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NASA/JPL-Caltech/University Arizona/Texas A&M University

Astronomy and astrophysics

Snow falls fast at night on Mars

Precipitation comes as powerful storms, not gentle drifts, on the Red Planet.

Mars has surprisingly powerful snowstorms, which form at night.

Although the planet has relatively little water vapour in its atmosphere, clouds of water-ice crystals can still develop. A team led by Aymeric Spiga of the Laboratory of Dynamic Meteorology in Paris used a high-resolution atmospheric model to study how those clouds behave over the Tharsis Montes region of Mars.

After sunset, when the air cools, water-ice clouds radiate away heat — a process that creates strong downward- and upward-flowing winds. This atmospheric churning carries water-ice particles downward, where they precipitate out as snow.

Spacecraft orbiting Mars have detected this night-time atmospheric mixing, and NASA’s Phoenix lander also spotted streaks suspected to be snow on the ground beneath a night-time cloud. The latest work ties those observations together.

Researchers had thought that snow formation on Mars was a slow and gentle process, and will now have to rethink their ideas about the Martian water cycle.