The symbols for the planets, dwarf planet Pluto, Moon and Sun (along with the symbols for the zodiac constellations) were developed for use in both astronomy and astrology.
The astronomical symbol for the Sun is a shield with a circle inside. Some believe this inner circle, or "boss" represents a central sun spot.
The symbol for Mercury represents the head and winged cap of Mercury, god of commerce and communication, surmounting his caduceus (staff).
The symbol for Venus is designated as the female symbol, thought to be the stylized representation of the hand mirror of this goddess of love.
The symbol for Earth shows a globe bisected by meridian lines into four quarters.
The symbol for the Moon is a crescent.
The symbol for Mars represents the shield and spear of the god of war, Mars; it is also the male or masculine symbol.
The symbol for Jupiter is said to represent a hieroglyph of the eagle, Jove's bird, or to be the initial letter of Zeus with a line drawn through it to indicate its abbreviation.
The symbol for Saturn is thought to be an ancient scythe or sickel, as Saturn was the god of seed-sowing and also of time.
The symbol for Uranus is represented by combined devices indicating the Sun plus the spear of Mars, as Uranus was the personification of heaven in Greek mythology, dominated by the light of the Sun and the power of Mars.
The symbol for Neptune is the trident (long three-pronged fork or weapon) of Neptune, god of the sea.
The symbol for dwarf planet Pluto is a monogram made up of P and L in Pluto (and also the initials of Percival Lowell, who predicted its discovery).