Cut-away computer illustration showing the interior of the Earth's Moon. It is the fifth largest satellite in the Solar System, with an average diameter of 3, 474 km. The average distance between Earth and Moon is 381 500 km. The Moon is the first and only non-terrestrial object visited by humans. The first to walk there was American astronaut Neil Armstrong on July 21, 1969. After him, eleven other men walked on the floor of the Moon, all members of the Apollo program. Its deep structure is not homogeneous but results from a process of cooling, crystallization of the original magma, and migration of the evolved magma. This differentiation resulted in a crust and a core, between which is the mantle. The lunar crust is composed of a wide variety of elements: oxygen, silicon, magnesium, iron, titanium, calcium, aluminium, potassium, uranium, thorium and hydrogen. A small core of 300-400 km radius. |