North Polar Cap (Released 26 October 2004)

This image shows an example of laminar wind flow on the north polar cap. On Earth, gravity-driven south polar cap winds are termed "catabatic" winds. Catabatic winds begin over the smooth expanse of the cap interior due to temperature differences between the atmosphere and the surface. Once begun, the winds sweep outward along the surface of the polar cap toward the sea. As the polar surface slopes down toward sealevel, the wind speeds increase. Catabatic wind speeds in the Antartic can reach several hundreds of miles per hour.<p>In the images of the Martian north polar cap we can seethese same type of winds. Notice the streamers of dustmoving downslope over the darker trough sides, thesestreamers show the laminar flow regime coming off the cap. Within the trough we see turbulent clouds of dust, kicked up at the trough base as the winds slow down and enter a chaotic flow regime.<p>The horizontal lines in these images are due to frameletoverlap and lighting conditions over the bright polar cap.