For many, winter means snow—a magical mix of branched, crystallized ice particles forming delicate flakes. While Earth hosts permanent snowcaps in some regions and rare flurries in others, scientists wonder: does this phenomenon occur elsewhere in the cosmos?
During cold seasons, snowfall blankets parts of Earth through precise atmospheric conditions of temperature and pressure. Astrophysicists, drawing on decades of planetary data, have investigated whether similar precipitation happens across the Solar System and beyond.
Planetary scientists have documented snow on Mars multiple times. With average temperatures around -60°C, the planet's frigid climate supports ice precipitation. In 2008, NASA's Phoenix lander detected falling icy snow near the north pole. The south pole features a year-round carbon dioxide ice cap, and in 2012, researchers observed dry ice snowfall there.
Mars' thin atmosphere—100 times less dense than Earth's—causes snow to vaporize quickly before accumulating, often forming virga clouds where precipitation evaporates mid-air (a process also seen on Earth).
Yet, surface snow is possible under ideal conditions, per a 2017 Nature Geoscience study. Extreme daily temperature swings up to 111°C drive turbulent clouds and winds reaching 10 meters per second, as noted by planetary scientist Aymeric Spiga of Sorbonne University. In such storms, snow can reach and briefly linger on the surface overnight before sublimating by morning.
Beyond Mars, Jupiter's swirling clouds, imaged in May 2017, likely harbor frozen water-ammonia mixtures akin to snow or hail, according to planetary experts.
Saturn's moon Enceladus is dusted in snow, as revealed by NASA's Cassini probe in 2011. Ice particles from geysers settle in predictable patterns, forming superfine crystal slopes—but at an glacial pace: less than a millimeter per thousand years. Building 100 meters would take tens of millions of years.
On exoplanet Kepler-13Ab, 1,730 light-years away and six times Jupiter's size, titanium dioxide—a sunscreen ingredient—falls as snow. Uranus and Neptune may see diamond rain.
