Revised February 10, 1998
Can you imagine what it was like to be one of the very first human beings, living thousands of years ago? The world you lived in was such a frightening, wonderful, mysterious place! You had to be careful that big animals didn't eat you, or other human beings living nearby didn't hurt you, and that you could either find or hunt for food so that you and your family wouldn't starve. A strange blazing fireball rose in the sky overhead each day, and then descended on the other side and was gone. And then began the scariest, most awesome time, when everything was dark and the many lights above appeared. Before you went to sleep, you looked up at all the little lights above you, moving slowly in the direction that the big light had disappeared. Sometimes another light, not as bright, would appear, but it was so different, since it didn't come every night, and sometimes it was a big circle, sometimes a half circle, or sometimes just a thin curve. You didn't know that was our moon.
If you really paid attention to the little lights, you got to notice the strange patterns that always seemed the same as they moved overhead. And then one day, in your favorite group of stars, a very bright new star appeared! The next night, it was still there, but it had moved a little. As you looked night after night, you saw the strange, bright star moving slowly one way, then another! How strange, what kind of star is that? It seems to be wandering, and won't stay with the other stars. You watch it night after night, until it's only seen far in the west right after the big light sets. You never guess that this is more than a star - it's a huge world, many times larger than the planet you lie on, looking up. Yes, it is Jupiter moving through the sky, but all you can see is a bright, eccentric star.
Since there is no one to explain anything to you, you have to decide for yourself what these things above you are! And that's exactly what men and women of long ago did. They looked up at the sky, and then used their imagination to explain what they saw. Since all they knew were how people and animals on Earth acted, they assumed that the sun, moon, planets, and stars were gods who acted in some ways like men, women, or animals. For example, some reasoned that the sun must really be a chariot of horses carrying a bright god through the sky. Others decided the moon was eaten by a great monster when they saw it go through its different phases. Each group of primitive people made up their own stories, and one example of these kinds of stories are the Greek myths that we read today for entertainment.
Myths not only tried to explain natural happenings, but also contained moral lessons. For example, the Greek story of Phoebus demonstrates the dangers of taking on too much responsibility too early. In that story, the sun king Apollo's son Phoebus asks to drive the sun's chariot through the sky, but the boy cannot control the chariot because he is too young and inexperienced. The Earth is parched with drought in some places, and frozen in others. This episode very likely explained a season of drought or a period of unusually cold weather, but it also taught the members of that community about the problems of granting a child's wish too hastily. Even today, people read and study mythology to get insight into social and psychological truths that apply to human behavior now as they did thousands of years ago.
Early Civilizations and Jupiter
Eventually, our ancestors went a step further and decided that something so grand and beautiful as the sky and these strange, seemingly unpredictable stars, the planets, must mean something more. They didn't know these were other worlds like Earth, actual places we would someday visit. Instead they believed that the lights of the planets moved in strange ways because they were alive or were moved by spiritual forces, and were trying to communicate with us here on Earth. In these still primitive communities, usually a wise man or woman would attempt to interpret the movements of the stars and the changing moon, to tell the future, to decide arguments between tribe members, or to give answers to other questions that people in the group needed answered. In this way, they attempted to read what the gods were saying in the sky and then interpret the message for their people.
Once people started living in cities, the roles of these wise men and women became an important profession. The first astronomers in the great civilizations of Sumeria in the Middle East, in Egypt, and in China were priests and soothsayers whose job it was to observe and predict celestial events and tell the king and his subjects what would happen. Because of the work of these early astronomers, mankind learned more and more about how to predict natural occurrences, like when the rainy season would come, when the best time for planting was, and other seasonal changes. In the process, they developed a fairly accurate calendar. Still no one imagined that the Earth rotated in empty space and orbited the sun. They naturally only trusted their senses, and so they believed the Earth was immobile. The sun must revolve around the Earth, they thought, along with all the other planets and the stars!
