 The surface composition of Ceres is broadly similar to that of C @-@ type asteroids . Some differences do exist . The ubiquitous features in Ceres ' IR spectrum are those of hydrated materials , which indicate the presence of significant amounts of water in its interior . Other possible surface constituents include iron @-@ rich clay minerals ( <unk> ) and carbonate minerals ( <unk> and <unk> ) , which are common minerals in <unk> <unk> meteorites . The spectral features of carbonates and clay minerals are usually absent in the spectra of other C @-@ type asteroids . Sometimes Ceres is classified as a G @-@ type asteroid . 
