In late May 2019, a spiraling dust storm on the north polar cap of Mars was observed by multiple instruments on board ESA's Mars Express spacecraft. This image was acquired on May 26 with the high-resolution stereo camera HRSC and covers an area approximately 2,000 by 5,000 km. The storm's spiraling shape results from the deflection of air masses due to the planet's rotation, a phenomenon known as the Coriolis force. This effect is also observed on Earth, where low-pressure areas in the northern hemisphere - cyclones, for example - have a clockwise spiral shape. Storms on Mars are generally weaker compared to storms on Earth because the air pressure on the Red Planet is much lower - less than one percent of the air pressure on Earth. Dust storms on Mars therefore reach less than half the typical wind speeds of hurricanes on Earth. The vortex pattern of the north polar cap can also be seen at the far right of the image. At the same time, isolated clouds can be seen at the edge of the ice cap and further south (to the left) around the large volcanoes. The dark areas around the polar cap are huge dune fields of volcanic ash transported to the polar region by global circulation. More on this: <a rel="nofollow" class="external text" href="https://www.dlr.de/dlr/desktopdefault.aspx/tabid-10453/651_read-36518/year-all/#/gallery/35875">www.dlr.de/dlr/desktopdefault.aspx/tabid-10453/651_read-3...</a> Source: ESA/DLR/FU Berlin, CC BY-SA 3.0 IGO
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<a rel="nofollow" class="external text" href="https://www.flickr.com/photos/dlr_de/48486533746">Spiralförmiger Staubsturm an der Nordpolkappe des Mars</a>