Sometimes it snows on Mars. In autumn, the snow is probably water ice, and in the depths of winter, when temperatures drop to -125 º C, it’s carbon dioxide snow.
The atmosphere is thin and dry, and the temperature drops very fast after sunset, so the snow flakes are tiny, about 7 microns in diameter, like a human red blood cell. In fact, it’s a lot like the diamond ice that forms in Antarctica – like fog, but with tiny ice crystals instead.
