Upside Down Snow Showers on Ganymede?

When the topic of moons with possible subsurface oceans is brought up, Jupiter's moon, Europa, and Saturn's moon, Enceladus, are two that often come to mind. Recently, however, another of Jupiter's moons, Ganymede--the largest moon in the solar system and the only moon known to have a magnetic field--is now thought to not only have a subsurface ocean, but there's also a possibility that this moon may actually have layers or shells of separate oceans. Because of Ganymede's unusual properties, one scientific model suggests that ice could form in one of the oceans, and as the salt precipitates out, the ice would float upwards, meaning that snow might actually fall upside down on Ganymede.