They look like fogs to me too. I don't know why fogs form on hillsides. Perhaps something an atmospheric scientist can answer.
I don't know the latitude and season of the image you posted, but keep in mind fogs on Earth can contain some proportion of liquid water droplets down to -40 C and the same is overwhelmingly likely to be the case on Mars as well.
Such supercooling is well known among atmospheric scientists who study Earth climate. It's also well known among atmospheric scientists who study Mars climate - they simply choose to ignore it.
I refer to this as "The Power of Paridigm." It's going to take some overwhelming observational fact to shake Mars atmospheric scientists into investigating the fact that supercooling can occur in clouds and fogs under Martian conditions as it does on Earth.
Note this has already occured in regards to liquid water on the surface. The overwhelming observational fact that was required was the Malin/Edgett gullies that appeared to be recently carved by flowing water. This led Mars geologists and geophysicists to investigate the cases where surface liquid water could exist and flow under Martian conditions.

Bob Clark