Earth’s Satellite: The Moon

The Moon was formed as a result of a collision between a young Earth and another planet of about the size of Mars. During the collision, a large amount of material was ejected from the Earth’s mantle, which started to orbit the Earth, forming a disc. The material of the disc soon collected into a spherical shape due to gravity, and the Moon was formed. At that time, it was about 20 times closer to the Earth than it is today.

The rotation and orbit of the Moon

While orbiting the Earth, the Moon
also rotates about its own axis. Its axial rotation and orbital period are the same (27.32 days), therefore, we always see
the same side. This is called tidal locking.

Earth’s Satellite: The Moon

The Earth’s only natural satellite is the Moon. It was formed not long after the formation of the planets, as a result of a collision between a young Earth and another ancient planet about the size of Mars. The Moon’s gravity creates tides, which keep the axis of rotation of the Earth at an almost constant angle and slow down the planet’s rotation slightly. As a result, the Moon is slowly moving away from the Earth. Apart from Earth, The Moon is the only celestial object where man has ever set foot.

The surface and internal structure of the Moon

Its surface is mainly composed of volcanic rocks. We can see darker, lower-lying basins, so-called seas, and lighter, higher plateaus on the Moon. Its internal structure, like that of the Earth, is composed of a crust, a mantle and a core.

Average distance from Earth: 384.000 km

Diameter: 3475 km

Mass: 7.348 · 1022 kg

Average density: 3.34 g/cm3

Surface gravity: 0.165 earth g (1/6 g)

Rotational period: 27.32 days

Orbital period: 27.32 days