A frozen patch ofwater ice. The robotic Mars Express spacecraft took the aboveimage in early February 2005. The ice pocket was found in a35-kilometer wide crater that resides 70 degrees north of theMartian equator. There, sunlight is blocked by the 300-meter tallcrater wall from vaporizing the water-ice on the crater floorinto the thin Martian atmosphere. The ice pocket may be as deepas 200 meters thick. Frost can be seen around the inner edge onthe upper right part of the crater, while part of the lower leftcrater wall is bathed in sunlight.