Curiosity Surveys a Martian 'Mojave Desert': Big Pic.
Aug. 8, 2012 --

The panoramic image, attached below, shows what appears to be "haze" at the base of the mountains in the distance in Gale crater. This was predicted prior to landing:

Pink skies, water ice haze in forecast for Curiosity landing.
12:56 PM, Aug 5, 2012

"PASADENA, CALIF. — Expect pink skies with a chance of a water ice haze over Gale Crater Monday when NASA’s Mars Science Laboratory and Curiosity rover arrive at the red planet.
"Seasonal winter temperatures are expected to be a balmy 10 degrees Fahrenheit when Curiosity touches down at 3 p.m. local Mars time."

It is important to realize that clouds, fogs and hazes can have some proportion of liquid water even well below freezing temperature. This is well known to happen when salts are dissolved in the water through freezing point depression. But it can also happen with pure water through supercooling.
The temperature at which supercooled liquid water can occur can even be below -40C, which coincidentally is also -40F:

Supercool Water.
Posted: 11/28/11

Liquid water as cold as minus 40 F has been found in clouds. Scientists have done experiments showing liquid water can exist at least down to minus 42 F.

Bob Clark