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Mercury is the closest planet to the sun. Its orbit, like that of Venus, is inside the earth's own orbit, so it is never further than 28 degrees away from the sun as viewed from earth (elongation). Consequently Mercury is always in the same sign as the sun or in an adjacent one. It has an equatorial diameter of 4876 km which means that is not even half the earth's size. Its average distance from the sun is 57.91 million km. It takes 88 days (sidereal) to orbit the sun and between 12 and 14 months to travel through the whole zodiac. Its maximum diurnal movement is 2 degrees and 25 minutes.

Like Venus, Mercury can be both an evening star or a morning star. It is an evening star and located before the sun in the zodiac when it descends after the sun on the western horizon and a morning star when it rises before the sun on the eastern horizon.

Physical characteristics

Mercury appears to have a solid silicate crust and mantle overlying a solid, iron sulfide outer core layer, a deeper liquid core layer, and a solid inner core. The planet's density is the second highest in the Solar System at 5.427 g/cm3, only slightly less than Earth's density of 5.515 g/cm3.
Mercury's core has a higher iron content than that of any other major planet in the Solar System.

Radar observations in 1965 proved that the planet has a 3:2 spin-orbit resonance, rotating three times for every two revolutions around the Sun.

Comparison in size

Mercury, Venus, Earth, Mars


Hermes (Latin: Mercury) was the son of Zeus (Jupiter) and the titan Maia who was the daughter of Atlas, the bearer of the celestial sphere. His father chose him early on to be his messenger because he was swift, cunning, eloquent and diplomatic. No one could really get angry with him. His most important characteristics were his winged sandals and caduceus garlanded with two snakes. He was the god of travellers, traders, craftsmen, players and thieves.

Hermes displayed his exceptional talents almost immediately after his birth. He made his first lyre from a turtle's shell and soon after stole fifty cattle from Apollo's herd. He wrapped the cattle's hooves in foliage, led them away backwards by their tails and, after he had hidden them, lay back down in his cradle. He feigned innocence in front of his half-brother but was nevertheless betrayed and was forced to appear before Zeus, whereupon he also stole Apollo's bow. Zeus ordered him to return the animals but Hermes managed to avoid this. He played on his lyre for Apollo and offered it to him in exchange. Apollo was so taken with the instrument that he immediately agreed and the two became inseparable friends after Hermes also returned his bow.

Hermes sent people dreams and accompanied the dead on their journey to the underworld. He was the only figure allowed to leave the kingdom of Hades after entering it.

The mythology of Hermes/Mercury suggests a Mesopotamian origin in his parallels with the Babylonian scribe god Nabu (Nebo) who in turn was probably an evolution of the Sumerian goddess of grain, astronomy, and accounting, Nisaba (Nidaba.) The Greeks also saw parallels between Hermes and the Egyptian scribe god Thoth, who was, however, associated with the moon. In the Hellenized culture of Roman Egypt, Hermes was associated with esoteric lore on magic, medicine, theology, and astrology. He was known as Hermes Trismegistus ("three-times great") or in combination with the Egyptian god of the dead Anubis, as Hermanubis. In this latter form, the Egyptianized Hermes/Hellenized Anubis served primarily as the conductor of the dead (psychopomp) on their journey through the afterlife.

Hermes with his emblems[2]


The spinal cord, which carries information in two directions, is associated with Mercury: The brain sends movement impulses to the muscles and receives sensory perceptions in return. It is also linked to the nervous system, the body's "news system", as well as to the respiratory organs which "transport" air. Mercury also rules the hands.

Mercury is the traditional ruler of astrology. (Uranus is the modern ruler.) The association of the god Mercury with astrology goes back to ancient times, when it was explained as the relationship of Atlas - bearer of the celestial sphere - with his grandson, the god of knowledge and intelligence.

In keeping with the god's mythology, the planet Mercury rules trade, thieves, liars, messengers, literacy, communication, and intelligence. As a symbol of the human mind, he has the ability to travel vicariously to different places, and to contemplate life after death. In ruling the hands, Mercury is associated with craftsmen as well as handwriting and typing.

Mercury rules two signs: Gemini and Virgo; the latter possibly indicating a connection with the Sumerian grain and astronomy goddess, Nisaba. He is also exalted in Virgo. It is in detriment in Sagittarius and Pisces; the former contrasting Gemini's collection and communication of information, and Sagittarius as exploring the "big picture." Mercury falls in Pisces.


Mercury embodies the principles of perception and orientation in the world. Its domain includes the assimilation and application of information. Mercury is therefore the symbol of thought processes, discriminative faculties and the intellect. Its house and sign position in the horoscope indicate how and what an individual learns.

When Mercury aspects another planet or axis the characteristics of the horoscope factor in question are present in an individual's thought process and communication. For example, a Venus conjunction softens the individual's speech, whereas a Mars conjunction promotes forthright or aggressive speech.

Transiting Mercury heightens perception in the area affected, although this influence usually only lasts for a few days because Mercury moves so quickly. Periods of Mercury retrograde are notorious for missed communications, misunderstandings, and disrupted transportation schedules. Just as natal Mercury retrograde represents a mind constantly looking inward on itself, Mercury retrograde by transit is a good time for introspection.

See also

Medieval Mercurius[3]



  • Edis, Freda, 1995. The God Between: A Study of Astrological Mercury, Arkana Penguin Books
  • Peay, Pythia, 2004. Mercury Retrograde: Its Myth and Meaning, Tarcher

Notes and References

  1. This NASA photograph taken from space was enhanced to show the planet's chemical and physical characteristics
  2. The winged hat and feet of the rapid messenger, the caduceus or serpent staff of the healer, and the purse of merchants and trade.4th century BCE, Roman
  3. From Guido Bonatti, De Astronomia Libri X (Basel, Nicolaus Pruknerus, 1550)