Moon

The Moon is the Earth's only natural satelite, and the only world explored by astronauts. It is a barren, rocky world with no atmosphere and no air. Due to the lack of no air, the sunlight does not scatter across the sky and heats the satellite up in daytime to 117°C. The nights are somewhat colder, with temperatures lowering down to -203°C. There is probably ice in the Moon's poles, caused by cometary bombardment and still survives because it is in the shade of the craters.

Formation
The Moon seems to have been a much larger body, which collided with Earth around 4,5 billion years ago. It probably was not formed by the nebula which created the rest of the Solar System, but was pulled by the Earth's gravity into the planet, causing it to explode. Some bits of the Earth also exploded and were flung into orbit around the planet. Together with pieces from the destroyed body, the Earth pieces created a ring around the planet, and were joined together by dust and rock to create the Moon. The satellite has grey pools, called mare which are actually lava plains. Lava plains were places in which molten rock burst from the interior and filled them. This only happened a while after the formation of the Moon and stopped a while after.