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Moon
Moon Intro:
The Moon is Earth's only natural satellite. At about one-quarter the diameter of Earth (comparable to the width of Australia),[15] it is the largest natural satellite in the Solar System relative to the size of its planet,[f] the fifth largest satellite in the Solar System overall, and is larger than any dwarf planet. Orbiting Earth at an average distance of 384,400 km (238,900 mi),[16] or about 30 times Earth's diameter, its gravitational influence slightly lengthens Earth's day and is the main driver of Earth's tides. The Moon is classified as a planetary-mass object and a differentiated rocky body, and lacks any significant atmosphere, hydrosphere, or magnetic field. Its surface gravity is about one-sixth of Earth's (0.1654 g); Jupiter's moon Io is the only satellite in the Solar System known to have a higher surface gravity and density.
The Moon is a very slightly scalene ellipsoid due to tidal stretching, with its long axis displaced 30° from facing the Earth, due to gravitational anomalies from impact basins. Its shape is more elongated than current tidal forces can account for. This 'fossil bulge' indicates that the Moon solidified when it orbited at half its current distance to the Earth, and that it is now too cold for its shape to adjust to its orbit.
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  1. Radius: 1,737.1 km
  2. Mass:
  3. Age: 4.53 billion years
  4. Gravity: 1.62 m/s²
  5. Orbital Period: 27 days
  6. Density: 3.34 g/cm³
  7. Surface area: about 14.6 million square miles (38 million square kilometers)
Compostion
Isotope dating of lunar samples suggests the Moon formed around 50 million years after the origin of the Solar System. Historically, several formation mechanisms have been proposed but none satisfactorily explained the features of the Earth–Moon system. A fission of the Moon from Earth's crust force would require too great an initial rotation rate of Earth. None of these hypotheses can account for the high angular momentum of the Earth–Moon system.
Moon Landing
The United States' Apollo 11 was the first crewed mission to land on the Moon, on 20 July 1969.
Crescetn & half Moon
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During the lunar phases, only portions of the Moon can be observed from Earth.
PROPERTIES OF MOON
Surface Area
The moon's surface area is about 14.6 million square miles (38 million square kilometers), which is less than the total surface area of the continent of Asia (17.2 million square miles or 44.5 million square km).
Gravitational field
The gravitational field of the Moon has been measured through tracking the Doppler shift of radio signals emitted by orbiting spacecraft. The main lunar gravity features are mascons, large positive gravitational anomalies associated with some of the giant impact basins, partly caused by the dense mare basaltic lava flows that fill those basins.[108][109] The anomalies greatly influence the orbit of spacecraft about the Moon.
Magnetic field
The Moon has an external magnetic field of generally less than 0.2 nanoteslas, [65] or less than one hundred thousandth that of Earth. The Moon does not currently have a global dipolar magnetic field and only has crustal magnetization likely acquired early in its history when a dynamo was still operating.[66][67] However, early in its history, 4 billion years ago, its magnetic field strength was likely close to that of Earth today.[65] This early dynamo field apparently expired by about one billion years ago, after the lunar core had completely crystallized.
Orbit
Unlike most satellites of other planets, the Moon orbits closer to the ecliptic plane than to the planet's equatorial plane. The Moon's orbit is subtly perturbed by the Sun and Earth in many small, complex and interacting ways. For example, the plane of the Moon's orbit gradually rotates once every 18.61 years
Relative size
The Moon is an exceptionally large natural satellite relative to Earth: Its diameter is more than a quarter and its mass is 1/81 of Earth's.[79] It is the largest moon in the Solar System relative to the size of its planet,[i] though Charon is larger relative to the dwarf planet Pluto, at 1/9 Pluto's mass.[j][152] The Earth and the Moon's barycentre, their common center of mass, is located 1,700 km (1,100 mi) (about a quarter of Earth's radius) the Earth's surface.