the Moon

For possible future research stations on the moon it is important to get water from the rocks on the Moon will probably be cheaper than to deliver it from the earth. The moon is smaller than the Earth density. This is because there is almost no heavy elements like iron and nickel. According to one version, in the initial stage of formation of more liquid the Earth, when the substance is almost re-allocated to strata: severe closer to the center (iron) and light (silicon, etc.) - on the surface of the body, similar in size to Mars in passing touched the earth, tearing off part of its outer layers, from which, supposedly, and formed a light Moon.