 Ceres ' <unk> is consistent with a differentiated body , a rocky core <unk> with an icy mantle . This 100 @-@ kilometer @-@ thick mantle ( 23 % – 28 % of Ceres by mass ; 50 % by volume ) contains up to 200 million cubic kilometers of water , which would be more than the amount of fresh water on Earth . This result is supported by the observations made by the Keck telescope in 2002 and by evolutionary modeling . Also , some characteristics of its surface and history ( such as its distance from the Sun , which weakened solar radiation enough to allow some fairly low @-@ freezing @-@ point components to be incorporated during its formation ) , point to the presence of volatile materials in the interior of Ceres . It has been suggested that a remnant layer of liquid water may have survived to the present under a layer of ice . Measurements taken by Dawn confirm that Ceres is both differentiated and has a shape consistent with hydrostatic equilibrium , which makes Ceres the smallest object confirmed to be in hydrostatic equilibrium , being 600 km smaller and less than half the mass of Saturn 's moon Rhea , the next smallest such object . <unk> has suggested Ceres could have a small metallic core from partial differentiation of its rocky fraction . 
