The proper name of earth's satellite is Luna. The grammar books say that "moon" (and likewise "earth" and "sun") should be lower case, with the exception of when "earth" is in a list with other planets. The earth is Terra; the sun is Sol. This is where we get the words "extraTERREstrial" and "SOLar".
Hope you were entertained by that - now laugh with Kim Cam - a cam of a bloke called Kim