Blowing in the Wind... (GIF-Movie; credits: NASA)

Caption NASA:"These are two separate, side-by-side animations made from the same 9 images the Surface Stereo Imager (SSI) on NASA's Phoenix Mars Lander took looking into the sky after 17:17 MLT on Sol 8 (June 2, 2008), such as the eighth Martian day of the mission. The SSI was pointed almost straight up, toward the South-West.
Zenith is near the top of the center frame.

In the left animation, the images were stretched to enhance contrast. The right animation highlights variations between each image and the next. The variations are likely dust blown by winds passing through the SSI's field of view. The images suggest the dust is blowing from West to East".