New computer models of Mars’ atmosphere are indicating that the Red Planet may experience rapidly-falling snowstorms at night, possibly sprinkling the surface below with a light layer of snow. It was previously assumed that snow that fell on Mars did so slowly, taking hours to drop a single mile, and typically evaporating before it reached the surface. But the new simulations show that ice crystals forming at night may only take about five to ten minutes to fall the same distance, explaining why NASA’s Phoenix lander observed a dusting of snow shortly after touchdown in 2008.

After studying Mars’ tenuous water clouds near the planet’s equator, a research team at France’s Université Pierre et Marie Curie found that there were incredibly fast winds being generated by a strong mixing of the air below them — an unexpected development. This new variable prompted the researchers to include the find into existing atmospheric models, that in turn yielded the formation of strong downdrafts that were generated when the temperature of the clouds dropped dramatically overnight.

These cold, downward winds drove the snow crystals rapidly downward, making it more likely that they would reach the surface — it was previously presumed that they would take too long to fall, sublimating back into water vapor before they got to the ground. This new finding would explain why Phoenix saw any snow to begin with.

The Phoenix lander mission’s principal investigator, Peter Smith, cautions that the new models may not pan out, as the lander was situated near Mars’ north pole, where the sun rarely sets, as opposed to the equatorial clouds that were observed by the study team.

"It’s comparing the weather in northern Alaska to down in Mexico City," cautions Smith. "The streaks we saw up there could be quite different than the mechanisms at 25 degrees latitude." However, if this finding turns out to be valid, then climate and atmospheric models for Mars will require a substantial update. 

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