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
Greenhouse and icehouse Earth of "scrubbing" of this carbon dioxide in the atmosphere, that the earth would return to a greenhouse state. Some scientists believe that the end of the snowball Earth caused an event known as the Cambrian Explosion, which produced the beginnings of multi-cellular life. However some biologists claim that a complete snowball Earth could not have happened since photosynthetic life would not have survived underneath many meters of ice without sunlight. However, it has been observed that, even under meters of thick ice around Antarctica, sunlight shows through. Most scientists today believe that a "hard" Snowball Earth, one completely covered by