Since there were no telescopes back then, there were only a few things these official stargazers could observe about any of the planets: where the planet moved in the sky, how fast it moved, and its brightness. Then, using their imagination, they decided what it all must mean. Other than the sun and moon, Jupiter and Venus are the two brightest objects in the sky, and so they were generally thought to bring good luck. Mars and Saturn were believed to bring bad luck or to be a sign of evil, probably because they are dimmer. Mars also appears red, like the color of blood, so it was associated with war.
In many different cultures, the planet Jupiter was named after the king of the local gods and often after the sky god of that region. The Romans called this god Jupiter; the Greeks called him Zeus, god of lightning and the sky; and the Germanic tribes called him Donar and later, Thor, both gods of thunder. When the seven days of the week were invented for calendars, they were named after the planets. Jupiter was considered to "rule" or in some way influence Thursday, German for Thor's day. In the romance languages of French, Spanish, and Italian, Jupiter's connection with Thursday is more obvious, since in those languages that day is called Jeudi, Jueves, and Giovedi.
The giant planet was crowned after such an important god in each culture, not only because of its brightness, but also perhaps because it moved through one of the 12 constellations each year, which seemed to be a sign of its power. The imagination of these ancient astronomer priests strangely hit on some truth, however, since not only is Jupiter king of the sky in brightness, but we now know it is the king of our solar system, being the largest planet. These first astronomers probably never dreamed that Jupiter was such a giant world, so large it could contain the mass of hundreds of Earths. Planet Jupiter's association with a god of lightning is also interesting, since we now know that lightning does exist on Jupiter. And lastly, at least in Greek and Roman mythology, the god Jupiter was notorious for having many lovers. Planet Jupiter also maintains a huge number of "followers," not only its 16 moons, but numerous captured asteroids, called the Trojans, which orbit with the planet, and even a number of comets (the comet Shoemaker Levy-9 which hit Jupiter in 1994 was not unusual in that it was orbiting Jupiter, but unusual in that we saw it hit the planet). All Jupiter's moons are named for the many lovers and other mortals abducted by Jupiter or Zeus, an appropriate choice since the 16 moons of Jupiter are indeed caught in its gravitational pull!
Some early civilizations were so influenced by the sun, moon, and planets that they felt moved to pattern their entire society after the order they saw in the sky. In Sumeria, the city itself was laid out in the same order that the astronomers imagined the planets moved through the heavens, and each profession was assigned a ruling planet. Jupiter was represented by the prime minister, and this began Jupiter's association with justice and law. This idea spread to other cultures, as even the distant Scandinavians honored their version of Jupiter, Thor, when they convened their assembly beginning on Jupiter's day, Thursday. Thor's hammer is still used today to bring order in courts, when the judge bangs his gavel.
As time went on, the priests who interpreted the sky for the king and his people became very powerful. And no wonder, since everyone believed that they read what the gods were saying in the sky - whatever they told the people and their ruler was believed to be true since their gods sent the message! In some civilizations, the astronomer priests watched for signs in the heavens to tell them when to make sacrifices. Sometimes the king himself was sacrificed, and on a somewhat regular basis - all on the word of the powerful sky-watching priests! For example, at one time, every king in Malabar in ancient India could only rule for the twelve years it took Jupiter to make its way through all the zodiac signs. Once Jupiter reached the sign of Cancer, the fatal time had come, according to the priests. They insisted that the king must commit a ritual, public suicide just as the planet, from our point of view on Earth, appeared to move backwards. In many early cultures, ceremonial murder of the king or other human beings was a common occurrence. Often such practices continued until a new young king, who may have been tutored abroad or simply cherished life above tradition, rejected such claims of divine commands from the astronomer priests and had them either dismissed or executed.
Other early cultures' ideas about the heavens were usually less bloody, although they still differed widely, and literature which survives today reflects this. The Jewish people, for example, were content just to know that God created the heavens. The Old Testament doesn't name or categorize the lights in the sky or explain at much length how they move and why. The Greeks, on the other hand, eventually created an entire philosophy of how the heavens were assembled. Aristotle, who lived in the third century BCE, proposed that the Earth was the center of the universe and above it the moon, sun, and planets orbited the Earth, held in place by crystal spheres. Higher than all were the fixed stars, which also revolved around the Earth, all embedded in the outermost sphere. Aristotle also claimed that while the Earth was corruptible and imperfect, the heavenly objects were perfect and in fact made not of the four elements of the world (which were believed to be fire, water, air, earth) but rather of an entirely different element, "quintessence" or "ether," which was also perfect. Aristotle's views were commonly accepted all the way until the 16th century.
