Cyclone!

NASA - Picture of the Day del 20 Maggio 1999:"Late last month (April 1999) a team of Mars-watching astronomers sighted an immense cyclonic storm system raging near the (...) North Pole. Their discovery picture, made with the HST on April 27, is seen at left while the projected insets (right) show closeups of the storm and surrounding areas. Shrunken to its martian midsummer state, Mars' north polar cap appears at the top of the picture and (...) it is clearly smaller than the storm just below it and farther left. Similar to the "spiral storms" detected on Mars over 20 years ago by the Viking spacecraft, this storm was marked by a system of swirling bright water-ice clouds instead of the billowing dust of a more typical martian wind storm. Measuring roughly 1.600 Km across (...) it was comparable in size to cyclones seen in planet Earth's polar regions. The storm (...) may have had a lifetime of only a few days". Commento: ma come si fa a dire che su Marte non piove da qualche milione di anni?!?!?!