Hidden side of the Moon

The hidden side of the Moon is the Hémisphère of the the Moon which is permanently turned back on the Ground, the other with dimensions being named visible Face of the Moon . Indeed, only one and even with dimensions of the Moon is visible since the Earth, because the Moon has a Period of rotation equal to its Period of revolution (27,3217 days), phenomenon called synchronous Rotation. With dimensions complementary one is thus invisible since the Earth, and was photographed and charted only thanks to the space probes, the first being the Soviet probe Luna 3 in 1959. The first men to see it were the crew of the mission Apollo 8 orbits about it around the Moon in 1968. The rough ground is remarkable as well by the multitude of craters as by its poverty in lunar Mare. This hidden side also has the broadest crater of known impact of the Solar system: the Basin Pole South-Aitken. She was also proposed to accommodate a giant Radiotélescope, since it would then be protected from the possible interferences with the Earth.

History

The Forces of tide between the Ground and the the Moon slowed down lunar rotation so much so that from now on, it is always the same face which is presented to the Earth. The other face, which is thus never visible in its totality since the Earth, is called the " hidden side of Lune". Not to confuse with the not-enlightened face (which is the hemisphere which is not illuminated by the Sun), although both correspond at the time of a full moon. Lastly, the visible face and the hidden side receive on average as much sunlight.

The two hemispheres have very distinct appearances: on a side the face visible abundant of lunar seas (which are not true seas as opposed to what thought the first astronomers), and other the hidden side, hammered craters and has only few seas. Indeed, only 2,5% of its surface are seas (31.2% on the visible face). The most probable explanation for this difference is related to the greatest concentration of elements producing of heat on the visible face, proven by the geochemical charts obtained in gamma rays by the spectrometer Lunar Prospector. Whereas other factors, such as the altitude or the thickness of the crust, could also influence the place of the basalt eruptions, they do not explain why the Bassin Pole South-Aitken (where one finds lowest altitudes lunar as well as a fine crust) was not as volcanic as the Océan of the Storms (For a more detailed explanation, to see lunar seas).

Exploration

Until the end of the Fifties, only few things were known about the hidden side. The Libration S periodicals of the Moon made it possible to briefly see zones of this face located close to the edge of the visible face. However, these zones were seen starting from a weak angle, preventing any observation with scientific goal (it is even difficult to distinguish a crater from an assembly line). The 82% of the hidden side remaining invisible, there were many speculations about it.

An example of a zone of the hidden side which can be observed thanks to libration is the Eastern sea, which is an imposing basin of impact measuring close to 1 000 kilometers diameter. However, it was not even referred until in 1906, by Julius Franz in Der Mond . The true nature of the basin was discovered in the Années 1960 when the corrected images were projected on a sphere. It was photographed in details by Lunar Orbiter 4 in 1967.

The October 7th 1959 the Soviet probe Luna 3 took the first photographs of the hidden side of the Moon, seventeen of them being exploitable and covering a third of invisible surface. The images were analyzed, and the first atlas of the hidden side of the Moon was published by the Academy of Science of Russia the November 6th 1960. It included/understood a catalog of 500 distinct formations. One year later, the first sphere (Scale 1:13 600 000) containing the invisible parts of the hidden side was published in the USSR, while being based on the images of Luna 3. The July 20th 1965, another Soviet probe Zond 3 transmitted 25 images of very good qualities of the hidden side, with a resolution much better than those of Luna 3, and based on the data of Zond 3, with a catalog including 4 now; 000 new formations of the hidden side.

As much of imposing formations of the face hidden were discovered by Soviet space probes, they are the Russian scientists who chose their names. That posed some controversies and the international astronomical Union, leaving many intact names, assumed the role later to re-elect certain formations of this hemisphere.

The hidden side was observed directly by a Man for the first time at the time of the mission Apollo 8 in 1968. The astronaut William Anders described the sight:

The other face resembles a sand heap with which my children played formerly. All as is destroyed, it does not have there words, just much of bumps and holes.

It was observed by all the members of the missions Apollo 8 and Apollo 10 until Apollo 17, and was photographed by many lunar probes. The space shuttles passing behind the Moon were in radio silence with the Earth and were to wait until the orbit allows the communications again. During the Apollo mission, the principal engine of the shuttle started when it was behind the Moon, which created moments of tensions to the control center of Houston before the shuttle reappears.

Possible uses of the hidden side

As the hidden side of the Moon is protected from the radio transmissions emitted since the Earth, she is seen as a good place to establish Radiotélescope S for the Astronome S. the small craters of spherical form are a natural formation being able to accommodate a Télescope such as that of Arecibo to Puerto Rico. For the telescopes of very big size, the crater Daedalus 100 km in diameter located close to the center of the hidden side is considered. Moreover, its 3 height km edges could largely help to block the interferences due to the satellites in orbit. Another candidate for the installation of a radio telescope is the crater Saha.

Before deploying radio telescopes on the hidden side, several problems must be regulated. Fine lunar dust can damage the space equipment, vehicles and diving-suits. The materials used for the instruments must be protected effectively from the effects of the solar eruptions. Lastly, the storage area of the telescopes must be isolated from any interference with another radio source.

The not of Lagrange L2 of the system the Ground-Moon is located at approximately 62 800 km of the Moon, in the direction opposed to the Earth. It was proposed to receive a future radio telescope, tracing a Orbite of Lissajous around the Lagrangian point.

One of the lunar missions under consideration by NASA would be to send a robot returning a sample of the Bassin Pole South-Aitken, the place of an important impact which created a formation of 2 400 km of diameter. Size of this impact because a deep penetration in lunar surface, and a sample of this site could be analyzed to obtain information concerning the interior of the Moon.

As the visible face is partly protected from the Solar wind by the Earth, it is supposed that it is in the seas of the hidden side that one finds the highest concentrations of Hélium 3 on the Moon. This Isotope is relatively rare on Earth, but has a great potential for a use as fuel in the engines with nuclear fusion. The partisans of lunar projects of bases quote in particular the presence of this element like argument to convince their developments.

Notes and references of the article

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