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This map shows the frequency of carbon dioxide frost's presence at sunrise on Mars, as a percentage of days year-round. Carbon dioxide ice more often covers the ground at night in some mid-latitude regions than in polar regions, where it is generally absent for much of summer and fall. Color coding is based on data from the Mars Climate Sounder instrument on NASA's Mars Reconnaissance Orbiter. A color-key bar below the map shows how colors correspond to frequencies. Yellow indicates high frequencies, identifying areas where carbon dioxide ice is present on the ground at night during most of t…