Comets
type: Concept
narrower: Dirty snowball model

Dirty snowball model
type: Concept
contributor: AAS Frey.Katie Admin
modified: 2020-11-05T15:40:22.12Z
modified: 2020-11-05T15:40:10.914Z
alternative label: Dirty iceball model
alternative label: Dirty snowball theory
broader: Comets
definition: A model for a cometary nucleus proposed by Fred Whipple (1950-51), according to which the nucleus is a solid body (a few kilometers across) made up of various ices (frozen water, methane, ammonia, carbon dioxide, and hydrogen cyanide) in which dust is embedded. Dust particles are liberated when the ices vaporize as the comet approaches the Sun, and they get blown away by solar radiation pressure, often forming impressive, gently curved dust tails.