Omega_SouthPole_17-3-2004

Transition from CO2 ice to H2O ice. a, MOC (NASA/JPL/MSSS) context image, exhibiting the bright polar areas. b, Map, within the same area, of the H2O ice as identified by OMEGA (processed 1.5mm feature, see Fig. 2), with a blue to red colour scale; the bluest is the richest in H2O. c, Same mapping of the CO2-ice features. d, Enlargement of the strip (image M13-01891, at L ( ¼ 325.38) marked by the red rectangles in a, b and
c. It exhibits the variety of terrains identified by the MOC, examples being enlarged following the arrows (e, f, g), from the bright ‘Swiss cheese’-like structured ice, towards the dark layer terrain on the left. The OMEGA-derived maps indicate the composition of each unit: CO2-rich ice for the bright unit; ice-free for the layer terrains; and H2O ice for the smooth dark terrains in between, with polygonal structures closer to the bright cap. These structures can also be observed in the transition zone (between f and g), through a thin covering layer of CO2 ice.