Evolution of the interior temperature (left) and the composition of the layers (right) as a function of distance from the planetesimal centre and time. The top panels show the results when starting at t₀ = 0 (assuming the maximal possible inventory of ²⁶Al) and the bottom panels when starting at t₀ = 3 Myr (four ²⁶Al half-lives later). The early-formed Vesta analogue heats rapidly to an interior temperature of 2000 K within 200 000 yr. The composition changes from primitive MetSilWat to FeSFeOCla at the melting temperature of water. The clay desiccates to form FeSFeOSil at 900 K. Finally, the FeS separates from the mantle material at the melting temperature of the silicates, to form an internally differentiated planetesimal with a high FeO content in the mantle as the only memory of its icy origins. The Ceres analogue starting after 3 Myr never heats above the desiccation temperature of clay. The clay interior is surrounded by a slowly freezing water ocean containing the excess water that could not enter the silicate minerals.