Martian water Cycle

The air on Mars appears to have less water in it than scientists had once thought. Clouds on Mars seem to have difficulty forming and often do not form until they reach temperatures below 212 degrees Fahrenheit. Because clouds form with such difficulty, there is less water content in the atmosphere. Tony Colaprete of NASA's Ames Research Center explains that, "Clouds are integral to this system, just as on Earth. However, assuming the clouds form or behave the same as on Earth, may be a bad assumption." Colaprete believes that finding out how the Martian water cycle works is key to learning about Mars' past.

http://www.space.com/scienceastronomy/071206-mars-air.html