Research Spotlight: Lost in a fog on Mars



[1] A pair of cameras mounted on the back of the Phoenix Mars Lander were used to capture how laser light, emitted by the lander's light detection and ranging (lidar) system, was scattered by water ice in the red planet's thin atmosphere.Moores et al. used the unique technique during four nights in 2008 to give the first detailed profile of the ice water content in the Martian near-surface atmosphere. The authors found that the icy fog is thickest around 50 meters above the surface, with a maximum concentration of 1.7 milligrams per cubic meter. They also found that the fog is not uniform but tends to decrease in thickness toward the surface. As the Martian night wears on, the surface of the planet cools below the frost point and water vapor in the atmosphere gets deposited on the ground. As the atmosphere is mixed by turbulence, more water is brought to lower altitudes, adding to the growing frost layer. Ice crystals also form in the air and precipitate to the ground from successively higher altitudes. The researchers estimate that by the time the Sun starts to rise in the morning, 2.5 micrometers of snow and frost have coated the surface of Mars in the northerly region around the Phoenix Lander. (Geophysical Research Letters, doi:10.1029/2010GL046315, 2011)