Water Ice in a Martian Crater

Explanation: What lies on the floor of this Martian crater? A frozen patch of water ice. The robotic Mars Express spacecraft took the above image in early February. The ice pocket was found in a 35-kilometer wide crater that resides 70 degrees north of the Martian equator . There, sunlight is blocked by the 300-meter tall crater wall from vaporizing the water-ice on the crater floor into the thin Martian atmosphere . The ice pocket may be as deep as 200 meters thick. Frost can be seen around the inner edge on the upper right part of the crater , while part of the lower left crater wall is bathed in sunlight. The existence of water-ice pockets inside craters near the Martian North Pole , like that pictured above and others noted previously , give clues not only about surface conditions in the Martian past but also possible places where future water-based astronauts might do well to land.