That is the south pole of Mars, as seen by the European Space Agency’s Mars Express orbiter. It’s a combination of blue, green, and infrared images (put together into that stunning picture by Riding with Robots creator Bill Dunford). This exaggerates the ruddy ochre hue of the planet, but magnifies the overall impact of the picture. It’s surreal; it looks a lot like the top of the mug of coffee I make myself every morning.
Where you see white is a vast region of permanently frozen water ice, many kilometers thick, covered in winter by a few-meter-deep veneer of frozen carbon dioxide, commonly called dry ice. In the Martian summer, the temperature at the pole gets high enough to turn the dry ice into a gas, but the water ice stays frozen. Not all the dry ice disappears, but even in winter the underlying water ice cap is far thicker than the dry ice above it.