How far will Zeus/Jupiter go to seduce a pretty girl? Well, don’t put anything past the King of the Olympians. In the case of Callisto, a virgin nymph who was a priestess in the cult of Artemis (Roman: Diana), this meant undergoing a sex change. But once again, don’t underestimate the lengths that Zeus will go to, or the rage that it will provoke in his wife, Hera/Juno.

The goddess Artemis/Diana is a huntress; she is also a virgin, beyond the reach of any man. The same was expected of her followers. Thus Callisto had never been with a man, let alone a god…but that would soon change.

Callisto’s name is very telling; in Greek, it reads as Kalliste, which translates as the “the fairest”. This was the word that Eris, the goddess of Discord, inscribed on the apple that led, in turn, to the Judgement of Paris and the subsequent Trojan war. It isn’t a name to be taken lightly.

So how does one seduce the fairest when she has dedicated her life to the worship of the divine huntress? Dress the part. Zeus literally transformed himself into Artemis to win Callisto’s embrace…

Of course, things don’t always end well for the objects of Zeus’ desire. In the case of Callisto, her violation became apparent to Artemis when Callisto showed visible signs of bearing a child. Thrown out of the cult, Callisto found herself alone, and decided to flee.

What followed is a typically tragic transformation, though who forced the change is unclear. Whether Zeus was trying to hide her identity from Hera, or Hera was just being spiteful is uncertain, but either way, Callisto was turned into a bear.

Many years later, Callisto’s semi-divine son, Arcas, would unknowingly try to slay her; she was after all, a bear. However, Zeus intervened, and transformed them both into constellations, as we’ve seen him do before.

Astronomers call her Ursa Major, the great bear, but most of us know her as the Big Dipper. And her son Arcas?

We know him too. He’s technically Ursa Minor, the small bear, the little dipper. He chases his mother, but he never catches up to her.

So what of the actual moon?

It is the most heavily cratered object in our solar system, having been the victim of an uncountable number of meteoric collisions. However, something is lurking under surface; there’s water beneath Callisto’s scarred skin, and while scientists think that her sister moon Europa is a likelier candidate for harboring life, there is always a possibility that something – or maybe someone – is waiting for us, just beneath the surface of Callisto’s battle hardened exterior.

Artemis would be proud.

Until next time, when we round up the four inner moons of Jupiter, keep looking up…

And if you see the Big Dipper, remember her name: Callisto, the fairest of them all…