Martian weather report reveals ice and fog near surface

A pair of cameras mounted on the back of the Phoenix Mars Lander captured 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 technique over 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 was thickest around 50 meters (164 feet) above the surface, with maximum concentration of 1.7 milligrams per cubic meter (0.000002 ounces per cubic foot).

They also found that the fog was not uniform but tended 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 started to rise in the morning, 2.5 micrograms (0.000000088 ounce) of snow and frost would have coated the surface of Mars in the northerly region around the Phoenix Lander.

The research paper has been published in Geophysical Research Letters (GRL).