Callisto

From a distance, Callisto has a mesmerizing unearthly beauty, like Wuthering Heights from the moors on a foggy night (see the global views inPlates JcO1, O2, and O3). The surface appears to be illuminated from within and resembles nothing so much as a sphere of stars, as if our Galaxy had collapsed inward on itself and then turned inside out. The “stars” are in fact thousands of impact craters, which overwhelmingly dominate the surface. Like the stars of our Galaxy, Callisto's craters come in all varieties of size and brightness, each a function of the size of the comet or asteroid that created it and the age since each crater was formed. Yet even from afar, this global pattern of innumerable star-like spots is deceptively simple. Strange diffuse nebula-like dark and bright features create a patchy pattern not unlike our Milky Way Galaxy on a cold crisp night.

The ethereal beauty of Callisto is appropriate. Callisto, rooted in the Greek Kalliste, means “most beautiful.” In various versions of the myth, she is a nymph or attendant of Artemis, and daughter of Lycaon, King of Arcadia, who took a vow of chastity. Zeus/Jupiter lured her and took her, but wrathful Juno/Hera turned her into a bear. To avoid being killed by a hunter (her own son), Zeus transformed both into Ursa Major and Ursa Minor, another gift to mortals from the gods.