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Super fast-falling snowstorms may rage on Mars at night

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New climate models show that Martian clouds may create strong winds

Mars’ northern pole, which consists of water and carbon dioxide snow.
Image: NASA / JPL-Caltech / MSSS

Fast-falling snowstorms may rage at night in certain regions of Mars. The phenomenon hasn’t been seen directly, but a group of researchers believe such storms are happening based on new computer models of the Martian atmosphere. These models suggest that it gets cold enough at night for ice particles to fall rapidly from thin clouds in the sky — possibly sprinkling certain parts of the Martian surface in snow.

The idea that snow falls on Mars isn’t a new concept. NASA’s Phoenix lander, which touched down on the Martian surface in 2008, was the first to measure snow particles falling from clouds above the planet. But at the time, scientists thought that this snow fell incredibly slowly, taking several hours to descend just one mile. But the new models, detailed in a new study in Nature Geoscience, suggest the snow could be falling much faster in some nighttime areas — taking just five to 10 minutes to drop a mile.

These snowstorms could have a big impact on how water-ice is distributed in the atmosphere, as well as how dust and other chemicals mix in the air. That means Martian climate models — for both the past and the present — may need to be updated, says lead author Aymeric Spiga, a planetary researcher at Université Pierre et Marie Curie. “We need to investigate what would be the impact of those phenomena on the global cycle of dust and water on Mars,” says Spiga.

Mars has far less water vapor in its atmosphere than Earth does, but it’s still enough for thin clouds to form. Spiga and his colleagues studied some of these clouds near the planet’s equator using data from two spacecraft in orbit around Mars: the Mars Global Surveyor and the Mars Reconnaissance Orbiter. They found that there was a strong mixing of air below the clouds, creating super fast winds. “That was surprising,” says Spiga. “We were not expecting the Martian clouds to trigger any strong winds.”

That prompted the researchers to create atmospheric models to see if they could predict how the clouds might behave. They found that the nighttime temperatures can make the clouds cold enough to become unstable, causing plumes of fast-moving wind that carries ice particles rapidly downward.

A rendering of the Phoenix lander.
Image: NASA / JPL / UA / Lockheed Martin

The authors argue that this may explain the snowfall that the Phoenix lander saw back in 2008. At the time, scientists thought the ice particles must be slowly falling under their own weight, instead of being pulled down by strong winds. Because of that, it was believed that the snow actually turned to gas before even reaching the ground. (Earth has a similar weather pattern called virga, where rain evaporates before hitting the planet.)

Spiga and his team still argue that the snowfall is behaving like virga on Mars, but it’s the strong winds — not gravity — that pulls the snow down. And if the clouds are low enough in the sky, the snow may actually sprinkle the surface of Mars, the authors say. It’s similar to “microbursts” here on Earth, when strong winds carry snow or rain swiftly from a cloud.

Whether or not this interpretation is true remains to be seen. Peter Smith, the principal investigator of the Phoenix lander mission, says it’s possible the new models don’t explain the snow that the spacecraft detected. “It’s comparing the weather in northern Alaska to down in Mexico City,” Smith tells The Verge. The Phoenix lander measured snow near the north pole of Mars when the Sun rarely sets, so the spacecraft never got to true nighttime conditions, says Smith. The clouds that Spiga and his team modeled were closer to the equator of Mars. “The streaks we saw up there could be quite different than the mechanisms at 25 degrees latitude,” says Smith, who’s a researcher at the University of Arizona’s Lunar and Planetary Laboratory.

Still, computer simulations like this one are invaluable to better understand other worlds in the Solar System. “We can’t send a mission to every part of the planet, so modeling is super important to Mars studies,” says Smith. Plus, there's something nice about thinking that Mars — just like Earth — may be sprinkled in snow when it gets cold.