Spring recently sprung in the northern hemisphere of Mars, which means the dust storm season there has begun. On cue, NASA's Mars Reconnaissance Orbiter spotted and is currently tracking a growing dust storm. It has become a regional storm and could possibly become a global one.
Both of NASA's operational rovers-- Opportunity and Curiosity, which are on opposite sides of the planet-- have picked up indications of the storm. If it does go global, the dust storm would be more of a problem for Opportunity, which gets its power from solar arrays gathering solar energy. Dust collecting on the solar panels would cut down on the energy the panels could harvest. Curiosity is nuclear powered, but dust in the air would cut down on the sharpness of the images sent home.