Diurnal variation in subsurface temperature as a function of depth in a conductive or radiative nucleus. The temperatures are graded in color scale and contoured between 100 and 220 K at an interval of 20 K. The results are for the latitude of 25°N on the nucleus of 67P with an unobstructed horizon (as on a spherical nucleus). The simulation parameters are listed in Table 2. The nucleus is assumed to be dry and to consist of aggregates 0.5 mm in radius. Results are obtained for the heliocentric distances of 3.27 au (panels a and b) and 1.35 au (panels c and d). The temperatures for constant conductivity are shown in panels a and c, and those for the radiative nucleus are plotted in panels b and d.