Observation of the sky and the planets was an absolute necessity for these early civilizations, so that they could track important information about the seasons and maintain an accurate calendar. But many misconceptions and superstitions also came along with that knowledge. Those intelligent and learned first astronomers knew there had to be some purpose to a bright, beautiful, wandering star like Jupiter, and likely they tried their best to piece out the truth. But many thousands of years had to go by before we would find out that Jupiter was much more than just a bright light above us. People needed to use more than just their eyes and imaginations to find out what Jupiter really was!
No one knows who first decided that the planet Jupiter should have that name, but when Jupiter's moons were discovered, eventually people thought it would be best to name those moons after other Greek and Roman mythological figures associated with Jupiter. The names that Simon Marius suggested for the first four moons began to be used in the seventeenth century, but most of the other moons' names were decided in just the last few decades. Here are the ancient stories behind the names given to Jupiter and its 16 moons.
Jupiter
Jupiter is the Roman name for the god Zeus of Greek mythology. Greek mythology is older and has many more stories that Roman mythology, so most of the stories about Jupiter's moons mention Zeus instead. Jupiter/Zeus was the king of the sky and Earth and all the Olympian gods. He was also known as the god of justice. He was named king of the gods in the special meeting that followed his overthrow of the god Cronus (Saturn in Roman mythology) and the Titans. Zeus's wife was the goddess Hera, who was very jealous of the attention that Zeus paid to other goddesses and women. In the Roman version, Jupiter's wife was named Juno. Early in the planning stages of the Galileo mission, there was a proposal to name the spacecraft "Juno," since the spacecraft in effect would be "watching over" Jupiter as well as keeping an eye on its moons (named after Jupiter's lovers), just as Jupiter's mythological goddess-wife did.
The Four Galilean Moons
Io was a beautiful priestess of the Greek goddess Hera. When Zeus fell in love with Io, he transformed himself into the shape of a dark cloud to hide himself from his jealous wife. However, Hera looking down on Earth noticed the small cloud and suspected that it was one of the tricks of her husband. She decided to check the true nature of this cloud.
As soon as Hera approached, Zeus transformed Io into a white cow to avoid his wife's anger. But Hera guessed his trick and asked to have the cow as a gift. Zeus could not refuse such a little gift without giving himself away. So Hera tied up the poor cow and sent her faithful servant Argus to watch over Io. Argus had a hundred eyes and only a few were ever closed at any time. To free Io, Zeus sent his son Hermes to sing and tell boring stories to make Argus sleep with all his eyes. Hermes told so many stories that finally Argus closed his hundred eyes. Then Hermes killed Argus and released Io.
When Hera discovered what had happened, she was so furious that she sent a vicious gadfly to sting the cow forever. Moreover, to honor the memory of her faithful servant, Hera put the hundred eyes of Argus on the tail of the peacock, her favorite bird, where they could no longer see but instead beautifully decorated the tail. Meanwhile, Io was still a prisoner in the shape of a cow and could not get rid of the malicious gadfly. Finally, after Jupiter vowed to no longer pursue his beloved Io, Juno released her. Io settled in Egypt, becoming the first queen of Egypt. Curiously, when Voyager 1 passed Io in March 1979 and imaged the surface, the picture showed what looked like the hoof print of a cow!
Europa was a beautiful princess. Her father was Agenor, the Phoenician king of the city of Tyre. Zeus fell in love with Europa after seeing her gathering flowers by the sea. To get close to her, Zeus changed his form into that of a magnificent white bull and appeared at the seashore where Europa was playing with her maidens. The great bull walked over to where Europa stood and knelt at her feet. The appearance and movements of the bull were so gentle that Europa spread flowers about its neck and dared to climb on its back. Suddenly the bull rushed into the sea with Europa still on its back. Only then did Zeus reveal his true identity and took Europa to the Mediterranean island of Crete. There Zeus cast off the shape of the white bull and made Europa his bride and the first queen of Crete. Zeus later reproduced the shape of the magic white bull in the stars, in the constellation Taurus.
