 Amalthea's irregular shape and large size led in the past to a conclusion that it is a fairly strong, rigid body, where it was argued that a body composed of ices or other weak materials would have been pulled into a more spherical shape by its own gravity.However, on 5 November 2002, the "Galileo" orbiter made a targeted flyby that came within 160 km of Amalthea and the deflection of its orbit was used to compute the moon's mass (its volume had been calculated previously—to within 10% or so—from a careful analysis of all extant images).In the end, Amalthea's density was found to be as low as , so it must be either a relatively icy body or very porous "rubble pile" or, more likely, something in between.