In astronomy and astrology:
In other uses:
In old manuscripts, the Mars symbol was drawn as a Venus symbol rotated 135 degrees anti-clockwise. So it originally had a cross instead of the arrow. Alchemists constructed the symbol from a cross (representing matter) above a circle (representing spirit). The later Mars symbol is usually interpreted as the spear and shield from the war god Mars/Ares.
The symbol has the Unicode entry U+2642.