who were also working on a similar project.[26]

See also[edit]


  1. ^ NASA. libration of the Moon. 
  2. ^ J. J. Gillis, P. D. Spudis; Spudis (1996). "The Composition and Geologic Setting of Lunar Far Side Maria". Lunar and Planetary Science 27: 413–404. Bibcode:1996LPI....27..413G. 
  5. ^ Luna 3. NASA
  8. ^ Aeronautics and Astronautics Chronology, 1960. NASA
  11. ^ Saving Globes an article in Sphaera: the Newsletter of the Museum of the History of Science, Oxford
  12. ^ Zond 3. NASA
  13. ^ АТЛАС ОБРАТНОЙ СТОРОНЫ ЛУНЫ, Ч. 2, Мoscow: Nauka, 1967
  14. ^ Observing the Moon Throughout History. Adler Planetarium
  15. ^ Works of the Department of lunar and planetary research of GAISh MGU. SAI
  16. ^ (Russian) Moon Maps. MSU
  20. ^ Schmitt, Harrision (2004-12-07). "Mining the Moon". Popular Mechanics. Archived from the original on 2013-10-07. Retrieved 2013-10-07. 
  21. ^ http://paranormal.about.com/od/lunaranomalies/a/aa011507_2.htm
  22. ^ http://ufos.about.com/od/nasaufos/p/moonufos1.htm
  23. ^ http://astrobiology2.arc.nasa.gov/ask-an-astrobiologist/question/?id=1606
  25. ^ Fog of War, Errol Morris, 2003. Retrieved, Oct. 19, 2013.

External links[edit]