The astronomers then conducted an analysis called a Bouger correction in order to subtract the gravitational effect of topological features, such as valleys and mountains, from the total gravity field. What is then left is the gravity field hidden beneath the lunar surface, existing within its crust.
Using computer models, the team of scientists came up with a complex interior structure for Ganymede, composed of an ocean sandwiched between up to three layers of ice--in addition to the very important rocky seafloor. The lightest ice, of course, would be on top, and the saltiest liquid would be heavy enough to sink to the bottom. Furthermore, the results suggest the existence of a truly weird phenomenon that would cause the oceans to "snow" upwards! This bizarre "snow" might develop because, as the oceans swirl and churn, and frigid plumes wind and whirl around, ice in the uppermost ocean layer, called Ice III, may form in the seawater. When ice forms, salts precipitate out. The heavier salts would then tumble down, and the lighter ice, or "snow," would flutter upward. The "snow" would them melt again before reaching the top of the ocean--and this would possibly leave slush lurking in the middle of the moon's odd sandwich!
The discovery of a moon can lead to a treasure chest filled with valuable information about the dwarf-planet system. This is because, by measuring the moon's orbit, astronomers can then go on to calculate a mass for the system and gain an important insight into its evolution.