Mars is the first planet whose orbit around the sun lies outside that of the earth and is therefore considered to be the first of the outer planets (although astrologers also consider Mars to be a personal planet.) Its equatorial diameter of 6794.4 km makes it only half the size of the Earth.
Its average distance from the Sun is 227.9 million km and has an orbital period of 687 days (about two Earth years). Its maximum diurnal movement is 52 arc minutes with the average being 31 minutes. Because its glow appeared red to ancient astrologers (who had no word for the color orange) it is often called the "red planet".
Ares (in Latin: Mars) was the god of war and one of the twelve Olympians. The son of Zeus and Hera, his siblings and descendants vary, depending upon the version of the myth. Ares did not seem to marry, but among his affairs the most prominent one was with Aphrodite (Venus), the goddess of love and beauty. As the symbol of male passion Ares fathered Eros (Cupid) with Aphrodite.
Ares is usually portrayed riding a chariot being pulled by two horses, Deimos (terror) and Phobos (fear) although sometimes Deimos and Phobos are considered to be his attendants or children. Ares symbolized the wild, unrestrained fight, usually involving great bloodshed. Rather than being the strategist who goes into battle with a plan, he was the firebrand with raw irrepressible power. Ares' choleric and argumentative temperament on and off the battlefield made him unpopular among gods and humans alike; he was therefore rarely honoured with temples.
Ares was the patron god of warriors, and the 8th century BC Homeric Hymn to Ares makes explicit the link between the god and the planet Mars.
"Ares, exceeding in strength, chariot-rider, golden-helmed, doughty in heart, shield-bearer, Saviour of cities, harnessed in bronze, strong of arm, unwearying, mighty with the spear, o defender of Olympos, father of warlike Nike (Victory), ally of Themis, stern governor of the rebellious, leader of the righteous men, sceptred King of manliness, who whirl your fiery sphere [the planet Mars] among the planets in their sevenfold courses through the ether wherein your blazing steeds ever bear you above the third firmament of heaven; hear me, helper of men, giver of dauntless youth! Shed down a kindly ray from above upon my life, and strength of war, that I may be able to drive away bitter cowardice from my head and crush down the deceitful impulses of my soul." 
The Roman god Mars, prior to the introduction of Ares from Greece, was originally a god of vegetation. With the increasing militarisation of Roman society Mars became associated with the Greek god Ares and his myths were applied to Mars, as well.
Mars is the traditional ruler of Scorpio (Pluto being the modern ruler) and the sole ruler of Aries. It is in detriment in Libra and Taurus, exalted in Capricorn, and falls in Cancer. In traditional astrology Mars is considered to be malefic.
The male sexual organs are associated with Mars, together with muscles, blood and arteries. Mars rules athletes as well as warriors and implements of war. Mars' association with cutting instruments may account for its rulership of surgeons. In a man's chart Mars indicates his masculinity and male sexuality. In a heterosexual woman's chart, Mars shows the kind of man to whom she is attracted. In either sex, Mars indicates one's innate assertiveness and aggression.
According to Dane Rudhyar, Mars "is the desire to move away from the center... It symbolizes all beginnings, all initiating impulses; self-projection as a release of sheer energy" Its house and sign position show where and how an individual initiates action, and goes about achieving something or asserting oneself. It also indicates the way an individual is likely to expend energy and get moving. Mars is associated with all kinds of instinctual drives and symbolises the personal will and love of conquest. But it can also stand for uncontrolled aggression, anger and rage. It describes sexual energy.
If the sun is the "hero" of one's personal hero's journey in life, Mars is like the "hero's sword and fighting spirit" necessary to defend him and accomplish his mission.
In a man's horoscope Mars represents his masculine identity. The sun indicates his core identity, but Mars gives that identity its expression as a male in the world. In a woman's horoscope Mars indicates her own initiative and aggression, as well as the type of man she finds attractive.
When natal Mars is in aspect to other planets or an axis it dynamises and activates the horoscope factor involved. In a difficult aspect it can indicate either someone who becomes embroiled in quarrels or who attracts quarrelsome people. Natal Mars retrograde can indicate someone with self-esteem issues because all of Mars's natural aggression is turned inward.
When transiting Mars aspects other planets it energises and motivates them to action, although the influence of Mars transits is usually felt only for a couple of days. (Mars usually spends two days in a single degree.) However, Mars transits that occur during periods of retrograde movement are more significant because it can then aspect the same horoscope factor three times.
- Our Solar System's Planets: Mars (Astronomical Demonstration, Astrum 2014; 11 min)
- List of articles on Mars (Skyscript)
- Review of the Movie "Gladiator" (Liz Greene; Astrodienst)
- Gustav Holst: Mars (Audio; 7 min)