The bulk, composition and mass of Adrastea are not known, but assuming that its mean density is like that of Amalthea,[4] around 0.86 g/cm3,[10] its mass can be estimated at about 2 × 1015 kg. Amalthea's density implies that the moon is composed of water ice with a porosity of 10–15%, and Adrastea may be similar.[10]