Winter on Mars...

While not the kind of snow you'd want to eat, as pure white as it might seem, the snowy dunes of Mars provide a brief season of delight on the planet's scoured red face. Below is a zoomable version of the photo taken by NASA's High Resolution Imaging Science Experiment (HiRISE) camera on the Mars Reconnaissance Orbiter.

The snow is dry ice or carbon dioxide that has covered the dunes during winter in the northern hemisphere. When the spring-time sun hits the dunes, the space agency writes, "the ice on the smooth surface of the dune cracks and escaping gas carries dark sand out from the dune below, often creating beautiful patterns. On the rough surface between the dunes, frost is trapped behind small sheltered ridges."

Mars' atmosphere is mostly carbon dioxide with some water vapor, with an average temperature of -81 F. The Red Planet does have four seasons taking 687 Earth days to make an orbit. However, seasons on Mars are far more extreme than on Earth because its distance from the sun varies greatly during its year and the planet's axial tilt is greater than Earth's, NASA explains.