Since Earth and Moon are in gravitational locking , we only see one side of the Moon from Earth. We may think that the side that we cannot see does not receive sunlight. We should not forget that the Moon is a celestial body that rotates around itself.
Although the moon rotates around itself, watching our video on why we see the same face will be enough to clear the question marks in your mind.
Until the 1960s, we did not have a chance to observe this region because we could not see it from Earth and could not send spacecraft. in 1959; The Soviet Union (today's Russia ) spacecraft named Luna 3 , which has only a camera, radio unit, battery and gyroscope on it, has photographed the back of the Moon for the first time. Although simple by today's standards, it had an ambitious setup. The camera was taking images with photographic films, and the films were scanned inside this unmanned spacecraft, converted into digital information, and sent to Earth by radio waves.
One of humanity's first photographs of the Soviet Union's Luna 3 spacecraft and the back of the Moon.Luna 3 was able to take 29 photos in total and transmit 17 of them on its return journey to Earth. On October 22, 1959, communication was lost. It is thought that it may have entered the atmosphere and burned, or may have been entangled in Earth's orbit for a while.
In 1965, the Soviet Union spacecraft, Zond 3 , increased our knowledge of the back of the Moon. But the main task of the Zond flights was actually to reach Mars, to show that there is technology that can communicate with the spacecraft when it is between Mars and Earth.
This spacecraft, which has two cameras, infrared and ultraviolet spectrometers, magnetometers, cosmic ray detectors, solar particle detectors and meteoroid detectors, reached and circled the Moon 33 hours after its take -off, while it spent 68 minutes on the Moon, especially in the places that Luna 3 could not photograph. It took very high quality photos compared to the Luna 3. Nine days later, he continued to transmit the photos he took to Earth for several months. During the journey to Mars, Zond 3 could not be contacted again after 95 million km from Earth, so Zond, whose main task was Mars, could not fulfill this goal.
With the photographs taken by Zond 3, the mountains, craters and plains on the back of the Moon can be distinguished. Therefore, the naming of many regions on the reverse side of the Moon was made by Soviet scientists, although some namings caused controversy for a while in the International Astronomical Union.
The United States sent five unmanned spacecraft between 1966 and 1967 as part of the Lunar Orbiter Program. Of these, the first two, in particular, are intended to determine a landing site for future manned explorations. Radiation density, gravitational field and physical structure of the Moon, and micrometeorite impact data were examined in the lunar orbiter program. Most of the extensive data on the back of the Moon have been obtained with the Lunar Orbiter 5 . 633 high-resolution, 211 medium-resolution photographs were taken, and in total the orbiters produced high-quality maps of 99 percent of the Moon's surface. (The smallest spot that can be discerned in the photos taken is one meter in size.) All of these spacecraft were crashed into the Moon in order not to pose a communication hazard during the Apollo flights.
Just one year later, in 1968, with the Apollo 8 mission , US Astronaut William Anders became the first person to see the reverse of the Moon. Astronauts in all spacecraft from Apollo 10 to Apollo 17 also had the opportunity to see the back of the Moon.
But just as we cannot see the back of the Moon when we look from the Earth, the Earth is not visible from the back of the Moon. These spacecraft, which revolve around the Moon , cannot communicate with the Earth when they pass behind the Moon . On Apollo missions, the service module would fire when the spacecraft was behind the Moon and would not be in communication with Houston until the spacecraft was visible again. Those who work in the control team on Earth say that these important moments without communication are very tense. This is actually the main reason why there is no landing on the back of the Moon. The lack of communication destroys any chance of directive action in the event of a mishap in mission control.
The geology of the front and back of the Moon is quite different from each other, and this is one of its most interesting features.
Left, the side of the Moon seen from Earth. On the right is the face we cannot see.There are not many dark plains on the back , which we see on the front surface, covering 31 percent . They take up only 1 % of the space. When the force of the meteorite hitting the surface is enough to break the outer crust, the liquid inner surface, namely lava, emerges and forms a flatter surface when it solidifies.
This basaltic part appears dark in color because they are very rich in iron content compared to the elevations on the surface . Ancient astronomers named these surface structures as mare (plural maria ) , meaning sea in Latin, because they really thought it was sea .
One of the most striking places on the back of the Moon is the Tsiolkovsky crater . The 185 km wide impact crater is quickly conspicuous because of its dark surrounding . There is a 3200 m high hill in the middle of the crater. Apollo 17 astronaut and geologist Harrison Schmitt , the first and only scientist to set foot on the Moon's surface , along with other scientists, requested that Apollo 17 land on Tsiolkovicky .
They put small communication satellites in the service module and put forward the idea that connection can be made from the back surface of the Moon. However, NASA chose the Taurus-Littrow valley on the front surface because it found it too risky. Another of the biggest structures noticed is the Mare Moscoviense , the Moscow Sea. The number of people close to this collision basin, which has a very deep depth, is very few.
While the solidified volcanic surfaces are dominant in the front and thus the front is flatter, the back has deeper craters and a mountainous structure. This may be due to internal causes (the effect of heat created by gravitational locking, asymmetric crystallization of magma) or external causes.
Simulations show that smaller moons may also form in the pre-moon disk, depending on the Theia hypothesis . The collision of a satellite with a very small or even no core, three times smaller than the Moon on average, to the Moon at a subsonic speed allows them to merge with such an accretion instead of forming a crater. Such an event is also compatible with the difference in crustal thickness in the two hemispheres and the abundance of mountain structures on the Moon's posterior surface.
Today, satellites of space agencies are orbiting the Moon and are able to take very high resolution images and conduct scientific analysis. Thanks to these satellites, hypotheses about the structure of the Moon are tested and theories continue to be developed. But since the return of Apollo 17 in 1972, humanity has not set foot on the Moon or even traveled far from Low Earth Orbit (160-2000 km above the ground) in manned flights. NASA plans to carry out a manned flight to the Moon orbit, away from Low Earth Orbit, again after 2021, with the Orion spacecraft , where it started unmanned trials.
In other words, humanity is preparing to explore space again in the next 20 years. One of the places to go would of course be the far side of the Moon. Examining these craters to better understand the evolution of the Earth and Moon is of great importance, as the geology of the two sides of the Moon is quite different. As a result of the research to be done here, a more complex formation process may emerge than we thought.
