Schematic representation of the temperature evolution at two different depths (full lines) and at the centre (dotted line) of a planetesimal of the 100 km size class. The horizontal dashed lines correspond to fixed temperatures equal to the closure temperatures in Table 1. The circles indicate the instants at which at a given depth the temperature drops below a given temperature. These instants correspond to the closure ages of the different thermochronometers used for meteorites.