Calculated diurnal surface temperatures for flat terrain terrain (dashed) and for fracture floor geometry A4 (inert: continuous; icy floor: dotted). The sublimation front is located at a depth of 1 mm (grey) and 5 mm (black). The heliocentric distance is 2.0 AU, the plane angle is η = 30°, and the sublimation front is identical to the surfacial node. Fracture temperatures are averaged over the four most central node positions at the fracture bottom.