Another spring has "sprung" in the northern hemisphere of Mars! Northern spring began in June 2000, and as we approach August 2000, sunlight is now illuminating most of the north polar cap each day. This is the second northern spring that MOC has viewed--we've now seen, in selected areas, a full Mars year of atmospheric and surface conditions. Although the pictures do not cover the exact same area, pictures from exactly two Earth years ago (26 July 1998) show very similar features in the north circum-polar dune field (see Spring Time View of North Polar Sand Dunes).
At this time, frost left-over from the recent winter is slowly subliming away to expose underlying northern plains and sand dune surfaces. The picture above shows a frost-covered portion of the vast dune fields that surround the north polar cap as they appeared on July 22, 2000. In summer, the dunes are dark, but in winter and early spring they are covered with bright frost. Small dark spots and streaks indicate areas where the frost has begun to disappear. This Mars Global Surveyor Mars Orbiter Camera image covers an area 2.3 km (1.4 mi) wide by 7.7 km (4.8 mi) long near 78°N, 107°W and is illuminated from the lower left.