These alternating views taken by the Hazard-Avoidance cameras on NASA's Curiosity rover show evidence for an impact plume created when the rover's sky crane fell to the Martian surface. The sky crane helped the rover gently land on Mars before flying away and crashing in a planned maneuver.
The view flips between images taken about 45 minutes apart. The image taken earlier shows evidence for the "blob" thought to be the impact plume; by the time the later image was taken, the blob had disappeared.
These images are from the rover's rear Hazard-Avoidance cameras. They are one-quarter of full resolution (256 by 256 pixels).