Because of the Viking landers, aeolian processes on Mars were also observed at the surface (Figure 5.15) . The top picture shows the landing site of Viking I in August, 1976. A year later, a view of the same area is given at the bottom of the image. Two significant changes marked by A and B can be recognized. A is a small circular formation downwind of the Whale Rock. B exposes a new rock surface near the Big Joe. These were believed to be the result of erosion of the dust layer at the Martian surface by high winds.

Wind deposition on the Martian surface can also occur (Figure 5.16) . This is a view of the landing site of Viking II. Notice the thin coating of a dust layer mixed with water ice on all the rocks in this area. These represent the deposition of dust particles from the atmosphere on the Martian surface. As the Martian atmosphere changed to a colder winter climate, water and carbon dioxide started to condense upon dust particles suspended in the atmosphere. The condensation increased the weight of the dust particles and caused them to settle onto the ground.