THE MOON

The Moon, Earth’s closest neighbor in the universe is also its only Natural Satellite. The Moon has a specific relationship with humanity. It is by far the brightest object of the night sky. As queen of the night, the Moon, along with the Sun, has been integrated into the system of symbols and religions of all early civilizations. Countless pages have been written on the role of the Moon in art, literature, music and culture in general. Most ancient civilizations had calendars which were either lunar (Such as the Jewish or Muslim calendars) or lunisolar (such as the Roman calendar which evolved into the Gregorian calendar now widely in use).

The Moon was undeniably, together with the Sun, the prime target of Naked-eye astronomy, possibly as early as the Stone Age. The Moon was the first celestial body observed by Galileo with a telescope in 1609, an event which marked the beginning of modern ground-based astronomy. He immediately identified countless round features, the lunar craters. The moon has a low mass and hence a weak gravitation force which is not strong enough to prevent its molecules of the atmosphere of escaping its gravitational field and as a result, it has a negligible atmosphere. The Moon is a differentiated body: it has a geologically distinct crust, mantle, and core. This structure developed through the fractional crystallization of a global magma ocean shortly after the Moon's formation 4.5 billion years ago.

The Earth–Moon system is unique in the solar system with its ratio of less than 4 between the sizes of the planet and its satellite, and, as seen from afar by departing space probes, it can indeed be considered as a double planet. Because of the large mass of the Moon and its proximity to the Earth, lunar tides are nearly three times larger than solar tides. The moon’s diameter is a quarter of the diameter of Earth and its mass is 1/81 of the Earth’s mass. It is the second densest satellite after Io in the entire Solar system.

The Moon is the only celestial body to which humans have made a manned landing. The former Soviet Union’s Luna Programme was the first to reach the Moon with an unmanned spacecraft. However, the first manned landing was made by the United States’ Apollo Mission. Neil Armstrong has had the privilege of being the first Man to land on the moon and he achieved this feat in 1969. Ever since, the US had made 6 more manned missions to the Moon. These missions brought back over 380 kg of lunar rocks, which have been used to develop a detailed geological understanding of the Moon's origins, the formation of its internal structure, and its subsequent history. Since 2004, Japan, China, India, the United States, and the European Space Agency have each sent lunar orbiters. These spacecraft have contributed to confirming the discovery of water in permanently shadowed craters at the poles and bound into the lunar regolith. Future manned missions to the Moon have been planned but not yet underway; the Moon remains, under the Outer Space Treaty, free to all nations to explore for peaceful purposes.

Questions to Ponder

• Very recently, NASA discovered plenty of water in the form of ice in certain craters in the Moon. Why do you think they couldn’t discover it in the previous Lunar Missions?
• Does presence of water in the Moon imply presence of life?
• The Moon slows the Earth's rotation, so how fast was it spinning billions of years ago?