Local dust storms often arise on Mars, especially at the edges of the polar carbon dioxide ice caps. The relatively dark martian soil and rock absorb more solar radiation than the relatively light ice caps, which remain at a constant temperature due to the sublimation of their carbon dioxide. The resulting large difference in temperature causes strong winds to flow around and off the ice. The temperature difference is also present in the atmosphere above the polar region from the surface through a height of about 40 miles, resulting in a strong martian jet stream with top westerly (west to east) wind speeds exceeding 360 miles per hour. The strong near-surface winds lift dust near the ice cap edge, forming small, local dust storms that last about seven to ten days. While this basic knowledge of cap-edge storms is relatively straightforward, a fuller and deeper understanding of their dynamics has been elusive.
To elucidate these dynamics, Agustín Sánchez-Lavega from the Universidad de Paíz Vasco in Bilbao, Spain, and colleagues closely studied cap-edge storms from March through July 2019, during early spring in the northern hemisphere of Mars. They examined images from the Visual Monitoring Camera (VMC), High Resolution Stereo Camera (HRSC), and Mars Color Imager (MARCI) cameras onboard the Mars Express and Mars Reconnaissance Orbiter satellites for cap-edge storms. They tracked the storms over their lifespans, examined the shapes of the dust clouds, and cross-referenced the storms with average winds during early spring from the Mars Climate Database. Sánchez-Lavega and colleagues propose that the storms they tracked closely resemble traveling weather systems common in Earth’s mid-latitudes, with fronts like those on Earth and convective dust plumes shaped like the cumulus clouds over small terrestrial thunderstorms. Improved characterization of these local dust storms could be useful for planning human or robotic exploration of the martian mid-latitudes and may also improve weather forecasts on Earth. READ MORE