ESA / DLR / FU Berlin (G Neukum); animation by Emily Lakdawalla
Martian clouds in motion (H8676)
The images that compose this animation were taken on October 14, 2010, on Mars Express' 8676th orbit, and show an area within Noachis Terra to the west of Hellas basin, around 45 degrees south, 38 east. There are two components to the apparent motions of the clouds. One is real west-to-east cloud motion over the two-minute period of the animation (readable from the motions of the shadows along the ground). The other component has to do with the different look angles of the different channels of HRSC and the significant thickness of the cloud layer. In the first frame, HRSC was looking forward (northward) along its south-to-north orbital path; in the last frame, it was looking backward (southward). Because of this changing perspective, the upper-level clouds appear to move southward with respect to the lower-level clouds.
The color comes from red, green, and blue channels of the HRSC channel and is an overlay applied to the animation, so the color information is actually not animated -- only the brightness information moves. This works visually because Mars is relatively monochromatic.