Four and a half billion years ago, the collapse of a huge cloud of dust and gas caused the solar system to form. Dust particles in cosmic space act as seeds for chemical reactions on the particle surfaces and thus for the formation of complex molecules. These processes are, however, substantially different from those in terrestrial laboratories because of the characteristically long time they take, the lack of thermodynamical equilibrium due to the absence of atmospheres, and the presence of strong radiation fields and penetrating high-energy particles. While some of the dust grains are produced in cool stars, other components are a product of the socalled hot chemistry of cosmic environmental conditions. Plasma and gas interactions, as well as the influence of radiation, play an important role in the physics of dust in space. One consequence is that the complete history of the evolution of cosmic dust is not yet well understood.
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