Figure 6-64 The Atmosphere of Mars (a) When Mars’s sky is relatively free of dust, it appears similar in color to our sky, as shown in this sunset photo taken by the rover Opportunity. The darker, brown color in which the Sun is immersed is due to lingering dust in the sky. When less dust is present, the Sun looks almost white during Martian sunsets. Most of the images we have of Mars’s sky show colors like those seen in (b). (b) Taken by the Mars Pathfinder, this photograph shows the Sojourner rover snuggled against a rock named Moe on the Ares Vallis to run tests on the rock. At the top of the image, the pink color of the Martian sky is evident.