ESA’s Mars Express has been monitoring the local and regional dust storms that are brewing at the Red Planet’s north pole over the past month, observing how they disperse towards the equator.
Local and regional storms that last a few days or weeks and are confined to a small area are commonplace on Mars, but at their most severe moment they can plunge the entire planet, as experienced last year in a global storm that surrounded the planet for many months.
It is now spring in the northern hemisphere of Mars, and water and ice clouds and small dusting events are often observed along the edge of the seasonally retreating ice sheet.
Many of the spacecraft on Mars return daily weather reports from orbit or from the surface, providing global and local impressions of changing atmospheric conditions. ESA’s Mars Express observed at least eight different storms at the edge of the ice sheet between 22 May and 10 June, which formed and dissipated very rapidly, one to three days.
The two cameras aboard the spacecraft, the High Resolution Stereo Camera (HRSC) and the Visual Monitoring Camera (VMC), have been monitoring the storms for the past few weeks. The image at the top of this page, taken by HRSC on May 26, captures a spiral-shaped dust storm, the brown color of which contrasts with the white ice of the North Pole ice sheet.
Meanwhile, the animated sequence (above) was compiled from images of a different storm captured by the VMC during a 70-minute period on May 29. This particular storm began on May 28 and continued around June 1, moving towards the equator during that time.
The image montage (below) shows three different storms unfolding on May 22, May 26, and June 6-10. In the latter case, the cameras observed the evolution of the storm for several days as it moved in an equatorial direction.
At the same time, on the outer edge of the polar cap and several thousand kilometers away, near the volcanoes Elysium Mons and Olympus Mons.
Along with the MARCI camera aboard NASA’s Mars Reconnaissance Orbiter, Mars Express observed that when dust storms reached the large volcanoes, the orographic clouds (clouds of water ice driven by the influence of the volcano’s leeward slope on the airflow) that had been developing earlier began to evaporate as a result of the mass of air warming due to dust ingress.
These regional dust storms last only a few days; the high dust is transported and spread by the global circulation in a fine mist in the lower atmosphere, about 20-40 km altitude. Some traces of dust and clouds remained in the volcanic province until mid-June.