Last time, we took a look at two of Mars’ moons, Phobos and Deimos (Fear and Dread). Today, we’re moving out past the inner planets to the large gas giants that make up the outer solar system. The first of these worlds is named for the Roman storm deity, Jupiter.
Jupiter, like most Roman gods, is a transplant from Greek mythology. In classical Greek culture, Jupiter is known as Zeus. Like Jupiter and the Indo-Aryan deity Indra, he wields a thunder bolt, rules over the other gods, and makes time to have amorous dalliances with goddesses and mortals alike. These amorous interludes typically do not sit well with his wife, Hera (Juno for the Romans), sometimes with cosmic consequences; our galaxy, in Greek cosmogony, resulted from Zeus attempting to give one of his children immortality (Heracles, Roman Hercules) by suckling at Hera’s breast; when she realized the ploy, she pulled away. The resultant spray of milk flew across the heavens, giving us what we call the Milky Way.
Just as with Mars, the moons of Jupiter are named for mythological beings associated with their planetary god. Given that there are sixty-plus cataloged moons, this will not be a comprehensive exploration of all of the Jovian satellites. Instead, I’ll be presenting eight major moons.
The first four are the Galilean moons, so called for their discovery by Italian astronomer Galileo Galilei between 1609-1610 CE (a similar observation was suggested by the Chinese astronomer Gan De around 364 BCE to less fanfare). Even though they are remembered for Galileo, the four moons of Io, Europa, Ganymede, and Callisto were named by a man who made the same discoveries, only one year later. Simon Marius may have been forgotten by the history books, but his naming convention has stuck around for over four centuries.
Beyond this so called main group of moons is another cluster of four satellites collectively known as the Inner Group. These four objects are named Metis, Adrastea, Amalthea, and Thebe; after working through the myths of the main group, we’ll spend a little time with these smaller objects.
After those explorations, we’ll turn our eyes out further away from the sun, and examine the bodies that circle Saturn, the cursed wanderer who takes his time slowly going across the heavens. But first, onto the Galilean moons…