Sublimation, defining characteristic of comets.
Sublimation, defining characteristic of comets.
Another defining characteristic of comets is their activity, especially sublimation – when frozen substances on the surface of the nucleus transition directly from solid to gaseous form when exposed to solar radiation. The gas molecules produced in the process together with dust particles escape the nucleus at high speeds to form a thin coma. Once there, they are split into daughter molecules by solar photons (photodissociation) or by collisions between them. Photoionisation will take place if suffi cient energy is transferred: the electrically charged ions are transported away by the charged particles in the solar wind, where they form the plasma tail. This diagram provides a simplified description of the process.
