Geophysical data from Dawn’s mission revealed complex and divergent internal structure evolutionary paths for Vesta and Ceres. Dawn’s data indicated that Vesta has a differentiated internal structure with uncompensated topography and Ceres is partially differentiated with compensated topography. Vesta experienced a magma ocean state, leading to effective early shape relaxation. Vesta’s current non-hydrostatic shape is dominated by Rheasilvia and Veneneia impact basins, formed when Vesta was too rigid to relax. However, northern terrains still reflect its pre-impact, closer-to-hydrostatic shape. Ceres incorporated abundant volatile material upon its accretion and subsequently underwent ice–rock fractionation. Observed surface aqueous alteration indicates extensive past hydrothermal circulation that facilitated efficient heat transfer and preserved Ceres’ interior in a relatively cool state. Lower viscosities at depth allowed isostatic compensation of Ceres’ long-wavelength topography. The high inferred abundance of water ice, hydrated salts, and/or clathrate phases suggest previous globally significant regions of solute-rich fluids that froze from the surface inward, leading to the vertical density gradient inferred from Dawn’s Second Extended Mission (XM2) high-resolution gravity data. This, coupled with thermal modeling, indicated that Ceres could have brine reservoirs, at least regionally, which were likely mobilized by the Occator crater-forming impact, leading to long-lived brine extrusion and faculae formation.

Ceres’ composition has been a long-standing issue since the first ground-based observations because of its peculiar spectrum and lack of an established connection with meteorites. NASA’s Dawn mission acquired unprecedented measurements of the surface of the dwarf planet Ceres, bringing a breakthrough in the comprehension of the mineralogy of the surface. Ceres’ surface is a mixture of ultra-carbonaceous material, Mg-phyllosilicates, NH4-phyllosilicates, carbonates, organics, Fe-oxides, and volatiles, as determined by remote sensing instruments onboard Dawn: Visible and InfraRed imaging spectrometer (VIR), Gamma Ray and Neutron Detector (GRAND), and the Framing Camera (FC). The average mineralogy of Ceres reveals a possible past global aqueous alteration. Regional variations of such materials unveil possible processing acting on large scales, both endogenous and exogenous. Local areas of Ceres surface, on a spatial scale of a few kilometers, present significant spectral variations with respect to the measured average spectrum, and thus significant variation on the inferred mineralogy. Most imply recent or ongoing geological activity involving upwelling of subsurface carbonate-rich and salt-rich brines (Occator crater and Ahuna Mons), organic material (Ernutet crater), hydrated carbonates, and water ice (Oxo and Juling craters). Global aqueous alteration and recent hydrothermal activity place Ceres among the most interesting targets in astrobiology.