Ganymede, the son of King Tros, was a beautiful Trojan boy who was so handsome that Zeus himself desired him for a companion. Disguised as an eagle, Zeus flew down to Earth and carried him off to Mount Olympus. There Ganymede was made Zeus' cupbearer, bringing him and the other gods and goddesses the ambrosia drink that gave them eternal youth. King Tros was compensated for this loss with a golden vine, two fine horses, and the assurance that his son had become immortal and therefore exempt from the miseries of old age. Zeus set Ganymede's image among the stars as Aquarius, the water-carrier.
Callisto was a river goddess. Her great grandfather was the river god Inachus, and her father was Lycaon. Callisto avoided the companionship of the young boys and gods who wanted to be with her, for she wanted to be like her patron Artemis, the goddess of the hunt. Callisto was the favorite companion of Artemis. She accompanied the goddess on the hunt, helping her and looking after her needs.
According to Ovid, one day as she was returning from the hunt, Callisto laid down her weapons in a thick grove of trees and layed down to rest. Zeus saw how beautiful she was and how she was alone, and decided she was a sexual conquest worth the danger of his wife's wrath. Knowing that Callisto was a follower of Artemis, and therefore preferred to remain a virgin, Zeus tricked her by appearing to her as the goddess. Callisto was delighted to see her mistress and was receptive to her kisses and embraces. She started to tell of her adventures hunting when Zeus gave away his disguise and raped her. She resisted as best she could, but Zeus was stronger. She became pregnant from their encounter, and soon Artemis and the other nymphs noticed this and cast her out of their group. She bore a son, Arcas.
Hera learned of her husband's encounter with Callisto and saw the birth of Arcas as a further insult. She turned Callisto into a bear in order to strip her of the beauty which Zeus had so appreciated. Arcas grew up, and when he was 15 years old, he was out hunting and met up with the bear who was his mother. She recognized him and began to approach him, but he didn't know her and prepared to throw his javelin at her. Zeus saw what was happening and stopped them there, turning them into two neighboring constellations. Callisto was turned into the constellation Ursa Major (Great Bear) and Arcas into Ursa Minor (Little Bear). Hera was angry that her rival and rival's son should be displayed in the night sky for all to see, so she made the sea god Poseidon agree that he would never let the two touch his waters.
The Inner Moons
Between the large Galilean moons and giant Jupiter are four small moons: Metis, Adrastea, Amalthea, and Thebe. All were discovered by Voyager in 1979 except for Amalthea, which was discovered in 1892. Nearly all of the stories behind their mythological names are on the theme of Jupiter's early life.
Metis, a Titaness, was visited by Zeus when he was very young and gave him counsel on how to overthrow his father Cronos. Her name means knowledge and she is described by Hesiod as "she who knows most of gods and mortal men." Later when Zeus became king of the gods, he lusted after Metis and seduced her. Some stories even say she was Zeus' first wife, before Hera. But a prophesy said that she was fated to bear a son who would overthrow Zeus. When she became pregnant, Zeus followed the advice of his grandparents, Uranus and Gaia, and swallowed her whole in order to avoid the fate of being overthrown. Later, Athena was born out of the head of Zeus. She is presumably the child whom Metis would have borne. Being the closest moon to Jupiter, Metis is aptly named, since it seems most in danger of being swallowed by the huge planet!
Adrastea figured in Zeus' early life, too, although Zeus had a daughter also named Adrastea (see Ananke's myth below). When Zeus was just a baby, his mother Rhea had to hide him from his father Cronus. That was because Cronus was told one of his offspring would overthrow him, so he swallowed up his children as soon as they were born. Rhea allowed Cronus to swallow a stone hidden in cloth which he thought was his latest newborn. Then she carried the baby Zeus to Mother Earth, who took him to Crete and hid him in the cave of Dicte on the Aegean Hill, although other stories say it was on Mount Ida. There he was nursed by the Ash-nymph Adrastea and her sister Io, both daughters of Melisseus, and by the Goat-nymph Amalthea.
