Ceres: a Case for Porous, Unfifferentiated, and Non-icy Hydrated Body

Introduction: The dwarf planet Ceres has a diameter of ~950 km, and it is the largest object in the asteroid belt. Ceres has a density of ~2040-2250 kg m, and a dark non-icy surface with signs of hydrated minerals [1-5]. The low density implies that Ceres contains a significant fraction of voids and/or low-density compounds. These compounds could be presented by hydrated and OH-bearing minerals (phyllosilicates, salts) and ices [1], as well as clathrate hydrates and organic species. McCord and Sotin [1] considered several models for the internal structure and advocated for a differentiated structure with a nonporous rocky core, a water mantle, and an uppermost rocky layer. As opposed to inferences presented in [1-3], this work argues for a porous rocky internal structure of Ceres that may not have the rocky core and the water mantle. Deductions from the body’s shape: Current astronomical data on Ceres’ size, shape, and mass are not certain enough to determine the degree of differentiation. Assuming hydrostatic equilibrium, Hubble Space Telescope (HST) data of Ceres’ shape and size imply a differentiated inferior structure [2]. However, Keck telescope observations [3] do not exclude partially differentiated or even undifferentiated interior structure (Fig. 1).