Massive dust storms on Mars Dallas Weather Examiner

Sky-watchers who routinely gaze at Mars observed an abrupt change in the appearance of the planet’s arctic zones. “Over the weekend (Jan 30-31) a dust stream appeared,” said Pete Lawrence of Selsey, UK, “and it is cutting across Mars’ north polar cap.”
He photographed the activity through a telescope as seen above. The bright white area is the polar ice cap of Mars which is composed of a surface layer of frozen carbon dioxide, and vast amounts of water ice beneath. Notice that in the rightmost image, the land mass is obscured. This is evidence of an enormous dust cloud.