Low Pressure Cell near North Pole. This Martian storm was observed by Viking Orbiter 1 at about 65 N latitude. The local season corresponds to late July on Earth. The storm is located near Mars' polar front, a strong thermal boundary that separates cold air over the pole from the more temperate air to the south.
Shadows indicate that clouds are relatively low in the atmosphere.
Because temperatures in this region are well above the condensation temperature of carbon dioxide, water ice is the probable constituent of the clouds. This system strongly resembles satellite pictures of extratropical cyclones near the polar front on Earth. The counterclockwise circulation is consistent with the winds expected in a normal low pressure situation. The white patches in the top center of the picture are outliers of the north polar cap. North is to the upper left.