Vertical cross-sections of a crater at different relaxation stages. The crater is initially 2 km in depth, 40 km in diameter, and the surface temperature is 38 K. Arrows represent N₂ ice velocities. The length scale of the maximum N₂ ice velocity is marked in the upper-right corner. (a) At the initial time; (b) within an Earth day; (c) after one month; and (d) after one year. In plots (c) and (d), the insets zoom in with greater vertical exaggeration.