Amalthea was the Goat-nymph who nursed the infant Zeus with her goat's milk on the Aegean Hill (or Mount Ida), where he was being hidden from Cronos, his father. His food was honey, and he shared the goat's milk with Pan, his foster brother. Zeus was grateful for Amalthea's kindness and set her image in the sky as Capricorn. Zeus also borrowed one of her horns and gave it to the sisters Adrastea and Io. It became the famous Cornucopia, or horn of plenty, which is always filled with whatever food or drink the owner may desire.
Thebe was a nymph and the daughter of the river god Asopus. She and her twin sister Aegina were both carried off and seduced by Zeus. Later she married Zethus who rebuilt Cadmea. The name of that city was later changed to Thebes in her honor.
The Outer Moons
These four moons lie far out past Callisto and are much smaller than the large Galilean moons. Their orbits are close to one another, so they are considered to be a group which may in fact be fragments of a destroyed moon or asteroid. Astronomers agreed that this group of moons' names should all end in the letter "a." Possibly because of this requirement, some of the moons' names do not have very well known myths associated with them. Here are their stories:
Leda was the daughter of Thespia who married Tyndareus and became queen of Sparta. Zeus desired her and approached her disguised as a swan. After the lovemaking beside the river Eurotas, she laid an egg from which were hatched Helen (the famous Helen of Troy), Castor, Polydeuces (or Pollux), and Clytaemnestra. Some stories had only Helen and Polydeuces as being children of Zeus, the other two offspring being fathered by Leda's husband Tyndareus.
Himalia was a nymph who bore three sons of Zeus. Very little is known about Himalia's myth, just as little is actually known about this moon of Jupiter.
Lysithea was a daughter of Oceanus and one of Zeus' lovers. Not much more is known about the story of Lysithea or the moon Lysithea.
Elara and Zeus were the parents of Tityus the giant. Very little is known about the Elara myth or the moon Elara. What is told is that her son Tityus was caught trying to violate Apollo's mother, Leto, at the sacred grove of Delphi, and for this he was killed by Apollo and Artemis. In Hades, Tityus was stretched out on nine acres of ground while two vultures ate his liver.
The Far Outer Moons
The last four of Jupiter's moons are also small and lie the farthest from giant Jupiter. Curiously, all orbit in reverse direction. These moons may also be fragments of a destroyed moon or asteroid, and by design their names all end in the letter "e." Again, possibly because of this naming scheme, some of the moons' names do not have very well known myths associated with them. Here are their stories.
Ananke and Zeus were the parents of Adrastea, the distributor of rewards and punishments (not the same Adrastea that the inner moon is named after). Very little is known about Ananke, myth or moon.
Carme was a nymph and attendant of Artemis. Carme and Zeus were the parents of Britomartis, a Cretan goddess. Not much is known about Carme's myth or the moon named after her. Carme's daughter Britomartis was beloved of King Minos of Crete and was known to have invented hunting nets. Britomartis was also a companion of Artemis like her mother, and held the hunting goddess' hounds on a leash.
Pasiphae was a daughter of Helios and the nymph Crete (also called Perseis), and sister of Aeetes and Circe. She was married to King Minos of Crete and was the mother of Ariadne, Androgeus, Phaedra, and the Minotaur. When her husband neglected to sacrifice a beautiful white bull to Poseidon, that god made Pasiphae fall in love with the bull. She mated with it by disguising herself inside a hollow wooden cow made by the craftsman Daedalus. Because of this unnatural encounter, she gave birth to the Minotaur, which had a bull's head and a man's body. Some stories claim it was Zeus whom Minos offended instead of Poseidon. Pasiphae's husband Minos had many lovers just like Zeus, and she was a jealous wife very much like Hera.
Sinope was the river god Asopus' daughter. Zeus fell in love with her and promised her whatever gift she wished. Sinope craftily chose virginity, and made her home in Paphlagonia, where she spent the remainder of her life in happy solitude. Being the farthest known moon from Jupiter, Sinope indeed resides far from Jupiter's strong grasp.