Introduction
The history of human existence is closely connected with the only natural satellite of the planet — the Moon. This celestial body accompanied the development of the Earth practically from the very beginning: Moon was present at all stages of the planet’s geochemical and biological evolution. Thus, the origin of the celestial body is one of the oldest mysteries of astronomy. Today there are many versions, but the main hypothesis is that the Moon originated from a planetary collision, and multiple factors confirm this. This research work is aimed at a detailed discussion of three versions of Moon formation, a description of the Apollo, and a study of the recent three lunar astronomical missions.
The Hypothesis of the Moon Formation
The astronomical community tends to believe that planets appear as a result of accretion when the gravitational forces of a massive object from celestial bodies out of dust and gas. One version of how the Moon was formed is an accretionary process that proposes that the Moon and proto-Earth formed almost simultaneously from a single gas and dust cloud (Redd, 2017). This version could confirm the closeness of the chemical structure of the planet and the satellite, but the density of celestial bodies is different, which questions the authenticity of the hypothesis. Simultaneously, there is the opinion that during the formation, Earth was rotating in orbit at an incredibly fast rate, which caused the outer layers to be torn away by centrifugal forces. As a result, the satellite “bounced off,” which confirms a relatively low density compared with the planet. It was probably the Earth’s crust and mantle that was detached.
However, the difference in density may also be justified by the theory of planetary collision. During the hardening phase, the Earth’s orbit coincided with the trajectory of the protoplanet Theia, which led to the planetary collision. The impact was tangential rather than in the center of the ball, leaving much of the planet intact. Nevertheless, the result of this cataclysm was the outburst of a significant amount of matter from the Earth’s mantle and crust into the Earth’s orbit, from which the Moon was soon formed. This version seems quite convincing if we consider the evidence of the connection between the Earth and the Moon (Canup, 2019). The substance of the satellite has a low density, and the Moon chemical composition is incredibly close to the structure of the Earth. Moreover, the Moon is known to have a small core: this explains that the satellite seems to have been formed from a matter of the Earth’s crust, while the massive Theia core merged with the Earth’s core. Finally, the Apollo mission brought samples of lunar soil to Earth, the radioisotope analysis of which discovered the age of the Moon and the Earth — these are extremely close.
Apollo
The only space mission with astronauts landing in the celestial body is the American Apollo program. The purpose of the space plan was clear: to bring American astronauts to the Moon and then return them to Earth. Thus, on 16 July 1969, the launch vehicle detached from the launch platform spacecraft “Apollo 11” with three astronauts on board: N. Armstrong, M. Collins, and E. Aldrin (Donovan, 2019). For the first time in human history, crew members set foot on the lunar surface near the Sea of Serenity, which is on the visible side of the Moon. They collected soil samples and left a message, and after completing the tasks, the crew returned to the lunar module. On the eighth day of the mission, the astronauts returned to Earth. The collected samples were subjected to radioisotope analysis and then became another confirmation of the chemical proximity of the Earth and the Moon.
The Last Three Missions
Half a century after the grandiose landing on the Moon, humanity continues to study the satellite. The last space missions were aimed at placing robotic devices on the lunar surface for videotaping and monitoring. It is worth noting that this section will not include the most recent missions, as they are not of research interest due to equipment failure, but those that were launched after 2018 and have contributed to the overall astronomical history. On 20 May 2018, China’s National Space Agency launched Queqiao, a small satellite that serves as a repeater of the connection between lunar rovers on the back of the celestial body and the Earth (Moon missions,” 2020). The main purpose of Queqiao is to provide communication with Chang’e 4, the interplanetary station launched on 3 January 2019 by the same Chinese Agency. Chang’e 4 was a breakthrough technology as it provided the first soft module landing of the station on the backside of the Moon. In addition, on 11 April 2019, SpaceIL, a private Israeli company, decided to demonstrate success in developing lunar technology, but the landing module’s engine failed, resulting in a device crash and loss of communication. However, this was the first attempt by a non-State space flight to land on another space object.
Conclusion
The exploration of the Moon is one of the key tasks of modern astronomy. Ongoing research is conducted in terms of satellite origin and physical analysis of solid lunar rocks and water samples. Many hypotheses about how a celestial body might have formed exist, but the evidence from radioisotope analysis, the Moon structure, and the volume of the nucleus proposes that the Moon is the product of a planetary collision between Theia and Earth. Even a certain part of astronomical forces will be directed to the study of the Moon, as it is the only natural satellite of the Earth.
References
Canup, R. M. (2019). Giant impact hypothesis: An evolving legacy of Apollo. Web.
Donovan, J. (2019). Shoot for the Moon: The space race and the voyage of Apollo 11. Amberley Publishing Limited.
Moon missions. (2020). NASA Science. Web.
Redd, N. T. (2017). How was the Moon formed? Space. Web.