These pictures showcase the planet in both visible and infrared light. In the image on the left, taken in visible light by the Wide Field and Planetary Camera 2, Mars appears in natural color or as we would see it close-up. The multicolor picture on the right was taken in infrared light by the Near Infrared Camera and Multi-Object Spectrometer.
Infrared light is invisible to the eye.
Therefore, astronomers have assigned false colors to highlight important features that cannot be seen in visible light. Mars Pathfinder also imaged clouds like these in 1997. The north polar cap, the bright region at the top of the image, is not actually white, but yellowish-pink. This color indicates the presence of small iron-bearing dust particles. These particles are covering or are suspended in the air above the blue-white water ice and carbon dioxide ice, which make up the polar cap.