Snowfall on Mars
Dry ice to be be specific
NASA's Mars Reconnaissance Orbiter (MRO) has returned the first definitive evidence of carbon dioxide snowfalls on Mars—the only place this is known to happen anywhere in our solar system.
Frozen carbon dioxide—better known as 'dry ice'—requires a temperature of about minus 193 degrees Fahrenheit. The snow was seen falling around Mars's south pole in winter.