Temperature maps of the north polar region. The maps are displayed in gnomonic map projection centered at the north pole and color-coded by temperature (a,b), height (c), and depths (d). Axis units are in kilometers. (a): average temperature map. (b): maximum temperature map. (c): location of possible surface ice (blue). (d): depth-to-ice map for the upper 2 m of regolith derived from the maximum temperature where temperatures are below 112 K.