This image shows geologically young lava flows west of Pavonis Mons. Pavonis Mons is one of the three Tharsis Montes, a group of giant shield volcanoes (they are broad and have gentle slopes, like a shield).
The lava flows show up best in the reduced-scale browse images. Zooming in at full resolution, we see that this area is mantled by thick dust deposits that have been eroded into northwest-southeast trending landforms. These patterns are used by scientists to map what direction the strongest winds blow on average and how the direction changes through time.
We can also see long linear tracks that are lighter-toned than the surrounding surface, and bluer in color. These tracks are formed by dust devils that remove some of the surface dust. The older, compacted dust has a different color that the fresh dust. Notice that the dust devils did not move in the same direction as the predominant winds that streamlined the surface.
Written by: Alfred McEwen (8 May 2008)
More info and image formats at http://hirise.lpl.arizona.edu/PSP_007840_1800
Image: NASA/JPL/University of Arizona