Geophys. Res. Lett. http://dx.doi.org/10.1002/grl.50326 (2013)
During the martian winter, carbon dioxide in the planet's atmosphere condenses to form ice clouds and snow. Model simulations suggest that the formation of airborne ice is promoted by the passage of planetary waves.
Takeshi Kuroda of Tohoku University, Japan, and colleagues identified the mechanisms of ice cloud formation in the high northern latitudes of Mars, using a general circulation model. In the model, ice clouds formed north of 70° N, at altitudes of up to 40 km. Ice cloud formation coincided with the presence of eastward-travelling planetary waves, a dominant feature of winter-time atmospheric dynamics in the north. The passage of these waves lowered local air temperatures below the carbon dioxide condensation level, at which point ice emerges.
Ice particles generated below about 20 km altitude fell to the surface as snow, potentially contributing to polar ice cap formation. Deposition was greatest in regions impacted by planetary waves. Given the regularity of these waves, the authors argue that deposition to the surface can be reliably predicted.