Some of the most prominent aeolian features on Mars are the wind streaks (Figure 5.1) . These are tear-shaped features appearing behind craters, ridges or cliffs. They may appear light colored or dark colored depending on the nature of the subsurface. These features are the result of wind erosion and deposition. Erosion might occur behind some obstacles where strong wind converged to sweep away fine particles, exposing lava plains underneath and resulting in dark streaks.

On the other hand, some obstacles might create a wind shadow where wind speeds died down, creating an environment for deposition of suspended particles. Thus, light-colored streaks formed. Figure 5.2 shows many light-colored wind streaks found at the base of the Olympus Mons, a huge shield volcano in the Tharsis region.

High resolution images obtained by the Mars Global Surveyor show that wind streaks can change over short period of time as indicated in Figure 5.3. This image compares an area with repeated observations obtained in August 1999 and April 2001. The white arrows show the new wind streaks of the area that did not exist on the 1999 image.