Blizzards on Mars strike at night

figure-3Mars researchers have long thought that because the water content of the martian atmosphere today is so low, any clouds that form will produce only modest precipitation. For example, in 2008 the Mars Phoenix lander detected falling snow from a cloud, but the flakes mostly evaporated before reaching the surface, producing no accumulation.

However, new research based on numerical simulations shows that martian clouds undergo rapid cooling at night. This sets up strong convective motions within the clouds, and the result can be heavy snowfall during nighttime.

The results are published in Nature Geoscience by a team led by Aymeric Spiga (Laboratoire de Météorologie Dynamique and Université Pierre-et-Marie-Curie, Paris). The scientists say that their simulations of the meteorology in martian cloudy regions show that strong localized snowstorms can occur on Mars. They add that such snowstorms, which they term “ice microbursts,” can explain deep convective layers detected from orbit at night, as well as the precipitation detected by the Phoenix lander falling from water-ice clouds.

Their simulations show that “convective snowstorms occur only during the martian night, and result from atmospheric instability due to radiative cooling of water-ice cloud particles.”  This, they say, “triggers strong convective plumes within and below clouds, with fast snow precipitation resulting from the vigorous descending currents.”

The team adds that the nighttime snowfall would be much stronger during epochs when the martian atmosphere contains more water vapor, such as when Mars’ axis is tilted more steeply to the planet’s orbit than the current 24°.  [More at link]

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