In addition to its mass and modeled geochemistry, researchers have also examined Enceladus's shape to determine if it is differentiated. Porco et al. (2006) used limb measurements to determine that its shape, assuming hydrostatic equilibrium, is consistent with an undifferentiated interior, in contradiction to the geological and geochemical evidence. However, the current shape also supports the possibility that Enceladus is not in hydrostatic equilibrium, and may have rotated faster at some point in the recent past (with a differentiated interior). Gravity measurements by "Cassini" show that the density of the core is low, indicating that the core contains water in addition to silicates.