Looking at this HIRISE image taken very near the Phoenix landing site, labeled Northern Plains Seasonal Frost on Patterned Ground :



Sure looks like clouds above the surface. Does "frost" refer to the whitish lines, while the more fuzzy larger scale white areas are clouds?

The image was taken during this past northern spring, so it would make sense that water vapor is coming off the ground and condensing as clouds. If so, what happens to the clouds from there?

It's interesting that the Sol 55 theme is "MRO-coordinated 24-hour atmospheric campaign."