Headed to Mars? Remember to pack your snow gear. Turns out that there are snowstorms on the Red Planet at night, according to a new paper.
The findings, published in the journal Nature Geoscience, could shed light on the dynamics of the planet’s ancient climate — and reveal that even today, Mars remains a more dynamic world than some scientists expected.
Today, the Red Planet seems dusty, rusty and dry, with an atmosphere that’s about 100 times thinner than Earth’s. But scientists say that early in its history, Mars probably looked a lot like Earth, with a thick atmosphere, puffy clouds and liquid water. That’s part of why researchers study Mars — to understand why our next-door neighbor ended up with such a different fate than that of our planetary home.
Even now, Mars has some thin clouds, as well as water-ice deposits on and beneath its surface. (It’s cold enough to have carbon dioxide ice deposits, too.) A laser instrument on NASA’s Phoenix Mars Lander even discovered signs of actual snowfall, years ago. But many scientists figured that whatever the contribution made by snowfall, it was very slow, building up gradually over time.
Temperature patterns
But lead author Aymeric Spiga, a planetary scientist at the Laboratoire de Meteorologie Dynamique in Paris, and his colleagues wondered if some other phenomenon was at work. Thanks to data from NASA’s Mars Reconnaissance Orbiter and Mars Global Surveyor, they had noticed strange temperature patterns beneath the Martian water-ice clouds that hinted at a surprising amount of air movement in the atmosphere.
“It was like the temperature profiles were showing very strong mixing and were representative of very strong winds below the clouds, and it was at night,” Spiga said. The understanding at the time, he added, “was that water-ice clouds on Mars were not supposed to create very strong winds, especially at night, and the winds at night were supposed to be very calm.”
After developing models that simulated these temperature patterns, Spiga and his colleagues realized that the natural explanation for these patterns were brief but strong snowstorms, triggered by radiative cooling at night. Snowfall on Mars, it turns out, could be much more dramatic than expected.
“It seems quite satisfying that data acquired quite a few years ago from the Phoenix lander can so nicely be explained by the model,” said Paul Mahaffy, a planetary scientist at NASA’s Goddard Space Flight Center who was not involved in the work.
These snowstorms aren’t quite like those on Earth, Spiga pointed out. For one thing, the “snow” probably isn’t made of delicate, crystalline snowflakes; instead, it’s probably more like tiny chunks of ice just a few micrometers thick. But the snow would be coming down fast, he added — about as fast as during a moderate thunderstorm on Earth.
“The amount of water overall is quite small — so you won’t be able to build any snowmen on Mars with that, and you won’t be able to put up a ski station,” Spiga quipped.
Still, the fact that so little water in such a thin atmosphere could have such a pronounced effect on the mixing of air shows that far more remains to be learned about the dynamics of the Martian atmosphere, he said.
Understanding the influence of these storms will also help researchers better understand the Red Planet’s dynamics many millions of years ago, when the planet’s axial tilt toward the sun was more pronounced — which meant that the poles received far more sunlight than they did before, resulting in a very different climate.
