Snow Snow Snow refers to forms of ice crystals that precipitate from the atmosphere (usually from clouds) and undergo changes on the Earth's surface. It pertains to frozen crystalline water throughout its life cycle, starting when, under suitable conditions, the ice crystals form in the atmosphere, increase to millimeter size, precipitate and accumulate on surfaces, then metamorphose in place, and ultimately melt, slide or sublimate away. Snowstorms organize and develop by feeding on sources of atmospheric moisture and cold air. Snowflakes nucleate around particles in the atmosphere by attracting supercooled water droplets, which freeze in hexagonal-shaped crystals. Snowflakes take on a
Atmosphere of Pluto Pluto. The question of composition was answered in 1992 via infrared spectra of Pluto by the 3.8-meter United Kingdom Infrared Telescope. The surface of Pluto turned out to be covered mainly by nitrogen ice. Since nitrogen is, in addition, more volatile than methane, this observation implied a prevalence of nitrogen also in the atmosphere (although gaseous nitrogen was not seen in the spectrum). Furthermore, a small admixture of frozen carbon monoxide was discovered. The same year observations by the 3.0-meter NASA Infrared Telescope Facility revealed the first conclusive evidence of gaseous methane. Understanding the state of the atmosphere requires knowing